Cycles: Calculate face normal on the fly.

Instead of pre-calculation and storage, we now calculate the face normal during render.
This gives a small slowdown (~1%) but decreases memory usage, which is especially important for GPUs,
where you have limited VRAM.

Part of my GSoC 2014.

1 files changed, 19 insertions, 3 deletions

diff --git a/intern/cycles/kernel/geom/geom_triangle.h b/intern/cycles/kernel/geom/geom_triangle.h
index 355e36fef0c..4ee5d5aa6d5 100644
--- a/intern/cycles/kernel/geom/geom_triangle.h
+++ b/intern/cycles/kernel/geom/geom_triangle.h
@@ -116,6 +116,20 @@ ccl_device_inline float3 triangle_refine_subsurface(KernelGlobals *kg, ShaderDat
 #endif
 }
 
+/* normal on triangle  */
+ccl_device_inline float3 triangle_normal(KernelGlobals *kg, int prim)
+{
+	/* load triangle vertices */
+	float3 tri_vindex = float4_to_float3(kernel_tex_fetch(__tri_vindex, prim));
+
+	float3 v0 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.x)));
+	float3 v1 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.y)));
+	float3 v2 = float4_to_float3(kernel_tex_fetch(__tri_verts, __float_as_int(tri_vindex.z)));
+	
+	/* return normal */
+	return normalize(cross(v1 - v0, v2 - v0));
+}
+
 /* point and normal on triangle  */
 ccl_device_inline void triangle_point_normal(KernelGlobals *kg, int prim, float u, float v, float3 *P, float3 *Ng, int *shader)
 {
@@ -130,9 +144,11 @@ ccl_device_inline void triangle_point_normal(KernelGlobals *kg, int prim, float
 	float t = 1.0f - u - v;
 	*P = (u*v0 + v*v1 + t*v2);
 
-	float4 Nm = kernel_tex_fetch(__tri_normal, prim);
-	*Ng = make_float3(Nm.x, Nm.y, Nm.z);
-	*shader = __float_as_int(Nm.w);
+	/* compute normal */
+	*Ng = normalize(cross(v1 - v0, v2 - v0));
+
+	/* shader`*/
+	*shader = __float_as_int(kernel_tex_fetch(__tri_shader, prim));
 }
 
 /* Triangle vertex locations */