Fix preview rendering for SSS to not show preprocessing pass that

leads to flickering, and a bug that would display parts of the
preview render as black for interrupted preview renders.

(sorry for the late fix, i've triple checked the code ..)

source/blender/render/intern/source/pipeline.c

@@ -1165,6 +1165,15 @@ void RE_AddObject(Render *re, Object *ob)
 
 /* *************************************** */
 
+static int render_display_draw_enabled(Render *re)
+{
+	/* don't show preprocess for previewrender sss */
+	if(re->sss_points)
+		return !(re->r.scemode & R_PREVIEWBUTS);
+	else
+		return 1;
+}
+
 static void *do_part_thread(void *pa_v)
 {
 	RenderPart *pa= pa_v;
@@ -1183,7 +1192,7 @@ static void *do_part_thread(void *pa_v)
 		/* merge too on break! */
 		if(R.result->exrhandle)
 			save_render_result_tile(&R, pa);
-		else
+		else if(render_display_draw_enabled(&R))
 			merge_render_result(R.result, pa->result);
 	}
 	
@@ -1226,7 +1235,8 @@ static void render_tile_processor(Render *re, int firsttile)
 			
 			if(pa->result) {
 				if(!re->test_break()) {
-					re->display_draw(pa->result, NULL);
+					if(render_display_draw_enabled(re))
+						re->display_draw(pa->result, NULL);
 					
 					re->i.partsdone++;
 					re->stats_draw(&re->i);
@@ -1432,7 +1442,8 @@ static void threaded_tile_processor(Render *re)
 				BLI_remove_thread(&threads, pa);
 				
 				if(pa->result) {
-					re->display_draw(pa->result, NULL);
+					if(render_display_draw_enabled(re))
+						re->display_draw(pa->result, NULL);
 					print_part_stats(re, pa);
 					
 					RE_FreeRenderResult(pa->result);
@@ -1444,7 +1455,8 @@ static void threaded_tile_processor(Render *re)
 			else {
 				rendering= 1;
 				if(pa->nr && pa->result && drawtimer>20) {
-					re->display_draw(pa->result, &pa->result->renrect);
+					if(render_display_draw_enabled(re))
+						re->display_draw(pa->result, &pa->result->renrect);
 					hasdrawn= 1;
 				}
 			}

source/blender/render/intern/source/rendercore.c

@@ -1264,20 +1264,20 @@ static void zbufshade_sss_free(RenderPart *pa)
 
 void zbufshade_sss_tile(RenderPart *pa)
 {
+	Render *re= &R;
 	ShadeSample ssamp;
 	ZBufSSSHandle handle;
 	RenderResult *rr= pa->result;
 	RenderLayer *rl= rr->layers.first;
 	VlakRen *vlr;
-	Material *mat= R.sss_mat;
+	Material *mat= re->sss_mat;
 	float (*co)[3], (*color)[3], *area, *fcol= rl->rectf;
-	int x, y, seed, quad, totpoint;
+	int x, y, seed, quad, totpoint, display = !(re->r.scemode & R_PREVIEWBUTS);
+	int *rz, *rp, *rbz, *rbp;
 #if 0
 	PixStr *ps;
 	long *rs;
 	int z;
-#else
-	int *rz, *rp, *rbz, *rbp;
 #endif
 
 	set_part_zbuf_clipflag(pa);
@@ -1312,7 +1312,7 @@ void zbufshade_sss_tile(RenderPart *pa)
 
 #if 0
 	/* create ISB (does not work currently!) */
-	if(R.r.mode & R_SHADOW)
+	if(re->r.mode & R_SHADOW)
 		ISB_create(pa, NULL);
 #endif
 
@@ -1324,9 +1324,11 @@ void zbufshade_sss_tile(RenderPart *pa)
 	ssamp.shi[0].combinedflag= ~(SCE_PASS_SPEC);
 	ssamp.tot= 1;
 
-	/* initialize scanline updates for main thread */
-	rr->renrect.ymin= 0;
-	rr->renlay= rl;
+	if(display) {
+		/* initialize scanline updates for main thread */
+		rr->renrect.ymin= 0;
+		rr->renlay= rl;
+	}
 	
 	seed= pa->rectx*pa->disprect.ymin;
 #if 0
@@ -1348,7 +1350,7 @@ void zbufshade_sss_tile(RenderPart *pa)
 			if(rs) {
 				/* for each sample in this pixel, shade it */
 				for(ps=(PixStr*)*rs; ps; ps=ps->next) {
-					vlr= RE_findOrAddVlak(&R, (ps->facenr-1) & RE_QUAD_MASK);
+					vlr= RE_findOrAddVlak(re, (ps->facenr-1) & RE_QUAD_MASK);
 					quad= (ps->facenr & RE_QUAD_OFFS);
 					z= ps->z;
 
