OpenGL的Frambuffers，渲染到深度纹理

Question

问题：

的代码应该渲染场景并将结果写入到一个深度纹理。当我在渲染之后检查纹理的内容时，它包含全部0个值。

我曾尝试：

我试图输出到屏幕上，而不是质地和它绘制的场景如预期，因此被正确读取顶点和矩阵值。我已经尝试了多个教程，他们都基本上说要将帧缓冲区绑定到纹理，这正是我所做的。我相信这个问题可能是某种版本问题，或者是我忽略了一些参数或其他内容。我已经在这里待了几个小时，但我无法发现它。希望有人能。

详情：

• 的OpenGL 3.1
• GLSL 140

注：这样做的目的是为了让阴影映射工作。所以有两套着色器和绘图函数。一个绘制到深度缓冲区，另一个绘制对象。

代码：

着色器的初始化代码：

void Engine::loadMObject() 
{ 
    glGenFramebuffers(1, &MObject::fbo); 
    glGenTextures(1, &MObject::shadowMap); 

    glBindFramebuffer(GL_FRAMEBUFFER, MObject::fbo); 
    glBindTexture(GL_TEXTURE_2D, MObject::shadowMap); 
    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, windowWidth, windowHeight, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); 
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP); 

    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, MObject::shadowMap, 0); 

    glDrawBuffer(GL_NONE); 
    glReadBuffer(GL_NONE); 

    GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER); 
    assi(status == GL_FRAMEBUFFER_COMPLETE, "FBO error!"); 

    glBindFramebuffer(GL_FRAMEBUFFER, 0); 

    MObject::shadowProgram = Shader::compile((char*)MObject::shadowVertexShaderFile, (char*)MObject::shadowFramentShaderFile); 

    MObject::shadowPositionLoc = glGetAttribLocation(MObject::shadowProgram, "position"); 

    MObject::shadowModelProjectionMatrixLoc = glGetUniformLocation(MObject::shadowProgram, "modelProjectionMatrix"); 

    MObject::objectProgram = Shader::compile((char*)MObject::objectVertexShaderFile, (char*)MObject::objectFragmentShaderFile); 

    MObject::objectPositionLoc = glGetAttribLocation(MObject::objectProgram, "position"); 
    MObject::objectTexCoordLoc = glGetAttribLocation(MObject::objectProgram, "texCoord"); 
    MObject::objectNormalLoc = glGetAttribLocation(MObject::objectProgram, "normal"); 

    MObject::objectWorldMatrixLoc = glGetUniformLocation(MObject::objectProgram, "worldMatrix"); 
    MObject::objectViewMatrixLoc = glGetUniformLocation(MObject::objectProgram, "viewMatrix"); 
    MObject::objectProjectionMatrixLoc = glGetUniformLocation(MObject::objectProgram, "projectionMatrix"); 
    MObject::objectTextureLoc = glGetUniformLocation(MObject::objectProgram, "texture"); 
    MObject::objectDepthModelProjectionMatrixLoc = glGetUniformLocation(MObject::objectProgram, "depthModelProjectionMatrix"); 

} 

对象的初始化代码

抽奖代码：

/*开始 - 主要更新循环部分*/ // |绘制更新|

// Shadow Pass 

// testing... 
if(isKeyDown(SDL_SCANCODE_0)){ 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glUseProgram(MObject::shadowProgram); 
    glBindFramebuffer(GL_FRAMEBUFFER, MObject::fbo); 
    glBindTexture(GL_TEXTURE_2D, MObject::shadowMap); 
    for(U32 i=0;i<mObjectList.length();++i) 
    { 
     drawShadow(mObjectList[i]); 
    } 
    glBindFramebuffer(GL_FRAMEBUFFER, 0); 
    glBindTexture(GL_TEXTURE_2D, MObject::shadowMap); 
    GLfloat* pixels = new GLfloat[windowWidth*windowHeight]; 
    glGetTexImage(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, GL_FLOAT, pixels); 
    for(U32 i=0;i<windowHeight*windowHeight;++i) 
    { 
     if(pixels[i] != 0.0f) 
      printd("I GOT IT!"); 
    } 
    delete[] pixels; 
}else{ 


    // Object Pass 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glUseProgram(MObject::objectProgram); 
    for(U32 i=0;i<mObjectList.length();++i) 
    { 
     drawObject(mObjectList[i]); 
    } 
} 


// Swapping buffers 
SDL_GL_SwapWindow(mainWindow); 

/* END - 部分主OF UPDATE LOOP */

void Engine::drawObject(MObject* object) 
{ 
    TransformMatrix matrix; 
    getOrthographicMatrix(matrix, -10, 10, 10, -10, -10, 20); 
    glBindVertexArray(object->objectvao); 
    glUniformMatrix4fv(MObject::objectWorldMatrixLoc, 1, GL_FALSE, (GLfloat*)&object->worldMatrix); 
    glUniformMatrix4fv(MObject::objectViewMatrixLoc, 1, GL_FALSE, (GLfloat*)&getViewMatrix()); 
    glUniformMatrix4fv(MObject::objectProjectionMatrixLoc, 1, GL_FALSE, (GLfloat*)&getProjectionMatrix()); 

    glUniformMatrix4fv(MObject::objectDepthModelProjectionMatrixLoc, 1, GL_FALSE, (GLfloat*)&getProjectionMatrix()); 
    glActiveTexture(GL_TEXTURE0); 
    glBindTexture(GL_TEXTURE_2D, object->tbo); 
    glUniform1i(MObject::objectTextureLoc, 0); 
    glDrawElements(GL_TRIANGLES, object->eboNumElements, GL_UNSIGNED_INT, 0); 
} 

void Engine::drawShadow(MObject* object) 
{ 
    TransformMatrix matrix; 
    //getOrthographicMatrix(matrix, -10, 10, 10, -10, -10, 20); 
    matrix = getProjectionMatrix() * getViewMatrix() * object->worldMatrix; 
    glBindVertexArray(object->shadowvao); 
    glUniformMatrix4fv(MObject::shadowModelProjectionMatrixLoc, 1, GL_FALSE, (GLfloat*)&matrix); 
    glDrawElements(GL_TRIANGLES, object->eboNumElements, GL_UNSIGNED_INT, 0); 

} 

顶点着色器：

#version 140 

in vec3 position; 

uniform mat4 modelProjectionMatrix; 

void main(){ 
    gl_Position = modelProjectionMatrix * vec4(position, 1.0f); 
} 

片段着色器：

#version 140 

out float fragmentdepth; 

void main(){ 
    fragmentdepth = gl_FragCoord.z; 
} 
/* 
out vec4 color; 

void main(){ 
    color = vec4(clamp(gl_FragCoord.z, 0.0f, 1.0f), 0.0f, 0.0f, 1.0f); 
}*/ 

Answer 1

我想通了。显然，如果你重新排列opengl调用一点点它的作品。我相信我所做的就是在glUseProgram之前放入glBindFramebuffer并且它工作正常。