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Add volume rendering example. (~2.3x speedup from SIMD vs serial code.)

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This commit is contained in:
Matt Pharr
2011-08-17 12:05:37 +01:00
parent fce183c244
commit ecaa57c7c6
14 changed files with 1691 additions and 0 deletions
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14
examples/README.txt
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@@ -93,3 +93,17 @@ Simple
This is a simple "hello world" type program that shows a ~10 line
application program calling out to a ~5 line ispc program to do a simple
computation.
Volume
======
Ray-marching volume rendering, with single scattering lighting model. To
run it, specify a camera parameter file and a volume density file, e.g.:
volume camera.dat density_highres.vol
(See, e.g. Chapters 11 and 16 of "Physically Based Rendering" for
information about the algorithm implemented here.) The volume data set
included here was generated by the example implementation of the "Wavelet
Turbulence for Fluid Simulation" SIGGRAPH 2008 paper by Kim et
al. (http://www.cs.cornell.edu/~tedkim/WTURB/)

9
examples/examples.sln
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@@ -17,6 +17,7 @@ Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "aobench_instrumented", "aob
EndProject
Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "noise", "noise\noise.vcxproj", "{0E0886D8-8B5E-4EAF-9A21-91E63DAF81FD}"
EndProject
Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "volume", "volume_rendering\volume.vcxproj", "{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}"
Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "stencil", "stencil\stencil.vcxproj", "{2EF070A1-F62F-4E6A-944B-88D140945C3C}"
EndProject
Global
@@ -91,6 +92,14 @@ Global
{0E0886D8-8B5E-4EAF-9A21-91E63DAF81FD}.Release|Win32.Build.0 = Release|Win32
{0E0886D8-8B5E-4EAF-9A21-91E63DAF81FD}.Release|x64.ActiveCfg = Release|x64
{0E0886D8-8B5E-4EAF-9A21-91E63DAF81FD}.Release|x64.Build.0 = Release|x64
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Debug|Win32.ActiveCfg = Debug|Win32
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Debug|Win32.Build.0 = Debug|Win32
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Debug|x64.ActiveCfg = Debug|x64
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Debug|x64.Build.0 = Debug|x64
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Release|Win32.ActiveCfg = Release|Win32
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Release|Win32.Build.0 = Release|Win32
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Release|x64.ActiveCfg = Release|x64
{DEE5733A-E93E-449D-9114-9BFFCAEB4DF9}.Release|x64.Build.0 = Release|x64
{2EF070A1-F62F-4E6A-944B-88D140945C3C}.Debug|Win32.ActiveCfg = Debug|Win32
{2EF070A1-F62F-4E6A-944B-88D140945C3C}.Debug|Win32.Build.0 = Debug|Win32
{2EF070A1-F62F-4E6A-944B-88D140945C3C}.Debug|x64.ActiveCfg = Debug|x64

2
examples/volume_rendering/.gitignore vendored Normal file
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@@ -0,0 +1,2 @@
mandelbrot
*.ppm

38
examples/volume_rendering/Makefile Normal file
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@@ -0,0 +1,38 @@
ARCH = $(shell uname)
TASK_CXX=tasks_pthreads.cpp
TASK_LIB=-lpthread
ifeq ($(ARCH), Darwin)
TASK_CXX=tasks_gcd.cpp
TASK_LIB=
endif
TASK_OBJ=$(addprefix objs/, $(TASK_CXX:.cpp=.o))
CXX=g++ -m64
CXXFLAGS=-Iobjs/ -O3 -Wall
ISPC=ispc
ISPCFLAGS=-O2 --target=sse4x2 --arch=x86-64
default: volume
.PHONY: dirs clean
dirs:
/bin/mkdir -p objs/
clean:
/bin/rm -rf objs *~ volume
volume: dirs objs/volume.o objs/volume_serial.o objs/volume_ispc.o $(TASK_OBJ)
$(CXX) $(CXXFLAGS) -o $@ objs/volume.o objs/volume_ispc.o objs/volume_serial.o $(TASK_OBJ) -lm $(TASK_LIB)
objs/%.o: %.cpp
$(CXX) $< $(CXXFLAGS) -c -o $@
objs/volume.o: objs/volume_ispc.h
objs/%_ispc.h objs/%_ispc.o: %.ispc
$(ISPC) $(ISPCFLAGS) $< -o objs/$*_ispc.o -h objs/$*_ispc.h

11
examples/volume_rendering/camera.dat Normal file
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@@ -0,0 +1,11 @@
896 1184
0.000155 0.000000 0.000000 -0.069927
0.000000 -0.000155 0.000000 0.093236
0.000000 0.000000 0.000000 1.000000
0.000000 0.000000 -99.999001 100.000000
1.000000 0.000000 0.000000 1.000000
0.000000 0.980129 -0.198360 2.900000
0.000000 0.198360 0.980129 -10.500000
0.000000 0.000000 0.000000 1.000000

5
examples/volume_rendering/density_highres.vol Normal file
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4
examples/volume_rendering/density_lowres.vol Normal file
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File diff suppressed because one or more lines are too long

141
examples/volume_rendering/tasks_concrt.cpp Normal file
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@@ -0,0 +1,141 @@
/*
Copyright (c) 2010-2011, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/* Simple task system implementation for ispc based on Microsoft's
Concurrency Runtime. */
#include <windows.h>
#include <concrt.h>
using namespace Concurrency;
#include <stdint.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
// ispc expects these functions to have C linkage / not be mangled
extern "C" {
void ISPCLaunch(void *f, void *data);
void ISPCSync();
void *ISPCMalloc(int64_t size, int32_t alignment);
void ISPCFree(void *ptr);
}
typedef void (*TaskFuncType)(void *, int, int);
struct TaskInfo {
TaskFuncType ispcFunc;
void *ispcData;
};
// This is a simple implementation that just aborts if more than MAX_TASKS
// are launched. It could easily be extended to be more general...