@@ -1367,7 +1369,7 @@ void zbufshade_sss_tile(RenderPart *pa)
 			if(rp) {
 				if(*rp != 0) {
 					/* shade front */
-					vlr= RE_findOrAddVlak(&R, (*rp-1) & RE_QUAD_MASK);
+					vlr= RE_findOrAddVlak(re, (*rp-1) & RE_QUAD_MASK);
 					quad= ((*rp) & RE_QUAD_OFFS);
 
 					shade_sample_sss(&ssamp, mat, vlr, quad, x, y, *rz,
@@ -1384,7 +1386,7 @@ void zbufshade_sss_tile(RenderPart *pa)
 			if(rbp) {
 				if(*rbp != 0 && *rbp != *(rp-1)) {
 					/* shade back */
-					vlr= RE_findOrAddVlak(&R, (*rbp-1) & RE_QUAD_MASK);
+					vlr= RE_findOrAddVlak(re, (*rbp-1) & RE_QUAD_MASK);
 					quad= ((*rbp) & RE_QUAD_OFFS);
 
 					shade_sample_sss(&ssamp, mat, vlr, quad, x, y, *rbz,
@@ -1404,12 +1406,12 @@ void zbufshade_sss_tile(RenderPart *pa)
 		}
 
 		if(y&1)
-			if(R.test_break()) break; 
+			if(re->test_break()) break; 
 	}
 
 	/* note: after adding we do not free these arrays, sss keeps them */
 	if(totpoint > 0) {
-		sss_add_points(&R, co, color, area, totpoint);
+		sss_add_points(re, co, color, area, totpoint);
 	}
 	else {
 		MEM_freeN(co);
@@ -1418,13 +1420,15 @@ void zbufshade_sss_tile(RenderPart *pa)
 	}
 	
 #if 0
-	if(R.r.mode & R_SHADOW)
+	if(re->r.mode & R_SHADOW)
 		ISB_free(pa);
 #endif
 		
-	/* display active layer */
-	rr->renrect.ymin=rr->renrect.ymax= 0;
-	rr->renlay= render_get_active_layer(&R, rr);
+	if(display) {
+		/* display active layer */
+		rr->renrect.ymin=rr->renrect.ymax= 0;
+		rr->renlay= render_get_active_layer(&R, rr);
+	}
 	
 	zbufshade_sss_free(pa);
 }

source/blender/render/intern/source/sss.c

@@ -839,6 +839,7 @@ typedef struct SSSPoints {
 static void sss_create_tree_mat(Render *re, Material *mat)
 {
 	SSSPoints *p;
+	RenderResult *rr;
 	ListBase layers, points;
 	float (*co)[3] = NULL, (*color)[3] = NULL, *area = NULL;
 	int totpoint = 0, osa, osaflag, partsdone;
@@ -848,11 +849,15 @@ static void sss_create_tree_mat(Render *re, Material *mat)
 	
 	points.first= points.last= NULL;
 
+	/* TODO: this is getting a bit ugly, copying all those variables and
+	   setting them back, maybe we need to create our own Render? */
+
 	/* do SSS preprocessing render */
 	layers= re->r.layers;
 	osa= re->osa;
 	osaflag= re->r.mode & R_OSA;
 	partsdone= re->i.partsdone;
+	rr= re->result;
 
 	re->r.layers.first= re->r.layers.last= NULL;
 	re->osa= 0;
@@ -860,15 +865,18 @@ static void sss_create_tree_mat(Render *re, Material *mat)
 	re->sss_points= &points;
 	re->sss_mat= mat;
 	re->i.partsdone= 0;
+	re->result= NULL;
 
-	RE_TileProcessor(re, 0, 1);
+	RE_TileProcessor(re, 0, !(re->r.mode & R_PREVIEWBUTS));
+	RE_FreeRenderResult(re->result);
 
+	re->result= rr;
+	re->i.partsdone= partsdone;
 	re->sss_mat= NULL;
 	re->sss_points= NULL;
 	re->r.layers= layers;
 	re->osa= osa;
 	if (osaflag) re->r.mode |= R_OSA;
-	re->i.partsdone= partsdone;
 
 	/* no points? no tree */
 	if(!points.first)
@@ -907,7 +915,7 @@ static void sss_create_tree_mat(Render *re, Material *mat)
 		float fw= mat->sss_front, bw= mat->sss_back;
 		float error = mat->sss_error;
 		
-		if((R.r.scemode & R_PREVIEWBUTS) && error < 0.5f)
+		if((re->r.scemode & R_PREVIEWBUTS) && error < 0.5f)
 			error= 0.5f;
 
 		sss->ss[0]= scatter_settings_new(col[0], radius[0], ior, cfac, fw, bw);