我目前正在使用我正在制作的粒子引擎。使用引擎，您可以在引擎中添加多个发射器，这个想法是每个粒子系统都可以发射自己的粒子。
然而我遇到的问题是，当我添加第二个粒子系统时，第一个粒子系统的绘图似乎受到影响，我的意思是它根本没有被绘制。正确调用每个粒子系统的绘制调用。
我认为问题在于虽然创建了多个VBO，但实际上只使用了一个。
我将展示影响VBO的函数的重要部分。我的着色器使用统一位置来存储WVP矩阵。我还应该提到每个粒子系统应该使用自己的着色器程序。
下面是我在创建粒子系统时调用的initializeBuffers函数：
void ParticleSystem::InitializeBuffers()
{
glGenVertexArrays(1, &VaoId);
glBindVertexArray(VaoId);
//glGenBuffers(1, &VboId);
glGenBuffers(1, &PositionBufferId);
glGenBuffers(1, &IndexBufferId);
glGenBuffers(1, &WVPId);
std::list<Particle>::iterator iterator = particles.begin();
//positions.reserve(5);
for (std::list<Particle>::iterator iterator = particles.begin(), end = particles.end(); iterator != end; ++iterator)
{
positions.push_back(iterator->GetPosition());
//verticesToDraw.insert(verticesToDraw.end(), iterator->GetVertices()->begin(), iterator->GetVertices()->end());
indicesToDraw.insert(indicesToDraw.end(), iterator->GetIndices()->begin(), iterator->GetIndices()->end());
}
//glBindBuffer(GL_ARRAY_BUFFER, VboId);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexBufferId);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indicesToDraw[0]) * indicesToDraw.size(), &indicesToDraw[0], GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, WVPId);
for (unsigned int i = 0; i < 4 ; i++) {
glEnableVertexAttribArray(WVP_LOCATION + i);
glVertexAttribPointer(WVP_LOCATION + i, 4, GL_FLOAT, GL_FALSE, sizeof(Matrix4f), (const GLvoid*)(sizeof(GLfloat) * i * 4));
glVertexAttribDivisor(WVP_LOCATION + i, 1);
}
for(std::list<BaseBuildingBlock*>::iterator iterator = buildingBlocks.begin(), end = buildingBlocks.end(); iterator != end; ++iterator)
{
(*iterator)->InitializeBuffer(programId);
}
/*
glBindBuffer(GL_ARRAY_BUFFER, WorldId);
for (unsigned int i = 0; i < 4 ; i++) {
glEnableVertexAttribArray(WORLD_LOCATION + i);
glVertexAttribPointer(WORLD_LOCATION + i, 4, GL_FLOAT, GL_FALSE, sizeof(Matrix4f), (const GLvoid*)(sizeof(GLfloat) * i * 4));
glVertexAttribDivisor(WORLD_LOCATION + i, 1);
}
*/
//return GLCheckError();
}
这是绘制函数和实际绘制实例元素的代码，wvp矩阵是由函数中较早的粒子系统形成的。
void ParticleSystem::Draw(Matrix4f perspectiveCameraMatrix)
{
// scale TEST
//GLint gScaleLocation = glGetUniformLocation(program, "gScale");
//assert(gScaleLocation != 0xFFFFFFFF);
//glUniform1f(gScaleLocation, scale);
//Pipeline p;
//Matrix4f* WVPMatrices = new Matrix4f[particles.size()];
//Matrix4f* WorldMatrices = new Matrix4f[particles.size()];
WVPMatrices.clear();
WorldMatrices.clear();
glUseProgram(0);
glUseProgram(programId);
//Matrix4f perspectiveMatrix;
//perspectiveMatrix.BuildPerspProjMat(90,1, 0.01, 200, 100 - 0 /*getWidth() / 32*/, 100 - 0 /*getHeight() / 32*/);
//********************************************************************************************************
// Method 1
// Think I need to next define a camera position.
