Strand Render Simplification

============================

- Strand render now has options to remove child strands as
  the object's faces becomes smaller, in the Simplification
  particle panel.
- "Reference Size" is the approximate size of the object on
  screen, after which simplification starts.
- "Rate" is how fast strands are removed.
- "Transition" is the percentage of strands being faded out as
  they are removed.

- Another "Viewport" option removes strands on faces that are
  outside of the viewport. "Rate" again controls how fast these
  are removed.

- Strand render in Blender Units now has an adjustable minimum
  width. Below this minimum width, strands start fading out
  instead of getting smaller.

6 files changed, 89 insertions, 30 deletions

diff --git a/source/blender/render/intern/include/render_types.h b/source/blender/render/intern/include/render_types.h
index 4a731878ffb..7fbbd0f5abc 100644
--- a/source/blender/render/intern/include/render_types.h
+++ b/source/blender/render/intern/include/render_types.h
@@ -343,7 +343,7 @@ typedef struct StrandBuffer {
 	unsigned int lay;
 	int overrideuv;
 	int flag, maxdepth;
-	float adaptcos;
+	float adaptcos, minwidth;
 
 	float winmat[4][4];
 	int winx, winy;
diff --git a/source/blender/render/intern/include/renderdatabase.h b/source/blender/render/intern/include/renderdatabase.h
index 0346f2d6413..c919a54008e 100644
--- a/source/blender/render/intern/include/renderdatabase.h
+++ b/source/blender/render/intern/include/renderdatabase.h
@@ -69,6 +69,7 @@ typedef struct StrandTableNode {
 	struct StrandRen *strand;
 	float *winspeed;
 	float *surfnor;
+	float *simplify;
 	struct MCol *mcol;
 	float *uv;
 	int totuv, totmcol;
@@ -112,6 +113,7 @@ int RE_vlakren_get_normal(struct Render *re, struct ObjectInstanceRen *obi, stru
 float *RE_strandren_get_surfnor(struct ObjectRen *obr, struct StrandRen *strand, int verify);
 float *RE_strandren_get_uv(struct ObjectRen *obr, struct StrandRen *strand, int n, char **name, int verify);
 struct MCol *RE_strandren_get_mcol(struct ObjectRen *obr, struct StrandRen *strand, int n, char **name, int verify);
+float *RE_strandren_get_simplify(struct ObjectRen *obr, struct StrandRen *strand, int verify);
 float *RE_strandren_get_winspeed(struct ObjectInstanceRen *obi, struct StrandRen *strand, int verify);
 
 struct VertRen *RE_vertren_copy(struct ObjectRen *obr, struct VertRen *ver);
diff --git a/source/blender/render/intern/include/strand.h b/source/blender/render/intern/include/strand.h
index 7f37317d4d5..34a147c1933 100644
--- a/source/blender/render/intern/include/strand.h
+++ b/source/blender/render/intern/include/strand.h
@@ -68,6 +68,9 @@ typedef struct StrandPoint {
 	/* screen space */
 	float hoco[4];
 	float x, y;
+
+	/* simplification */
+	float alpha;
 } StrandPoint;
 
 typedef struct StrandSegment {
diff --git a/source/blender/render/intern/source/convertblender.c b/source/blender/render/intern/source/convertblender.c
index de3bd6079a4..eb5bb3f2f71 100644
--- a/source/blender/render/intern/source/convertblender.c
+++ b/source/blender/render/intern/source/convertblender.c
@@ -983,7 +983,7 @@ static void static_particle_strand(Render *re, ObjectRen *obr, Material *ma, flo
 {
 	static VertRen *v1= NULL, *v2= NULL;
 	VlakRen *vlr;
-	float nor[3], cross[3], w, dx, dy, width;
+	float nor[3], cross[3], crosslen, w, dx, dy, width;
 	static float anor[3], avec[3];
 	int flag, i;
 	static int second=0;
@@ -992,14 +992,11 @@ static void static_particle_strand(Render *re, ObjectRen *obr, Material *ma, flo
 	Normalize(nor);		// nor needed as tangent 
 	Crossf(cross, vec, nor);
 
