   Issue with MRTs using FBO
  Alright, so I'm attempting to render to multiple textures using an FBO. I've read through quite a bit of stuff on FBOs and how to set up MRTs in OpenGL, but I just can't seem to get it working. Here's what I'm doing:I create an FBO using glGenFramebuffersEXT. Then, I use glBindFrameBufferEXT before attaching a RenderBuffer for the depth attachment and 2 textures at GL_COLOR_ATTACHMENT0_EXT and GL_COLOR_ATTACHMENT1_EXT. Then, I call glDrawBuffers with the 2 color attachments. glCheckFramebufferStatusEXT says that it's GL_FRAMEBUFFER_COMPLTE_EXT. So then, when I want to use my FBO, I bind the FBO, and in my fragment shader I use gl_FragData[0] and gl_FragData[1]. However, when I try to just render these textures to te screen, only the texture corresponding to GL_COLOR_ATTACHMENT0_EXT will display properly. What I mean is that even if I swap ordering for glDrawBuffers to be {GL_COLOR_ATTACHMENT1_EXT, GL_COLOR_ATTACHMENT0_EXT}, then gl_FragData[1] will output properly, but gl_FragData[0] won't. Any ideas? Should I post some code?   
  Yes, you should post code.   ;  Alright, I found out what the problem was, but now I'm running into another problem. Basically I'm trying to implement deferred shading, but now that I've rendered out my G-Buffer, I'm not sure how to accumulate the lighting equations for each light. My first thought would just be, for each light, render a quad in orthographic mode to the screen, calculating the light properties and adding it to the frame buffer. But, it seems you can't just do gl_FragData[0] += color. So, what's the best way to accumulate this data? Should I just, for each light, update a texture, and feed that texture in for the next pass, repeating until I have done all the lights? That seems like there would be lots of shader swapping or attachment point swapping.Also, I know that I shouldn't render an entire quad for each light, but I'm just trying to get it working right now...   