GPencil: Improve Thickness handling for Outline operator

Actually, when you increase the thickness of the stroke in the outline conversion, the shape of the stroke changes and becomes thicker.

This commit includes a new algorithm to correct this problem. A new `Keep Shape`  parameter allows you to disable it because, for artist reasons, it may be good to keep the old algorithm and change the shape.

2 files changed, 16 insertions, 4 deletions

diff --git a/source/blender/editors/gpencil/gpencil_edit.c b/source/blender/editors/gpencil/gpencil_edit.c
index c4aa5218360..9843bd22bb6 100644
--- a/source/blender/editors/gpencil/gpencil_edit.c
+++ b/source/blender/editors/gpencil/gpencil_edit.c
@@ -3987,6 +3987,7 @@ static int gpencil_stroke_outline_exec(bContext *C, wmOperator *op)
   bGPdata *gpd = (bGPdata *)ob->data;
   const int subdivisions = RNA_int_get(op->ptr, "subdivisions");
   const float length = RNA_float_get(op->ptr, "length");
+  const bool keep = RNA_boolean_get(op->ptr, "keep");
   const int thickness = RNA_int_get(op->ptr, "thickness");
 
   const int view_mode = RNA_enum_get(op->ptr, "view_mode");
@@ -4104,8 +4105,9 @@ static int gpencil_stroke_outline_exec(bContext *C, wmOperator *op)
           CLAMP_MIN(gps_duplicate->thickness, 1.0f);
 
           /* Stroke. */
+          const float ovr_thickness = keep ? thickness : 0.0f;
           bGPDstroke *gps_perimeter = BKE_gpencil_stroke_perimeter_from_view(
-              rv3d, gpd, gpl, gps_duplicate, subdivisions, diff_mat);
+              rv3d, gpd, gpl, gps_duplicate, subdivisions, diff_mat, ovr_thickness);
           gps_perimeter->flag &= ~GP_STROKE_SELECT;
           /* Assign material. */
           switch (material_mode) {
@@ -4216,8 +4218,12 @@ void GPENCIL_OT_stroke_outline(wmOperatorType *ot)
 
   /* properties */
   ot->prop = RNA_def_enum(ot->srna, "view_mode", view_mode, GP_PERIMETER_VIEW, "View", "");
-  RNA_def_enum(
-      ot->srna, "material_mode", material_mode, GP_STROKE_USE_ACTIVE_MATERIAL, "Material Mode", "");
+  RNA_def_enum(ot->srna,
+               "material_mode",
+               material_mode,
+               GP_STROKE_USE_ACTIVE_MATERIAL,
+               "Material Mode",
+               "");
 
   RNA_def_int(ot->srna,
               "thickness",
@@ -4228,6 +4234,12 @@ void GPENCIL_OT_stroke_outline(wmOperatorType *ot)
               "Thickness of the stroke perimeter",
               1,
               1000);
+  RNA_def_boolean(ot->srna,
+                  "keep",
+                  true,
+                  "Keep Shape",
+                  "Try to keep global shape when the stroke thickness change");
+
   RNA_def_int(ot->srna, "subdivisions", 3, 0, 10, "Subdivisions", "", 0, 10);
 
   RNA_def_float(ot->srna, "length", 0.0f, 0.0f, 100.0f, "Sample Length", "", 0.0f, 100.0f);
diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index 7f11ff7ebd5..b196fcae51c 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -944,7 +944,7 @@ static bGPDstroke *gpencil_stroke_to_outline(tGPsdata *p, bGPDstroke *gps)
   float diff_mat[4][4];
   unit_m4(diff_mat);
   bGPDstroke *gps_perimeter = BKE_gpencil_stroke_perimeter_from_view(
-      rv3d, p->gpd, gpl, gps_duplicate, 3, diff_mat);
+      rv3d, p->gpd, gpl, gps_duplicate, 3, diff_mat, 0.0f);
   /* Assign material. */
   if (gpencil_settings->material_alt == NULL) {
     gps_perimeter->mat_nr = gps->mat_nr;