#define MAX_TASKS 32768
static int taskOffset;
static TaskInfo taskInfo[MAX_TASKS];
static event *events[MAX_TASKS];
static CRITICAL_SECTION criticalSection;
static bool initialized = false;
void
TasksInit() {
InitializeCriticalSection(&criticalSection);
for (int i = 0; i < MAX_TASKS; ++i)
events[i] = new event;
initialized = true;
}
void __cdecl
lRunTask(LPVOID param) {
TaskInfo *ti = (TaskInfo *)param;
// Actually run the task.
// FIXME: like the tasks_gcd.cpp implementation, this is passing bogus
// values for the threadIndex and threadCount builtins, which in turn
// will cause bugs in code that uses those. FWIW this example doesn't
// use them...
int threadIndex = 0;
int threadCount = 1;
ti->ispcFunc(ti->ispcData, threadIndex, threadCount);
// Signal the event that this task is done
int taskNum = ti - &taskInfo[0];
events[taskNum]->set();
}
void
ISPCLaunch(void *func, void *data) {
if (!initialized) {
fprintf(stderr, "You must call TasksInit() before launching tasks.\n");
exit(1);
}
// Get a TaskInfo struct for this task
EnterCriticalSection(&criticalSection);
TaskInfo *ti = &taskInfo[taskOffset++];
assert(taskOffset < MAX_TASKS);
LeaveCriticalSection(&criticalSection);
// And pass it on to the Concurrency Runtime...
ti->ispcFunc = (TaskFuncType)func;
ti->ispcData = data;
CurrentScheduler::ScheduleTask(lRunTask, ti);
}
void ISPCSync() {
if (!initialized) {
fprintf(stderr, "You must call TasksInit() before launching tasks.\n");
exit(1);
}
event::wait_for_multiple(&events[0], taskOffset, true,
COOPERATIVE_TIMEOUT_INFINITE);
for (int i = 0; i < taskOffset; ++i)
events[i]->reset();
taskOffset = 0;
}
void *ISPCMalloc(int64_t size, int32_t alignment) {
return _aligned_malloc(size, alignment);
}
void ISPCFree(void *ptr) {
_aligned_free(ptr);
}

103
examples/volume_rendering/tasks_gcd.cpp Normal file
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@@ -0,0 +1,103 @@
/*
Copyright (c) 2010-2011, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/* A simple task system for ispc programs based on Apple's Grand Central
Dispatch. */
#include <dispatch/dispatch.h>
#include <stdio.h>
#include <stdlib.h>
static bool initialized = false;
static dispatch_queue_t gcdQueue;
static dispatch_group_t gcdGroup;
// ispc expects these functions to have C linkage / not be mangled
extern "C" {
void ISPCLaunch(void *f, void *data);
void ISPCSync();
}
struct TaskInfo {
void *func;
void *data;
};
void
TasksInit() {
gcdQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
gcdGroup = dispatch_group_create();
initialized = true;
}
static void
lRunTask(void *ti) {
typedef void (*TaskFuncType)(void *, int, int);
TaskInfo *taskInfo = (TaskInfo *)ti;
TaskFuncType func = (TaskFuncType)(taskInfo->func);
// FIXME: these are bogus values; may cause bugs in code that depends
// on them having unique values in different threads.
int threadIndex = 0;
int threadCount = 1;
// Actually run the task
func(taskInfo->data, threadIndex, threadCount);
// FIXME: taskInfo leaks...
