Scalable shader to blend multiple materials in general form

kotets · 2024-08-27T13:50:16

Hi folks, My first post here as part of my journey to learn gamedev I started ~5 months ago. I'm learning GLSL/shaders at the moment and trying to do a seemingly simple thing, but not sure what the best practice here is, not to reinvent something. Task Shader that blends between materials (up to 6 in any single pixel anywhere), but has no limit on number of total possible materials Imagine 256 materials, defined in their own shader graphs / GLSL files Each vertex has only a single material assigned. Always 100%, never a mix at the vertex position itself. Each vertex has neighbors with a maximum of N other different materials Most cases — one or two; Extreme cases: up to 6, in 0.000001% of cases Where materials change — I want them to blend between each other smoothly, instead of just abruptly becoming different --------- Many tutorials I've seen do the following: if you have 6 materials, they just suggest 6 channels, set them per vertex and then just mix ~6 varyings; All these tutorials start with “Ok, let's do dirt, grass and sand”, but then the solution doesn't seem scalable. Channel/varying per material is trivial and obvious. But it doesn't scale: if talking about potential 256 materials — that sounds extreme, like imagine 256 channels and 256 varyings and overhead. And some sophisticated colony management game that would aim to have ~45 different metals and 14 biomes would easily have even more. And also having a channel/varying per material doesn't utilize the fact that materials change only between neighbors. Each vertex = always 100% specific material, no blend at all, all blending — only if two direct neighbors have different materials. Any distant neighbor (i/j/k different by 2 or more) — never affect voxel at [i, j, k]. And all the blending needs to be just around the transition, I've attached the image above And now imagine what an overkill it would be to have 255 uniforms always unused and passing 255 zeroes to GPU for each vertex in 99.9999% of cases. --------- I'd love something similar to: For each triangle: say “In this triangle, we are blending between stone/dirt/sand” “Vertex 1 is stone, vertex 2 is sand, vertex 3 is dirt” Blending logic is always the same, doesn't matter what it is, we can assume some smoothstep 0->1 or anything trivial. So how do you usually do this? Do I use 6 flat int varyings per vertex to map each of 6 channels to a specific material to tell the drawn triangle what material each verying is mapped to? Or do I better make all existing combinations of blends as separate materials with different 6 uniforms that map channels to materials for this specific triangle? Given 99% of the map is single material — that sounds more optimal in terms of performance, but not sure. Am I overcomplicating this and there are simpler tools? Thank you!

For Beginners GLSL OpenGL Shaders

Started by kotets August 24, 2024 10:20 AM

10 comments, last by kotets 4 months ago

kotets

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August 27, 2024 01:50 PM

My algorithm / logic is maybe a bit random, first thing I ended up with, so vertex re-use patterns become really strange with a lot of materials 😂

Purple = reused vertex. Empty = duplicated vertex.

So a chunk (32x32x32 in my case) with ≥ 4 materials might have its reuse rate lowered, but these chunks are pretty rare in general and even when they happen, there is usually a biome transition or some specific place, so it reduces reuse only around transition area.

But as a benefit — it is a single material and one shader for every possible terrain material in the game, under a switch statement in the fragment shader, blended using 4 blend weights.

Scalable shader to blend multiple materials in general form

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Scalable shader to blend multiple materials in general form

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