intern/cycles/kernel/closure/bsdf_hair_microfacet.h

@@ -16,7 +16,7 @@ typedef struct MicrofacetHairExtra {
   float TT;
   float TRT;
 
-  float eccentricity;
+  float aspect_ratio;
 
   /* Geometry data. */
   float4 geom;
@@ -844,7 +844,7 @@ ccl_device float3 bsdf_microfacet_hair_eval_r_elliptic(ccl_private const ShaderC
   /* get elliptical cross section characteristic */
   const float a = 1.0f;
   /* TODO: rename this as aspect ratio? e is in [0, 0.85], b is in [0.52, 1]. */
-  const float b = bsdf->extra->eccentricity;
+  const float b = bsdf->extra->aspect_ratio;
   const float e2 = 1.0f - sqr(b / a);
 
   /* this follows blender's convention (unlike the circular case?) */
@@ -966,8 +966,8 @@ ccl_device float3 bsdf_microfacet_hair_eval_tt_trt_elliptic(KernelGlobals kg,
 
   /* get elliptical cross section characteristic */
   const float a = 1.0f;
-  const float b = bsdf->extra->eccentricity;
-  const float e2 = 1.0f - sqr(b / a);
+  const float b = bsdf->extra->aspect_ratio;
+  const float e2 = 1.0f - sqr(b / a); /* Squared Eccentricity. */
 
   float gamma_m_min = to_gamma(phi_m_min, a, b) + 1e-3f;
   float gamma_m_max = to_gamma(phi_m_max, a, b) - 1e-3f;
@@ -1138,7 +1138,7 @@ ccl_device Spectrum bsdf_microfacet_hair_eval_elliptic(KernelGlobals kg,
   const float3 wo = make_float3(dot(omega_in, X), dot(omega_in, Y), dot(omega_in, Z));
 
   /* Treat as transparent material if intersection lies outside of the projected radius. */
-  const float e2 = 1.0f - sqr(bsdf->extra->eccentricity);
+  const float e2 = 1.0f - sqr(bsdf->extra->aspect_ratio);
   const float radius = sqrtf(1.0f - e2 * sqr(sin_phi(wi)));
   if (fabsf(bsdf->extra->geom.w) > radius) {
     *pdf = 0.0f;
@@ -1180,7 +1180,7 @@ ccl_device int bsdf_microfacet_hair_sample_elliptic(const KernelGlobals kg,
 
   /* get elliptical cross section characteristic */
   const float a = 1.0f;
-  const float b = bsdf->extra->eccentricity;
+  const float b = bsdf->extra->aspect_ratio;
   const float e2 = 1.0f - sqr(b / a);
 
   /* macronormal */

intern/cycles/kernel/svm/closure.h

@@ -1017,20 +1017,20 @@ ccl_device_noinline int svm_node_closure_bsdf(KernelGlobals kg,
         if (model_type == NODE_MICROFACET_HAIR_ELLIPTIC_GGX ||
             model_type == NODE_MICROFACET_HAIR_ELLIPTIC_BECKMANN) {
 
-          uint eccentricity_ofs, temp;
-          svm_unpack_node_uchar4(data_node5.x, &eccentricity_ofs, &temp, &temp, &temp);
+          uint aspect_ratio_ofs, temp;
+          svm_unpack_node_uchar4(data_node5.x, &aspect_ratio_ofs, &temp, &temp, &temp);
 
-          float eccentricity = stack_load_float_default(stack, eccentricity_ofs, data_node5.y);
+          float aspect_ratio = stack_load_float_default(stack, aspect_ratio_ofs, data_node5.y);
 
-          /* Eccentricity */
-          bsdf->extra->eccentricity = (eccentricity > 1.0f) ? 1.0f / eccentricity : eccentricity;
+          /* Aspect Ratio */
+          bsdf->extra->aspect_ratio = (aspect_ratio > 1.0f) ? 1.0f / aspect_ratio : aspect_ratio;
 
           const AttributeDescriptor attr_descr_normal = find_attribute(kg, sd, data_node5.z);
           const float3 normal = curve_attribute_float3(kg, sd, attr_descr_normal, NULL, NULL);
           const float3 binormal = safe_normalize(cross(sd->dPdu, normal));
 