}
void ISPCLaunch(void *func, void *data) {
if (!initialized) {
fprintf(stderr, "You must call TasksInit() before launching tasks.\n");
exit(1);
}
TaskInfo *ti = new TaskInfo;
ti->func = func;
ti->data = data;
dispatch_group_async_f(gcdGroup, gcdQueue, ti, lRunTask);
}
void ISPCSync() {
if (!initialized) {
fprintf(stderr, "You must call TasksInit() before launching tasks.\n");
exit(1);
}
// Wait for all of the tasks in the group to complete before returning
dispatch_group_wait(gcdGroup, DISPATCH_TIME_FOREVER);
}

295
examples/volume_rendering/tasks_pthreads.cpp Normal file
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@@ -0,0 +1,295 @@
/*
Copyright (c) 2010-2011, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <pthread.h>
#include <semaphore.h>
#include <string.h>
#include <unistd.h>
#include <assert.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <sys/sysctl.h>
#include <stdint.h>
#include <stdlib.h>
#include <errno.h>
#include <vector>
// ispc expects these functions to have C linkage / not be mangled
extern "C" {
void ISPCLaunch(void *f, void *data);
void ISPCSync();
}
static int nThreads;
static pthread_t *threads;
static pthread_mutex_t taskQueueMutex;
static std::vector<std::pair<void *, void *> > taskQueue;
static sem_t *workerSemaphore;
static uint32_t numUnfinishedTasks;
static pthread_mutex_t tasksRunningConditionMutex;
static pthread_cond_t tasksRunningCondition;
static void *lTaskEntry(void *arg);
/** Figure out how many CPU cores there are in the system
*/
static int
lNumCPUCores() {
#if defined(__linux__)
return sysconf(_SC_NPROCESSORS_ONLN);
#else
// Mac
int mib[2];
mib[0] = CTL_HW;
size_t length = 2;
if (sysctlnametomib("hw.logicalcpu", mib, &length) == -1) {
fprintf(stderr, "sysctlnametomib() filed. Guessing 2 cores.");
return 2;
}
assert(length == 2);
int nCores = 0;
size_t size = sizeof(nCores);
if (sysctl(mib, 2, &nCores, &size, NULL, 0) == -1) {
fprintf(stderr, "sysctl() to find number of cores present failed. Guessing 2.");
return 2;
}
return nCores;
#endif
}
void
TasksInit() {
nThreads = lNumCPUCores();
threads = new pthread_t[nThreads];
int err;
if ((err = pthread_mutex_init(&taskQueueMutex, NULL)) != 0) {
fprintf(stderr, "Error creating mutex: %s\n", strerror(err));
exit(1);
}
char name[32];
sprintf(name, "ispc_task.%d", (int)getpid());
workerSemaphore = sem_open(name, O_CREAT, S_IRUSR|S_IWUSR, 0);
if (!workerSemaphore) {
fprintf(stderr, "Error creating semaphore: %s\n", strerror(err));
exit(1);
}
if ((err = pthread_cond_init(&tasksRunningCondition, NULL)) != 0) {
fprintf(stderr, "Error creating condition variable: %s\n", strerror(err));
exit(1);
}
if ((err = pthread_mutex_init(&tasksRunningConditionMutex, NULL)) != 0) {
fprintf(stderr, "Error creating mutex: %s\n", strerror(err));
exit(1);
}
for (int i = 0; i < nThreads; ++i) {
err = pthread_create(&threads[i], NULL, &lTaskEntry, reinterpret_cast<void *>(i));
if (err != 0) {
fprintf(stderr, "Error creating pthread %d: %s\n", i, strerror(err));
exit(1);
}
}
}
void
ISPCLaunch(void *f, void *d) {
if (threads == NULL) {
fprintf(stderr, "You must call TasksInit() before launching tasks.\n");
exit(1);
}
//
// Acquire mutex, add task
//
int err;
if ((err = pthread_mutex_lock(&taskQueueMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
taskQueue.push_back(std::make_pair(f, d));
if ((err = pthread_mutex_unlock(&taskQueueMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_unlock: %s\n", strerror(err));
exit(1);
}
//
// Update count of number of tasks left to run
//
if ((err = pthread_mutex_lock(&tasksRunningConditionMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
++numUnfinishedTasks;
if ((err = pthread_mutex_unlock(&tasksRunningConditionMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
//
// Post to the worker semaphore to wake up worker threads that are
// sleeping waiting for tasks to show up
//
if ((err = sem_post(workerSemaphore)) != 0) {
fprintf(stderr, "Error from sem_post: %s\n", strerror(err));
exit(1);
}
}
static void *
lTaskEntry(void *arg) {
int threadIndex = int(reinterpret_cast<int64_t>(arg));
int threadCount = nThreads;
while (true) {
int err;
if ((err = sem_wait(workerSemaphore)) != 0) {
fprintf(stderr, "Error from sem_wait: %s\n", strerror(err));
exit(1);
}
std::pair<void *, void *> myTask;
//
// Acquire mutex, get task
//
if ((err = pthread_mutex_lock(&taskQueueMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
if (taskQueue.size() == 0) {
//
// Task queue is empty, go back and wait on the semaphore
//
if ((err = pthread_mutex_unlock(&taskQueueMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_unlock: %s\n", strerror(err));
exit(1);
}
continue;
}
myTask = taskQueue.back();
taskQueue.pop_back();
if ((err = pthread_mutex_unlock(&taskQueueMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_unlock: %s\n", strerror(err));
exit(1);
}
//
// Do work for _myTask_
//
typedef void (*TaskFunType)(void *, int, int);
TaskFunType func = (TaskFunType)myTask.first;
func(myTask.second, threadIndex, threadCount);
//
// Decrement the number of unfinished tasks counter
//
if ((err = pthread_mutex_lock(&tasksRunningConditionMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
int unfinished = --numUnfinishedTasks;
if (unfinished == 0) {
//
// Signal the "no more tasks are running" condition if all of
// them are done.
//
int err;
if ((err = pthread_cond_signal(&tasksRunningCondition)) != 0) {
fprintf(stderr, "Error from pthread_cond_signal: %s\n", strerror(err));
exit(1);
}
}
if ((err = pthread_mutex_unlock(&tasksRunningConditionMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
}
pthread_exit(NULL);
return 0;
}
void ISPCSync() {
if (threads == NULL) {
fprintf(stderr, "You must call TasksInit() before launching tasks.\n");
exit(1);
}
int err;
if ((err = pthread_mutex_lock(&tasksRunningConditionMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
// As long as there are tasks running, wait on the condition variable;
// doing so causes this thread to go to sleep until someone signals on
// the tasksRunningCondition condition variable.
while (numUnfinishedTasks > 0) {
if ((err = pthread_cond_wait(&tasksRunningCondition,
&tasksRunningConditionMutex)) != 0) {
fprintf(stderr, "Error from pthread_cond_wait: %s\n", strerror(err));
exit(1);
}
}
// We acquire ownership of the condition variable mutex when the above
// pthread_cond_wait returns.
