Hair Info Length Attribute

Goal is to add the length attribute to the Hair Info node, for better control over color gradients or similar along the hair.

Reviewed By: #eevee_viewport, brecht

Differential Revision: https://developer.blender.org/D10481

1 files changed, 6 insertions, 1 deletions

diff --git a/source/blender/nodes/shader/nodes/node_shader_hair_info.c b/source/blender/nodes/shader/nodes/node_shader_hair_info.c
index 843185befb6..559c5cf7ae8 100644
--- a/source/blender/nodes/shader/nodes/node_shader_hair_info.c
+++ b/source/blender/nodes/shader/nodes/node_shader_hair_info.c
@@ -22,6 +22,7 @@
 static bNodeSocketTemplate outputs[] = {
     {SOCK_FLOAT, N_("Is Strand"), 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
     {SOCK_FLOAT, N_("Intercept"), 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
+    {SOCK_FLOAT, N_("Length"), 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
     {SOCK_FLOAT, N_("Thickness"), 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
     {SOCK_VECTOR, N_("Tangent Normal"), 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
     // { SOCK_FLOAT,  0, N_("Fade"),             0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
@@ -35,7 +36,11 @@ static int node_shader_gpu_hair_info(GPUMaterial *mat,
                                      GPUNodeStack *in,
                                      GPUNodeStack *out)
 {
-  return GPU_stack_link(mat, node, "node_hair_info", in, out);
+  /* Length: don't request length if not needed. */
+  const static float zero = 0;
+  GPUNodeLink *length_link = (!out[2].hasoutput) ? GPU_constant(&zero) :
+                                                   GPU_attribute(mat, CD_HAIRLENGTH, "");
+  return GPU_stack_link(mat, node, "node_hair_info", in, out, length_link);
 }
 
 /* node type definition */