Skip to content

Terrain shader: Fix incorrect tangent normals sampled using seamless UV method #66

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wheatleymf wants to merge 2 commits into from
Closed

Terrain shader: Fix incorrect tangent normals sampled using seamless UV method #66

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
d7f2589
Output rotation matrix along with seamless UV
wheatleymf Nov 29, 2025
85f29b0
Transform tangent normal along seamless UV angle
wheatleymf Nov 29, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 7 additions & 1 deletion game/addons/base/Assets/shaders/terrain.shader
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -173,7 +173,9 @@ PS
for ( int i = 0; i < 4; i++ )
{
float2 layerUV = texUV * g_TerrainMaterials[ i ].uvscale;
float2 seamlessUV = Terrain_SampleSeamlessUV( layerUV );

float2x2 uvRotation;
float2 seamlessUV = Terrain_SampleSeamlessUV( layerUV, uvRotation );

Texture2D tBcr = Bindless::GetTexture2D( g_TerrainMaterials[ i ].bcr_texid );
Texture2D tNho = Bindless::GetTexture2D( g_TerrainMaterials[ i ].nho_texid );
Expand All @@ -183,6 +185,10 @@ PS

float3 normal = ComputeNormalFromRGTexture( nho.rg );
normal.xz *= g_TerrainMaterials[ i ].normalstrength;

// Rotate normal map to match seamless UV angle and avoid shading errors
normal.xy = mul( uvRotation, normal.xy );

normal = normalize( normal );

albedos[i] = SrgbGammaToLinear( bcr.rgb );
Expand Down
11 changes: 10 additions & 1 deletion game/addons/base/Assets/shaders/terrain/TerrainCommon.hlsl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,7 @@ class Terrain

// Get UV with per-tile UV offset to reduce visible tiling
// Works by offsetting UVs within each tile using a hash of the tile coordinate
float2 Terrain_SampleSeamlessUV( float2 uv )
float2 Terrain_SampleSeamlessUV( float2 uv, out float2x2 uvAngle )
{
float2 tileCoord = floor( uv );
float2 localUV = frac( uv );
Expand All @@ -89,13 +89,22 @@ float2 Terrain_SampleSeamlessUV( float2 uv )
float sinA = sin(angle);
float2x2 rot = float2x2(cosA, -sinA, sinA, cosA);

// Output rotation matrix
uvAngle = rot;

// Rotate around center
localUV = mul(rot, localUV - 0.5) + 0.5;

// Apply random offset
return tileCoord + frac(localUV + hash);
}

float2 Terrain_SampleSeamlessUV( float2 uv )
{
float2x2 dummy;
return Terrain_SampleSeamlessUV( uv, dummy );
}

// Move to another file:

//
Expand Down