if(particles.size() == 0)
{
return;
}
verticesToDraw.clear();
Matrix4f scaleMatrix;
Matrix4f worldMatrix;
Matrix4f rotateMatrix;
Matrix4f finalMatrix;
//ColourId = glGetUniformLocation(programId, "UniformColour");
int i = 0;
for (std::list<Particle>::iterator iterator = particles.begin(), end = particles.end(); iterator != end; ++iterator)
{
verticesToDraw = *iterator->GetVertices();
indicesToDraw = *iterator->GetIndices();
//positions.push_back(iterator->GetPosition());
worldMatrix.InitTranslationTransform(iterator->GetPosition().x, iterator->GetPosition().y, iterator->GetPosition().z);
rotateMatrix.InitRotateTransform(iterator->GetRotation().x, iterator->GetRotation().y, iterator->GetRotation().z);
scaleMatrix.InitScaleTransform(iterator->GetScale().x, iterator->GetScale().y, iterator->GetScale().z);
finalMatrix = perspectiveCameraMatrix * worldMatrix * rotateMatrix * scaleMatrix;
//p.WorldPos(iterator->GetPosition());
//p.Rotate(iterator->GetRotation());
WVPMatrices.push_back(finalMatrix.Transpose());
/*glUniform4f(ColourId, iterator->GetColour().r, iterator->GetColour().g, iterator->GetColour().b,
iterator->GetColour().a);*/
//WorldMatrices[i] = p.GetWorldTrans();
i++;
//iterator->Draw();
}
//glEnableVertexAttribArray(0);
if(colourOverLifeBuildingBlock != NULL)
{
colourOverLifeBuildingBlock->Test();
}
glBindBuffer(GL_ARRAY_BUFFER, VboId);
glBufferData(GL_ARRAY_BUFFER, verticesToDraw.size() * sizeof(verticesToDraw[0]), &verticesToDraw.front(), GL_STATIC_DRAW);
glEnableVertexAttribArray(POSITION_LOCATION);
glVertexAttribPointer(POSITION_LOCATION, 3, GL_FLOAT, GL_FALSE, 0, 0);
int size = particles.size();
glBindBuffer(GL_ARRAY_BUFFER, WVPId);
glBufferData(GL_ARRAY_BUFFER, sizeof(Matrix4f) * size, &WVPMatrices.front(), GL_DYNAMIC_DRAW);
glDrawElementsInstanced(GL_TRIANGLES, indicesToDraw.size(), GL_UNSIGNED_BYTE, 0, particles.size());
glBindBuffer(GL_ARRAY_BUFFER, 0);
//glDisableVertexAttribArray(0);
//glFlush();
}
粒子系统整个标题如下：
#include <gl\glew.h>
#include <array>
#include <vector>
class ParticleSystem
{
public:
ParticleSystem(Vector3 pos, Quaternion rot, float spawnRate, int particlesToSpawn); // Constructs a particle system.
~ParticleSystem(); // Destructor.
void Update(float elapsedTime); // Updates the particle system.
void Draw(Matrix4f perspectiveMatrix); // Draw the particle system
void CreateShaders();
void InitializeBuffers();
// Long amount of get sets.
/*float* GetMinLifeTime();
void SetMinLifeTime(float lt);
float* GetMaxLifeTime();
void SetMaxLifeTime(float lt);*/
int* GetParticlesToSpawnAtATime();
void SetParticlesToSpawnAtATime(int particlesToSpawn);
float* GetSpawnRate();
void SetSpawnRate(float spawnRate);
Vector3* GetPosition();
void SetPosition(Vector3 newPosition);
Quaternion* GetRotation();
void SetRotation(Quaternion rotation);
std::list<BaseBuildingBlock*> GetBuildingBlocks();
VelocityBuildingBlock* GetVelocityBuilding();
ColourOverLifeBuildingBlock* GetColourOverLifeBuildingBlock();
LifeTimeBuildingBlock* GetLifeTimeBuildingBlock();
UniformColourBuildingBlock* GetUniformColourBuildingBlock();
ScaleBuildingBlock* GetScaleBuildingBlock();
/*Vector3* GetMinVelocity();
void SetMinVelocity(Vector3 min);
Vector3* GetMaxVelocity();
void SetMaxVelocity(Vector3 maxVelocity);*/
Vector3 GetMinParticleStartPoint();
void SetMinParticleStartPoint(Vector3 minParticleStartPoint);
Vector3 GetMaxParticleStartPoint();
void SetMaxParticleStartPoint(Vector3 maxParticleStartPoint);
bool CreateColourOverLifeBuildingBlock();
bool DeleteColourOverLifeBuildingBlock();
bool CreateUniformColourBuildingBlock();
bool DeleteUniformColourBuildingBlock();
bool CreateScaleBuildingBlock();
bool DeleteScaleBuildingBlock();
/*Colour GetStartColour();
void SetStartColour(Colour startColour);
Colour GetEndColour();
void SetEndColour(Colour endColour);*/
Vector3* GetMinParticleRotationAmountPerFrame();
void SetMinParticleRotationAmountPerFrame(Vector3 minParticleRotationAmount);
Vector3* GetMaxParticleRotationAmountPerFrame();
void SetMaxParticleRotationAmountPerFrame(Vector3 maxParticleRotationAmount);
void Save(TiXmlElement* element);
private:
// Spawns a particle.
