[Bf-blender-cvs] [260b747d33b] greasepencil-object: GP Build Modifier: Fix "Concurrent" Mode

[Joshua Leung]

Commit: 260b747d33b5128e89e0faad251e08297b5de1f6
Author: Joshua Leung
Date:   Fri Nov 24 02:57:30 2017 +1300
Branches: greasepencil-object
https://developer.blender.org/rB260b747d33b5128e89e0faad251e08297b5de1f6

GP Build Modifier: Fix "Concurrent" Mode

The last segment of shorter strokes was always suddenly appearing.
it turns out the at the formulations for those factors was off.

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

M	source/blender/modifiers/intern/MOD_gpencilbuild.c

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

diff --git a/source/blender/modifiers/intern/MOD_gpencilbuild.c b/source/blender/modifiers/intern/MOD_gpencilbuild.c
index 6715dc333e3..39814eef5a5 100644
--- a/source/blender/modifiers/intern/MOD_gpencilbuild.c
+++ b/source/blender/modifiers/intern/MOD_gpencilbuild.c
@@ -320,7 +320,7 @@ static void build_concurrent(GpencilBuildModifierData *mmd, bGPDlayer *gpl, bGPD
 		/* Relative Length of Stroke - Relative to the longest stroke,
 		 * what proportion of the available time should this stroke use
 		 */
-		const float relative_len = (float)gps->totpoints / max_points;
+		const float relative_len = (float)gps->totpoints / (float)max_points;
 		
 		/* Determine how many points should be left in the stroke */
 		int num_points = 0;
@@ -329,13 +329,16 @@ static void build_concurrent(GpencilBuildModifierData *mmd, bGPDlayer *gpl, bGPD
 			case GP_BUILD_TIMEALIGN_START: /* all start on frame 1 */
 			{
 				/* Build effect occurs over when fac = 0, to fac = relative_len */
-				if (fac < relative_len) {
-					/* Use fac directly */
+				if (fac <= relative_len) {
+					/* Scale fac to fit relative_len */
+					/* FIXME: prevent potential div by zero (e.g. very short stroke vs one very long one) */
+					const float scaled_fac = fac / relative_len;
+					
 					if (reverse) {
-						num_points = (int)roundf((1.0f - fac) * gps->totpoints);
+						num_points = (int)roundf((1.0f - scaled_fac) * gps->totpoints);
 					}
 					else {
-						num_points = (int)roundf(fac * gps->totpoints);
+						num_points = (int)roundf(scaled_fac * gps->totpoints);
 					}
 				}
 				else {
@@ -357,12 +360,13 @@ static void build_concurrent(GpencilBuildModifierData *mmd, bGPDlayer *gpl, bGPD
 				
 				if (fac >= start_fac) {
 					/* FIXME: prevent potential div by zero (e.g. very short stroke vs one very long one) */
-					float f = fac - start_fac / relative_len;
+					const float scaled_fac = (fac - start_fac) / relative_len;
+					
 					if (reverse) {
-						num_points = (int)roundf((1.0f - f) * gps->totpoints);
+						num_points = (int)roundf((1.0f - scaled_fac) * gps->totpoints);
 					}
 					else {
-						num_points = (int)roundf(f * gps->totpoints);
+						num_points = (int)roundf(scaled_fac * gps->totpoints);
 					}	
 				}
 				else {
@@ -382,7 +386,7 @@ static void build_concurrent(GpencilBuildModifierData *mmd, bGPDlayer *gpl, bGPD
 		}
 		
 		/* Modify the stroke geometry */
-		if (num_points == 0) {
+		if (num_points <= 0) {
 			/* Nothing Left - Delete the stroke */
 			clear_stroke(gpf, gps, modifier_index);
 		}