2 files changed, 81 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_gpencil.h b/source/blender/blenkernel/BKE_gpencil.h
index 0e3b0181fb9..ae1000d1b99 100644
--- a/source/blender/blenkernel/BKE_gpencil.h
+++ b/source/blender/blenkernel/BKE_gpencil.h
@@ -215,6 +215,7 @@ bool BKE_gpencil_smooth_stroke(struct bGPDstroke *gps, int i, float inf);
 bool BKE_gpencil_smooth_stroke_strength(struct bGPDstroke *gps, int point_index, float influence);
 bool BKE_gpencil_smooth_stroke_thickness(struct bGPDstroke *gps, int point_index, float influence);
 bool BKE_gpencil_smooth_stroke_uv(struct bGPDstroke *gps, int point_index, float influence);
+bool BKE_gpencil_close_stroke(struct bGPDstroke *gps);
 
 void BKE_gpencil_get_range_selected(struct bGPDlayer *gpl, int *r_initframe, int *r_endframe);
 float BKE_gpencil_multiframe_falloff_calc(
diff --git a/source/blender/blenkernel/intern/gpencil.c b/source/blender/blenkernel/intern/gpencil.c
index 842fa85bf76..ff638eaf082 100644
--- a/source/blender/blenkernel/intern/gpencil.c
+++ b/source/blender/blenkernel/intern/gpencil.c
@@ -1958,3 +1958,83 @@ bool BKE_gpencil_trim_stroke(bGPDstroke *gps)
   }
   return intersect;
 }
+
+/**
+ * Close stroke
+ * \param gps: Stroke to close
+ */
+bool BKE_gpencil_close_stroke(bGPDstroke *gps)
+{
+  bGPDspoint *pt1 = NULL;
+  bGPDspoint *pt2 = NULL;
+
+  /* Only can close a stroke with 3 points or more. */
+  if (gps->totpoints < 3) {
+    return false;
+  }
+
+  /* Calc average distance between points to get same level of sampling. */
+  float dist_tot = 0.0f;
+  for (int i = 0; i < gps->totpoints - 1; i++) {
+    pt1 = &gps->points[i];
+    pt2 = &gps->points[i + 1];
+    dist_tot += len_v3v3(&pt1->x, &pt2->x);
+  }
+  /* Calc the average distance. */
+  float dist_avg = dist_tot / (gps->totpoints - 1);
+
+  /* Calc distance between last and first point. */
+  pt1 = &gps->points[gps->totpoints - 1];
+  pt2 = &gps->points[0];
+  float dist_close = len_v3v3(&pt1->x, &pt2->x);
+
+  /* Calc number of points required using the average distance. */
+  int tot_newpoints = MAX2(dist_close / dist_avg, 1);
+
+  /* Resize stroke array. */
+  int old_tot = gps->totpoints;
+  gps->totpoints += tot_newpoints;
+  gps->points = MEM_recallocN(gps->points, sizeof(*gps->points) * gps->totpoints);
+  if (gps->dvert != NULL) {
+    gps->dvert = MEM_recallocN(gps->dvert, sizeof(*gps->dvert) * gps->totpoints);
+  }
+
+  /* Generate new points */
+  pt1 = &gps->points[old_tot - 1];
+  pt2 = &gps->points[0];
+  bGPDspoint *pt = &gps->points[old_tot];
+  for (int i = 1; i < tot_newpoints + 1; i++, pt++) {
+    float step = ((float)i / (float)tot_newpoints);
+    /* Clamp last point to be near, but not on top of first point. */
+    CLAMP(step, 0.0f, 0.99f);
+
+    /* Average point. */
+    interp_v3_v3v3(&pt->x, &pt1->x, &pt2->x, step);
+    pt->pressure = interpf(pt2->pressure, pt1->pressure, step);
+    pt->strength = interpf(pt2->strength, pt1->strength, step);
+    pt->flag = 0;
+
+    /* Set weights. */
+    if (gps->dvert != NULL) {
+      MDeformVert *dvert1 = &gps->dvert[old_tot - 1];
+      MDeformWeight *dw1 = defvert_verify_index(dvert1, 0);
+      float weight_1 = dw1 ? dw1->weight : 0.0f;
+
+      MDeformVert *dvert2 = &gps->dvert[0];
+      MDeformWeight *dw2 = defvert_verify_index(dvert2, 0);
+      float weight_2 = dw2 ? dw2->weight : 0.0f;
+
+      MDeformVert *dvert_final = &gps->dvert[old_tot + i - 1];
+      dvert_final->totweight = 0;
+      MDeformWeight *dw = defvert_verify_index(dvert_final, 0);
+      if (dvert_final->dw) {
+        dw->weight = interpf(weight_2, weight_1, step);
+      }
+    }
+  }
+
+  /* Enable cyclic flag. */
+  gps->flag |= GP_STROKE_CYCLIC;
+
+  return true;
+}