Terrain fixes to match vanilla better - vertices need to be mapped directly to texels for colormap and blendmap (this also caused seams at cell borders), layer uv scale appears to be 8 not 10

apps/openmw/mwrender/terrain.cpp

@@ -45,7 +45,7 @@ namespace MWRender
         // Setting this to 0 seems to cause glitches though. :/
         mTerrainGlobals->setMaxPixelError(1);
 
-        mTerrainGlobals->setLayerBlendMapSize(32);
+        mTerrainGlobals->setLayerBlendMapSize(ESM::Land::LAND_TEXTURE_SIZE/2 + 1);
 
         //10 (default) didn't seem to be quite enough
         mTerrainGlobals->setSkirtSize(128);
@@ -352,9 +352,9 @@ namespace MWRender
         }
 
         //covert the ltex data into a set of blend maps
-        for ( int texY = fromY - 1; texY < fromY + size + 1; texY++ )
+        for ( int texY = fromY; texY < fromY + size + 1; texY++ )
         {
-            for ( int texX = fromX - 1; texX < fromX + size + 1; texX++ )
+            for ( int texX = fromX - 1; texX < fromX + size; texX++ ) // NB we wrap X from the other side because Y is reversed
             {
                 const uint16_t ltexIndex = getLtexIndexAt(cellX, cellY, texX, texY);
 
@@ -367,7 +367,7 @@ namespace MWRender
 
                 //while texX is the splat index relative to the entire cell,
                 //relX is relative to the current segment we are splatting
-                const int relX = texX - fromX;
+                const int relX = texX - fromX + 1;
                 const int relY = texY - fromY;
 
                 const int layerIndex = indexes.find(ltexIndex)->second;
@@ -375,35 +375,15 @@ namespace MWRender
                 float* const pBlend = terrain->getLayerBlendMap(layerIndex)
                                              ->getBlendPointer();
 
-                for ( int y = -1; y < splatSize + 1; y++ )
-                {
-                    for ( int x = -1; x < splatSize + 1; x++ )
-                    {
-
                         //Note: Y is reversed
-                        const int splatY = blendMapSize - 1 - relY * splatSize - y;
-                        const int splatX = relX * splatSize + x;
-
-                        if ( splatX >= 0 && splatX < blendMapSize &&
-                             splatY >= 0 && splatY < blendMapSize )
-                        {
-                            const int index = (splatY)*blendMapSize + splatX;
-
-                            if ( y >= 0 && y < splatSize &&
-                                 x >= 0 && x < splatSize )
-                            {
-                                pBlend[index] = 1;
-                            }
-                            else
-                            {
-                                //this provides a transition shading but also
-                                //rounds off the corners slightly
-                                pBlend[index] = std::min(1.0f, pBlend[index] + 0.5f);
-                            }
-                        }
+                        const int splatY = blendMapSize - relY - 1;
+                        const int splatX = relX;
 
-                    }
-                }
+                        assert(splatX >= 0 && splatX < blendMapSize);
+                        assert(splatY >= 0 && splatY < blendMapSize);
+
+                        const int index = (splatY)*blendMapSize + splatX;
+                        pBlend[index] = 1;
             }
         }
 

files/materials/terrain.shader

@@ -205,7 +205,6 @@
         shUniform(float, waterLevel) @shSharedParameter(waterLevel)
 #endif
 
-
     SH_START_PROGRAM
     {
 
@@ -232,35 +231,46 @@ float previousAlpha = 1.f;
 #endif
 
         // Layer calculations 
+// rescale UV to directly map vertices to texel centers
+// TODO: parameterize texel size
+float2 blendUV = (UV - 0.5) * (8.0 / (8.0+1.0)) + 0.5;
 @shForeach(@shPropertyString(num_blendmaps))
-        float4 blendValues@shIterator = shSample(blendMap@shIterator, UV);
+        float4 blendValues@shIterator = shSample(blendMap@shIterator, blendUV);
 @shEndForeach
 
         float3 albedo = float3(0,0,0);
+
+        float2 layerUV = UV * 8;
+
 @shForeach(@shPropertyString(num_layers))
 
 
 #if IS_FIRST_PASS
         #if @shIterator == 0
         // first layer of first pass is the base layer and doesn't need a blend map
-        albedo = shSample(diffuseMap0, UV * 10).rgb;
+        albedo = shSample(diffuseMap0, layerUV).rgb;
         #else
-        albedo = shLerp(albedo, shSample(diffuseMap@shIterator, UV * 10).rgb, blendValues@shPropertyString(blendmap_component_@shIterator));
+        albedo = shLerp(albedo, shSample(diffuseMap@shIterator, layerUV).rgb, blendValues@shPropertyString(blendmap_component_@shIterator));
         #endif
 #else
         #if @shIterator == 0
-        albedo = shSample(diffuseMap@shIterator, UV * 10).rgb, blendValues@shPropertyString(blendmap_component_@shIterator);
+        albedo = shSample(diffuseMap@shIterator, layerUV).rgb, blendValues@shPropertyString(blendmap_component_@shIterator);
         #else
-        albedo = shLerp(albedo, shSample(diffuseMap@shIterator, UV * 10).rgb, blendValues@shPropertyString(blendmap_component_@shIterator));
+        albedo = shLerp(albedo, shSample(diffuseMap@shIterator, layerUV).rgb, blendValues@shPropertyString(blendmap_component_@shIterator));
         #endif
         previousAlpha *= 1.f-blendValues@shPropertyString(blendmap_component_@shIterator);
 #endif
 @shEndForeach
         
         shOutputColour(0) = float4(1,1,1,1);
+
         
 #if COLOUR_MAP
-        shOutputColour(0).rgb *= shSample(colourMap, UV).rgb;
+        // Since we're emulating vertex colors here,
+        // rescale UV to directly map vertices to texel centers. TODO: parameterize texel size
+        const float colourmapSize = 33.f;
+        float2 colourUV = (UV - 0.5) * (colourmapSize / (colourmapSize+1.f)) + 0.5;
+        shOutputColour(0).rgb *= shSample(colourMap, colourUV).rgb;
 #endif
 
         shOutputColour(0).rgb *= albedo;
@@ -347,6 +357,7 @@ float previousAlpha = 1.f;
 #else
         shOutputColour(0).a = 1.f-previousAlpha;
 #endif
+
     }
 
 #endif