GP: Primitive: Fix flickering when using a noise brush

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

1 files changed, 17 insertions, 12 deletions

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);
 		}