Subframe calculations for particles, original patch by Raul Fernandez Hernandez

* Increasing subframe count increases stability for SPH fluid and Newtonian particles
* Also small tweaks into physics ui panel to better fit new subframes value
* This commit also fixes the moving fluid emitter problem as described by Raul in the mailinglist

3 files changed, 17 insertions, 8 deletions

diff --git a/source/blender/blenkernel/intern/particle_system.c b/source/blender/blenkernel/intern/particle_system.c
index 54abfd8fd40..389b31a20c7 100644
--- a/source/blender/blenkernel/intern/particle_system.c
+++ b/source/blender/blenkernel/intern/particle_system.c
@@ -2308,8 +2308,7 @@ void particle_fluidsim(ParticleSystem *psys, ParticleData *pa, ParticleSettings
 	VECCOPY(start, pa->prev_state.co);
 	VECCOPY(end, pa->state.co);
 
-	sub_v3_v3v3(v, end, start);
-	mul_v3_fl(v, 1.f/dtime);
+	VECCOPY(v, pa->state.vel);
 
 	neighbours = BLI_kdtree_range_search(tree, radius, start, NULL, &ptn);
 
@@ -3790,18 +3789,23 @@ static void system_step(ParticleSimulationData *sim, float cfra)
 	}
 
 	if(psys->totpart) {
-		int dframe, totframesback = 0;
-
+		int dframe, subframe = 0, totframesback = 0, totsubframe = part->subframes+1;
+		float fraction;
+		
 		/* handle negative frame start at the first frame by doing
 		 * all the steps before the first frame */
 		if(framenr == startframe && part->sta < startframe)
 			totframesback = (startframe - (int)part->sta);
-
+		
 		for(dframe=-totframesback; dframe<=0; dframe++) {
 			/* ok now we're all set so let's go */
-			dynamics_step(sim, cfra+dframe);
-			psys->cfra = cfra+dframe;
+			for (subframe = 1; subframe <= totsubframe; subframe++) {
+				fraction = (float)subframe/(float)totsubframe;
+				dynamics_step(sim, cfra+dframe+fraction - 1.f);
+				psys->cfra = cfra+dframe+fraction - 1.f;
+			}
 		}
+		
 	}
 	
 /* 4. only write cache starting from second frame */
diff --git a/source/blender/makesdna/DNA_particle_types.h b/source/blender/makesdna/DNA_particle_types.h
index 8367875aa7a..105fa6d5289 100644
--- a/source/blender/makesdna/DNA_particle_types.h
+++ b/source/blender/makesdna/DNA_particle_types.h
@@ -136,7 +136,7 @@ typedef struct ParticleSettings {
 	/* physics modes */
 	short phystype, rotmode, avemode, reactevent;
 	short draw, draw_as, draw_size, childtype;
-	short ren_as, rt2;
+	short ren_as, subframes;
 	/* number of path segments, power of 2 except */
 	short draw_step, ren_step;
 	short hair_step, keys_step;
diff --git a/source/blender/makesrna/intern/rna_particle.c b/source/blender/makesrna/intern/rna_particle.c
index 4e8776eff6a..4e728d57290 100644
--- a/source/blender/makesrna/intern/rna_particle.c
+++ b/source/blender/makesrna/intern/rna_particle.c
@@ -1476,6 +1476,11 @@ static void rna_def_particle_settings(BlenderRNA *brna)
 	RNA_def_property_ui_range(prop, 0, 10, 1, 3);
 	RNA_def_property_ui_text(prop, "Tweak", "A multiplier for physics timestep (1.0 means one frame = 1/25 seconds)");
 	RNA_def_property_update(prop, 0, "rna_Particle_reset");
+	
+	prop= RNA_def_property(srna, "subframes", PROP_INT, PROP_NONE);
+	RNA_def_property_range(prop, 0, 1000);	
+	RNA_def_property_ui_text(prop, "Subframes", "Subframes to simulate for improved stability and finer granularity simulations");
+	RNA_def_property_update(prop, 0, "rna_Particle_reset");
 
 	prop= RNA_def_property(srna, "jitter_factor", PROP_FLOAT, PROP_NONE);
 	RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);