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, 26 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/particle.c b/source/blender/blenkernel/intern/particle.c
index 8aa7b167b85..ea27e23ed2f 100644
--- a/source/blender/blenkernel/intern/particle.c
+++ b/source/blender/blenkernel/intern/particle.c
@@ -405,6 +405,8 @@ void BKE_particlesettings_free(ParticleSettings *part)
 		curvemapping_free(part->clumpcurve);
 	if (part->roughcurve)
 		curvemapping_free(part->roughcurve);
+	if (part->twistcurve)
+		curvemapping_free(part->twistcurve);
 	
 	free_partdeflect(part->pd);
 	free_partdeflect(part->pd2);
@@ -2152,6 +2154,13 @@ static bool psys_thread_context_init_path(
 	else {
 		ctx->roughcurve = NULL;
 	}
+	if ((part->child_flag & PART_CHILD_USE_TWIST_CURVE) && part->twistcurve) {
+		ctx->twistcurve = curvemapping_copy(part->twistcurve);
+		curvemapping_changed_all(ctx->twistcurve);
+	}
+	else {
+		ctx->twistcurve = NULL;
+	}
 
 	return true;
 }
@@ -3337,6 +3346,18 @@ void BKE_particlesettings_rough_curve_init(ParticleSettings *part)
 	part->roughcurve = cumap;
 }
 
+void BKE_particlesettings_twist_curve_init(ParticleSettings *part)
+{
+	CurveMapping *cumap = curvemapping_add(1, 0.0f, 0.0f, 1.0f, 1.0f);
+
+	cumap->cm[0].curve[0].x = 0.0f;
+	cumap->cm[0].curve[0].y = 1.0f;
+	cumap->cm[0].curve[1].x = 1.0f;
+	cumap->cm[0].curve[1].y = 1.0f;
+
+	part->twistcurve = cumap;
+}
+
 /**
  * Only copy internal data of ParticleSettings ID from source to already allocated/initialized destination.
  * You probably nerver want to use that directly, use id_copy or BKE_id_copy_ex for typical needs.
@@ -3359,6 +3380,9 @@ void BKE_particlesettings_copy_data(
 	if (part_src->roughcurve) {
 		part_dst->roughcurve = curvemapping_copy(part_src->roughcurve);
 	}
+	if (part_src->twistcurve) {
+		part_dst->twistcurve = curvemapping_copy(part_src->twistcurve);
+	}
 
 	part_dst->boids = boid_copy_settings(part_src->boids);
 
@@ -3935,6 +3959,7 @@ void psys_get_particle_on_path(ParticleSimulationData *sim, int p, ParticleKey *
 			modifier_ctx.par_vel = par->vel;
 			modifier_ctx.par_rot = par->rot;
 			modifier_ctx.par_orco = par_orco;
+			modifier_ctx.parent_keys = psys->childcache ? psys->childcache[p - totpart] : NULL;
 			do_child_modifiers(&modifier_ctx, hairmat, state, t);
 
 			/* try to estimate correct velocity */
@@ -4048,6 +4073,7 @@ int psys_get_particle_state(ParticleSimulationData *sim, int p, ParticleKey *sta
 			modifier_ctx.par_vel = key1->vel;
 			modifier_ctx.par_rot = key1->rot;
 			modifier_ctx.par_orco = par_orco;
+			modifier_ctx.parent_keys = psys->childcache ? psys->childcache[p - totpart] : NULL;
 
 			do_child_modifiers(&modifier_ctx, mat, state, t);