GPencil: Code Cleanup - Simplify and clarify the code for subdividing a stroke

3 files changed, 28 insertions, 30 deletions

diff --git a/source/blender/editors/gpencil/gpencil_intern.h b/source/blender/editors/gpencil/gpencil_intern.h
index c3fafaae9c3..368da618a1d 100644
--- a/source/blender/editors/gpencil/gpencil_intern.h
+++ b/source/blender/editors/gpencil/gpencil_intern.h
@@ -137,9 +137,9 @@ void gp_stroke_delete_tagged_points(bGPDframe *gpf, bGPDstroke *gps, bGPDstroke
 bool gp_smooth_stroke(bGPDstroke *gps, int i, float inf, bool affect_pressure);
 
 /**
- * Subdivide a stroke
+ * Subdivide a stroke once, by adding points at the midpoint between each pair of points
  * \param gps           Stroke data
- * \param new_totpoints Total number of points
+ * \param new_totpoints Total number of points (after subdividing)
  */
 void gp_subdivide_stroke(bGPDstroke *gps, const int new_totpoints);
 
diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index 740fb8e0096..ac949775fd0 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -572,7 +572,7 @@ static void gp_stroke_newfrombuffer(tGPsdata *p)
 	bGPDstroke *gps;
 	bGPDspoint *pt;
 	tGPspoint *ptc;
-
+	
 	int i, totelem;
 	/* since strokes are so fine, when using their depth we need a margin otherwise they might get missed */
 	int depth_margin = (p->gpd->flag & GP_DATA_DEPTH_STROKE) ? 4 : 0;
@@ -614,6 +614,7 @@ static void gp_stroke_newfrombuffer(tGPsdata *p)
 	/* allocate enough memory for a continuous array for storage points */
 	int sublevel = gpl->sublevel;
 	int new_totpoints = gps->totpoints;
+	
 	for (i = 0; i < sublevel; i++) {
 		/* Avoid error if subdivide is too big (assume totpoints is right) */
 		if (new_totpoints + (new_totpoints - 1) > GP_STROKE_BUFFER_MAX) {
@@ -624,7 +625,7 @@ static void gp_stroke_newfrombuffer(tGPsdata *p)
 		new_totpoints += new_totpoints - 1;
 	}
 	gps->points = MEM_callocN(sizeof(bGPDspoint) * new_totpoints, "gp_stroke_points");
-
+	
 	/* set pointer to first non-initialized point */
 	pt = gps->points + (gps->totpoints - totelem);
 	
@@ -745,19 +746,22 @@ static void gp_stroke_newfrombuffer(tGPsdata *p)
 		
 		/* subdivide the stroke */
 		if (sublevel > 0) {
-			int sub = gps->totpoints;
+			int totpoints = gps->totpoints;
 			for (i = 0; i < sublevel; i++) {
-				sub += sub - 1;
-				gp_subdivide_stroke(gps, sub);
+				/* we're adding one new point between each pair of verts on each step */
+				totpoints += totpoints - 1;
+				
+				gp_subdivide_stroke(gps, totpoints);
 			}
 		}
+		
 		/* smooth stroke - only if there's something to do */
 		if (gpl->smooth_drawfac > 0.0f) {
 			for (i = 0; i < gps->totpoints; i++) {
 				gp_smooth_stroke(gps, i, gpl->smooth_drawfac, true);
 			}
 		}
-
+		
 		if (depth_arr)
 			MEM_freeN(depth_arr);
 	}
diff --git a/source/blender/editors/gpencil/gpencil_utils.c b/source/blender/editors/gpencil/gpencil_utils.c
index 30558b00b9f..64cb0b5bb6a 100644
--- a/source/blender/editors/gpencil/gpencil_utils.c
+++ b/source/blender/editors/gpencil/gpencil_utils.c
@@ -606,40 +606,34 @@ bool gp_smooth_stroke(bGPDstroke *gps, int i, float inf, bool affect_pressure)
 }
 
 /**
- * Subdivide a stroke
+ * Subdivide a stroke once, by adding a point half way between each pair of existing points
  * \param gps           Stroke data
- * \param new_totpoints Total number of points
+ * \param new_totpoints Total number of points (after subdividing)
  */
 void gp_subdivide_stroke(bGPDstroke *gps, const int new_totpoints)
 {
-	int i;
-	/* Subdivide stroke adding a point half way existing points */
-	bGPDspoint *pt_a;
-	bGPDspoint *pt_b;
-	bGPDspoint *pt_n;
-	
-	/* Move points to insert subdivision */
+	/* Move points towards end of enlarged points array to leave space for new points */
 	int y = 1;
-	for (i = gps->totpoints - 1; i > 0; i--) {
-		pt_n = &gps->points[i];
-		gps->points[new_totpoints - y] = *pt_n;
-		y = y + 2;
+	for (int i = gps->totpoints - 1; i > 0; i--) {
+		gps->points[new_totpoints - y] = gps->points[i];
+		y += 2;
 	}
 	
 	/* Create interpolated points */
-	for (i = 0; i < new_totpoints - 1; i++) {
-		pt_a = &gps->points[i];
-		pt_n = &gps->points[i + 1];
-		pt_b = &gps->points[i + 2];
+	for (int i = 0; i < new_totpoints - 1; i += 2) {
+		bGPDspoint *prev  = &gps->points[i];
+		bGPDspoint *pt    = &gps->points[i + 1];
+		bGPDspoint *next  = &gps->points[i + 2];
+		
 		/* Interpolate all values */
-		interp_v3_v3v3(&pt_n->x, &pt_a->x, &pt_b->x, 0.5f);
-		pt_n->pressure = interpf(pt_a->pressure, pt_b->pressure, 0.5f);
-		pt_n->time = interpf(pt_a->time, pt_b->time, 0.5f);
+		interp_v3_v3v3(&pt->x, &prev->x, &next->x, 0.5f);
 		
-		i++; /* add to loop to jump next pair */
+		pt->pressure = interpf(prev->pressure, next->pressure, 0.5f);
+		pt->time     = interpf(prev->time, next->time, 0.5f);
 	}
 	
-	gps->totpoints = new_totpoints;  /* Increase number of points */
+	/* Update to new total number of points */
+	gps->totpoints = new_totpoints;
 }
 
 /* ******************************************************** */