// FIXME: is there a lurking issue here if numUnfinishedTasks gets back
// to zero by the time we get to ISPCSync() and thence we're trying to
// unlock a mutex we don't have a lock on?
if ((err = pthread_mutex_unlock(&tasksRunningConditionMutex)) != 0) {
fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
exit(1);
}
}

251
examples/volume_rendering/volume.cpp Normal file
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@@ -0,0 +1,251 @@
/*
Copyright (c) 2011, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifdef _MSC_VER
#define _CRT_SECURE_NO_WARNINGS
#define NOMINMAX
#pragma warning (disable: 4244)
#pragma warning (disable: 4305)
#endif
#include <stdio.h>
#include <algorithm>
#include "../timing.h"
#include "../cpuid.h"
#include "volume_ispc.h"
using namespace ispc;
extern void volume_serial(float density[], int nVoxels[3],
const float raster2camera[4][4],
const float camera2world[4][4],
int width, int height, float image[]);
/* Write a PPM image file with the image */
static void
writePPM(float *buf, int width, int height, const char *fn) {
FILE *fp = fopen(fn, "wb");
fprintf(fp, "P6\n");
fprintf(fp, "%d %d\n", width, height);
fprintf(fp, "255\n");
for (int i = 0; i < width*height; ++i) {
float v = buf[i] * 255.f;
if (v < 0.f) v = 0.f;
else if (v > 255.f) v = 255.f;
unsigned char c = (unsigned char)v;
for (int j = 0; j < 3; ++j)
fputc(c, fp);
}
fclose(fp);
printf("Wrote image file %s\n", fn);
}
// Make sure that the vector ISA used during compilation is supported by
// the processor. The ISPC_TARGET_* macro is set in the ispc-generated
// header file that we include above.
static void
ensureTargetISAIsSupported() {
#if defined(ISPC_TARGET_SSE2)
bool isaSupported = CPUSupportsSSE2();
const char *target = "SSE2";
#elif defined(ISPC_TARGET_SSE4)
bool isaSupported = CPUSupportsSSE4();
const char *target = "SSE4";
#elif defined(ISPC_TARGET_AVX)
bool isaSupported = CPUSupportsAVX();
const char *target = "AVX";
#else
#error "Unknown ISPC_TARGET_* value"
#endif
if (!isaSupported) {
fprintf(stderr, "***\n*** Error: the ispc-compiled code uses the %s instruction "
"set, which isn't\n*** supported by this computer's CPU!\n", target);
fprintf(stderr, "***\n*** Please modify the "
#ifdef _MSC_VER
"MSVC project file "
#else
"Makefile "
#endif
"to select another target (e.g. sse2)\n***\n");
exit(1);
}
}
/* Load image and viewing parameters from a camera data file.
FIXME: we should add support to be able to specify viewing parameters
in the program here directly. */
static void
loadCamera(const char *fn, int *width, int *height, float raster2camera[4][4],
float camera2world[4][4]) {
FILE *f = fopen(fn, "r");
if (!f) {
perror(fn);
exit(1);
}
if (fscanf(f, "%d %d", width, height) != 2) {
fprintf(stderr, "Unexpected end of file in camera file\n");
exit(1);
}
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
if (fscanf(f, "%f", &raster2camera[i][j]) != 1) {
fprintf(stderr, "Unexpected end of file in camera file\n");
exit(1);
}
}
}
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
if (fscanf(f, "%f", &camera2world[i][j]) != 1) {
fprintf(stderr, "Unexpected end of file in camera file\n");
exit(1);
}
}
}
fclose(f);
}
/* Load a volume density file. Expects the number of x, y, and z samples
as the first three values (as integer strings), then x*y*z
floating-point values (also as strings) to give the densities. */
static float *
loadVolume(const char *fn, int n[3]) {
FILE *f = fopen(fn, "r");
if (!f) {
perror(fn);
exit(1);
}
if (fscanf(f, "%d %d %d", &n[0], &n[1], &n[2]) != 3) {
fprintf(stderr, "Couldn't find resolution at start of density file\n");
exit(1);
}
int count = n[0] * n[1] * n[2];
float *v = new float[count];
for (int i = 0; i < count; ++i) {
if (fscanf(f, "%f", &v[i]) != 1) {
fprintf(stderr, "Unexpected end of file at %d'th density value\n", i);
exit(1);
}
}
return v;
}
int main(int argc, char *argv[]) {
if (argc != 3) {
fprintf(stderr, "usage: volume <camera.dat> <volume_density.vol>\n");
return 1;
}
ensureTargetISAIsSupported();
extern void TasksInit();
TasksInit();
//
// Load viewing data and the volume density data
//
int width, height;
float raster2camera[4][4], camera2world[4][4];
loadCamera(argv[1], &width, &height, raster2camera, camera2world);
float *image = new float[width*height];
int n[3];
float *density = loadVolume(argv[2], n);
//
// Compute the image using the ispc implementation; report the minimum
// time of three runs.
//
double minISPC = 1e30;
for (int i = 0; i < 3; ++i) {
reset_and_start_timer();
volume_ispc(density, n, raster2camera, camera2world,
width, height, image);
double dt = get_elapsed_mcycles();
minISPC = std::min(minISPC, dt);
}
printf("[volume ispc 1 core]:\t\t[%.3f] million cycles\n", minISPC);
writePPM(image, width, height, "volume-ispc-1core.ppm");
// Clear out the buffer
for (int i = 0; i < width * height; ++i)
image[i] = 0.;
//
// Compute the image using the ispc implementation that also uses
// tasks; report the minimum time of three runs.
