Fix T38124: Grease Pencil Line thickness

Issue was in GP draw code: line thickness was not initiated properly (and a null one makes OGL draw a unity-width line).

Also tweaked threshold (when to start a new, width-different OGL linestrip), to make it inversaly proportional to thickness
(so that now, it's 0.2 for a thickness of 1, 0.1 for a thickness of 2, etc.), avoids too big steps when using large thickness.

1 files changed, 6 insertions, 5 deletions

diff --git a/source/blender/editors/gpencil/drawgpencil.c b/source/blender/editors/gpencil/drawgpencil.c
index bb0a753d9c6..294a50909cb 100644
--- a/source/blender/editors/gpencil/drawgpencil.c
+++ b/source/blender/editors/gpencil/drawgpencil.c
@@ -206,18 +206,21 @@ static void gp_draw_stroke_point(bGPDspoint *points, short thickness, short dfla
 static void gp_draw_stroke_3d(bGPDspoint *points, int totpoints, short thickness, short debug)
 {
 	bGPDspoint *pt;
-	float oldpressure = 0.0f;
+	float curpressure = points[0].pressure;
 	int i;
 	
 	/* draw stroke curve */
+	glLineWidth(curpressure * thickness);
 	glBegin(GL_LINE_STRIP);
 	for (i = 0, pt = points; i < totpoints && pt; i++, pt++) {
 		/* if there was a significant pressure change, stop the curve, change the thickness of the stroke,
 		 * and continue drawing again (since line-width cannot change in middle of GL_LINE_STRIP)
+		 * Note: we want more visible levels of pressures when thickness is bigger.
 		 */
-		if (fabsf(pt->pressure - oldpressure) > 0.2f) {
+		if (fabsf(pt->pressure - curpressure) > 0.2f / (float)thickness) {
 			glEnd();
-			glLineWidth(pt->pressure * thickness);
+			curpressure = pt->pressure;
+			glLineWidth(curpressure * thickness);
 			glBegin(GL_LINE_STRIP);
 			
 			/* need to roll-back one point to ensure that there are no gaps in the stroke */
@@ -225,8 +228,6 @@ static void gp_draw_stroke_3d(bGPDspoint *points, int totpoints, short thickness
 			
 			/* now the point we want... */
 			glVertex3fv(&pt->x);
-			
-			oldpressure = pt->pressure;
 		}
 		else {
 			glVertex3fv(&pt->x);