How to render scene to custom UV space on a texture

I have a world in which each rendered object is assigned a remapped UV space on a large texture. I want to be able to write a custom color to this texture on the remapped UV coordinates at the pixel level so that, at render time, the main material can sample it and determine whether to output one color or another.

I’ve looked into several resources regarding material inputs, shader development, compute shaders, etc. and found nothing that simply lets me output a color to a custom texture at a custom UV at the pixel level.

Can anyone help?

I’m not sure how effective I can be with that. The idea is, a world manager assigns a portion of a large texture to each object in the world. Then, each object does a rendering pass where each fragment writes an encoded color to a specific pixel on the texture based on some logic about its position. Then the main render pass samples that pixel on the large texture to output one color or another.

Normally I would accomplish the task in one pass using math, but the nugget of this problem is in permanently changing the way the world is rendered by writing to a texture (succeeding the math check for a pixel turns it “on” forever). But the resolution needs to be high and the information to effect the change is contained at the pixel level, as it determines on interpolated world coordinates.

Your description is a bit unclear. Are you able to provide a screenshot or sketch that shows what end result you’re are trying to achieve?