//
double minISPCtasks = 1e30;
for (int i = 0; i < 3; ++i) {
reset_and_start_timer();
volume_ispc_tasks(density, n, raster2camera, camera2world,
width, height, image);
double dt = get_elapsed_mcycles();
minISPCtasks = std::min(minISPCtasks, dt);
}
printf("[volume ispc + tasks]:\t\t[%.3f] million cycles\n", minISPCtasks);
writePPM(image, width, height, "volume-ispc-tasks.ppm");
// Clear out the buffer
for (int i = 0; i < width * height; ++i)
image[i] = 0.;
//
// And run the serial implementation 3 times, again reporting the
// minimum time.
//
double minSerial = 1e30;
for (int i = 0; i < 3; ++i) {
reset_and_start_timer();
volume_serial(density, n, raster2camera, camera2world,
width, height, image);
double dt = get_elapsed_mcycles();
minSerial = std::min(minSerial, dt);
}
printf("[volume serial]:\t\t[%.3f] millon cycles\n", minSerial);
writePPM(image, width, height, "volume-serial.ppm");
printf("\t\t\t\t(%.2fx speedup from ISPC serial, %.2fx from ISPC+tasks)\n",
minSerial/minISPC, minSerial / minISPCtasks);
return 0;
}

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/*
Copyright (c) 2011, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
typedef float<3> float3;
struct Ray {
float3 origin, dir;
};
static void
generateRay(const uniform float raster2camera[4][4],
const uniform float camera2world[4][4],
float x, float y, reference Ray ray) {
// transform raster coordinate (x, y, 0) to camera space
float camx = raster2camera[0][0] * x + raster2camera[0][1] * y + raster2camera[0][3];
float camy = raster2camera[1][0] * x + raster2camera[1][1] * y + raster2camera[1][3];
float camz = raster2camera[2][3];
float camw = raster2camera[3][3];
camx /= camw;
camy /= camw;
camz /= camw;
ray.dir.x = camera2world[0][0] * camx + camera2world[0][1] * camy + camera2world[0][2] * camz;
ray.dir.y = camera2world[1][0] * camx + camera2world[1][1] * camy + camera2world[1][2] * camz;
ray.dir.z = camera2world[2][0] * camx + camera2world[2][1] * camy + camera2world[2][2] * camz;
ray.origin.x = camera2world[0][3] / camera2world[3][3];
ray.origin.y = camera2world[1][3] / camera2world[3][3];
ray.origin.z = camera2world[2][3] / camera2world[3][3];
}
static inline bool
Inside(float3 p, float3 pMin, float3 pMax) {
return (p.x >= pMin.x && p.x <= pMax.x &&
p.y >= pMin.y && p.y <= pMax.y &&
p.z >= pMin.z && p.z <= pMax.z);
}
static bool
IntersectP(Ray ray, float3 pMin, float3 pMax, reference float hit0, reference float hit1) {
float t0 = -1e30, t1 = 1e30;
float3 tNear = (pMin - ray.origin) / ray.dir;
float3 tFar = (pMax - ray.origin) / ray.dir;
if (tNear.x > tFar.x) {
float tmp = tNear.x;
tNear.x = tFar.x;
tFar.x = tmp;
}
t0 = max(tNear.x, t0);
t1 = min(tFar.x, t1);
if (tNear.y > tFar.y) {
float tmp = tNear.y;
tNear.y = tFar.y;
tFar.y = tmp;
}
t0 = max(tNear.y, t0);
t1 = min(tFar.y, t1);
if (tNear.z > tFar.z) {
float tmp = tNear.z;
tNear.z = tFar.z;
tFar.z = tmp;
}
t0 = max(tNear.z, t0);
t1 = min(tFar.z, t1);
if (t0 <= t1) {
hit0 = t0;
hit1 = t1;
return true;
}
else
return false;
}
static inline float Lerp(float t, float a, float b) {
return (1.f - t) * a + t * b;
}
static inline float D(int x, int y, int z, uniform int nVoxels[3],
uniform float density[]) {
x = clamp(x, 0, nVoxels[0]-1);
y = clamp(y, 0, nVoxels[1]-1);
z = clamp(z, 0, nVoxels[2]-1);
#if 0
uniform int ux, uy, uz;
if (reduce_equal(x, ux) && reduce_equal(y, uy) && reduce_equal(z, uz))
return density[uz*nVoxels[0]*nVoxels[1] + uy*nVoxels[0] + ux];
else
#endif
return density[z*nVoxels[0]*nVoxels[1] + y*nVoxels[0] + x];
}
static inline float3 Offset(float3 p, float3 pMin, float3 pMax) {
return (p - pMin) / (pMax - pMin);
}
static inline float Density(float3 Pobj, float3 pMin, float3 pMax,
uniform float density[], uniform int nVoxels[3]) {
if (!Inside(Pobj, pMin, pMax))
return 0;
// Compute voxel coordinates and offsets for _Pobj_
float3 vox = Offset(Pobj, pMin, pMax);
vox.x = vox.x * nVoxels[0] - .5f;
vox.y = vox.y * nVoxels[1] - .5f;
vox.z = vox.z * nVoxels[2] - .5f;
int vx = (int)(vox.x), vy = (int)(vox.y), vz = (int)(vox.z);
float dx = vox.x - vx, dy = vox.y - vy, dz = vox.z - vz;
// Trilinearly interpolate density values to compute local density
float d00 = Lerp(dx, D(vx, vy, vz, nVoxels, density),
D(vx+1, vy, vz, nVoxels, density));
float d10 = Lerp(dx, D(vx, vy+1, vz, nVoxels, density),
D(vx+1, vy+1, vz, nVoxels, density));
float d01 = Lerp(dx, D(vx, vy, vz+1, nVoxels, density),
D(vx+1, vy, vz+1, nVoxels, density));
float d11 = Lerp(dx, D(vx, vy+1, vz+1, nVoxels, density),
D(vx+1, vy+1, vz+1, nVoxels, density));
float d0 = Lerp(dy, d00, d10);
float d1 = Lerp(dy, d01, d11);
return Lerp(dz, d0, d1);
}
/* Returns the transmittance between two points p0 and p1, in a volume
with extent (pMin,pMax) with transmittance coefficient sigma_t,
defined by nVoxels[3] voxels in each dimension in the given density
array. */
static float
transmittance(uniform float3 p0, float3 p1, uniform float3 pMin,
uniform float3 pMax, uniform float sigma_t,
uniform float density[], uniform int nVoxels[3]) {
float rayT0, rayT1;
Ray ray;
ray.origin = p1;
ray.dir = p0 - p1;
// Find the parametric t range along the ray that is inside the volume.
