Cycles code refactor: improve vertex motion attribute storage and export.

This now supports multiple steps and subframe sampling of motion.

There is one difference for object and camera transform motion blur. It still
only supports two steps there, but the transforms are now sampled at subframe
times instead of the previous and next frame and then interpolated/extrapolated.
This will give different render results in some cases but it's more accurate.

Part of the code is from the summer of code project by Gavin Howard, but it has
been significantly rewritten and extended.

1 files changed, 36 insertions, 16 deletions

diff --git a/intern/cycles/blender/blender_curves.cpp b/intern/cycles/blender/blender_curves.cpp
index 4420a306e31..22de7b64273 100644
--- a/intern/cycles/blender/blender_curves.cpp
+++ b/intern/cycles/blender/blender_curves.cpp
@@ -612,16 +612,23 @@ void ExportCurveSegments(Scene *scene, Mesh *mesh, ParticleCurveData *CData)
 	}
 }
 
-static void ExportCurveSegmentsMotion(Scene *scene, Mesh *mesh, ParticleCurveData *CData, int motion)
+static void ExportCurveSegmentsMotion(Scene *scene, Mesh *mesh, ParticleCurveData *CData, int time_index)
 {
+	/* find attribute */
+	Attribute *attr_mP = mesh->curve_attributes.find(ATTR_STD_MOTION_VERTEX_POSITION);
+	bool new_attribute = false;
+
+	/* add new attribute if it doesn't exist already */
+	if(!attr_mP) {
+		attr_mP = mesh->curve_attributes.add(ATTR_STD_MOTION_VERTEX_POSITION);
+		new_attribute = true;
+	}
+
 	/* export motion vectors for curve keys */
-	AttributeStandard std = (motion == -1)? ATTR_STD_MOTION_PRE: ATTR_STD_MOTION_POST;
-	Attribute *attr_motion = mesh->curve_attributes.add(std);
-	float4 *data_motion = attr_motion->data_float4();
-	float4 *current_motion = data_motion;
-	size_t size = mesh->curve_keys.size();
-	size_t i = 0;
+	size_t numkeys = mesh->curve_keys.size();
+	float4 *mP = attr_mP->data_float4() + time_index*numkeys;
 	bool have_motion = false;
+	int i = 0;
 
 	for(int sys = 0; sys < CData->psys_firstcurve.size(); sys++) {
 		if(CData->psys_curvenum[sys] == 0)
@@ -640,16 +647,14 @@ static void ExportCurveSegmentsMotion(Scene *scene, Mesh *mesh, ParticleCurveDat
 					if(CData->psys_closetip[sys] && (curvekey == CData->curve_firstkey[curve] + CData->curve_keynum[curve] - 1))
 						radius = 0.0f;
 
-					*current_motion = float3_to_float4(ickey_loc);
-					current_motion->w = radius;
+					mP[i] = float3_to_float4(ickey_loc);
+					mP[i].w = radius;
 
 					/* unlike mesh coordinates, these tend to be slightly different
 					 * between frames due to particle transforms into/out of object
 					 * space, so we use an epsilon to detect actual changes */
-					if(len_squared(*current_motion - mesh->curve_keys[i]) > 1e-5f*1e-5f)
+					if(len_squared(mP[i] - mesh->curve_keys[i]) > 1e-5f*1e-5f)
 						have_motion = true;
-
-					current_motion++;
 				}
 
 				i++;
@@ -657,8 +662,23 @@ static void ExportCurveSegmentsMotion(Scene *scene, Mesh *mesh, ParticleCurveDat
 		}
 	}
 
-	if(i != size || !have_motion)
-		mesh->curve_attributes.remove(std);
+	/* in case of new attribute, we verify if there really was any motion */
+	if(new_attribute) {
+		if(i != numkeys || !have_motion) {
+			/* no motion, remove attributes again */
+			mesh->curve_attributes.remove(ATTR_STD_MOTION_VERTEX_POSITION);
+		}
+		else if(time_index > 0) {
+			/* motion, fill up previous steps that we might have skipped because
+			 * they had no motion, but we need them anyway now */
+			for(int step = 0; step < time_index; step++) {
+				float4 *mP = attr_mP->data_float4() + step*numkeys;
+
+				for(int key = 0; key < numkeys; key++)
+					mP[key] = mesh->curve_keys[key];
+			}
+		}
+	}
 }
 
 void ExportCurveTriangleUV(Mesh *mesh, ParticleCurveData *CData, int vert_offset, int resol, float3 *uvdata)
@@ -804,7 +824,7 @@ void BlenderSync::sync_curve_settings()
 		curve_system_manager->tag_update(scene);
 }
 
-void BlenderSync::sync_curves(Mesh *mesh, BL::Mesh b_mesh, BL::Object b_ob, int motion)
+void BlenderSync::sync_curves(Mesh *mesh, BL::Mesh b_mesh, BL::Object b_ob, bool motion, int time_index)
 {
 	if(!motion) {
 		/* Clear stored curve data */
@@ -859,7 +879,7 @@ void BlenderSync::sync_curves(Mesh *mesh, BL::Mesh b_mesh, BL::Object b_ob, int
 	}
 	else {
 		if(motion)
-			ExportCurveSegmentsMotion(scene, mesh, &CData, motion);
+			ExportCurveSegmentsMotion(scene, mesh, &CData, time_index);
 		else
 			ExportCurveSegments(scene, mesh, &CData);
 	}