-	if(ma->mode&MA_STR_B_UNITS)
-		Normalize(cross);
-
 	/* turn cross in pixelsize */
 	w= vec[2]*re->winmat[2][3] + re->winmat[3][3];
-	dx= re->winx*cross[0]*re->winmat[0][0]/w;
-	dy= re->winy*cross[1]*re->winmat[1][1]/w;
-	w= sqrt(dx*dx + dy*dy);
+	dx= re->winx*cross[0]*re->winmat[0][0];
+	dy= re->winy*cross[1]*re->winmat[1][1];
+	w= sqrt(dx*dx + dy*dy)/w;
 	
 	if(w!=0.0f) {
 		float fac;
@@ -1013,12 +1010,16 @@ static void static_particle_strand(Render *re, ObjectRen *obr, Material *ma, flo
 
 		width= ((1.0f-fac)*ma->strand_sta + (fac)*ma->strand_end);
 
-		/* use actual Blender units for strand width and fall back to min 1px */
+		/* use actual Blender units for strand width and fall back to minimum width */
 		if(ma->mode & MA_STR_B_UNITS){
-			if(width < 1.0f/w)
-				width= 1.0f/w;
+            crosslen= VecLength(cross);
+            w= 2.0f*crosslen*ma->strand_min/w;
+
+			if(width < w)
+				width= w;
+
 			/*cross is the radius of the strand so we want it to be half of full width */
-			VecMulf(cross,0.5);
+			VecMulf(cross,0.5/crosslen);
 		}
 		else
 			width/=w;
@@ -1496,7 +1497,8 @@ static int render_new_particle_system(Render *re, ObjectRen *obr, ParticleSystem
 	float *orco=0,*surfnor=0,*uvco=0, strandlen=0.0f, curlen=0.0f;
 	float hasize, pa_size, pa_time, r_tilt, cfra=bsystem_time(ob,(float)CFRA,0.0);
 	float loc_tex[3], size_tex[3], adapt_angle=0.0, adapt_pix=0.0, random;
-	int i, a, k, max_k=0, totpart, totuv=0, override_uv=-1;
+	float simplify[2];
+	int i, a, k, max_k=0, totpart, totuv=0, override_uv=-1, dosimplify = 0;
 	int path_possible=0, keys_possible=0, baked_keys=0, totchild=psys->totchild;
 	int seed, path_nbr=0, path=0, orco1=0, adapt=0, uv[3]={0,0,0};
 	char **uv_name=0;
@@ -1639,9 +1641,10 @@ static int render_new_particle_system(Render *re, ObjectRen *obr, ParticleSystem
 				Mat4CpyMat4(strandbuf->winmat, re->winmat);
 				strandbuf->winx= re->winx;
 				strandbuf->winy= re->winy;
-				strandbuf->maxdepth= 2; /* TODO */
+				strandbuf->maxdepth= 2;
 				strandbuf->adaptcos= cos((float)part->adapt_angle*(float)(M_PI/180.0));
 				strandbuf->overrideuv= override_uv;
+				strandbuf->minwidth= ma->strand_min;
 
 				if(part->flag & PART_HAIR_BSPLINE)
 					strandbuf->flag |= R_STRAND_BSPLINE;
@@ -1720,7 +1723,7 @@ static int render_new_particle_system(Render *re, ObjectRen *obr, ParticleSystem
 
 			if(totchild && (part->draw&PART_DRAW_PARENT)==0) continue;
 		}
-		else{
+		else {
 			ChildParticle *cpa= psys->child+a-totpart;
 			
 			pa_time=psys_get_child_time(psys, cpa, cfra);
@@ -1778,6 +1781,8 @@ static int render_new_particle_system(Render *re, ObjectRen *obr, ParticleSystem
 				}
 			}
 
+			dosimplify= psys_render_simplify_params(psys, cpa, simplify);
+
 			if(path_nbr) {
 				cache = psys->childcache[a-totpart];
 				max_k = (int)cache->steps;
@@ -1805,6 +1810,12 @@ static int render_new_particle_system(Render *re, ObjectRen *obr, ParticleSystem
 			strand->vert= svert;
 			VECCOPY(strand->orco, orco);
 
