/*
  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.  
*/

#ifdef _MSC_VER
#define _CRT_SECURE_NO_WARNINGS
#define NOMINMAX
#pragma warning (disable: 4244)
#pragma warning (disable: 4305)
#endif

#include <algorithm>
#include <stdint.h>

// 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); 
    }
    float x, y, z;
    float pad;  // match padding/alignment of ispc version 
}
#ifndef _MSC_VER
__attribute__ ((aligned(16)))
#endif
;

struct Ray {
    float3 origin, dir, invDir;
    unsigned int dirIsNeg[3];
    float mint, maxt;
    int hitId;
};


// Declare these in a namespace so the mangling matches
namespace ispc {
    struct Triangle {
        float p[3][4]; // extra float pad after each vertex
        int32_t id;
        int32_t pad[3]; // make 16 x 32-bits
    };

    struct LinearBVHNode {
        float bounds[2][3];
        int32_t offset;     // primitives for leaf, second child for interior
        uint8_t nPrimitives;
        uint8_t splitAxis;
        uint16_t pad;
    };
}

using namespace ispc;

inline float3 Cross(const float3 &v1, const float3 &v2) {
    float v1x = v1.x, v1y = v1.y, v1z = v1.z;
    float v2x = v2.x, v2y = v2.y, v2z = v2.z;
    float3 ret;
    ret.x = (v1y * v2z) - (v1z * v2y);
    ret.y = (v1z * v2x) - (v1x * v2z);
    ret.z = (v1x * v2y) - (v1y * v2x);
    return ret;
}

inline float Dot(const float3 &a, const float3 &b) {
    return a.x * b.x + a.y * b.y + a.z * b.z;
}


static void generateRay(const float raster2camera[4][4], 
                        const float camera2world[4][4],
                        float x, float y, Ray &ray) {
    ray.mint = 0.f;
    ray.maxt = 1e30f;

    ray.hitId = 0;

    // 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];

    ray.invDir.x = 1.f / ray.dir.x;
    ray.invDir.y = 1.f / ray.dir.y;
    ray.invDir.z = 1.f / ray.dir.z;

    ray.dirIsNeg[0] = (ray.invDir.x < 0) ? 1 : 0;
    ray.dirIsNeg[1] = (ray.invDir.y < 0) ? 1 : 0;
    ray.dirIsNeg[2] = (ray.invDir.z < 0) ? 1 : 0;
}


static inline bool BBoxIntersect(const float bounds[2][3], 
                                 const Ray &ray) {
    float3 bounds0(bounds[0][0], bounds[0][1], bounds[0][2]);
    float3 bounds1(bounds[1][0], bounds[1][1], bounds[1][2]);
    float t0 = ray.mint, t1 = ray.maxt;

    float3 tNear = (bounds0 - ray.origin) * ray.invDir;
    float3 tFar  = (bounds1 - ray.origin) * ray.invDir;
    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);
    
    return (t0 <= t1);
}



inline bool TriIntersect(const Triangle &tri, Ray &ray) {
    float3 p0(tri.p[0][0], tri.p[0][1], tri.p[0][2]);
    float3 p1(tri.p[1][0], tri.p[1][1], tri.p[1][2]);
    float3 p2(tri.p[2][0], tri.p[2][1], tri.p[2][2]);
    float3 e1 = p1 - p0;
    float3 e2 = p2 - p0;

    float3 s1 = Cross(ray.dir, e2);
    float divisor = Dot(s1, e1);

    if (divisor == 0.)
        return false;
    float invDivisor = 1.f / divisor;

    // Compute first barycentric coordinate
    float3 d = ray.origin - p0;
    float b1 = Dot(d, s1) * invDivisor;
    if (b1 < 0. || b1 > 1.)
        return false;

    // Compute second barycentric coordinate
    float3 s2 = Cross(d, e1);
    float b2 = Dot(ray.dir, s2) * invDivisor;
    if (b2 < 0. || b1 + b2 > 1.)
        return false;

    // Compute _t_ to intersection point
    float t = Dot(e2, s2) * invDivisor;
    if (t < ray.mint || t > ray.maxt)
        return false;

    ray.maxt = t;
    ray.hitId = tri.id;
    return true;
}


bool BVHIntersect(const LinearBVHNode nodes[], const Triangle tris[], 
                  Ray &r) {
    Ray ray = r;
    bool hit = false;
    // Follow ray through BVH nodes to find primitive intersections
    int todoOffset = 0, nodeNum = 0;
    int todo[64];

    while (true) {
        // Check ray against BVH node
        const LinearBVHNode &node = nodes[nodeNum];
        if (BBoxIntersect(node.bounds, ray)) {
            unsigned int nPrimitives = node.nPrimitives;
            if (nPrimitives > 0) {
                // Intersect ray with primitives in leaf BVH node
                unsigned int primitivesOffset = node.offset;
                for (unsigned int i = 0; i < nPrimitives; ++i) {
                    if (TriIntersect(tris[primitivesOffset+i], ray))
                        hit = true;
                }
                if (todoOffset == 0) 
                    break;
                nodeNum = todo[--todoOffset];
            }
            else {
                // Put far BVH node on _todo_ stack, advance to near node
                if (r.dirIsNeg[node.splitAxis]) {
                   todo[todoOffset++] = nodeNum + 1;
                   nodeNum = node.offset;
                }
                else {
                   todo[todoOffset++] = node.offset;
                   nodeNum = nodeNum + 1;
                }
            }
        }
        else {
            if (todoOffset == 0)
                break;
            nodeNum = todo[--todoOffset];
        }
    }
    r.maxt = ray.maxt;
    r.hitId = ray.hitId;

    return hit;
}


void raytrace_serial(int width, int height, int baseWidth, int baseHeight,
                     const float raster2camera[4][4], 
                     const float camera2world[4][4],
                     float image[],
                     int id[],
                     const LinearBVHNode nodes[],
                     const Triangle triangles[]) {
    float widthScale = float(baseWidth) / float(width);
    float heightScale = float(baseHeight) / float(height);

    for (int y = 0; y < height; ++y) {
        for (int x = 0; x < width; ++x) {
                Ray ray;
                generateRay(raster2camera, camera2world, x * widthScale,
                            y * heightScale, ray);
                BVHIntersect(nodes, triangles, ray);

                int offset = y * width + x;
                image[offset] = ray.maxt;
                id[offset] = ray.hitId;
        }
    }
}
