Cycles microdisplacement: preserve smooth normals for linear subdivison

This way we prevent cracks in the model due to discontinuous normals, by using
smooth normals for displacement instead of always getting flat normals after
linear subdivision.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D1916

1 files changed, 40 insertions, 8 deletions

diff --git a/intern/cycles/render/mesh.cpp b/intern/cycles/render/mesh.cpp
index aa9f773917a..241a1c44ebf 100644
--- a/intern/cycles/render/mesh.cpp
+++ b/intern/cycles/render/mesh.cpp
@@ -1451,31 +1451,63 @@ void Mesh::tessellate(DiagSplit *split)
 {
 	int num_faces = triangles.size();
 
+	add_face_normals();
+	add_vertex_normals();
+
+	Attribute *attr_fN = attributes.find(ATTR_STD_FACE_NORMAL);
+	float3 *fN = attr_fN->data_float3();
+
+	Attribute *attr_vN = attributes.find(ATTR_STD_VERTEX_NORMAL);
+	float3 *vN = attr_vN->data_float3();
+
 	for(int f = 0; f < num_faces; f++) {
 		if(!forms_quad[f]) {
 			/* triangle */
-			LinearTrianglePatch* patch = new LinearTrianglePatch();
-			float3 *hull = patch->hull;
+			LinearTrianglePatch patch;
+			float3 *hull = patch.hull;
+			float3 *normals = patch.normals;
 
 			for(int i = 0; i < 3; i++) {
 				hull[i] = verts[triangles[f].v[i]];
 			}
 
-			split->split_triangle(patch);
-			delete patch;
+			if(smooth[f]) {
+				for(int i = 0; i < 3; i++) {
+					normals[i] = vN[triangles[f].v[i]];
+				}
+			}
+			else {
+				for(int i = 0; i < 3; i++) {
+					normals[i] = fN[f];
+				}
+			}
+
+			split->split_triangle(&patch);
 		}
 		else {
 			/* quad */
-			LinearQuadPatch* patch = new LinearQuadPatch();
-			float3 *hull = patch->hull;
+			LinearQuadPatch patch;
+			float3 *hull = patch.hull;
+			float3 *normals = patch.normals;
 
 			hull[0] = verts[triangles[f  ].v[0]];
 			hull[1] = verts[triangles[f  ].v[1]];
 			hull[3] = verts[triangles[f  ].v[2]];
 			hull[2] = verts[triangles[f+1].v[2]];
 
-			split->split_quad(patch);
-			delete patch;
+			if(smooth[f]) {
+				normals[0] = vN[triangles[f  ].v[0]];
+				normals[1] = vN[triangles[f  ].v[1]];
+				normals[3] = vN[triangles[f  ].v[2]];
+				normals[2] = vN[triangles[f+1].v[2]];
+			}
+			else {
+				for(int i = 0; i < 4; i++) {
+					normals[i] = fN[f];
+				}
+			}
+
+			split->split_quad(&patch);
 
 			// consume second triangle in quad
 			f++;