Subdiv: Clarity resolution parameter

Was a bit misleading, since different ptex faces will be
tessellated at different resolution, depending whether they
are coming from quad or not.

source/blender/blenkernel/BKE_subdiv_mesh.h

@@ -38,9 +38,11 @@ struct Mesh;
 struct Subdiv;
 
 typedef struct SubdivToMeshSettings {
-	/* Resolution at which ptex are being evaluated.
-	 * This defines how many vertices final mesh will have: every ptex has
-	 * resolution^2 vertices.
+	/* Resolution at which regular ptex (created for quad polygon) are being
+	 * evaluated. This defines how many vertices final mesh will have: every
+	 * regular ptex has resolution^2 vertices. Special (irregular, or ptex
+	 * crated for a corner of non-quad polygon) will have resolution of
+	 * `resolution - 1`.
 	 */
 	int resolution;
 } SubdivToMeshSettings;