FBO and stencil

OpenGL OpenGL: Basic Coding
1

Hi all

I’ve rendered to texture the values of the stencil buffer. That’s my code:

glEnable(GL_TEXTURE_RECTANGLE_ARB);
glGenTextures(1, &depthStencilTexID);
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, depthStencilTexID);
…
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_DEPTH24_STENCIL8_EXT, SCREEN_RES_X, SCREEN_RES_Y, 0, GL_RGBA, GL_INT, NULL);
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0);

glGenFramebuffersEXT(1, &fboID);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fboID);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_TEXTURE_RECTANGLE_ARB, depthStencilTexID, 0);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_STENCIL_ATTACHMENT_EXT, GL_TEXTURE_RECTANGLE_ARB, depthStencilTexID, 0);

Now I want to get the stencil value of the texture in a fragment shader. I think the stencil value should be the alpha channel but seems it doesn’t work.

What I’m doing wrong?

Thanks

2

You can’t both read and write to the same texture in the FBO.
Usually, when a texture is bound to the FBO it’s going to be written to - so there is no way to read its contents until you unbind the FBO.

3

Maybe I’ve explained in wrong way.

What I mean is,

glEnable(GL_TEXTURE_RECTANGLE_ARB);
glGenTextures(1, &depthStencilTexID);
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, depthStencilTexID);
…
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_DEPTH24_STENCIL8_EXT, SCREEN_RES_X, SCREEN_RES_Y, 0, GL_RGBA, GL_INT, NULL);
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0);

glGenFramebuffersEXT(1, &fboID);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fboID);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_TEXTURE_RECTANGLE_ARB, depthStencilTexID, 0);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_STENCIL_ATTACHMENT_EXT, GL_TEXTURE_RECTANGLE_ARB, depthStencilTexID, 0);

--------- Render my scene -------------

unattachment of textures anf FBO.

Now I’ve the values of the stencil in depthStencilTexID I render a GL_QUADS of all my screen to activate all fragments. In my fragment I use the texture depthStencilTexID to get the values.

Tnaks anyway.