Enable smooth triangle shading (custom per-vertex normals) (#2067)

* Removed triangle normal recalculation to enable smooth triangle shading.

* Updated comment

src/main/java/net/coderbot/iris/mixin/vertices/MixinBufferBuilder.java

@@ -244,7 +244,8 @@ private void fillExtendedData(int vertexAmount) {
 		midV /= vertexAmount;
 
 		if (vertexAmount == 3) {
-			NormalHelper.computeFaceNormalTri(normal, polygon);
+      			// Removed to enable smooth shaded triangles. Mods rendering triangles with bad normals need to recalculate their normals manually or otherwise shading might be inconsistent.
+			// NormalHelper.computeFaceNormalTri(normal, polygon);
 		} else {
 			NormalHelper.computeFaceNormal(normal, polygon);
 		}