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// Simple 3D volume renderer

#ifndef _VOLUMERENDER_KERNEL_CU_
#define _VOLUMERENDER_KERNEL_CU_

#include <helper_cuda.h>
#include <helper_math.h>

typedef unsigned int  uint;
typedef unsigned char uchar;

cudaArray *d_volumeArray = 0;
cudaArray *d_transferFuncArray;

typedef unsigned char VolumeType;
// typedef unsigned short VolumeType;

cudaTextureObject_t texObject;   // For 3D texture
cudaTextureObject_t transferTex; // For 1D transfer function texture

typedef struct
{
    float4 m[3];
} float3x4;

__constant__ float3x4 c_invViewMatrix; // inverse view matrix

struct Ray
{
    float3 o; // origin
    float3 d; // direction
};

// intersect ray with a box
// http://www.siggraph.org/education/materials/HyperGraph/raytrace/rtinter3.htm

__device__ int intersectBox(Ray r, float3 boxmin, float3 boxmax, float *tnear, float *tfar)
{
    // compute intersection of ray with all six bbox planes
    float3 invR = make_float3(1.0f) / r.d;
    float3 tbot = invR * (boxmin - r.o);
    float3 ttop = invR * (boxmax - r.o);

    // re-order intersections to find smallest and largest on each axis
    float3 tmin = fminf(ttop, tbot);
    float3 tmax = fmaxf(ttop, tbot);

    // find the largest tmin and the smallest tmax
    float largest_tmin  = fmaxf(fmaxf(tmin.x, tmin.y), fmaxf(tmin.x, tmin.z));
    float smallest_tmax = fminf(fminf(tmax.x, tmax.y), fminf(tmax.x, tmax.z));

    *tnear = largest_tmin;
    *tfar  = smallest_tmax;

    return smallest_tmax > largest_tmin;
}

// transform vector by matrix (no translation)
__device__ float3 mul(const float3x4 &M, const float3 &v)
{
    float3 r;
    r.x = dot(v, make_float3(M.m[0]));
    r.y = dot(v, make_float3(M.m[1]));
    r.z = dot(v, make_float3(M.m[2]));
    return r;
}

// transform vector by matrix with translation
__device__ float4 mul(const float3x4 &M, const float4 &v)
{
    float4 r;
    r.x = dot(v, M.m[0]);
    r.y = dot(v, M.m[1]);
    r.z = dot(v, M.m[2]);
    r.w = 1.0f;
    return r;
}

__device__ uint rgbaFloatToInt(float4 rgba)
{
    rgba.x = __saturatef(rgba.x); // clamp to [0.0, 1.0]
    rgba.y = __saturatef(rgba.y);
    rgba.z = __saturatef(rgba.z);
    rgba.w = __saturatef(rgba.w);
    return (uint(rgba.w * 255) << 24) | (uint(rgba.z * 255) << 16) | (uint(rgba.y * 255) << 8) | uint(rgba.x * 255);
}

__global__ void d_render(uint               *d_output,
                         uint                imageW,
                         uint                imageH,
                         float               density,
                         float               brightness,
                         float               transferOffset,
                         float               transferScale,
                         cudaTextureObject_t tex,
                         cudaTextureObject_t transferTex)
{
    const int    maxSteps         = 500;
    const float  tstep            = 0.01f;
    const float  opacityThreshold = 0.95f;
    const float3 boxMin           = make_float3(-1.0f, -1.0f, -1.0f);
    const float3 boxMax           = make_float3(1.0f, 1.0f, 1.0f);

    uint x = blockIdx.x * blockDim.x + threadIdx.x;
    uint y = blockIdx.y * blockDim.y + threadIdx.y;

    if ((x >= imageW) || (y >= imageH))
        return;

    float u = (x / (float)imageW) * 2.0f - 1.0f;
    float v = (y / (float)imageH) * 2.0f - 1.0f;

    // calculate eye ray in world space
    Ray eyeRay;
    eyeRay.o = make_float3(mul(c_invViewMatrix, make_float4(0.0f, 0.0f, 0.0f, 1.0f)));
    eyeRay.d = normalize(make_float3(u, v, -2.0f));
    eyeRay.d = mul(c_invViewMatrix, eyeRay.d);

    // find intersection with box
    float tnear, tfar;
    int   hit = intersectBox(eyeRay, boxMin, boxMax, &tnear, &tfar);

    if (!hit)
        return;

    if (tnear < 0.0f)
        tnear = 0.0f; // clamp to near plane

    // march along ray from front to back, accumulating color
    float4 sum  = make_float4(0.0f);
    float  t    = tnear;
    float3 pos  = eyeRay.o + eyeRay.d * tnear;
    float3 step = eyeRay.d * tstep;

    for (int i = 0; i < maxSteps; i++) {
        // read from 3D texture
        // remap position to [0, 1] coordinates
        float sample = tex3D<float>(tex, pos.x * 0.5f + 0.5f, pos.y * 0.5f + 0.5f, pos.z * 0.5f + 0.5f);
        // sample *= 64.0f;    // scale for 10-bit data

        // lookup in transfer function texture
        float4 col = tex1D<float4>(transferTex, (sample - transferOffset) * transferScale);
        col.w *= density;

        // "under" operator for back-to-front blending
        // sum = lerp(sum, col, col.w);

        // pre-multiply alpha
        col.x *= col.w;
        col.y *= col.w;
        col.z *= col.w;
        // "over" operator for front-to-back blending
        sum = sum + col * (1.0f - sum.w);

        // exit early if opaque
        if (sum.w > opacityThreshold)
            break;

        t += tstep;

        if (t > tfar)
            break;

        pos += step;
    }

    sum *= brightness;

