/* change stroke thickness */
static void deformStroke(GpencilModifierData *md,
                         Depsgraph *UNUSED(depsgraph),
                         Object *ob,
                         bGPDlayer *gpl,
                         bGPDframe *UNUSED(gpf),
                         bGPDstroke *gps)
{
  WeightCurvGpencilModifierData *mmd = (WeightCurvGpencilModifierData *)md;
  const int def_nr = BKE_object_defgroup_name_index(ob, mmd->vgname);

  if (!is_stroke_affected_by_modifier(ob,
                                      mmd->layername,
                                      mmd->material,
                                      mmd->pass_index,
                                      mmd->layer_pass,
                                      1,
                                      gpl,
                                      gps,
                                      mmd->flag & GP_WEIGHT_INVERT_LAYER,
                                      mmd->flag & GP_WEIGHT_INVERT_PASS,
                                      mmd->flag & GP_WEIGHT_INVERT_LAYERPASS,
                                      mmd->flag & GP_WEIGHT_INVERT_MATERIAL)) {
    return;
  }

  const int target_def_nr = BKE_object_defgroup_name_index(ob, mmd->target_vgname);

  if (target_def_nr == -1) {
    return;
  }

  /* Ensure there is a vertex group. */
  BKE_gpencil_dvert_ensure(gps);

  float *angle_weighted = MEM_callocN(sizeof(float) * (gps->totpoints - 2) * 3,
                                      "gp angle weighted");
  float *dists = MEM_callocN(sizeof(float) * gps->totpoints - 1, "gp dist weighted");
  float dist_sum = 0;

  float vec1[3], vec2[3];
  sub_v3_v3v3(vec1, &gps->points[1].x, &gps->points->x);
  for (int i = 1; i < gps->totpoints; i++) {
    bGPDspoint *pt = &gps->points[i - 1];
    dists[i - 1] = len_v3v3(&pt->x, &pt[1].x);
    dist_sum += dists[i - 1];
    if (i < gps->totpoints - 1) {
      float *no = &angle_weighted[(i - 1) * 3];
      float angle = angle_normalized_v3v3(vec1, vec2);
      sub_v3_v3v3(vec2, &pt[2].x, &pt[1].x);
      cross_v3_v3v3(no, vec1, vec2);
      normalize_v3_length(no, angle);
      copy_v3_v3(vec1, vec2);
    }
  }

  float dist_lim = mmd->overshoot_distance / 2; /* Half the distance for each side. */
  if (mmd->flag & GP_WEIGHT_CURVATURE_RELATIVE_LENGTH) {
    dist_lim *= dist_sum;
  }

  float weight_pt = 1.0f;
  for (int i = 1; i < gps->totpoints - 1; i++) {
    MDeformVert *dvert = gps->dvert != NULL ? &gps->dvert[i] : NULL;
    /* Verify point is part of vertex group. */
    float weight = get_modifier_point_weight(
        dvert, (mmd->flag & GP_WEIGHT_INVERT_VGROUP) != 0, def_nr);
    if (weight < 0.0f) {
      continue;
    }

    // what now

    bGPDspoint *pt = &gps->points[i];
    float use_dist = 0;
    float sum_angle[3] = {0};
    for (int j = i + 1; j < gps->totpoints; j++) {
      if ((use_dist + dists[j]) < dist_lim) {
        add_v3_v3(sum_angle, )
      }
    }

    // float angle = angle_v3v3v3(&pt[0].x, &pt[1].x, &pt[2].x);
    float abc = len_v3v3(&pt[0].x, &pt[1].x) * len_v3v3(&pt[1].x, &pt[2].x) *
                len_v3v3(&pt[0].x, &pt[2].x);
    float v1[3], v2[3], crs[3];
    sub_v3_v3v3(v1, &pt[0].x, &pt[1].x);
    sub_v3_v3v3(v2, &pt[1].x, &pt[2].x);
    cross_v3_v3v3(crs, v1, v2);
    float k4 = len_v3(crs) * 2; /* = Area * 4 */
    float radius = k4 == 0 ? 0 : (abc / k4);
    weight_pt = radius == 0 ? 0 : (mmd->min_radius / radius);
    CLAMP(weight_pt, 0, 1);

