LineArt: Camera Overscan

Expand camera effective region to a portion beyond image frame so strokes won't end right at the border.

Reviewed By: Antonio Vazquez (antoniov)

Differential Revision: https://developer.blender.org/D12049

source/blender/gpencil_modifiers/intern/MOD_gpencillineart.c

@@ -380,6 +380,8 @@ static void options_panel_draw(const bContext *UNUSED(C), Panel *panel)
     return;
   }
 
+  uiItemR(layout, ptr, "overscan", 0, NULL, ICON_NONE);
+
   uiLayout *col = uiLayoutColumn(layout, true);
 
   uiItemR(col, ptr, "use_remove_doubles", 0, NULL, ICON_NONE);

source/blender/gpencil_modifiers/intern/lineart/MOD_lineart.h

@@ -228,6 +228,8 @@ typedef struct LineartRenderBuffer {
   double view_projection[4][4];
   double view[4][4];
 
+  float overscan;
+
   struct LineartBoundingArea *initial_bounding_areas;
   unsigned int bounding_area_count;
 

source/blender/gpencil_modifiers/intern/lineart/lineart_cpu.c

@@ -2013,7 +2013,10 @@ static void lineart_geometry_load_assign_thread(LineartObjectLoadTaskInfo *olti_
   use_olti->pending = obi;
 }
 
-static bool lineart_geometry_check_visible(double (*model_view_proj)[4], Object *use_ob)
+static bool lineart_geometry_check_visible(double (*model_view_proj)[4],
+                                           double shift_x,
+                                           double shift_y,
+                                           Object *use_ob)
 {
   BoundBox *bb = BKE_object_boundbox_get(use_ob);
   if (!bb) {
@@ -2027,6 +2030,8 @@ static bool lineart_geometry_check_visible(double (*model_view_proj)[4], Object
     copy_v3db_v3fl(co[i], bb->vec[i]);
     copy_v3_v3_db(tmp, co[i]);
     mul_v4_m4v3_db(co[i], model_view_proj, tmp);
+    co[i][0] -= shift_x * 2 * co[i][3];
+    co[i][1] -= shift_y * 2 * co[i][3];
   }
 
   bool cond[6] = {true, true, true, true, true, true};
@@ -2062,11 +2067,6 @@ static void lineart_main_load_geometries(
   int fit = BKE_camera_sensor_fit(cam->sensor_fit, rb->w, rb->h);
   double asp = ((double)rb->w / (double)rb->h);
 
-  double t_start;
-
-  if (G.debug_value == 4000) {
-    t_start = PIL_check_seconds_timer();
-  }
   int bound_box_discard_count = 0;
 
   if (cam->type == CAM_PERSP) {
@@ -2076,14 +2076,20 @@ static void lineart_main_load_geometries(
     if (fit == CAMERA_SENSOR_FIT_HOR && asp < 1) {
       sensor /= asp;
     }
-    double fov = focallength_to_fov(cam->lens, sensor);
+    const double fov = focallength_to_fov(cam->lens / (1 + rb->overscan), sensor);
     lineart_matrix_perspective_44d(proj, fov, asp, cam->clip_start, cam->clip_end);
   }
   else if (cam->type == CAM_ORTHO) {
-    double w = cam->ortho_scale / 2;
+    const double w = cam->ortho_scale / 2;
     lineart_matrix_ortho_44d(proj, -w, w, -w / asp, w / asp, cam->clip_start, cam->clip_end);
   }
 
+  double t_start;
+
+  if (G.debug_value == 4000) {
+    t_start = PIL_check_seconds_timer();
+  }
+
   invert_m4_m4(inv, rb->cam_obmat);
   mul_m4db_m4db_m4fl_uniq(result, proj, inv);
   copy_m4_m4_db(proj, result);
@@ -2130,7 +2136,7 @@ static void lineart_main_load_geometries(
       continue;
     }
 
-    if (!lineart_geometry_check_visible(obi->model_view_proj, use_ob)) {
+    if (!lineart_geometry_check_visible(obi->model_view_proj, rb->shift_x, rb->shift_y, use_ob)) {
       if (G.debug_value == 4000) {
         bound_box_discard_count++;
       }
@@ -3023,6 +3029,11 @@ static LineartRenderBuffer *lineart_create_render_buffer(Scene *scene,
   rb->shift_x = fit == CAMERA_SENSOR_FIT_HOR ? c->shiftx : c->shiftx / asp;
   rb->shift_y = fit == CAMERA_SENSOR_FIT_VERT ? c->shifty : c->shifty * asp;
 
+  rb->overscan = lmd->overscan;
+
+  rb->shift_x /= (1 + rb->overscan);
+  rb->shift_y /= (1 + rb->overscan);
+
   rb->crease_threshold = cos(M_PI - lmd->crease_threshold);
   rb->angle_splitting_threshold = lmd->angle_splitting_threshold;
   rb->chaining_image_threshold = lmd->chaining_image_threshold;

source/blender/makesdna/DNA_gpencil_modifier_defaults.h

@@ -307,6 +307,7 @@
     .calculation_flags = LRT_ALLOW_DUPLI_OBJECTS | LRT_ALLOW_CLIPPING_BOUNDARIES, \
     .angle_splitting_threshold = DEG2RAD(60.0f), \
     .chaining_image_threshold = 0.001f, \
+    .overscan = 0.1f,\
   }
 
 #define _DNA_DEFAULT_LengthGpencilModifierData \

source/blender/makesdna/DNA_gpencil_modifier_types.h

@@ -963,6 +963,12 @@ typedef struct LineartGpencilModifierData {
   char source_vertex_group[64];
   char vgname[64];
 
+  /* Camera focal length is divided by (1 + overscan), before caluclation, which give a wider FOV,
+   * this doesn't change coordinates range internally (-1, 1), but makes the caluclated frame
+   * bigger than actual output. This is for the easier shifting calculation. A value of 0.5 means
+   * the "internal" focal length become 2/3 of the actual camera. */
+  float overscan;
+
   float opacity;
   short thickness;
 
@@ -970,7 +976,7 @@ typedef struct LineartGpencilModifierData {
   unsigned char material_mask_bits;
   unsigned char intersection_mask;
 
-  char _pad[7];
+  char _pad[3];
 
   /** `0..1` range for cosine angle */
   float crease_threshold;

source/blender/makesrna/intern/rna_gpencil_modifier.c

@@ -3137,6 +3137,15 @@ static void rna_def_modifier_gpencillineart(BlenderRNA *brna)
                            "Certain settings will be unavailable");
   RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
 
+  prop = RNA_def_property(srna, "overscan", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_ui_text(
+      prop,
+      "Overscan",
+      "A margin to prevent strokes from ending abruptly at the edge of the image");
+  RNA_def_property_ui_range(prop, 0.0f, 0.5f, 0.01f, 3);
+  RNA_def_property_range(prop, 0.0f, 0.5f);
+  RNA_def_property_update(prop, NC_SCENE, "rna_GpencilModifier_update");
+
   prop = RNA_def_property(srna, "thickness", PROP_INT, PROP_NONE);
   RNA_def_property_ui_text(prop, "Thickness", "The thickness for the generated strokes");
   RNA_def_property_ui_range(prop, 1, 100, 1, 1);