    // write output color
    d_output[y * imageW + x] = rgbaFloatToInt(sum);
}

extern "C" void setTextureFilterMode(bool bLinearFilter)
{
    if (texObject) {
        checkCudaErrors(cudaDestroyTextureObject(texObject));
    }
    cudaResourceDesc texRes;
    memset(&texRes, 0, sizeof(cudaResourceDesc));

    texRes.resType         = cudaResourceTypeArray;
    texRes.res.array.array = d_volumeArray;

    cudaTextureDesc texDescr;
    memset(&texDescr, 0, sizeof(cudaTextureDesc));

    texDescr.normalizedCoords = true;
    texDescr.filterMode       = bLinearFilter ? cudaFilterModeLinear : cudaFilterModePoint;

    texDescr.addressMode[0] = cudaAddressModeWrap;
    texDescr.addressMode[1] = cudaAddressModeWrap;
    texDescr.addressMode[2] = cudaAddressModeWrap;

    texDescr.readMode = cudaReadModeNormalizedFloat;

    checkCudaErrors(cudaCreateTextureObject(&texObject, &texRes, &texDescr, NULL));
}

extern "C" void initCuda(void *h_volume, cudaExtent volumeSize)
{
    // create 3D array
    cudaChannelFormatDesc channelDesc = cudaCreateChannelDesc<VolumeType>();
    checkCudaErrors(cudaMalloc3DArray(&d_volumeArray, &channelDesc, volumeSize));

    // copy data to 3D array
    cudaMemcpy3DParms copyParams = {0};
    copyParams.srcPtr =
        make_cudaPitchedPtr(h_volume, volumeSize.width * sizeof(VolumeType), volumeSize.width, volumeSize.height);
    copyParams.dstArray = d_volumeArray;
    copyParams.extent   = volumeSize;
    copyParams.kind     = cudaMemcpyHostToDevice;
    checkCudaErrors(cudaMemcpy3D(&copyParams));

    cudaResourceDesc texRes;
    memset(&texRes, 0, sizeof(cudaResourceDesc));

    texRes.resType         = cudaResourceTypeArray;
    texRes.res.array.array = d_volumeArray;

    cudaTextureDesc texDescr;
    memset(&texDescr, 0, sizeof(cudaTextureDesc));

    texDescr.normalizedCoords = true;                 // access with normalized texture coordinates
    texDescr.filterMode       = cudaFilterModeLinear; // linear interpolation

    texDescr.addressMode[0] = cudaAddressModeClamp; // clamp texture coordinates
    texDescr.addressMode[1] = cudaAddressModeClamp;
    texDescr.addressMode[2] = cudaAddressModeClamp;

    texDescr.readMode = cudaReadModeNormalizedFloat;

    checkCudaErrors(cudaCreateTextureObject(&texObject, &texRes, &texDescr, NULL));

    // create transfer function texture
    float4 transferFunc[] = {
        {
            0.0,
            0.0,
            0.0,
            0.0,
        },
        {
            1.0,
            0.0,
            0.0,
            1.0,
        },
        {
            1.0,
            0.5,
            0.0,
            1.0,
        },
        {
            1.0,
            1.0,
            0.0,
            1.0,
        },
        {
            0.0,
            1.0,
            0.0,
            1.0,
        },
        {
            0.0,
            1.0,
            1.0,
            1.0,
        },
        {
            0.0,
            0.0,
            1.0,
            1.0,
        },
        {
            1.0,
            0.0,
            1.0,
            1.0,
        },
        {
            0.0,
            0.0,
            0.0,
            0.0,
        },
    };

    cudaChannelFormatDesc channelDesc2 = cudaCreateChannelDesc<float4>();
    cudaArray            *d_transferFuncArray;
    checkCudaErrors(cudaMallocArray(&d_transferFuncArray, &channelDesc2, sizeof(transferFunc) / sizeof(float4), 1));
    checkCudaErrors(cudaMemcpy2DToArray(
        d_transferFuncArray, 0, 0, transferFunc, 0, sizeof(transferFunc), 1, cudaMemcpyHostToDevice));

    memset(&texRes, 0, sizeof(cudaResourceDesc));

    texRes.resType         = cudaResourceTypeArray;
    texRes.res.array.array = d_transferFuncArray;

    memset(&texDescr, 0, sizeof(cudaTextureDesc));

    texDescr.normalizedCoords = true; // access with normalized texture coordinates
    texDescr.filterMode       = cudaFilterModeLinear;

    texDescr.addressMode[0] = cudaAddressModeClamp; // wrap texture coordinates

    texDescr.readMode = cudaReadModeElementType;

    checkCudaErrors(cudaCreateTextureObject(&transferTex, &texRes, &texDescr, NULL));
}

extern "C" void freeCudaBuffers()
{
    checkCudaErrors(cudaDestroyTextureObject(texObject));
    checkCudaErrors(cudaDestroyTextureObject(transferTex));
    checkCudaErrors(cudaFreeArray(d_volumeArray));
    checkCudaErrors(cudaFreeArray(d_transferFuncArray));
}

extern "C" void render_kernel(dim3  gridSize,
                              dim3  blockSize,
                              uint *d_output,
                              uint  imageW,
                              uint  imageH,
                              float density,
                              float brightness,
                              float transferOffset,
                              float transferScale)
{
    d_render<<<gridSize, blockSize>>>(
        d_output, imageW, imageH, density, brightness, transferOffset, transferScale, texObject, transferTex);
}

extern "C" void copyInvViewMatrix(float *invViewMatrix, size_t sizeofMatrix)
{
    checkCudaErrors(cudaMemcpyToSymbol(c_invViewMatrix, invViewMatrix, sizeofMatrix));
}

#endif // #ifndef _VOLUMERENDER_KERNEL_CU_
