I'm sorry, I tried upvoting your post and accidentally clicked the wrong thing and now i don't know how to reverse it -.-
Pretty sure gl_FragColor is deprecated in glsl version 150.
Unfortunately, votes are final immediately. I would definitely like to see some grace period though so silly mistakes like that can be corrected. I'll bump him up a step so the post doesn't show a -1 at least.
If gl_FragColor is deprecated, then how do I tell the GPU what color the pixel should be??
You use custom out variables in the fragment shader, just like the inputs to the vertex shader are custom in variables. The variable on location 0 goes to the primary render target, the variable on location 1 goes to the second render target, and so on. If you're not working with multiple render targets, then just define an out variable in the fragment shader and write to it.
Aaah, thanks, that makes sense. Thank you to everyone who helped