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我正在尝试（徒劳地）使用 OpenGL 和 NVIDIA 的 Cg 着色器系统设置 MRT，最终目标是延迟渲染。我已经成功地为单个目标工作了着色器和渲染到纹理，但是一旦我尝试将一个对象渲染到多个渲染目标，它就无法显示在其中任何一个目标中。

我正在通过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（使用返回的配置文件编译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;
}

有没有人知道为什么这可能会失败？

4

1 回答 1

2

上述方法是正确的。问题似乎与硬件和 Cg 的组合有关。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 失败并发生了许多其他与着色器相关的问题。在我的配备 GeForce GTX260 的台式机上，一切正常。

于 2012-05-02T02:51:09.447 回答