[Interest] [Qt3D] Get OpenGL texture data / Send preprocessor instructions to shaders

[Léo Adam]

Hi,

I am new to Qt3D and there's a few things I was wondering how to achieve:

- I need to read and write an opengl texture from C++.
For example, I am rendering a scene into a texture during a first render
pass, and then performing some postprocess effect before rendering that
texture in a fullscreen quad during a second render pass.
I would like to access that texture from C++, and can't manage to do that.
I've found the classes *QTextureImageData*/*QTextureData*/
*QTextureDataGenerator*, but I don't know if that's really what I'm looking
for and if it is, how to use it.

- I also would like to send preprocessor instructions to a shader from
C++/QML and I don't know if this is possible.
For example, if I want to use *#ifdef* in a shader with a value defined in
C++, I would need to send that value to the shader just like *QParameter*
do with uniforms.
I've searched in the documentation and on internet, but I didn't find
anything.

Any help would be highly appreciated :-)

Sincerely,
Léo.
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