What

hvTerrain is a terrain shader for URP I ended up making for my game. I got inspired by KUF2 terrain system (ps only, no clipmap stuff).

This is not a total replacement to Unity's terrain shader. You should still use it for painting/viewing in-editor. Use hvTerrain once you finish your terrain and want more performance in-game. Baking is not destructive to original terrain.

I got a lot of help from around the web, forums and gamedev communities in general, so I decided to release it under MIT.

Also, it's not production ready as I haven't tested it fully yet. Give it a try and tell me how it goes.

Features

• Pros
  • up to 256 textures
  • triplanar
  • per pixel normals
  • holes support
  • should be more perfomant than Unity's Terrain
    • specially when using lots of textures
    • also, when NOT using triplanar
  • normal blending is correct (no multi-pass hacks)
• Cons
  • no 'Draw Instanced' support (Shader graph issue I guess)
  • needs baking
  • layers blend not so smooth
  • use of Texture2DArray
    • it might not work on some old devices
    • it requires same-sized textures
    • no compression
    • also needs manual handling per Graphics API (so I was told, haven't tested on mobiles yet)

Why

Because Unity's Terrain frag shader is slow, specially when you need lots of textures, as it relies on control maps (or alpha maps / splat maps). It means that every 4 textures the terrain has to 're-render'.

For example, lets say we have 16 layers (albedo + normals):

• 4 * [n of passes] draw calls per terrain patch
• 4 samples for control maps
• 16 albedo samples + 16 normal samples
• what if we want triplanar ?
  • then we get 3 * 32 + 4 = 100 samples per pixel
  • and most of the sampled textures don't even contribute

How it works

It actually is more of a baking system than a shader. It works by baking Unity's Terrain data to textures.

I believe the shader ends up being a 'constant-cost' shader giving the sample count is mostly constant.

It should also have a higher overhead compared to Unity's terrain shader though, since it is always going to sample 2 blendMaps + 8 albedos + 4 normals (if not using triplanar).

So for terrains with <= 4 textures, Unity's terrain shader should be more efficient.

Here is the rundown:

• Bakes Terrain layers to Texture2DArrays
  • currently only bakes albedo_smooth + normalsTS_rg
  • also bakes layer's normalScale and smoothness factors into textures
    • scaling normals to a texture might be bad a idea, need to test that more
  • bakes tile sizes to an array (_TexturesScale)
• Bakes SplatMaps to a texture called BlendMap0
  • blendMap0 channel layout = (id0, id1, weight, alpha)
    • alpha is a bitMask = [00000bxz] (applyBilinear isX isZ)
  • it supports blending up to 2 textures
  • axis is used for 'triplanar' (see KUF2 presentation)
  • ids need manual bilinear filtering on ps
  • normal mapping uses id0 only (for perf)
• Bakes Terrain surface data (normals + triplanar axis blend zones) to BlendMap1
  • blendMap1 channel layout = (x, y, z, axisBlend)
    • axisBlend is used for more efficient triplanar mapping
    • it's a mask used to perform triplanar only at seam areas

In the PS:

• branch on blendMap0.a to decide to use bilinear or not
• branch on blendMap1.a to decide to use triplanar or not

So, if my math is right:

Best-case scenario:

• no bilinear
• no triplanar
• 2 blendMap (BlendMap0 + BlendMap1)
• 2 albedo (id0 + id1) (sometimes id0 == id1 so this could get cache optimized too)
• 1 normal (id0)
• Totals to 5 samples

Average-case scenario:

• bilinear
• no triplanar
• 5 blendMap (4 * BlendMap0 + BlendMap1)
• 4 * 2 * albedo (4 * (id0 + id1))
• 4 * normal (only id0)
• Totals to 17 samples

Worst-case scenario:

• bilinear
• triplanar
• triplanar = 17 * 3 (for each axis)
• Totals to 51 samples

Worst case is present at places where uv axis change (surface edges/ridges etc).

How to use

• Add hvTerrain component to a terrain gameobject
• Create a Unity Terrain material
• Create a hvTerrain material
• Assign materials to the hvTerrain component
• Create/Paint terrain as you normaly would
  • you can swtich materials by hvTerrain -> context menu -> switch material
  • you obviously should use Unity Terrain material while painting/sculpting for realtime preview
• Bake (hvTerrain -> contex menu -> bake)
• You can switch features on/off at the hvTerrain material
• Enabling/Disabling holes is a bit tricky
  • Make sure you enable 'Alpha Clipping' at shader graph + 'Holes' checkbox (also 'Terrain Holes' at the URPSettings asset)

More Images