+			if(dosimplify) {
+				float *ssimplify= RE_strandren_get_simplify(obr, strand, 1);
+				ssimplify[0]= simplify[0];
+				ssimplify[1]= simplify[1];
+			}
+
 			if(surfnor) {
 				float *snor= RE_strandren_get_surfnor(obr, strand, 1);
 				VECCOPY(snor, surfnor);
@@ -3886,7 +3897,7 @@ static void add_render_object(Render *re, Object *ob, Object *par, int index, in
 		show_emitter= 0;
 		for(psys=ob->particlesystem.first; psys; psys=psys->next) {
 			show_emitter += psys->part->draw & PART_DRAW_EMITTER;
-			psys_particles_to_render_backup(ob, psys);
+			psys_render_set(ob, psys, re->viewmat, re->winmat, re->winx, re->winy);
 		}
 
 		/* if no psys has "show emitter" selected don't render emitter */
@@ -3910,7 +3921,7 @@ static void add_render_object(Render *re, Object *ob, Object *par, int index, in
 		for(psys=ob->particlesystem.first; psys; psys=psys->next, psysindex++) {
 			obr= RE_addRenderObject(re, ob, par, index, psysindex);
 			init_render_object_data(re, obr, only_verts);
-			psys_render_backup_to_particles(ob, psys);
+			psys_render_restore(ob, psys);
 
 			/* only add instance for objects that have not been used for dupli */
 			if(!(ob->transflag & OB_RENDER_DUPLI))
@@ -4666,7 +4677,7 @@ void RE_Database_FromScene_Vectors(Render *re, Scene *sce)
 				} else {
 					/* check if both have same amounts of vertices */
 					if(obi->totvector!=oldobi->totvector) {
-						printf("Warning: object %s has different amount of vertices on other frame\n", obi->ob->id.name+2);
+						printf("Warning: object %s has different amount of vertices or strands on other frame\n", obi->ob->id.name+2);
 						continue;
 					}
 					
diff --git a/source/blender/render/intern/source/renderdatabase.c b/source/blender/render/intern/source/renderdatabase.c
index 3906b1fc001..79c87252fc2 100644
--- a/source/blender/render/intern/source/renderdatabase.c
+++ b/source/blender/render/intern/source/renderdatabase.c
@@ -104,6 +104,7 @@
 #define RE_MCOL_ELEMS		4
 #define RE_UV_ELEMS			2
 #define RE_SURFNOR_ELEMS	3
+#define RE_SIMPLIFY_ELEMS	2
 
 float *RE_vertren_get_sticky(ObjectRen *obr, VertRen *ver, int verify)
 {
@@ -590,6 +591,21 @@ MCol *RE_strandren_get_mcol(ObjectRen *obr, StrandRen *strand, int n, char **nam
 	return node->mcol + index*RE_MCOL_ELEMS;
 }
 
+float *RE_strandren_get_simplify(struct ObjectRen *obr, struct StrandRen *strand, int verify)
+{
+	float *simplify;
+	int nr= strand->index>>8;
+	
+	simplify= obr->strandnodes[nr].simplify;
+	if(simplify==NULL) {
+		if(verify) 
+			simplify= obr->strandnodes[nr].simplify= MEM_callocN(256*RE_SIMPLIFY_ELEMS*sizeof(float), "simplify table");
+		else
+			return NULL;
+	}
+	return simplify + (strand->index & 255)*RE_SIMPLIFY_ELEMS;
+}
+
 /* winspeed is exception, it is stored per instance */
 float *RE_strandren_get_winspeed(ObjectInstanceRen *obi, StrandRen *strand, int verify)
 {
@@ -743,6 +759,8 @@ void free_renderdata_strandnodes(StrandTableNode *strandnodes)
 			MEM_freeN(strandnodes[a].winspeed);
 		if(strandnodes[a].surfnor)
 			MEM_freeN(strandnodes[a].surfnor);
+		if(strandnodes[a].simplify)
+			MEM_freeN(strandnodes[a].simplify);
 	}
 	
