OpenGL的Frambuffers，渲染到深度紋理

Question

問題：

的代碼應該渲染場景並將結果寫入到一個深度紋理。當我在渲染之後檢查紋理的內容時，它包含全部0個值。

我曾嘗試：

我試圖輸出到屏幕上，而不是質地和它繪製的場景如預期，因此被正確讀取頂點和矩陣值。我已經嘗試了多個教程，他們都基本上說要將幀緩衝區綁定到紋理，這正是我所做的。我相信這個問題可能是某種版本問題，或者是我忽略了一些參數或其他內容。我已經在這裏待了幾個小時，但我無法發現它。希望有人能。

詳情：

• 的OpenGL 3.1
• GLSL 140

注：這樣做的目的是爲了讓陰影映射工作。所以有兩套着色器和繪圖函數。一個繪製到深度緩衝區，另一個繪製對象。

代碼：

着色器的初始化代碼：

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"); 

} 

對象的初始化代碼

抽獎代碼：

/*開始 - 主要更新循環部分*/ // |繪製更新|

// 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); 

} 

頂點着色器：

#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。顯然，如果你重新排列opengl調用一點點它的作品。我相信我所做的就是在glUseProgram之前放入glBindFramebuffer並且它工作正常。