T3D 1.2 terrain shader Detail channel as 2nd layer diffuse

T3D 1.2 terrain system uses by default, a diffuse bitmap of the entire terrain and an 8 bit detail channel to hide the low resolution of the diffuse.

This modification (hack) reworks the terrain shader so that the detail channel functions as a second layer diffuse with TGEA style tiling, while the normal diffuse channel hides the tiling. In my own testing, I've found this to produce very high quality results given the right combination of textures.

This hack was something created for my own work. I'm publishing it as a resource in response to a request to do so. Comments, suggestions and improvements are strongly welcomed!

To use this modification I suggest the following setup for terrain materials.

new TerrainMaterial()
{
   diffuseMap = "art/terrains/xgrassgreen10";
   diffuseSize = "256";
   detailMap = "art/terrains/xgrassgreen10";
   detailSize = "10";
   detailDistance = "9999";
   internalName = "grass-0-20";
};

Experiment with diffuseSize depending on the resolution of the texture. Do this with the detailMap unassigned so you can see what effects the scaling has. Target should be a blurry camouflage look with very little obvious tiling.

The detailSize at 10 is slightly soft at normal viewing angle when looking down at terrain. Smaller number will tighten it up but make the 2nd layer tiling more obvious.

With both, these are significantly affected by the texture itself. The more uniform the texture, the less tiling. The larger the features are on the texture, the more obvious the tiling becomes. It's a tough one to balance.

The detailDistance at 9999 has not shown to be much, if any, in terms of performance hit. Because the 2nd layer textures are mipmapped, there isn't aliasing noise.


NOTE: This will change terrain lighting, however I've found that once illumination is adjusted the terrain lighting is a closer match to the rest of the scene lighting.


Source patch. These are all in Engine/source/terrain/hlsl/terrFeatureHLSL.cpp

//KENHACK TGEA TERRAIN MOD
   //blendtotal is now TOTAL not highest
   meta->addStatement( new GenOp( "   @ = saturate( @ + @ ); //total not highestrn", blendTotal, blendTotal, detailBlend ) );
   // Add to the blend total.
   //meta->addStatement( new GenOp( "   @ = max( @, @ );rn", blendTotal, blendTotal, detailBlend ) );
//END

//KENHACK TGEA TERRAIN MOD
   //Removes the *2-1 scaling (it's not needed for detail textures to work, not sure why it is here)

   if ( fd.features.hasFeature( MFT_TerrainSideProject, detailIndex ) )
   {
      meta->addStatement( new GenOp( "      @ = lerp( tex2D( @, @.yz ), tex2D( @, @.xz ), @.z );rn", 
                                                detailColor, detailMap, inDet, detailMap, inDet, inTex ) );
   }
   else
   {
      meta->addStatement( new GenOp( "      @ = tex2D( @, @.xy ); //xyzzyrn", 
                                       detailColor, detailMap, inDet ) );
   }
/* ORIGINAL 1.2 CODE
   if ( fd.features.hasFeature( MFT_TerrainSideProject, detailIndex ) )
   {
      meta->addStatement( new GenOp( "      @ = ( lerp( tex2D( @, @.yz ), tex2D( @, @.xz ), @.z ) * 2.0 ) - 1.0;rn", 
                                                detailColor, detailMap, inDet, detailMap, inDet, inTex ) );
   }
   else
   {
      meta->addStatement( new GenOp( "      @ = ( tex2D( @, @.xy ) * 2.0 ) - 1.0;rn", 
                                       detailColor, detailMap, inDet ) );
   }
*/
//END

//KENHACK TGEA TERRAIN MOD
   //KENHACK average outColor and detail (now 2nd layer diffuse) so they BLEND, was ADD.
   meta->addStatement( new GenOp( "      @ = lerp( @, (@ + @)*0.5, @ );rn",
                                    outColor, outColor, baseColor, detailColor, detailBlend ) );
   //meta->addStatement( new GenOp( "      @ = lerp( @, @ + @, @ );rn",
   //                                 outColor, outColor, baseColor, detailColor, detailBlend ) );
//END

This last part is optional. It looks like it might be an optimization for when no detail is present. In my own work detail is always present. Leaving it in might save load if detailDistance is set lower, but it might not work as intended. I removed it in mine because the blendTotal calculation is changed from max to accumulator.

//KENHACK TGEA TERRAIN MOD
   //not sure why GG would discard a pixel.
   //in theory it might cause artifacts.
   //leaving line in the shader but commenting it out so it doesn't run.
   meta->addStatement( new GenOp( "   //clip( @ - 0.0001 ); //WARNING clip removed, not sure why this is here. KEN 2012-10-18.rn", blendTotal ) );
   //meta->addStatement( new GenOp( "   clip( @ - 0.0001 );rn", blendTotal ) );
//END