if (!IntersectP(ray, pMin, pMax, rayT0, rayT1))
return 1.;
rayT0 = max(rayT0, 0.f);
// Accumulate beam transmittance in tau
float tau = 0;
float rayLength = sqrt(ray.dir.x * ray.dir.x + ray.dir.y * ray.dir.y +
ray.dir.z * ray.dir.z);
uniform float stepDist = 0.2;
float stepT = stepDist / rayLength;
float t = rayT0;
float3 pos = ray.origin + ray.dir * rayT0;
float3 dirStep = ray.dir * stepT;
while (t < rayT1) {
tau += stepDist * sigma_t * Density(pos, pMin, pMax, density, nVoxels);
pos = pos + dirStep;
t += stepT;
}
return exp(-tau);
}
static inline float
distanceSquared(float3 a, float3 b) {
float3 d = a-b;
return d.x*d.x + d.y*d.y + d.z*d.z;
}
static float
raymarch(uniform float density[], uniform int nVoxels[3], Ray ray) {
float rayT0, rayT1;
uniform float3 pMin = {.3, -.2, .3}, pMax = {1.8, 2.3, 1.8};
uniform float3 lightPos = { -1, 4, 1.5 };
cif (!IntersectP(ray, pMin, pMax, rayT0, rayT1))
return 0.;
rayT0 = max(rayT0, 0.f);
// Parameters that define the volume scattering characteristics and
// sampling rate for raymarching
uniform float Le = .25; // Emission coefficient
uniform float sigma_a = 10; // Absorption coefficient
uniform float sigma_s = 10; // Scattering coefficient
uniform float stepDist = 0.025; // Ray step amount
uniform float lightIntensity = 40; // Light source intensity
float tau = 0.f; // accumulated beam transmittance
float L = 0; // radiance along the ray
float rayLength = sqrt(ray.dir.x * ray.dir.x + ray.dir.y * ray.dir.y +
ray.dir.z * ray.dir.z);
float stepT = stepDist / rayLength;
float t = rayT0;
float3 pos = ray.origin + ray.dir * rayT0;
float3 dirStep = ray.dir * stepT;
cwhile (t < rayT1) {
float d = Density(pos, pMin, pMax, density, nVoxels);
// terminate once attenuation is high
float atten = exp(-tau);
if (atten < .005)
cbreak;
// direct lighting
float Li = lightIntensity / distanceSquared(lightPos, pos) *
transmittance(lightPos, pos, pMin, pMax, sigma_a + sigma_s,
density, nVoxels);
L += stepDist * atten * d * sigma_s * (Li + Le);
// update beam transmittance
tau += stepDist * (sigma_a + sigma_s) * d;
pos = pos + dirStep;
t += stepT;
}
// Gamma correction
return pow(L, 1.f / 2.2f);
}
/* Utility routine used by both the task-based and the single-core entrypoints.
Renders a tile of the image, covering [x0,x0) * [y0, y1), storing the
result into the image[] array.
*/
static void
volume_tile(uniform int x0, uniform int y0, uniform int x1,
uniform int y1, uniform float density[], uniform int nVoxels[3],
const uniform float raster2camera[4][4],
const uniform float camera2world[4][4],
uniform int width, uniform int height, uniform float image[]) {
// Work on 4x4=16 pixel big tiles of the image. This function thus
// implicitly assumes that both (x1-x0) and (y1-y0) are evenly divisble
// by 4.
for (uniform int y = y0; y < y1; y += 4) {
for (uniform int x = x0; x < x1; x += 4) {
// For each such tile, process programCount pixels at a time,
// until we've done all 16 of them. Thus, we're also assuming
// that programCount <= 16 and that 16 is evenly dividible by
// programCount.