    /* Invert weight if required. */
    if (mmd->flag & GP_WEIGHT_INVERT_OUTPUT) {
      weight_pt = 1.0f - weight_pt;
    }
    weight_pt = 0;

    /* Assign weight. */
    dvert = gps->dvert != NULL ? &gps->dvert[i] : NULL;
    if (dvert != NULL) {
      MDeformWeight *dw = BKE_defvert_ensure_index(dvert, target_def_nr);
      if (dw) {
        dw->weight = (mmd->flag & GP_WEIGHT_MULTIPLY_DATA) ? dw->weight * weight_pt : weight_pt;
        CLAMP(dw->weight, mmd->min_weight, 1.0f);
      }
    }
  }
}
/* change stroke thickness */
static void deformStroke(GpencilModifierData *md,
                         Depsgraph *UNUSED(depsgraph),
                         Object *ob,
                         bGPDlayer *gpl,
                         bGPDframe *UNUSED(gpf),
                         bGPDstroke *gps)
{
  WeightCurvGpencilModifierData *mmd = (WeightCurvGpencilModifierData *)md;
  const int def_nr = BKE_object_defgroup_name_index(ob, mmd->vgname);

  if (!is_stroke_affected_by_modifier(ob,
                                      mmd->layername,
                                      mmd->material,
                                      mmd->pass_index,
                                      mmd->layer_pass,
                                      1,
                                      gpl,
                                      gps,
                                      mmd->flag & GP_WEIGHT_INVERT_LAYER,
                                      mmd->flag & GP_WEIGHT_INVERT_PASS,
                                      mmd->flag & GP_WEIGHT_INVERT_LAYERPASS,
                                      mmd->flag & GP_WEIGHT_INVERT_MATERIAL)) {
    return;
  }

  const int target_def_nr = BKE_object_defgroup_name_index(ob, mmd->target_vgname);

  if (target_def_nr == -1) {
    return;
  }

  /* Ensure there is a vertex group. */
  BKE_gpencil_dvert_ensure(gps);

  float *angle_weighted = MEM_callocN(sizeof(float) * (gps->totpoints - 2) * 3,
                                      "gp angle weighted");
  float *dists = MEM_callocN(sizeof(float) * gps->totpoints - 1, "gp dist weighted");
  float dist_sum = 0;

  float vec1[3], vec2[3];
  sub_v3_v3v3(vec1, &gps->points[1].x, &gps->points->x);
  for (int i = 1; i < gps->totpoints; i++) {
    bGPDspoint *pt = &gps->points[i - 1];
    dists[i - 1] = len_v3v3(&pt->x, &pt[1].x);
    dist_sum += dists[i - 1];
    if (i < gps->totpoints - 1) {
      float *no = &angle_weighted[(i - 1) * 3];
      float angle = angle_normalized_v3v3(vec1, vec2);
      sub_v3_v3v3(vec2, &pt[2].x, &pt[1].x);
      cross_v3_v3v3(no, vec1, vec2);
      normalize_v3_length(no, angle);
      copy_v3_v3(vec1, vec2);
    }
  }

  float dist_lim = mmd->overshoot_distance / 2; /* Half the distance for each side. */
  if (mmd->flag & GP_WEIGHT_CURVATURE_RELATIVE_LENGTH) {
    dist_lim *= dist_sum;
  }

  float weight_pt = 1.0f;
  for (int i = 1; i < gps->totpoints - 1; i++) {
    MDeformVert *dvert = gps->dvert != NULL ? &gps->dvert[i] : NULL;
    /* Verify point is part of vertex group. */
    float weight = get_modifier_point_weight(
        dvert, (mmd->flag & GP_WEIGHT_INVERT_VGROUP) != 0, def_nr);
    if (weight < 0.0f) {
      continue;
    }

    // what now?

    /* Assign weight. */
    dvert = gps->dvert != NULL ? &gps->dvert[i] : NULL;
    if (dvert != NULL) {
      MDeformWeight *dw = BKE_defvert_ensure_index(dvert, target_def_nr);
      if (dw) {
        dw->weight = (mmd->flag & GP_WEIGHT_MULTIPLY_DATA) ? dw->weight * weight_pt : weight_pt;
        CLAMP(dw->weight, mmd->min_weight, 1.0f);
      }
    }
  }
}