[Interest] Qt3D, Framebuffer and MultiSampling

[Thomas Senyk]

On Fri, March 22, 2013 09:01:29 Federico J. Fernández wrote:
> All,
> 
> I'm doing some experiments with GLSL shaders these days. For some of them,
> I need to first render to a FBO, and then use that information to process
> the final image. The main surface used is multisampled, which implies,
> according to the documentation, that the FBO will not render to a texture
> but to a render buffer.
> 
> The question is how to access to the ID of that buffer, to be used as a
> uniform for the shader. In the texture case, there is a texture() projector
> in the FBO class, but there is no one for the render buffer.

Keep reading the next paragraph:


http://qt-project.org/doc/qt-5.0/qtgui/qopenglframebufferobject.html#details
the last paragraph (before 'Threading'):
"If you want to use a framebuffer object with multisampling enabled as a 
texture, you first need to copy from it to a regular framebuffer object using 
QOpenGLContext::blitFramebuffer()."


One simply can't use a multi-sampled surfaces as texture directly
(until OpenGL4.x (or 3.x with extensions)).
This has nothing to do with Qt, but with OpenGL limitations.

> 
> Thanks.
> 
> --
> fede