for (uniform int o = 0; o < 16; o += programCount) {
// These two arrays encode the mapping from [0,15] to
// offsets within the 4x4 pixel block so that we render
// each pixel inside the block
const uniform int xoffsets[16] = { 0, 1, 0, 1, 2, 3, 2, 3,
0, 1, 0, 1, 2, 3, 2, 3 };
const uniform int yoffsets[16] = { 0, 0, 1, 1, 0, 0, 1, 1,
2, 2, 3, 3, 2, 2, 3, 3 };
// Figure out the pixel to render for this program instance
int xo = x + xoffsets[o + programIndex];
int yo = y + yoffsets[o + programIndex];
// Use viewing parameters to compute the corresponding ray
// for the pixel
Ray ray;
generateRay(raster2camera, camera2world, xo, yo, ray);
// And raymarch through the volume to compute the pixel's
// value
int offset = yo * width + xo;
image[offset] = raymarch(density, nVoxels, ray);
}
}
}
}
task void
volume_task(uniform int x0, uniform int y0, uniform int x1,
uniform int y1, uniform float density[], uniform int nVoxels[3],
const uniform float raster2camera[4][4],
const uniform float camera2world[4][4],
uniform int width, uniform int height, uniform float image[]) {
volume_tile(x0, y0, x1, y1, density, nVoxels, raster2camera,
camera2world, width, height, image);
}
export void
volume_ispc(uniform float density[], uniform int nVoxels[3],
const uniform float raster2camera[4][4],
const uniform float camera2world[4][4],
uniform int width, uniform int height, uniform float image[]) {
volume_tile(0, 0, width, height, density, nVoxels, raster2camera,
camera2world, width, height, image);
}
export void
volume_ispc_tasks(uniform float density[], uniform int nVoxels[3],
const uniform float raster2camera[4][4],
const uniform float camera2world[4][4],
uniform int width, uniform int height, uniform float image[]) {
// Launch tasks to work on (dx,dy)-sized tiles of the image
uniform int dx = 8, dy = 8;
for (uniform int y = 0; y < height; y += dy)
for (uniform int x = 0; x < width; x += dx)
launch < volume_task(x, y, x+dx, y+dy, density, nVoxels,
raster2camera, camera2world, width, height,
image) >;
}

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/*
Copyright (c) 2011, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <assert.h>
#include <math.h>
#include <algorithm>
// Just enough of a float3 class to do what we need in this file.
#ifdef _MSC_VER
__declspec(align(16))
#endif
struct float3 {
float3() { }
float3(float xx, float yy, float zz) { x = xx; y = yy; z = zz; }
float3 operator*(float f) const { return float3(x*f, y*f, z*f); }
float3 operator-(const float3 &f2) const {
return float3(x-f2.x, y-f2.y, z-f2.z);
}
float3 operator*(const float3 &f2) const {
return float3(x*f2.x, y*f2.y, z*f2.z);
}
float3 operator+(const float3 &f2) const {
return float3(x+f2.x, y+f2.y, z+f2.z);
}
float3 operator/(const float3 &f2) const {
return float3(x/f2.x, y/f2.y, z/f2.z);
}
float operator[](int i) const { return (&x)[i]; }
float &operator[](int i) { return (&x)[i]; }
float x, y, z;
float pad; // match padding/alignment of ispc version
}
#ifndef _MSC_VER
__attribute__ ((aligned(16)))
#endif
;
struct Ray {
float3 origin, dir;
};
static void
generateRay(const float raster2camera[4][4], const float camera2world[4][4],
float x, float y, Ray &ray) {
// transform raster coordinate (x, y, 0) to camera space
float camx = raster2camera[0][0] * x + raster2camera[0][1] * y + raster2camera[0][3];
float camy = raster2camera[1][0] * x + raster2camera[1][1] * y + raster2camera[1][3];
float camz = raster2camera[2][3];
float camw = raster2camera[3][3];
camx /= camw;
camy /= camw;
camz /= camw;
ray.dir.x = camera2world[0][0] * camx + camera2world[0][1] * camy + camera2world[0][2] * camz;
ray.dir.y = camera2world[1][0] * camx + camera2world[1][1] * camy + camera2world[1][2] * camz;
ray.dir.z = camera2world[2][0] * camx + camera2world[2][1] * camy + camera2world[2][2] * camz;
ray.origin.x = camera2world[0][3] / camera2world[3][3];
ray.origin.y = camera2world[1][3] / camera2world[3][3];
ray.origin.z = camera2world[2][3] / camera2world[3][3];
}
static bool
Inside(float3 p, float3 pMin, float3 pMax) {
return (p.x >= pMin.x && p.x <= pMax.x &&
p.y >= pMin.y && p.y <= pMax.y &&
p.z >= pMin.z && p.z <= pMax.z);
}
static bool
IntersectP(const Ray &ray, float3 pMin, float3 pMax, float *hit0, float *hit1) {
float t0 = -1e30, t1 = 1e30;
float3 tNear = (pMin - ray.origin) / ray.dir;
float3 tFar = (pMax - ray.origin) / ray.dir;
if (tNear.x > tFar.x) {
float tmp = tNear.x;
tNear.x = tFar.x;
tFar.x = tmp;
}
t0 = std::max(tNear.x, t0);
t1 = std::min(tFar.x, t1);
if (tNear.y > tFar.y) {
float tmp = tNear.y;
tNear.y = tFar.y;
tFar.y = tmp;
