对于要渲染的所有对象,我使用 glDrawElements。然而,我对 Compute Shaders 的冒险给我留下了一个使用 glDrawArrays 的设置。与许多违反该主题的人一样,我使用此PDF作为基础。问题是当它被渲染时,什么都没有出现。
#include "LogoTail.h"
LogoTail::LogoTail(int tag1) {
tag = tag1;
needLoad = false;
shader = LoadShaders("vertex-shader[LogoTail].txt","fragment-shader[LogoTail].txt");
shaderCompute = LoadShaders("compute-shader[LogoTail].txt");
for( int i = 0; i < NUM_PARTICLES; i++ )
{
points[ i ].x = 0.0f;
points[ i ].y = 0.0f;
points[ i ].z = 0.0f;
points[ i ].w = 1.0f;
}
glGenBuffers( 1, &posSSbo);
glBindBuffer( GL_SHADER_STORAGE_BUFFER, posSSbo );
glBufferData( GL_SHADER_STORAGE_BUFFER, sizeof(points), points, GL_STATIC_DRAW );
glUnmapBuffer(GL_SHADER_STORAGE_BUFFER);
for( int i = 0; i < NUM_PARTICLES; i++ )
{
times[ i ].x = 0.0f;
}
glGenBuffers( 1, &birthSSbo);
glBindBuffer( GL_SHADER_STORAGE_BUFFER, birthSSbo );
glBufferData( GL_SHADER_STORAGE_BUFFER, sizeof(times), times, GL_STATIC_DRAW );
glUnmapBuffer(GL_SHADER_STORAGE_BUFFER);
for( int i = 0; i < NUM_PARTICLES; i++ )
{
vels[ i ].vx = 0.0f;
vels[ i ].vy = 0.0f;
vels[ i ].vz = 0.0f;
vels[ i ].vw = 0.0f;
}
glGenBuffers( 1, &velSSbo );
glBindBuffer( GL_SHADER_STORAGE_BUFFER, velSSbo );
glBufferData( GL_SHADER_STORAGE_BUFFER, sizeof(vels), vels, GL_STATIC_DRAW );
glUnmapBuffer(GL_SHADER_STORAGE_BUFFER);
}
void LogoTail::Update(const double dt, float sunTime,glm::vec3 sunN) {
position=glm::translate(glm::mat4(), glm::vec3(4.5f,0,0));
}
void LogoTail::Draw(shading::Camera& camera){
shaderCompute->use();
glBindBufferBase( GL_SHADER_STORAGE_BUFFER, 4, posSSbo );
glBindBufferBase( GL_SHADER_STORAGE_BUFFER, 5, velSSbo );
glBindBufferBase( GL_SHADER_STORAGE_BUFFER, 6, birthSSbo );
glDispatchCompute( NUM_PARTICLES / WORK_GROUP_SIZE, 1, 1 );
glMemoryBarrier( GL_VERTEX_ATTRIB_ARRAY_BARRIER_BIT );
shaderCompute->stopUsing();
shader->use();
shader->setUniform("camera", camera.matrix());
shader->setUniform("model",position);
glBindBuffer( GL_ARRAY_BUFFER, posSSbo );
glVertexPointer( 4, GL_FLOAT, 0, (void *)0 );
glEnableClientState( GL_VERTEX_ARRAY );
glDrawArrays( GL_POINTS, 0, NUM_PARTICLES );
glDisableClientState( GL_VERTEX_ARRAY );
glBindBuffer( GL_ARRAY_BUFFER, 0 );
shader->stopUsing();
}
标头包含所需的结构和其他变量,因此它们不会超出特定对象的范围。
这是计算着色器本身。
#version 430 core
#extension GL_ARB_compute_shader : enable
#extension GL_ARB_shader_storage_buffer_object : enable
layout( std140, binding=4 ) buffer Pos
{
vec4 Positions[ ]; // array of vec4 structures
};
layout( std140, binding=5 ) buffer Vel
{
vec4 Velocities[ ]; // array of vec4 structures
};
layout( std140, binding=6 ) buffer Tim
{
float BirthTimes[ ]; // array of structures
};
layout( local_size_x = 128, local_size_y = 1, local_size_z = 1 ) in;
const vec3 G = vec3( 0., -0.2, 0. );
const float DT = 0.016666;
void main() {
uint gid = gl_GlobalInvocationID.x; // the .y and .z are both 1
vec3 p = Positions[ gid ].xyz;
vec3 v = Velocities[ gid ].xyz;
vec3 pp = p + v*DT + .5*DT*DT*G;
vec3 vp = v + G*DT;
Positions[ gid ].xyz = pp;
Velocities[ gid ].xyz = vp;
}
出于测试目的,我降低了重力。我相信没有什么是超出范围的,也没有必要的绑定,但它暗示了我为什么粒子没有绘制。此外,我还添加了一个几何着色器,它围绕每个点构建一个四边形,但它没有解决任何问题。