Resolve z-fighting with tiebreaker variable in manual z-test

Hello,

I'm building a game where players can place blocks where they like. I provide tools to make it easy to align edges. By design, blocks can overlap. Unfortunately, this makes it really easy to introduce z-fighting.

I would like to perform my own manual z test that works as follows:
If the fragment is being compared to another fragment whose depth is 'very close', then use the fragment whose variable 'x' is larger.

When I generate my block meshes, I'd like to store an incrementing int in the vertex data of that block so that in the case of a z-depth clash, take the block that was generated last.

Can anyone help me figure out how I might accomplish this? Can the depth buffer store a second variable and can I use it in a manual test? Also, will it be performant?

Thanks.

 

That won't really work. The depth buffer has some extra room, the stencil buffer, but you can't really store a depth value there.

You could disable z-testing altogether and just draw the blocks front back to front.

 

The 'blocks' are part of larger meshes which overlap, so I don't have any reliable order and hence the z-testing is necessary. I can stored data in each 'blocks' vertex data. I can state this another way by saying "I know which triangle I would like to draw last in the event of a 'very close' z-depth by looking at some vertex data".

I'll look into what the stencil buffer is. Is there really no other way to implement custom z-test behaviour?

 

There are plenty of ways to configure the z-testing, but in the case of "very close" that won't help much. Could you share some screenshots? That might help visualizing your case.