带有Cg的OpenGL中的多个渲染目标

Question

我试图（徒劳地）使用OpenGL和NVIDIA的Cg着色器系统设置MRT，最终目的是推迟渲染。我已经成功为单个目标同时使用了着色器和“渲染到纹理”，但是当我尝试将一个对象渲染到多个渲染目标时，它在任何一个中都无法显示。

我以以下方式设置帧缓冲区对象：

// Initialize textures
// (I'll spare you the code since I've  done that without issues)

// Initialize the FBO
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glGenRenderbuffers(1, &depthBuff);
glBindRenderbuffer(GL_RENDERBUFFER, depthBuff);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
                          GL_RENDERBUFFER, depthBuff);

// -snip-

// Bind each texture we want to use to the FBO at rtNum
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + rtNum,
                       GL_TEXTURE_2D, tex->getID(), 0);
// Check to make sure we're good to go
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
    throw Exceptions::GLException("Frame buffer object is not complete.",
                                __FUNCTION__);
}

// -snip-

// Call glDrawBuffers with the RTs we want to render to
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
unique_ptr<GLenum[]> arr(new GLenum[num]);
for (size_t c = 0; c < num; ++c)
    arr[c] = GL_COLOR_ATTACHMENT0 + c;
glDrawBuffers(num, arr.get());
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
    throw Exceptions::GLException("Frame buffer object is not complete.",
                                __FUNCTION__);

// -snip-

// Set up the FBO for rendering
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glPushAttrib(GL_VIEWPORT_BIT);
glViewport(0, 0, width, height);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Draw calls here

glBindFramebuffer(GL_FRAMEBUFFER, 0);
glPopAttrib();

我的着色器（使用所返回的配置文件进行编译cgGLGetLatestProfile）是：

struct VertexShaderOutput {
    float4 position : POSITION;
    float3 normal : TEXCOORD0;
    float4 color : COLOR;
};

VertexShaderOutput VS_Main(float4 local : POSITION,
                        float4 normal : NORMAL,
                        float4 color : COLOR,
                        uniform float4x4 modelViewProj,
                        uniform float4x4 modelViewIT)
{
    VertexShaderOutput OUT;
    OUT.position = mul(modelViewProj, local);
    OUT.normal= mul(modelViewIT, normal).xyz;
    OUT.color = color;
    return OUT;
}

struct FragmentShaderOutput {
    float4 unlit : COLOR0;
    float4 normAndDepth : COLOR1;
};

FragmentShaderOutput FS_Main(VertexShaderOutput vsOut)
{
    FragmentShaderOutput OUT;
    OUT.unlit = float4(1.0f, 1.0f, 0.0f, 1.0f);//vsOut.color;
    OUT.normAndDepth.rgb = vsOut.normal;
    // Calculate depth later
    OUT.normAndDepth.a = 1.0f;
    return OUT;
}

有谁知道为什么会失败吗？

Answer 1

上述方法是正确的。问题似乎出在硬件和CG 的结合上。在我的带有集成芯片组的笔记本电脑上，尽管 Cg 没有返回任何错误，但 MRT 会失败，并且会发生大量其他与着色器相关的问题。在我配备 GeForce GTX260 的台式机上，一切运行良好。