           /* Align X axis with the ellipse major axis. */
-          if (eccentricity > 1.0f) {
+          if (aspect_ratio > 1.0f) {
             const float3 normal = safe_normalize(cross(binormal, sd->dPdu));
             bsdf->extra->geom = make_float4(normal.x, normal.y, normal.z, 0.0f);
           }

intern/cycles/scene/shader_nodes.cpp

@@ -3665,7 +3665,7 @@ NODE_DEFINE(MicrofacetHairBsdfNode)
                    make_float3(0.245531f, 0.52f, 1.365f),
                    SocketType::VECTOR);
 
-  SOCKET_IN_FLOAT(eccentricity, "Eccentricity", 0.85f);
+  SOCKET_IN_FLOAT(aspect_ratio, "Aspect Ratio", 0.85f);
 
   SOCKET_IN_FLOAT(offset, "Offset", 2.f * M_PI_F / 180.f);
   SOCKET_IN_FLOAT(roughness, "Roughness", 0.3f);
@@ -3725,7 +3725,7 @@ void MicrofacetHairBsdfNode::compile(SVMCompiler &compiler)
   ShaderInput *TRT_in = input("TRT lobe");
   ShaderInput *Blur_in = input("Blur");
 
-  ShaderInput *eccentricity_in = input("Eccentricity");
+  ShaderInput *aspect_ratio_in = input("Aspect Ratio");
 
   int color_ofs = compiler.stack_assign(input("Color"));
   int tint_ofs = compiler.stack_assign(input("Tint"));
@@ -3789,11 +3789,11 @@ void MicrofacetHairBsdfNode::compile(SVMCompiler &compiler)
                     __float_as_uint(TRT));
 
   /* data node 5 */
-  compiler.add_node(compiler.encode_uchar4(compiler.stack_assign_if_linked(eccentricity_in),
+  compiler.add_node(compiler.encode_uchar4(compiler.stack_assign_if_linked(aspect_ratio_in),
                                            SVM_STACK_INVALID,
                                            SVM_STACK_INVALID,
                                            SVM_STACK_INVALID),
-                    __float_as_uint(eccentricity),
+                    __float_as_uint(aspect_ratio),
                     compiler.attribute(ATTR_STD_VERTEX_NORMAL),
                     0);
 }

intern/cycles/scene/shader_nodes.h

@@ -907,8 +907,8 @@ class MicrofacetHairBsdfNode : public BsdfBaseNode {
   /* Absorption coefficient (unfiltered). */
   NODE_SOCKET_API(float3, absorption_coefficient)
 
-  /* Eccentricity. */
-  NODE_SOCKET_API(float, eccentricity)
+  /* Aspect Ratio. */
+  NODE_SOCKET_API(float, aspect_ratio)
   /* Randomization factor for axis rotation. */
   NODE_SOCKET_API(float, random_axis)
   /* Twist rate. */

source/blender/gpu/shaders/material/gpu_shader_material_hair.glsl

@@ -56,7 +56,7 @@ void node_bsdf_hair_microfacet(vec4 color,
                                float TRT,
                                float ior,
                                float offset,
-                               float eccentricity,
+                               float aspect_ratio,
                                float random_axis,
                                float twist_rate,
                                float Blur,

source/blender/nodes/shader/nodes/node_shader_bsdf_hair_microfacet.cc

@@ -27,7 +27,7 @@ static void node_declare(NodeDeclarationBuilder &b)
       .default_value({0.245531f, 0.52f, 1.365f})
       .min(0.0f)
       .max(1000.0f);
-  b.add_input<decl::Float>(N_("Eccentricity"))
+  b.add_input<decl::Float>(N_("Aspect Ratio"))
       .default_value(0.85f)
       .min(0.0f)
       .max(1.0f)
@@ -124,7 +124,7 @@ static void node_shader_update_hair_microfacet(bNodeTree *ntree, bNode *node)
       nodeSetSocketAvailability(
           ntree, sock, parametrization == SHD_MICROFACET_HAIR_PIGMENT_CONCENTRATION);
     }
-    else if (STREQ(sock->name, "Eccentricity")) {
+    else if (STREQ(sock->name, "Aspect Ratio")) {
       nodeSetSocketAvailability(ntree, sock, elliptical);
     }
   }