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

9 files changed, 41 insertions, 0 deletions

diff --git a/intern/cycles/blender/blender_curves.cpp b/intern/cycles/blender/blender_curves.cpp
index 6fe5ea41fff..c7851e40543 100644
--- a/intern/cycles/blender/blender_curves.cpp
+++ b/intern/cycles/blender/blender_curves.cpp
@@ -283,10 +283,13 @@ static void ExportCurveSegments(Scene *scene, Hair *hair, ParticleCurveData *CDa
     return;
 
   Attribute *attr_intercept = NULL;
+  Attribute *attr_length = NULL;
   Attribute *attr_random = NULL;
 
   if (hair->need_attribute(scene, ATTR_STD_CURVE_INTERCEPT))
     attr_intercept = hair->attributes.add(ATTR_STD_CURVE_INTERCEPT);
+  if (hair->need_attribute(scene, ATTR_STD_CURVE_LENGTH))
+    attr_length = hair->attributes.add(ATTR_STD_CURVE_LENGTH);
   if (hair->need_attribute(scene, ATTR_STD_CURVE_RANDOM))
     attr_random = hair->attributes.add(ATTR_STD_CURVE_RANDOM);
 
@@ -336,6 +339,11 @@ static void ExportCurveSegments(Scene *scene, Hair *hair, ParticleCurveData *CDa
         num_curve_keys++;
       }
 
+      if (attr_length != NULL)
+      {
+        attr_length->add(CData->curve_length[curve]);
+      }
+
       if (attr_random != NULL) {
         attr_random->add(hash_uint2_to_float(num_curves, 0));
       }
@@ -657,11 +665,16 @@ static void export_hair_curves(Scene *scene, Hair *hair, BL::Hair b_hair)
 
   /* Add requested attributes. */
   Attribute *attr_intercept = NULL;
+  Attribute *attr_length = NULL;
   Attribute *attr_random = NULL;
 
   if (hair->need_attribute(scene, ATTR_STD_CURVE_INTERCEPT)) {
     attr_intercept = hair->attributes.add(ATTR_STD_CURVE_INTERCEPT);
   }
+  if (hair->need_attribute(scene, ATTR_STD_CURVE_LENGTH))
+  {
+    attr_length = hair->attributes.add(ATTR_STD_CURVE_LENGTH);
+  }
   if (hair->need_attribute(scene, ATTR_STD_CURVE_RANDOM)) {
     attr_random = hair->attributes.add(ATTR_STD_CURVE_RANDOM);
   }
@@ -714,6 +727,11 @@ static void export_hair_curves(Scene *scene, Hair *hair, BL::Hair b_hair)
       }
     }
 
+  	if (attr_length) 
+    {
+      attr_length->add(length);
+    }
+
     /* Random number per curve. */
     if (attr_random != NULL) {
       attr_random->add(hash_uint2_to_float(b_curve.index(), 0));
diff --git a/intern/cycles/kernel/kernel_types.h b/intern/cycles/kernel/kernel_types.h
index 66b7310ab65..3cc42bf7a85 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -572,6 +572,7 @@ typedef enum AttributeStandard {
   ATTR_STD_MOTION_VERTEX_NORMAL,
   ATTR_STD_PARTICLE,
   ATTR_STD_CURVE_INTERCEPT,
+  ATTR_STD_CURVE_LENGTH,
   ATTR_STD_CURVE_RANDOM,
   ATTR_STD_PTEX_FACE_ID,
   ATTR_STD_PTEX_UV,
diff --git a/intern/cycles/kernel/osl/osl_services.cpp b/intern/cycles/kernel/osl/osl_services.cpp
index 396f42080e4..4fc46a255a8 100644
--- a/intern/cycles/kernel/osl/osl_services.cpp
+++ b/intern/cycles/kernel/osl/osl_services.cpp
@@ -107,6 +107,7 @@ ustring OSLRenderServices::u_geom_undisplaced("geom:undisplaced");
 ustring OSLRenderServices::u_is_smooth("geom:is_smooth");
 ustring OSLRenderServices::u_is_curve("geom:is_curve");
 ustring OSLRenderServices::u_curve_thickness("geom:curve_thickness");
+ustring OSLRenderServices::u_curve_length("geom:curve_length");
 ustring OSLRenderServices::u_curve_tangent_normal("geom:curve_tangent_normal");
 ustring OSLRenderServices::u_curve_random("geom:curve_random");
 ustring OSLRenderServices::u_path_ray_length("path:ray_length");
diff --git a/intern/cycles/kernel/osl/osl_services.h b/intern/cycles/kernel/osl/osl_services.h
index 58accb46e7d..2a5400282b3 100644
--- a/intern/cycles/kernel/osl/osl_services.h
+++ b/intern/cycles/kernel/osl/osl_services.h
@@ -294,6 +294,7 @@ class OSLRenderServices : public OSL::RendererServices {
   static ustring u_is_smooth;
   static ustring u_is_curve;
   static ustring u_curve_thickness;
+  static ustring u_curve_length;
   static ustring u_curve_tangent_normal;
   static ustring u_curve_random;
   static ustring u_path_ray_length;
diff --git a/intern/cycles/kernel/shaders/node_hair_info.osl b/intern/cycles/kernel/shaders/node_hair_info.osl
index ee08ea57e68..ddc2e28b83a 100644
--- a/intern/cycles/kernel/shaders/node_hair_info.osl
+++ b/intern/cycles/kernel/shaders/node_hair_info.osl
@@ -18,12 +18,14 @@
 
