Writing to FBO at multiple coords possible?

OpenGL
1

Standard syntax for writing to FBO:

layout(location = 1) out vec4 colOut;
...
colOut=col;

Assuming the FBO texture attached has the FBO id fboc, am I constrained to writing to fboc at the set of coordinates associated with colOut, or can I offset the texel colOut will write to? What I have in mind is generating a shadow map for the floor:

if the fragment belongs to an occluding object:
  calculate the vector from the light to this fragment;
  extend the vector away from the fragment 
  foreach texel coincident with the vector darken it.
2

No, you cannot write to arbitrary offsets. The location is decided based on the location of the current fragment where the fragment shader is running. You can output to a different attachment but the output will be written to the same location for all the attachments as well. This is the limitation of the shader APIs.

3

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