[Bf-blender-cvs] SVN commit: /data/svn/bf-blender [52948] trunk/blender: Can now set a lower bound on the number of subframes (i.e.

[Alex Fraser]

Revision: 52948
          http://projects.blender.org/scm/viewvc.php?view=rev&root=bf-blender&revision=52948
Author:   z0r
Date:     2012-12-12 22:42:55 +0000 (Wed, 12 Dec 2012)
Log Message:
-----------
Can now set a lower bound on the number of subframes (i.e. an upper bound on the time step size) for fluid simulations. Previously, the "subframes" parameter was not available when the adaptive time step was enabled; now they can both be set. The two settings can be used together to greatly increase simulation stability.

Modified Paths:
--------------
    trunk/blender/release/scripts/startup/bl_ui/properties_particle.py
    trunk/blender/source/blender/blenkernel/intern/particle_system.c
    trunk/blender/source/blender/makesrna/intern/rna_particle.c

Modified: trunk/blender/release/scripts/startup/bl_ui/properties_particle.py
===================================================================
--- trunk/blender/release/scripts/startup/bl_ui/properties_particle.py	2012-12-12 22:02:08 UTC (rev 52947)
+++ trunk/blender/release/scripts/startup/bl_ui/properties_particle.py	2012-12-12 22:42:55 UTC (rev 52948)
@@ -490,11 +490,13 @@
             col.prop(part, "integrator", text="")
             col.prop(part, "timestep")
             sub = col.row()
-            if part.adaptive_subframes:
-                sub.prop(part, "courant_target", text="Threshold")
-            else:
-                sub.prop(part, "subframes")
-            sub.prop(part, "adaptive_subframes", text="")
+            sub.prop(part, "subframes")
+            supports_courant = part.physics_type == 'FLUID'
+            subsub = sub.row()
+            subsub.enabled = supports_courant
+            subsub.prop(part, "adaptive_subframes", text="")
+            if supports_courant and part.adaptive_subframes:
+                col.prop(part, "courant_target", text="Threshold")
 
             row = layout.row()
             row.prop(part, "use_size_deflect")

Modified: trunk/blender/source/blender/blenkernel/intern/particle_system.c
===================================================================
--- trunk/blender/source/blender/blenkernel/intern/particle_system.c	2012-12-12 22:02:08 UTC (rev 52947)
+++ trunk/blender/source/blender/blenkernel/intern/particle_system.c	2012-12-12 22:42:55 UTC (rev 52948)
@@ -3781,11 +3781,12 @@
 
 /* Code for an adaptive time step based on the Courant-Friedrichs-Lewy
  * condition. */
-#define MIN_TIMESTEP 1.0f / 101.0f
+static const float MIN_TIMESTEP = 1.0f / 101.0f;
 /* Tolerance of 1.5 means the last subframe neither favors growing nor
  * shrinking (e.g if it were 1.3, the last subframe would tend to be too
  * small). */
-#define TIMESTEP_EXPANSION_TOLERANCE 1.5f
+static const float TIMESTEP_EXPANSION_FACTOR = 0.1f;
+static const float TIMESTEP_EXPANSION_TOLERANCE = 1.5f;
 
 /* Calculate the speed of the particle relative to the local scale of the
  * simulation. This should be called once per particle during a simulation
@@ -3802,15 +3803,32 @@
 	if (sim->courant_num < speed * dtime / sphdata->element_size)
 		sim->courant_num = speed * dtime / sphdata->element_size;
 }
+static float get_base_time_step(ParticleSettings *part) {
+	return 1.0f / (float) (part->subframes + 1);
+}
 /* Update time step size to suit current conditions. */
 static float update_timestep(ParticleSystem *psys, ParticleSimulationData *sim, float t_frac)
 {
+	float dt_target;
 	if (sim->courant_num == 0.0f)
-		psys->dt_frac = 1.0f;
+		dt_target = 1.0f;
 	else
-		psys->dt_frac *= (psys->part->courant_target / sim->courant_num);
-	CLAMP(psys->dt_frac, MIN_TIMESTEP, 1.0f);
+		dt_target = psys->dt_frac * (psys->part->courant_target / sim->courant_num);
 
+	/* Make sure the time step is reasonable.
+	 * For some reason, the CLAMP macro doesn't work here. The time step becomes
+	 * too large. - z0r */
+	if (dt_target < MIN_TIMESTEP)
+		dt_target = MIN_TIMESTEP;
+	else if (dt_target > get_base_time_step(psys->part))
+		dt_target = get_base_time_step(psys->part);
+
+	/* Decrease time step instantly, but expand slowly. */
+	if (dt_target > psys->dt_frac)
+		psys->dt_frac = interpf(dt_target, psys->dt_frac, TIMESTEP_EXPANSION_FACTOR);
+	else
+		psys->dt_frac = dt_target;
+
 	/* Sync with frame end if it's close. */
 	if (t_frac == 1.0f)
 		return psys->dt_frac;
@@ -4307,14 +4325,16 @@
 		if ((int)cfra == startframe && part->sta < startframe)
 			totframesback = (startframe - (int)part->sta);
 
+		/* Initialise time step. This may change if automatic subframes are
+		 * enabled. */
 		if (!(part->time_flag & PART_TIME_AUTOSF)) {
 			/* Constant time step */
-			psys->dt_frac = 1.0f / (float) (part->subframes + 1);
+			psys->dt_frac = get_base_time_step(part);
 		}
 		else if ((int)cfra == startframe) {
 			/* Variable time step; use a very conservative value at the start.
 			 * If it doesn't need to be so small, it will quickly grow. */
-			psys->dt_frac = 1.0;
+			psys->dt_frac = get_base_time_step(part);
 		}
 		else if (psys->dt_frac < MIN_TIMESTEP) {
 			psys->dt_frac = MIN_TIMESTEP;

Modified: trunk/blender/source/blender/makesrna/intern/rna_particle.c
===================================================================
--- trunk/blender/source/blender/makesrna/intern/rna_particle.c	2012-12-12 22:02:08 UTC (rev 52947)
+++ trunk/blender/source/blender/makesrna/intern/rna_particle.c	2012-12-12 22:42:55 UTC (rev 52948)
@@ -2129,11 +2129,11 @@
 	RNA_def_property_update(prop, 0, "rna_Particle_reset");
 
 	prop = RNA_def_property(srna, "courant_target", PROP_FLOAT, PROP_NONE);
-	RNA_def_property_range(prop, 0.01, 10);
-	RNA_def_property_float_default(prop, 0.2);
+	RNA_def_property_range(prop, 0.0001, 10);
+	RNA_def_property_float_default(prop, 0.1);
 	RNA_def_property_ui_text(prop, "Adaptive Subframe Threshold",
 	                         "The relative distance a particle can move before requiring more subframes "
-	                         "(target Courant number); 0.1-0.3 is the recommended range");
+	                         "(target Courant number); 0.01-0.3 is the recommended range");
 	RNA_def_property_update(prop, 0, "rna_Particle_reset");
 
 	prop = RNA_def_property(srna, "jitter_factor", PROP_FLOAT, PROP_NONE);