5

I have a system to render different objects into different RGBA textures using OpenGL in C++. I'd like to layer these textures on top of eachother, but my problem is that each texture has the glClearColor rendered into it.

How to tell OpenGL to make the ClearColor parts of the texture transparent (0.0f alpha), so I can still see parts of layers behind other layers?

GDN9
  • 329
  • 3
  • 15

1 Answers1

3

The fourth parameter of glClearColor allows you to specify an alpha value to set when you clear the render target, so you can just pass 0 to make it clear to transparent.

Your render target obviously needs to have an alpha channel. Also, the clearing of the alpha channel using the value specified using glClearColor can be enabled or disabled using glColorMask.

samgak
  • 23,944
  • 4
  • 60
  • 82
  • Thanks! Can't believe I didn't even think of that! It's kinda working, the background of the textures are gone! But I'm getting a brutal film-grain like flickering, any idea why that could be? Using glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); Thanks again! – GDN9 Jan 04 '17 at 10:43
  • The flickering sounds like some kind of synchronization issue. https://www.khronos.org/opengl/wiki/Synchronization – samgak Jan 04 '17 at 18:26