[Bf-blender-cvs] [1a918cb] master: Fix for slow deformation-motionblur in Cycles using the new spiral kink mode.

[Lukas Tönne]

Commit: 1a918cb66e45d2bfa1ac2153c08f81b09429695a
Author: Lukas Tönne
Date:   Fri Jan 16 16:04:10 2015 +0100
Branches: master
https://developer.blender.org/rB1a918cb66e45d2bfa1ac2153c08f81b09429695a

Fix for slow deformation-motionblur in Cycles using the new spiral kink
mode.

This was caused by variation of the number of keys on child hairs due
to shortening of hair curves based on euclidian distances. The other
kink modes also shorten hairs, but use the parametric distance instead,
which does not vary with deformation of hairs.

===================================================================

M	source/blender/blenkernel/intern/particle_child.c

===================================================================

diff --git a/source/blender/blenkernel/intern/particle_child.c b/source/blender/blenkernel/intern/particle_child.c
index 5bc79d1..fb877e4 100644
--- a/source/blender/blenkernel/intern/particle_child.c
+++ b/source/blender/blenkernel/intern/particle_child.c
@@ -199,10 +199,11 @@ static void do_kink_spiral(ParticleThreadContext *ctx, ParticleTexture *ptex, co
 	float spiral_par_co[3] = {0.0f, 0.0f, 0.0f};
 	float spiral_par_vel[3] = {0.0f, 0.0f, 0.0f};
 	float spiral_par_rot[4] = {1.0f, 0.0f, 0.0f, 0.0f};
-	float len, totlen, cutlen;
+	float totlen;
+	float cut_time;
 	int start_index = 0, end_index = 0;
 	float kink_base[3];
-
+	
 	if (ptex) {
 		kink_amp *= ptex->kink_amp;
 		kink_freq *= ptex->kink_freq;
@@ -211,19 +212,12 @@ static void do_kink_spiral(ParticleThreadContext *ctx, ParticleTexture *ptex, co
 		rough_end *= ptex->roughe;
 	}
 	
-	totlen = 0.0f;
-	for (k = 0, key = keys; k < totkeys-1; k++, key++)
-		totlen += len_v3v3((key+1)->co, key->co);
-	
-	cutlen = max_ff(ptex->length * totlen - fabsf(kink_amp), 0.0f);
+	cut_time = (totkeys - 1) * ptex->length;
 	zero_v3(spiral_start);
 	
-	len = 0.0f;
 	for (k = 0, key = keys; k < totkeys-1; k++, key++) {
-		float seglen = len_v3v3((key+1)->co, key->co);
-		
-		if (seglen > 0.0f && len + seglen >= cutlen) {
-			float fac = (cutlen - len) / seglen;
+		if ((float)(k + 1) >= cut_time) {
+			float fac = cut_time - (float)k;
 			ParticleCacheKey *par = parent_keys + k;
 			
 			start_index = k + 1;
@@ -238,7 +232,6 @@ static void do_kink_spiral(ParticleThreadContext *ctx, ParticleTexture *ptex, co
 			
 			break;
 		}
-		len += seglen;
 	}
 	
 	zero_v3(dir);