GPencil: Add small offset to follow the drawing path for single points

The offset added allows to generate a vector to determine direction. This direction will be used when rotate the object to rotate texture.

The solution is not 100% perfect, but it's far better that having an unpredictable rotation.

1 files changed, 6 insertions, 2 deletions

diff --git a/source/blender/draw/engines/gpencil/gpencil_draw_cache_impl.c b/source/blender/draw/engines/gpencil/gpencil_draw_cache_impl.c
index ea33c004191..c1014bb5ca4 100644
--- a/source/blender/draw/engines/gpencil/gpencil_draw_cache_impl.c
+++ b/source/blender/draw/engines/gpencil/gpencil_draw_cache_impl.c
@@ -176,16 +176,20 @@ void DRW_gpencil_get_point_geom(GpencilBatchCacheElem *be,
 
     /* use previous point to determine stroke direction */
     bGPDspoint *pt2 = NULL;
+    float fpt[3];
     if (i == 0) {
       if (gps->totpoints > 1) {
         /* extrapolate a point before first point */
-        float fpt[3];
         pt2 = &gps->points[1];
         interp_v3_v3v3(fpt, &pt2->x, &pt->x, 1.5f);
         GPU_vertbuf_attr_set(be->vbo, be->prev_pos_id, be->vbo_len, fpt);
       }
       else {
-        GPU_vertbuf_attr_set(be->vbo, be->prev_pos_id, be->vbo_len, &pt->x);
+        /* add small offset to get a vector */
+        copy_v3_v3(fpt, &pt->x);
+        fpt[0] += 0.00001f;
+        fpt[1] += 0.00001f;
+        GPU_vertbuf_attr_set(be->vbo, be->prev_pos_id, be->vbo_len, fpt);
       }
     }
     else {