Curves: use consistent default radius for Cycles, Eevee, Set Curve Radius node

To avoid Cycles not showing any hair by default, and to avoid very slow render
due to many overlaps with the previous 1 meter default in the node.

Fixes T97584, T99319

Differential Revision: https://developer.blender.org/D15405

intern/cycles/blender/curves.cpp

@@ -868,7 +868,7 @@ static void export_hair_curves(Scene *scene,
     for (int i = 0; i < num_points; i++) {
       const float3 co = get_float3(b_curves.position_data[first_point_index + i].vector());
       const float radius = b_attr_radius ? b_attr_radius->data[first_point_index + i].value() :
-                                           0.0f;
+                                           0.005f;
       hair->add_curve_key(co, radius);
 
       if (attr_intercept) {

source/blender/nodes/geometry/nodes/node_geo_set_curve_radius.cc

@@ -10,7 +10,7 @@ static void node_declare(NodeDeclarationBuilder &b)
   b.add_input<decl::Bool>(N_("Selection")).default_value(true).hide_value().supports_field();
   b.add_input<decl::Float>(N_("Radius"))
       .min(0.0f)
-      .default_value(1.0f)
+      .default_value(0.005f)
       .supports_field()
       .subtype(PROP_DISTANCE);
   b.add_output<decl::Geometry>(N_("Curve"));