}
t0 = std::max(tNear.y, t0);
t1 = std::min(tFar.y, t1);
if (tNear.z > tFar.z) {
float tmp = tNear.z;
tNear.z = tFar.z;
tFar.z = tmp;
}
t0 = std::max(tNear.z, t0);
t1 = std::min(tFar.z, t1);
if (t0 <= t1) {
*hit0 = t0;
*hit1 = t1;
return true;
}
else
return false;
}
static inline float Lerp(float t, float a, float b) {
return (1.f - t) * a + t * b;
}
static inline int Clamp(int v, int low, int high) {
return std::min(std::max(v, low), high);
}
static inline float D(int x, int y, int z, int nVoxels[3], float density[]) {
x = Clamp(x, 0, nVoxels[0]-1);
y = Clamp(y, 0, nVoxels[1]-1);
z = Clamp(z, 0, nVoxels[2]-1);
return density[z*nVoxels[0]*nVoxels[1] + y*nVoxels[0] + x];
}
static inline float3 Offset(float3 p, float3 pMin, float3 pMax) {
return float3((p.x - pMin.x) / (pMax.x - pMin.x),
(p.y - pMin.y) / (pMax.y - pMin.y),
(p.z - pMin.z) / (pMax.z - pMin.z));
}
static inline float Density(float3 Pobj, float3 pMin, float3 pMax,
float density[], int nVoxels[3]) {
if (!Inside(Pobj, pMin, pMax))
return 0;
// Compute voxel coordinates and offsets for _Pobj_
float3 vox = Offset(Pobj, pMin, pMax);
vox.x = vox.x * nVoxels[0] - .5f;
vox.y = vox.y * nVoxels[1] - .5f;
vox.z = vox.z * nVoxels[2] - .5f;
int vx = (int)(vox.x), vy = (int)(vox.y), vz = (int)(vox.z);
float dx = vox.x - vx, dy = vox.y - vy, dz = vox.z - vz;
// Trilinearly interpolate density values to compute local density
float d00 = Lerp(dx, D(vx, vy, vz, nVoxels, density),
D(vx+1, vy, vz, nVoxels, density));
float d10 = Lerp(dx, D(vx, vy+1, vz, nVoxels, density),
D(vx+1, vy+1, vz, nVoxels, density));
float d01 = Lerp(dx, D(vx, vy, vz+1, nVoxels, density),
D(vx+1, vy, vz+1, nVoxels, density));
float d11 = Lerp(dx, D(vx, vy+1, vz+1, nVoxels, density),
D(vx+1, vy+1, vz+1, nVoxels, density));
float d0 = Lerp(dy, d00, d10);
float d1 = Lerp(dy, d01, d11);
return Lerp(dz, d0, d1);
}
static float
transmittance(float3 p0, float3 p1, float3 pMin,
float3 pMax, float sigma_t, float density[], int nVoxels[3]) {
float rayT0, rayT1;
Ray ray;
ray.origin = p1;
ray.dir = p0 - p1;
// Find the parametric t range along the ray that is inside the volume.
if (!IntersectP(ray, pMin, pMax, &rayT0, &rayT1))
return 1.;
rayT0 = std::max(rayT0, 0.f);
// Accumulate beam transmittance in tau
float tau = 0;
float rayLength = sqrtf(ray.dir.x * ray.dir.x + ray.dir.y * ray.dir.y +
ray.dir.z * ray.dir.z);
float stepDist = 0.2;
float stepT = stepDist / rayLength;
float t = rayT0;
float3 pos = ray.origin + ray.dir * rayT0;
float3 dirStep = ray.dir * stepT;
while (t < rayT1) {
tau += stepDist * sigma_t * Density(pos, pMin, pMax, density, nVoxels);
pos = pos + dirStep;
t += stepT;
}
return expf(-tau);
}
static float
distanceSquared(float3 a, float3 b) {
float3 d = a-b;
return d.x*d.x + d.y*d.y + d.z*d.z;
}
static float
raymarch(float density[], int nVoxels[3], const Ray &ray) {
float rayT0, rayT1;
float3 pMin(.3, -.2, .3), pMax(1.8, 2.3, 1.8);
float3 lightPos(-1, 4, 1.5);
if (!IntersectP(ray, pMin, pMax, &rayT0, &rayT1))
return 0.;
rayT0 = std::max(rayT0, 0.f);
// Parameters that define the volume scattering characteristics and
// sampling rate for raymarching
float Le = .25; // Emission coefficient
float sigma_a = 10; // Absorption coefficient
float sigma_s = 10; // Scattering coefficient
float stepDist = 0.025; // Ray step amount
float lightIntensity = 40; // Light source intensity
float tau = 0.f; // accumulated beam transmittance
float L = 0; // radiance along the ray
float rayLength = sqrtf(ray.dir.x * ray.dir.x + ray.dir.y * ray.dir.y +
ray.dir.z * ray.dir.z);
float stepT = stepDist / rayLength;
float t = rayT0;
float3 pos = ray.origin + ray.dir * rayT0;
float3 dirStep = ray.dir * stepT;
while (t < rayT1) {
float d = Density(pos, pMin, pMax, density, nVoxels);
// terminate once attenuation is high
float atten = expf(-tau);
if (atten < .005)
break;
// direct lighting
float Li = lightIntensity / distanceSquared(lightPos, pos) *
transmittance(lightPos, pos, pMin, pMax, sigma_a + sigma_s,
density, nVoxels);
L += stepDist * atten * d * sigma_s * (Li + Le);
// update beam transmittance
tau += stepDist * (sigma_a + sigma_s) * d;
pos = pos + dirStep;
t += stepT;
}
// Gamma correction
return powf(L, 1.f / 2.2f);
}
void
volume_serial(float density[], int nVoxels[3], const float raster2camera[4][4],
const float camera2world[4][4],
int width, int height, float image[]) {
int offset = 0;
for (int y = 0; y < height; ++y) {
for (int x = 0; x < width; ++x, ++offset) {
Ray ray;
generateRay(raster2camera, camera2world, x, y, ray);
image[offset] = raymarch(density, nVoxels, ray);
}
}
}