Switch specular AA to Tokuyoshi and Kaplanyan (#1218)

This replaces the previous "curvature to roughness" method. Both are related
and rely on the screen space variance of geometric normals but this new
solution offers more control (the screen space variance and the clamping
threshold can be controlled).

samples/sample_normal_map.cpp

@@ -260,9 +260,9 @@ static void setup(Engine* engine, View*, Scene* scene) {
         )SHADER";
     } else {
         shader += R"SHADER(
-            material.baseColor.rgb = float3(0.6, 0.6, 0.6);
+            material.baseColor.rgb = float3(0.3, 0.0, 0.0);
             material.metallic = 0.0;
-            material.roughness = 0.7;
+            material.roughness = 0.0;
         )SHADER";
     }
 
@@ -276,6 +276,7 @@ static void setup(Engine* engine, View*, Scene* scene) {
     MaterialBuilder builder = MaterialBuilder()
             .name("DefaultMaterial")
             .material(shader.c_str())
+            .specularAntiAliasing(true)
             .shading(Shading::LIT);
 
     if (hasNormalMap) {