java - JOGL 2.0，将深度缓冲区渲染到纹理

Question

我正在尝试在 JOGL 2.0 中实现简单的阴影映射技术，并且我在将深度值渲染到纹理中时遇到了困难。也许我做错了，但奇怪的是，用彩色渲染场景可以正常工作。我在stackoverflow上也发现了一个类似的问题，在这里被问到：Render the depth buffer into a texture using a frame buffer

问题通过调用解决

gl.glDrawBuffer(GL2.GL_NONE);
gl.glReadBuffer(GL2.GL_NONE);

但是，这对我没有帮助。当我像往常一样用颜色渲染场景时，功能正常工作。结果如下：

但是，在尝试渲染深度值之后，它只会渲染白色（以及与场景完全不对应的东西）

---- 更新的代码，现在可以正常工作：

private void initializeFBO3(GL2 gl) {

//Create frame buffer
gl.glGenFramebuffers(1, frameBufferID, 0);
gl.glBindFramebuffer(GL2.GL_FRAMEBUFFER, frameBufferID[0]);

// ------------- Depth buffer texture --------------
gl.glGenTextures(1,depthBufferID,0);
gl.glBindTexture(GL2.GL_TEXTURE_2D, depthBufferID[0]);

gl.glTexImage2D(GL2.GL_TEXTURE_2D,          // target texture type
        0,                                  // mipmap LOD level
        GL2.GL_DEPTH_COMPONENT,         // internal pixel format
                                            //GL2.GL_DEPTH_COMPONENT
        shadowMapWidth,                     // width of generated image
        shadowMapHeight,                    // height of generated image
        0,                          // border of image
        GL2.GL_DEPTH_COMPONENT,     // external pixel format 
        GL2.GL_UNSIGNED_INT,        // datatype for each value
        null);  // buffer to store the texture in memory

//Some parameters
gl.glTexParameteri(GL2.GL_TEXTURE_2D, GL2.GL_TEXTURE_MIN_FILTER, GL2.GL_NEAREST);
gl.glTexParameteri(GL2.GL_TEXTURE_2D, GL2.GL_TEXTURE_MAG_FILTER, GL2.GL_NEAREST);
gl.glTexParameteri(GL2.GL_TEXTURE_2D, GL2.GL_TEXTURE_WRAP_S, GL2.GL_CLAMP_TO_EDGE);
gl.glTexParameteri(GL2.GL_TEXTURE_2D, GL2.GL_TEXTURE_WRAP_T, GL2.GL_CLAMP_TO_EDGE);     


//Attach 2D texture to this FBO
gl.glFramebufferTexture2D(GL2.GL_FRAMEBUFFER,
        GL2.GL_DEPTH_ATTACHMENT,
        GL2.GL_TEXTURE_2D,
        depthBufferID[0],0);

gl.glBindTexture(GL2.GL_TEXTURE_2D, 0);

//Disable color buffer
//https://stackoverflow.com/questions/12546368/render-the-depth-buffer-into-a-texture-using-a-frame-buffer
gl.glDrawBuffer(GL2.GL_NONE);
gl.glReadBuffer(GL2.GL_NONE);

//Set pixels ((width*2)* (height*2))
//It has to have twice the size of shadowmap size
pixels = GLBuffers.newDirectByteBuffer(shadowMapWidth*shadowMapHeight*4);

//Set default frame buffer before doing the check
//http://www.opengl.org/wiki/FBO#Completeness_Rules
gl.glBindFramebuffer(GL2.GL_FRAMEBUFFER, 0);

int status = gl.glCheckFramebufferStatus(GL2.GL_FRAMEBUFFER);

// Always check that our framebuffer is ok
if(gl.glCheckFramebufferStatus(GL2.GL_FRAMEBUFFER) != GL2.GL_FRAMEBUFFER_COMPLETE)
{
    System.err.println("Can not use FBO! Status error:" + status);
} 
}

public void display(GLAutoDrawable drawable) {
    GL2 gl = drawable.getGL().getGL2(); // get the OpenGL graphics context
    gl.glClear(GL2.GL_COLOR_BUFFER_BIT | GL2.GL_DEPTH_BUFFER_BIT); 

    gl.glLoadIdentity();  // reset the model-view matrix

    //Render scene into Frame buffer first
    gl.glBindFramebuffer(GL2.GL_FRAMEBUFFER, frameBufferID[0]);
        renderSmallScene(gl);

    //Read pixels from buffer
    gl.glBindFramebuffer(GL2.GL_READ_FRAMEBUFFER, frameBufferID[0]);
    //Read pixels 
    gl.glReadPixels(0, 0, shadowMapWidth, shadowMapHeight, GL2.GL_DEPTH_COMPONENT , GL2.GL_UNSIGNED_BYTE, pixels);

    //Switch back to default FBO
    gl.glBindFramebuffer(GL2.GL_FRAMEBUFFER, 0);
        drawSceneObjects(gl);


    //Draw pixels, format has to have only one 
    gl.glDrawPixels(shadowMapWidth, shadowMapHeight, GL2.GL_LUMINANCE , GL2.GL_UNSIGNED_BYTE, pixels);

   }

工作结果：

Answer 1

您必须阅读有关使用 FBO 和 OpenGL 的一般信息。

在您的代码中，您在每一帧中创建 FBO 及其附件。这是错误的。这是巨大的开销。只在 init 上构造一次 FBO。其次，您必须绑定 FBO 才能绘制到它（或从中读取），否则 OpenGL 将绘制到默认的 FBO。看看这里和这里

所以，一旦你的 FBO 准备好了，你就可以像这样渲染它：

glBindFrameBuffer((GL_DRAW_FRAMEBUFFER, yourFbo);

   drawSceneObjects(gl);

glBindFrameBuffer((GL_READ_FRAMEBUFFER, yourFbo);

   readPixelsHere()


 glBindFrameBuffer((GL_FRAMEBUFFER, 0);///switch to default FBO

事实上，在你的情况下，当你离开 FBO 绑定时，只需调用

    glBindFrameBuffer((GL_READ_FRAMEBUFFER, yourFbo);

绘制几何图形后。

此外，如果您不使用着色器，则没有理由将纹理用作 FBO 附件。改为创建渲染缓冲区。