GteFluid2ComputeDivergence.cpp

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// David Eberly, Geometric Tools, Redmond WA 98052
// Copyright (c) 1998-2017
// Distributed under the Boost Software License, Version 1.0.
// http://www.boost.org/LICENSE_1_0.txt
// http://www.geometrictools.com/License/Boost/LICENSE_1_0.txt
// File Version: 3.0.0 (2016/06/19)

#include <GTEnginePCH.h>
#include <Physics/GteFluid2ComputeDivergence.h>
#include <Graphics/GteGraphicsEngine.h>
#include <Graphics/GteProgramFactory.h>
using namespace gte;

Fluid2ComputeDivergence::Fluid2ComputeDivergence(std::shared_ptr<ProgramFactory> const& factory,
    int xSize, int ySize, int numXThreads, int numYThreads,
    std::shared_ptr<ConstantBuffer> const& parameters)
    :
    mNumXGroups(xSize/numXThreads),
    mNumYGroups(ySize/numYThreads)
{
    mDivergence = std::make_shared<Texture2>(DF_R32_FLOAT, xSize, ySize);
    mDivergence->SetUsage(Resource::SHADER_OUTPUT);

    int i = factory->GetAPI();
    factory->PushDefines();
    factory->defines.Set("NUM_X_THREADS", numXThreads);
    factory->defines.Set("NUM_Y_THREADS", numYThreads);
    mComputeDivergence = factory->CreateFromSource(*msSource[i]);
    if (mComputeDivergence)
    {
        mComputeDivergence->GetCShader()->Set("Parameters", parameters);
        mComputeDivergence->GetCShader()->Set("divergence", mDivergence);
    }

    factory->PopDefines();
}

void Fluid2ComputeDivergence::Execute(std::shared_ptr<GraphicsEngine> const& engine,
    std::shared_ptr<Texture2> const& state)
{
    std::shared_ptr<ComputeShader> cshader = mComputeDivergence->GetCShader();
    cshader->Set("state", state);
    engine->Execute(mComputeDivergence, mNumXGroups, mNumYGroups, 1);
}


std::string const Fluid2ComputeDivergence::msGLSLSource =
"uniform Parameters\n"
"{\n"
"    vec4 spaceDelta;    // (dx, dy, 0, 0)\n"
"    vec4 halfDivDelta;  // (0.5/dx, 0.5/dy, 0, 0)\n"
"    vec4 timeDelta;     // (dt/dx, dt/dy, 0, dt)\n"
"    vec4 viscosityX;    // (velVX, velVX, 0, denVX)\n"
"    vec4 viscosityY;    // (velVX, velVY, 0, denVY)\n"
"    vec4 epsilon;       // (epsilonX, epsilonY, 0, epsilon0)\n"
"};\n"
"\n"
"layout(rgba32f) uniform readonly image2D state;\n"
"layout(r32f) uniform writeonly image2D divergence;\n"
"\n"
"layout (local_size_x = NUM_X_THREADS, local_size_y = NUM_Y_THREADS, local_size_z = 1) in;\n"
"void main()\n"
"{\n"
"    ivec2 c = ivec2(gl_GlobalInvocationID.xy);\n"
"    ivec2 dim = imageSize(state);\n"
"\n"
"    int x = int(c.x);\n"
"    int y = int(c.y);\n"
"    int xm = max(x - 1, 0);\n"
"    int xp = min(x + 1, dim.x - 1);\n"
"    int ym = max(y - 1, 0);\n"
"    int yp = min(y + 1, dim.y - 1);\n"
"\n"
"    vec2 velocityGradient = vec2\n"
"    (\n"
"        imageLoad(state, ivec2(xp, y)).x - imageLoad(state, ivec2(xm, y)).x,\n"
"        imageLoad(state, ivec2(x, yp)).y - imageLoad(state, ivec2(x, ym)).y\n"
"    );\n"
"\n"
"    float divergenceValue = dot(halfDivDelta.xy, velocityGradient);\n"
"    imageStore(divergence, c, vec4(divergenceValue, 0.0f, 0.0f, 0.0f));\n"
"}\n";

std::string const Fluid2ComputeDivergence::msHLSLSource =
"cbuffer Parameters\n"
"{\n"
"    float4 spaceDelta;    // (dx, dy, 0, 0)\n"
"    float4 halfDivDelta;  // (0.5/dx, 0.5/dy, 0, 0)\n"
"    float4 timeDelta;     // (dt/dx, dt/dy, 0, dt)\n"
"    float4 viscosityX;    // (velVX, velVX, 0, denVX)\n"
"    float4 viscosityY;    // (velVX, velVY, 0, denVY)\n"
"    float4 epsilon;       // (epsilonX, epsilonY, 0, epsilon0)\n"
"};\n"
"\n"
"Texture2D<float4> state;\n"
"RWTexture2D<float> divergence;\n"
"\n"
"[numthreads(NUM_X_THREADS, NUM_Y_THREADS, 1)]\n"
"void CSMain(uint2 c : SV_DispatchThreadID)\n"
"{\n"
"    uint2 dim;\n"
"    state.GetDimensions(dim.x, dim.y);\n"
"\n"
"    int x = int(c.x);\n"
"    int y = int(c.y);\n"
"    int xm = max(x - 1, 0);\n"
"    int xp = min(x + 1, dim.x - 1);\n"
"    int ym = max(y - 1, 0);\n"
"    int yp = min(y + 1, dim.y - 1);\n"
"\n"
"    float2 velocityGradient = float2(\n"
"        state[int2(xp, y)].x - state[int2(xm, y)].x,\n"
"        state[int2(x, yp)].y - state[int2(x, ym)].y\n"
"    );\n"
"\n"
"    divergence[c] = dot(halfDivDelta.xy, velocityGradient);\n"
"}\n";

std::string const* Fluid2ComputeDivergence::msSource[] =
{
    &msGLSLSource,
    &msHLSLSource
};