Always Draw Behind Everything

Unity Engine
1

I’m relatively new to shaders, but I’m trying to achieve something specific to make life a lot easier. I have a ground plane mesh which is perfectly flat (the grass), on top of which sits a flat road mesh. Ideally these need to be at the exact same level - offsetting the road is not feasible without creating more problems.

Since the ground plane is flat, it never needs to obscure anything. So I thought finding a way to force it to “always draw behind everything” would be very handy. My current attempt involves modifying a standard Diffuse shader to include the following:

Pass {
ZTest Always
Offset 1, 1
}

This has the opposite intended effect of always drawing the ground plane ON TOP of everything. Which is strange because using -1, -1 for Offset achieves the same thing, but turns the grass plane completely BLACK. Is there a way to flip this around and force the ground plane BEHIND everything?

2

I tried a quick test with two planes in the same level, one using the standard diffuse shader, and one using the diffuse shader modified with Offset -1, -1. In this case the plane with the modified shader drew on top, and changing it to Offset 1, 1 made it draw behind.

–Eric

3

Yes, but for some reason when I try that the road is completely black.

4

Ah, I fixed the problem by not putting the Offset inside Pass. Now it’s simply under SubShader.