[Bf-blender-cvs] [12d6c138999] blender2.8: GP: Primitive: Fix flickering when using a noise brush

[Charlie Jolly]

Commit: 12d6c138999bd6e3637af773c44155f3e1c3b67d
Author: Charlie Jolly
Date:   Tue Dec 18 15:51:46 2018 +0000
Branches: blender2.8
https://developer.blender.org/rB12d6c138999bd6e3637af773c44155f3e1c3b67d

GP: Primitive: Fix flickering when using a noise brush

Previously, the random values were generated every draw, now they are generated once.

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

M	source/blender/editors/gpencil/gpencil_primitive.c
M	source/blender/editors/include/ED_gpencil.h

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

diff --git a/source/blender/editors/gpencil/gpencil_primitive.c b/source/blender/editors/gpencil/gpencil_primitive.c
index c88d0a346dd..f13235926f1 100644
--- a/source/blender/editors/gpencil/gpencil_primitive.c
+++ b/source/blender/editors/gpencil/gpencil_primitive.c
@@ -356,7 +356,8 @@ static void gp_primitive_set_initdata(bContext *C, tGPDprimitive *tgpi)
 	gpencil_primitive_allocate_memory(tgpi);
 
 	/* Random generator, only init once. */
-	tgpi->rng = BLI_rng_new((uint)0);
+	uint rng_seed = (uint)(PIL_check_seconds_timer_i() & UINT_MAX);
+	tgpi->rng = BLI_rng_new(rng_seed);
 }
 
 /* add new segment to curve */
@@ -782,6 +783,13 @@ static void gp_primitive_update_strokes(bContext *C, tGPDprimitive *tgpi)
 		bGPDspoint *pt = &gps->points[i];
 		tGPspoint *p2d = &points2D[i];
 
+		/* set rnd value for reuse */
+		if (p2d->rnd_dirty != true) {
+			p2d->rnd[0] = BLI_rng_get_float(tgpi->rng);
+			p2d->rnd[1] = BLI_rng_get_float(tgpi->rng);
+			p2d->rnd_dirty = true;
+		}
+
 		/* Copy points to buffer */
 		tGPspoint *tpt = ((tGPspoint *)(gpd->runtime.sbuffer) + gpd->runtime.sbuffer_size);
 
@@ -817,9 +825,8 @@ static void gp_primitive_update_strokes(bContext *C, tGPDprimitive *tgpi)
 
 			/* exponential value */
 			const float exfactor = SQUARE(brush->gpencil_settings->draw_jitter + 2.0f);
-			const float rnd = BLI_rng_get_float(tgpi->rng);
-			const float fac = rnd * exfactor * jitter;
-			if (rnd > 0.5f) {
+			const float fac = p2d->rnd[0] * exfactor * jitter;
+			if (p2d->rnd[0] > 0.5f) {
 				add_v2_fl(&p2d->x, -fac);
 			}
 			else {
@@ -831,12 +838,11 @@ static void gp_primitive_update_strokes(bContext *C, tGPDprimitive *tgpi)
 		if ((brush->gpencil_settings->flag & GP_BRUSH_GROUP_RANDOM) &&
 		    (brush->gpencil_settings->draw_random_press > 0.0f))
 		{
-			float rnd = BLI_rng_get_float(tgpi->rng);
-			if (rnd > 0.5f) {
-				pressure -= brush->gpencil_settings->draw_random_press * rnd;
+			if (p2d->rnd[0] > 0.5f) {
+				pressure -= brush->gpencil_settings->draw_random_press * p2d->rnd[0];
 			}
 			else {
-				pressure += brush->gpencil_settings->draw_random_press * rnd;
+				pressure += brush->gpencil_settings->draw_random_press * p2d->rnd[0];
 			}
 		}
 
@@ -853,12 +859,11 @@ static void gp_primitive_update_strokes(bContext *C, tGPDprimitive *tgpi)
 		if ((brush->gpencil_settings->flag & GP_BRUSH_GROUP_RANDOM) &&
 		    (brush->gpencil_settings->draw_random_strength > 0.0f))
 		{
-			const float rnd = BLI_rng_get_float(tgpi->rng);
-			if (rnd > 0.5f) {
-				strength -= strength * brush->gpencil_settings->draw_random_strength * rnd;
+			if (p2d->rnd[1] > 0.5f) {
+				strength -= strength * brush->gpencil_settings->draw_random_strength * p2d->rnd[1];
 			}
 			else {
-				strength += strength * brush->gpencil_settings->draw_random_strength * rnd;
+				strength += strength * brush->gpencil_settings->draw_random_strength * p2d->rnd[1];
 			}
 			CLAMP(strength, GPENCIL_STRENGTH_MIN, 1.0f);
 		}
diff --git a/source/blender/editors/include/ED_gpencil.h b/source/blender/editors/include/ED_gpencil.h
index 06869cd226b..4c453c67f6b 100644
--- a/source/blender/editors/include/ED_gpencil.h
+++ b/source/blender/editors/include/ED_gpencil.h
@@ -73,12 +73,14 @@ struct wmWindowManager;
  * Used as part of the 'stroke cache' used during drawing of new strokes
  */
 typedef struct tGPspoint {
-	float x, y;               /* x and y coordinates of cursor (in relative to area) */
+	float x, y;             /* x and y coordinates of cursor (in relative to area) */
 	float pressure;         /* pressure of tablet at this point */
 	float strength;         /* pressure of tablet at this point for alpha factor */
 	float time;             /* Time relative to stroke start (used when converting to path) */
 	float uv_fac;           /* factor of uv along the stroke */
 	float uv_rot;           /* uv rotation for dor mode */
+	float rnd[2];           /* rnd value */
+	bool rnd_dirty;         /* rnd flag */
 } tGPspoint;
 
 /* used to sort by zdepth gpencil objects in viewport */