Cycles Hair: Strand Minimum Pixel Size

Code is added to restrict the pixel size of strands in cycles. It works best with ribbon primitives and a preset for these is included. It uses distance dependent expansion of the strands and then stochastic strand removal to give a fading. To prevent a slowdown for triangle mesh objects in the BVH an extra visibility flag has been added. It is also only applied for camera rays.

The strand width settings are also changed, so that the particle size is not included in the width calculation. Instead there is a separate particle system parameter for width scaling.

1 files changed, 9 insertions, 1 deletions

diff --git a/intern/cycles/blender/blender_curves.cpp b/intern/cycles/blender/blender_curves.cpp
index 768a5a6ee3a..4e0aad8ad14 100644
--- a/intern/cycles/blender/blender_curves.cpp
+++ b/intern/cycles/blender/blender_curves.cpp
@@ -195,7 +195,7 @@ bool ObtainCacheParticleData(Mesh *mesh, BL::Mesh *b_mesh, BL::Object *b_ob, Par
 				CData->psys_curvenum.push_back(totcurves);
 				CData->psys_shader.push_back(shader);
 
-				float radius = b_psys.settings().particle_size() * 0.5f;
+				float radius = get_float(cpsys, "radius_scale") * 0.5f;
 	
 				CData->psys_rootradius.push_back(radius * get_float(cpsys, "root_width"));
 				CData->psys_tipradius.push_back(radius * get_float(cpsys, "tip_width"));
@@ -884,6 +884,8 @@ void BlenderSync::sync_curve_settings()
 	CurveSystemManager prev_curve_system_manager = *curve_system_manager;
 
 	curve_system_manager->use_curves = get_boolean(csscene, "use_curves");
+	curve_system_manager->minimum_width = get_float(csscene, "minimum_width");
+	curve_system_manager->maximum_width = get_float(csscene, "maximum_width");
 
 	if(preset == CURVE_CUSTOM) {
 		/*custom properties*/
@@ -957,6 +959,12 @@ void BlenderSync::sync_curve_settings()
 				curve_system_manager->use_backfacing = true;
 				curve_system_manager->subdivisions = 4;
 				break;
+			case CURVE_SMOOTH_RIBBONS:
+				/*Cardinal ribbons preset*/
+				curve_system_manager->primitive = CURVE_RIBBONS;
+				curve_system_manager->use_backfacing = false;
+				curve_system_manager->subdivisions = 4;
+				break;
 		}
 		
 	}