SSBO 写入不可见

Question

我正在使用 OpenGL 开发一个小粒子系统。
问题是更新计算着色器中的位置似乎不起作用。

代码如下：

缓冲区

struct ParticleInfo {

    Vec4f position; // w: s coordinate
    Vec4f normal; // w: t coordinate
    float materialIndex;
    Vec3f oldPosition;

};

初始化缓冲区

glGenVertexArrays(1, &mParticleVAO);
glBindVertexArray(mParticleVAO);

glGenBuffers(1, &mParticleVBO);
glBindBuffer(GL_ARRAY_BUFFER, mParticleVBO);

glBufferData(GL_ARRAY_BUFFER, sizeof(ParticleInfo) * mNumParticles, particleData.data(), GL_STATIC_DRAW);

glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, sizeof(ParticleInfo), (void*)NULL);

glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, sizeof(ParticleInfo), (void*)(NULL + sizeof(Vec4f)));

glEnableVertexAttribArray(2);
glVertexAttribPointer(2, 1, GL_FLOAT, GL_FALSE, sizeof(ParticleInfo), (void*)(NULL + 2*sizeof(Vec4f)));

glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);

使用计算着色器更新缓冲区

     gl->setUniform(mParticleMoveProgram->getUniformLoc("numParticles"), mNumParticles);
glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, mParticleVBO);
glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, mAttractorSSBO);

int localSizeX = 64*8;

int groupSizeX = (mNumParticles + localSizeX - 1) / localSizeX;

glDispatchCompute(groupSizeX, 1, 1);
glMemoryBarrier(GL_ALL_BARRIER_BITS);

glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 0, 0);
glBindBufferBase(GL_SHADER_STORAGE_BUFFER, 1, 0);

着色器代码

#version 450

layout(local_size_x = 64) in;

struct ParticleInfo {

    vec4 position; // modify only the position;
    vec4 normal;
    float materialIndex;
    vec3 oldPosition;

};

struct Attractor {

    vec3 position;
    float mass;

};

layout(binding = 0, std430) buffer ParticleArray {

    ParticleInfo particles[];

};

layout(binding = 1, std430) buffer AttractorArray {

    Attractor attractors[];

};

uniform int numParticles;


vec3 verlet(in vec3 a, in vec3 x, in vec3 xOld, in float dt) {

    return 2.0 * x - xOld + a * dt*dt;

}

void main() {

    const int PARTICLES_PER_THREAD = 8;

    int index = int(gl_LocalInvocationIndex)*PARTICLES_PER_THREAD;

    if (index >= numParticles) return;

    Attractor attr = attractors[0];

    const float G = 9.8;

    for (int i = 0; i < PARTICLES_PER_THREAD; ++i)
    {


        particles[i+index].position = vec4(0.0);
        particles[i+index].normal = vec4(0.0);
        particles[i+index].oldPosition = vec3(0.0);
    }



}

Answer 1

正如@derhass 评论的那样。内存结构不匹配。每个线程的正确索引似乎也存在问题。我通过将每个线程的索引设置为：

来修复它

index = PARTICLES_PER_THREAD * int(gl_WorkGroupSize.x * gl_WorkGroupID.x + gl_LocalInvocationID.x);

感谢您的帮助。

SSBO 写入不可见

SSBO writes are not visible

opengl

glsl

particles

compute-shader

particle-system