 	MEM_freeN(strandnodes);
diff --git a/source/blender/render/intern/source/strand.c b/source/blender/render/intern/source/strand.c
index 42c6d559f65..4f0e9764a43 100644
--- a/source/blender/render/intern/source/strand.c
+++ b/source/blender/render/intern/source/strand.c
@@ -321,7 +321,8 @@ void strand_eval_point(StrandSegment *sseg, StrandPoint *spoint)
 {
 	Material *ma;
 	StrandBuffer *strandbuf;
-	float p[4][3], data[4], cross[3], w, dx, dy, t;
+	float *simplify;
+	float p[4][3], data[4], cross[3], crosslen, w, dx, dy, t;
 	int type;
 
 	strandbuf= sseg->buffer;
@@ -378,25 +379,34 @@ void strand_eval_point(StrandSegment *sseg, StrandPoint *spoint)
 	Normalize(spoint->nor);
 
 	spoint->width= strand_eval_width(ma, spoint->strandco);
+	
+	/* simplification */
+	simplify= RE_strandren_get_simplify(strandbuf->obr, sseg->strand, 0);
+	spoint->alpha= (simplify)? simplify[1]: 1.0f;
 
 	/* outer points */
 	Crossf(cross, spoint->co, spoint->tan);
 
-	if(strandbuf->flag & R_STRAND_B_UNITS)
-		Normalize(cross);
-
 	w= spoint->co[2]*strandbuf->winmat[2][3] + strandbuf->winmat[3][3];
-	dx= strandbuf->winx*cross[0]*strandbuf->winmat[0][0]/w;
-	dy= strandbuf->winy*cross[1]*strandbuf->winmat[1][1]/w;
-	w= sqrt(dx*dx + dy*dy);
+	dx= strandbuf->winx*cross[0]*strandbuf->winmat[0][0];
+	dy= strandbuf->winy*cross[1]*strandbuf->winmat[1][1];
+	w= sqrt(dx*dx + dy*dy)/w;
 
 	if(w > 0.0f) {
 		if(strandbuf->flag & R_STRAND_B_UNITS) {
-			w= 1.0f/w;
+			crosslen= VecLength(cross);
+			w= 2.0f*crosslen*strandbuf->minwidth/w;
 
-			if(spoint->width < w)
+			if(spoint->width < w) {
+				spoint->alpha= spoint->width/w;
 				spoint->width= w;
-			VecMulf(cross, spoint->width*0.5f);
+			}
+
+			if(simplify)
+				/* squared because we only change width, not length */
+				spoint->width *= simplify[0]*simplify[0];
+
+			VecMulf(cross, spoint->width*0.5f/crosslen);
 		}
 		else
 			VecMulf(cross, spoint->width/w);
@@ -528,7 +538,7 @@ static void strand_project_point(float winmat[][4], float winx, float winy, Stra
 }
 
 #include "BLI_rand.h"
-void strand_shade_point(Render *re, ShadeSample *ssamp, StrandSegment *sseg, StrandPoint *spoint);
+static void strand_shade_point(Render *re, ShadeSample *ssamp, StrandSegment *sseg, StrandPoint *spoint);
 
 static void strand_shade_get(StrandPart *spart, int lookup, ShadeSample *ssamp, StrandPoint *spoint, StrandVert *svert, StrandSegment *sseg)
 {
@@ -653,7 +663,7 @@ static int strand_test_clip(float winmat[][4], ZSpan *zspan, float *bounds, floa
 	return clipflag;
 }
 
-void strand_shade_point(Render *re, ShadeSample *ssamp, StrandSegment *sseg, StrandPoint *spoint)
+static void strand_shade_point(Render *re, ShadeSample *ssamp, StrandSegment *sseg, StrandPoint *spoint)
 {
 	ShadeInput *shi= ssamp->shi;
 	ShadeResult *shr= ssamp->shr;
@@ -685,6 +695,21 @@ void strand_shade_point(Render *re, ShadeSample *ssamp, StrandSegment *sseg, Str
 	shade_samples_do_AO(ssamp);
 	shade_input_do_shade(shi, shr);
 
+	/* apply simplification */
+	if(spoint->alpha < 1.0f) {
+		shr->combined[0] *= spoint->alpha;
+		shr->combined[1] *= spoint->alpha;
+		shr->combined[2] *= spoint->alpha;
+		shr->combined[3] *= spoint->alpha;
+
+		shr->col[0] *= spoint->alpha;
+		shr->col[1] *= spoint->alpha;
+		shr->col[2] *= spoint->alpha;
+		shr->col[3] *= spoint->alpha;
+
+		shr->alpha *= spoint->alpha;
+	}
+
 	/* include lamphalos for strand, since halo layer was added already */
 	if(re->flag & R_LAMPHALO)
 		if(shi->layflag & SCE_LAY_HALO)