 shader node_hair_info(output float IsStrand = 0.0,
                       output float Intercept = 0.0,
+                      output float Length = 0.0,
                       output float Thickness = 0.0,
                       output normal TangentNormal = N,
                       output float Random = 0)
 {
   getattribute("geom:is_curve", IsStrand);
   getattribute("geom:curve_intercept", Intercept);
+  getattribute("geom:curve_length", Length);
   getattribute("geom:curve_thickness", Thickness);
   getattribute("geom:curve_tangent_normal", TangentNormal);
   getattribute("geom:curve_random", Random);
diff --git a/intern/cycles/kernel/svm/svm_geometry.h b/intern/cycles/kernel/svm/svm_geometry.h
index 10e9f291d0e..432529eb061 100644
--- a/intern/cycles/kernel/svm/svm_geometry.h
+++ b/intern/cycles/kernel/svm/svm_geometry.h
@@ -213,6 +213,8 @@ ccl_device_noinline void svm_node_hair_info(
     }
     case NODE_INFO_CURVE_INTERCEPT:
       break; /* handled as attribute */
+    case NODE_INFO_CURVE_LENGTH:
+      break; /* handled as attribute */
     case NODE_INFO_CURVE_RANDOM:
       break; /* handled as attribute */
     case NODE_INFO_CURVE_THICKNESS: {
diff --git a/intern/cycles/kernel/svm/svm_types.h b/intern/cycles/kernel/svm/svm_types.h
index c053be96c51..313bc3235b9 100644
--- a/intern/cycles/kernel/svm/svm_types.h
+++ b/intern/cycles/kernel/svm/svm_types.h
@@ -173,6 +173,7 @@ typedef enum NodeParticleInfo {
 typedef enum NodeHairInfo {
   NODE_INFO_CURVE_IS_STRAND,
   NODE_INFO_CURVE_INTERCEPT,
+  NODE_INFO_CURVE_LENGTH,
   NODE_INFO_CURVE_THICKNESS,
   /* Fade for minimum hair width transiency. */
   // NODE_INFO_CURVE_FADE,
diff --git a/intern/cycles/render/attribute.cpp b/intern/cycles/render/attribute.cpp
index ea5a5f50f2d..aaf21ad9fd2 100644
--- a/intern/cycles/render/attribute.cpp
+++ b/intern/cycles/render/attribute.cpp
@@ -342,6 +342,8 @@ const char *Attribute::standard_name(AttributeStandard std)
       return "particle";
     case ATTR_STD_CURVE_INTERCEPT:
       return "curve_intercept";
+    case ATTR_STD_CURVE_LENGTH:
+      return "curve_length";
     case ATTR_STD_CURVE_RANDOM:
       return "curve_random";
     case ATTR_STD_PTEX_FACE_ID:
@@ -586,6 +588,9 @@ Attribute *AttributeSet::add(AttributeStandard std, ustring name)
       case ATTR_STD_CURVE_INTERCEPT:
         attr = add(name, TypeDesc::TypeFloat, ATTR_ELEMENT_CURVE_KEY);
         break;
+      case ATTR_STD_CURVE_LENGTH:
+        attr = add(name, TypeDesc::TypeFloat, ATTR_ELEMENT_CURVE);
+        break;
       case ATTR_STD_CURVE_RANDOM:
         attr = add(name, TypeDesc::TypeFloat, ATTR_ELEMENT_CURVE);
         break;
diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index 03b79d7de3e..e5071c25730 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -4368,6 +4368,7 @@ NODE_DEFINE(HairInfoNode)
 
   SOCKET_OUT_FLOAT(is_strand, "Is Strand");
   SOCKET_OUT_FLOAT(intercept, "Intercept");
+  SOCKET_OUT_FLOAT(size, "Length");
   SOCKET_OUT_FLOAT(thickness, "Thickness");
   SOCKET_OUT_NORMAL(tangent_normal, "Tangent Normal");
 #if 0 /* Output for minimum hair width transparency - deactivated. */
@@ -4390,6 +4391,9 @@ void HairInfoNode::attributes(Shader *shader, AttributeRequestSet *attributes)
     if (!intercept_out->links.empty())
       attributes->add(ATTR_STD_CURVE_INTERCEPT);
 
+  	if (!output("Length")->links.empty())
+      attributes->add(ATTR_STD_CURVE_LENGTH);
+
     if (!output("Random")->links.empty())
       attributes->add(ATTR_STD_CURVE_RANDOM);
   }
@@ -4412,6 +4416,12 @@ void HairInfoNode::compile(SVMCompiler &compiler)
     compiler.add_node(NODE_ATTR, attr, compiler.stack_assign(out), NODE_ATTR_OUTPUT_FLOAT);
   }
 
+  out = output("Length");
+  if (!out->links.empty()) {
+    int attr = compiler.attribute(ATTR_STD_CURVE_LENGTH);
+    compiler.add_node(NODE_ATTR, attr, compiler.stack_assign(out), NODE_ATTR_OUTPUT_FLOAT);
+  }
+
   out = output("Thickness");
   if (!out->links.empty()) {
     compiler.add_node(NODE_HAIR_INFO, NODE_INFO_CURVE_THICKNESS, compiler.stack_assign(out));