Getting bits from fbo generated texture?


I’m trying to get my mouse picking back in based on coloring. What I do is that I generate a new texture that I bind to an fbo on color attachment 1, and then write colors to the texels there. Back on the C++ side, my plan is to use the mouse’s position, do a lookup in the texture and find out what color the mouse hovers over.

void GenericManager::update(double dt)
	siut::simd::Vec2f pickCoord = siut::simd::Vec2f(0.0f, 0.0f);
		pickCoord = this->getState()->getMousePos();

	if(pickCoord.x() < 0.001f && pickCoord.y() < 0.001f)

	GLint viewport[4];
	glGetIntegerv(GL_VIEWPORT, viewport);

	pickCoord[1] = viewport[3] - pickCoord[1]; //port to opengl coords

	unsigned int dpp = 3; //rgb

	int aux = dpp*((int)pickCoord.y()*pickingMapSize + (int)pickCoord.x());
	float r = pickingTextureBits[aux+0];
	float g = pickingTextureBits[aux+1];
	float b = pickingTextureBits[aux+2];

How do I get the pickingTextureBits from the opengl state though? I realized quickly that I had no idea how to get to that data. When loading a texture from disk, that’s no problem, but is it possible to get a byte array (unsigned char) from a generated texture like I explained above?

Hm, so I can either use glReadPixels from glRealBuffer(GL_COLOR_ATTACHMENT1), or do a full glGetTexImage?

I guess I only need to do the first approach in that case, and I guess I’ll also have to perform the picking while the fbo is bound… got to test this :slight_smile:

Ok, that worked :stuck_out_tongue: