2 Replies Latest reply on Nov 16, 2015 5:01 PM by codr

    Weird issue where a certain color causes render failure

    codr

      I'm having an issue where triangles won't render if their green color component is greater than 55 (that's of 0-255 ubyte).

       

      I'm using Ubuntu 15.10 with the fglrx-updates 2:15.201-0ubuntu1 driver. Hardware is R9 280x.

       

      I'm rendering in orthographic "2D" mode using OpenGL 4.2 with 64-bit vertex coordinates.

       

      I have created a simple SDL program that demonstrates the issue. See here:

      c---/opengl-test · GitHub

       

      I realize GL_QUADS are deprecated but I have also tested with GL_TRIANGLE_STRIP and it behaves the same way. If I set the color to 0,55,0,255 then everything renders fine. However, if I change the green color to anything higher than 55, then nothing renders. They seem to not even enter the shader because if I hard-code the vertex shader to always output the same color (frag_color in shader) I still see nothing rendering on the screen unless I set the green to 55 or less.

       

      Bizarre eh? Bug in the driver or am I doing something wrong? This code works 100% correctly on nVidia hardware. I'm not sure about Intel, I'm trying to set up a new machine that will run the newer mesa with OGL4 support.