"Fix" for [#30098] Particle rotation wrong / explode modifier

- The main problem was that in order to be accurate all particle
  rotations have to be calculated incrementally so the only working
  solution is to store rotations to the point cache (previously
  this was only done for dynamic rotations). This can nearly double
  the point cache size so it's not ideal to have this as a default
  as in many cases you don't care about particle rotations.
- Particle rotation panel now has a new "enable" checkbox that
  enables rotation calculations and the storing of rotations to
  point cache.
- Old files will have rotations enabled via do_versions so that in
  the worst case old files will only get bigger point caches, but no
  sudden loss of particle rotations.

1 files changed, 6 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/particle_system.c b/source/blender/blenkernel/intern/particle_system.c
index 8b34bafc417..c3e7e4531b9 100644
--- a/source/blender/blenkernel/intern/particle_system.c
+++ b/source/blender/blenkernel/intern/particle_system.c
@@ -2684,6 +2684,12 @@ static void basic_rotate(ParticleSettings *part, ParticleData *pa, float dfra, f
 {
 	float rotfac, rot1[4], rot2[4]={1.0,0.0,0.0,0.0}, dtime=dfra*timestep;
 
+	if((part->flag & PART_ROTATIONS)==0) {
+		pa->state.rot[0]=1.0f;
+		pa->state.rot[1]=pa->state.rot[2]=pa->state.rot[3]=0;
+		return;
+	}
+
 	if((part->flag & PART_ROT_DYN)==0) {
 		if(part->avemode==PART_AVE_SPIN) {
 			float angle;