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, 1 insertions, 0 deletions

diff --git a/source/blender/blenkernel/particle_private.h b/source/blender/blenkernel/particle_private.h
index 00a7637e246..2189527118b 100644
--- a/source/blender/blenkernel/particle_private.h
+++ b/source/blender/blenkernel/particle_private.h
@@ -41,6 +41,7 @@ typedef struct ParticleChildModifierContext {
 	const float *par_rot;   /* float4 */
 	const float *par_orco;  /* float3 */
 	const float *orco;      /* float3 */
+	ParticleCacheKey *parent_keys;
 } ParticleChildModifierContext;
 
 void do_kink(ParticleKey *state, const float par_co[3], const float par_vel[3], const float par_rot[4], float time, float freq, float shape, float amplitude, float flat,