Simple hair children: Initial implementation of twist control

It allows to have children hair to be twisted around parent curve, which is
quite an essential feature when creating hair braids.

There are currently two controls:

- Number of turns around parent children.
- Influence curve, which allows to modify "twistness" along the strand.

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_particle.h b/source/blender/blenkernel/BKE_particle.h
index 2c72373c2a9..747a6b65bb0 100644
--- a/source/blender/blenkernel/BKE_particle.h
+++ b/source/blender/blenkernel/BKE_particle.h
@@ -162,6 +162,7 @@ typedef struct ParticleThreadContext {
 
 	struct CurveMapping *clumpcurve;
 	struct CurveMapping *roughcurve;
+	struct CurveMapping *twistcurve;
 } ParticleThreadContext;
 
 typedef struct ParticleTask {
@@ -349,6 +350,7 @@ int psys_get_particle_state(struct ParticleSimulationData *sim, int p, struct Pa
 /* child paths */
 void BKE_particlesettings_clump_curve_init(struct ParticleSettings *part);
 void BKE_particlesettings_rough_curve_init(struct ParticleSettings *part);
+void BKE_particlesettings_twist_curve_init(struct ParticleSettings *part);
 void psys_apply_child_modifiers(struct ParticleThreadContext *ctx, struct ListBase *modifiers,
                                 struct ChildParticle *cpa, struct ParticleTexture *ptex, const float orco[3], const float ornor[3], float hairmat[4][4],
                                 struct ParticleCacheKey *keys, struct ParticleCacheKey *parent_keys, const float parent_orco[3]);