void SpawnParticle();
GLuint VaoId;
GLuint VboId;
GLuint IndexBufferId;
GLuint PositionBufferId;
GLuint WVPId;
GLenum programId;
std::vector<GLfloat> verticesToDraw;
std::vector<GLubyte> indicesToDraw;
std::vector<Vector3> positions;
std::vector<Matrix4f> WVPMatrices;
std::vector<Matrix4f> WorldMatrices;
std::list<Particle> particles; // List of particles
Vector3 position; // position of the emitter
Quaternion rotation; // rotation of the emitter.
float spawnRate; // spawnrate of the emitter.
int particlesToSpawnAtATime; // The amount of particles to spawn at a time.
float minLifeTime; // The minimum time a particle can live for.
float maxLifeTime; // The maximum time a particle can live for.
float timer; // Timer
ShaderCreator* shaderCreator;
//Vector3 minVelocity; // The minimum velocity a particle can have.
//Vector3 maxVelocity; // The maximum velocity a particle can have/
//std::list<BaseBuildingBlock> buildingBlocks;
// I'm thinking of eventually making a list of baseBuildingBlocks.
std::list<BaseBuildingBlock*> buildingBlocks;
VelocityBuildingBlock* velocityBuildingBlock;
ColourOverLifeBuildingBlock* colourOverLifeBuildingBlock;
LifeTimeBuildingBlock* lifeTimeBuildingBlock;
UniformColourBuildingBlock* uniformColourBuildingBlock;
ScaleBuildingBlock* scaleBuildingBlock;
Vector3 minParticleStartPoint; // The minimum position a particle can start at.
Vector3 maxParticleStartPoint; // The maximum position a particle can start at.
Vector3 minParticleRotationAmountPerFrame; // The minimum amount of rotation that a particle can rotate every frame.
Vector3 maxParticleRotationAmountPerFrame; // The maximum amount of rotation that a particle can rotate every frame.
Colour startColour; // StartColour is the colour that a particle will start with.
Colour endColour; // EndColour is the colour that a particle will end with.
//TEST
float scale;
};
#endif
现在我想知道，有什么方法可以切换活动的VBO吗？或者我完全走错了路。我使用了着色器调试器，并且两个VBO都存在defreetely。
答案 0 :(得分：0)
您需要在每次绘制调用之前正确设置顶点属性 - 即，您必须调用 glBindBuffer ，然后调用 glEnableVertexArray ＆amp;每次绘制调用之前，每个属性都有 glVertexAttribPointer 。在您发布的代码中，这只发生在粒子位置，但不适用于显然包含转换矩阵的'WVP_LOCATION'属性（您通过 glBufferData 将数据上传到GPU，但不要'设置属性） - 意味着一旦你拥有多个粒子系统，就只能访问第二个粒子系统的变换矩阵进行渲染。
一方面没有，你在这里尝试做的事情看起来效率很低 - 你实际上是每帧为每个粒子推动一个转换矩阵到GPU。根据您想要的粒子数量，这会破坏您的表现 - 您应该考虑使用transform feedback更新粒子的位置等。
编辑：刚才意识到opengl wiki链接并没有真正解释很多。变换反馈是一种记录顶点着色器输出的方法（或者，如果存在几何/曲面细分着色器，则会记录该输出）。输出变量被写入VBO - 之后，它们可以像任何其他顶点属性一样用于渲染。整个概念与使用帧缓冲对象记录片段着色器输出非常相似;它允许完全存在于GPU上的粒子系统，顶点着色器计算更新的位置，寿命和时间。每帧中的其他属性。可以找到一个非常好的教程，它显示了这种变换反馈的基本设置here