Terrain Materials

[TokisanGames]

Juan Wrote:

Terrain Materials

For modern terrain rendering, texture arrays must be used. This ensures quick access to all textures needed to render terrain. For creating these textures, we would need something similar to how atlas textures work:

A texture would need to be imported as a Terrain texture, this type change can happen at the time its assigned to the terrain.
The terrain will have material slots, which are basically albedo, normal and ORM and emissive textures. They need to be filled but can be skipped if not used.

The textures selected will probably need to be encoded to an RGBA texture array (3 slots). Emission can be encoded in Albedo with alpha be used as interpolation + energy. Normal can use RA format for quality.

...
Up to a certain distance (1km ? 2 km?) the shader reads the "material index" texture, which is basically a 16 bits 4096 x 4096 (as example, can be changed) containing material indices.

The 4 materials to blend are obtained, materials are read and blended (most likely using triplanar).
Beyond that distance, to avoid aliasing in the algorithm above, the terrain is blended into low resolution albedo+e, metallic textures that are read directly.

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My Interpretation:

• Texture arrays - of course. But creating them is a PITA for end users. We need a system that generates them, somewhat like yours, but it should also compose alpha, taking in a separate heightmap as well. So we should have a set up tool where users provide separate maps, and the tool generates and saves RGBA files to disk, so they can remove their originals.
• Albedo, normal, AO, Rough, Metal, Emissive - eh... We need Albedo, normal, rough, height. AO is nice but doesn't fit. It's not worth another map for it. Metal, and emissive are going to be so rarely used. These can be in the custom shader category where devs do it themselves if needed.
• Encoded as 3 RGBA texture arrays - 1) Albedo+Height, 2) NRM+Rough, 3) AO,Metal,Emissive,Energy? # 3 as an optional map that doesn't cost anything if unused? Maybe. Maybe a low priority issue that can be implemented much further down the road if people need it.
• Imported as a Terrain texture - So a new import type. It's an option to consider. A custom resource loader, or custom material are other options. I don't like the import system in Godot because it requires a restart to change settings.
• Normal can use RA format for quality. - Something to look into. I don't know about this.
• Up close 4 textures blended - same as Zylann's. Far away read from a low resolution albedo + metal - OK, minus metal. Though I've had no problems with aliasing. But using a branch to eliminate 3 texture lookups for the blend is probably fine. W3 said they found on high end hardware branching is better than more lookups.
• a 16 bits 4096k map containing material indices - 32k textures??? what? Number of textures discussed below.
• Triplanar - Godot's triplanar algorithm kills texture normals. Let's do 3D projection instead.

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Goal: * High number of textures.

16 at least. Witcher3 has 32. Up to 256 is nice, but is it necessary?

I had a hard enough time filling out 16 textures for my game, and it's a big game for the Godot community. It already takes a lot of vram. 32 is more than I need. With W3 techniques I'll be able to blend textures in unique ways that results in many variations (eg grass, cobblestone, grass covered cobblestone, cobblestone poking through grass). And I have a color map, which can vary any of the obvious textures, but it can also create more based on variable textures. eg. Snow + light desaturated brown is sand, +dark brown is mud or dirt. + other colors can be a blending agent between other materials.

256 textures is a shiny feature number, but I can't imagine any game actually using it, or using that much of precious vram. If it's free, then fine, but if an index based shader is significantly more expensive than one that only supports 16-32, I have a hard time justifying the performance.

What do you think about Juan's notes, my interpretations, and the number of textures?

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Reference:
Index map terrain w/ 3D projection and detiling

• https://github.com/cdxntchou/IndexMapTerrain

The Witcher 3 Clipmap Terrain and Texturing

• https://archive.org/details/GDC2014Gollent
• https://ubm-twvideo01.s3.amazonaws.com/o1/vault/GDC2014/Presentations/Gollent_Marcin_Landscape_Creation_and.pdf

[outobugi]

Again, Juan confuses me.

I'll answer in a weird order...here we GO

index based shader is significantly more expensive

It's not because it will only use constant lookup. 19 is not much but we can go lower, down to 8-11 with branching. The vram would become issue if all 256 slots were used. 32 would be ideal. MicroSplat for Unity has 32, and MegaSplat 256. I need look into the Witcher 3 papers.

Texture arrays...
Imported as a Terrain texture

Like I said in the TerrainStorage discussion, TextureArray should not be saved. They need to be generated often (textures being edited a lot), so why not generate them every time? For the editor they should be only partially updated!
Well, ok, they can be saved but I don't see the benefit.

And it would be best if the textures could be use anywhere, not just in terrain. So, no new import thingy.

Normal can use RA format for quality

Godot normal maps are RA format, meaning they only use 2 channels (RG in reality, actual format is RA_AS_RG). This does not allow to have anything else on any other channel. But we could still use RG channels, AO in B and roughness in A.
The RA format is 16bits, because two 8bit channels are not used.

[TokisanGames]

TextureArray should not be saved.

If generating 3-4 4k-16k texture arrays is fast, fine. If it takes significant time, it's a drain on development time as we switch scenes in the editor, restart test scenes, and are constantly regenerating the texture arrays.

They need to be generated often (textures being edited a lot),
Once the materials are defined, how are they being changed? Only the height and controlmaps should be changing frequently due to sculpting or painting. But not the material texture maps.

[TokisanGames]

We have a solid material class with 32 textures. There's nothing remaining in this conversation so it is archived.