I’d like to use the Composite TOP for 2D images as if it were a Render TOP for 3D instanced objects. The exact function I want to use is the maximum of two colors. Please check out my attached project.
3D Compositing.zip (49.5 KB)
Couple of things, you wrote ‘maximum’ but your COMP TOP is using a ‘multiply’, not a ‘max’…
Regardless, a half-way option is to enable blending on your material and set your destination color to ‘src color’. It’s not a good solution however as draw order of all those instances is killing the intention.
As with many things TD you’ll have to creatively work around it 
Perhaps you can split the render up into layers and then comp them.
I got good results by modifying the Phong MAT:
- Blending (Transparency): ON
- Destination Color: One Minus Src Color
- Depth Test: OFF