UV: extend custom grid sizes to set each axis separately

For example, allows a custom UV grid size of 4 x 12.

TODO: Fix snapping with custom UV grid sizes.

Manifest Tasks: T78391

Differential Revision: https://developer.blender.org/D16000

10 files changed, 103 insertions, 82 deletions

diff --git a/release/scripts/startup/bl_ui/space_image.py b/release/scripts/startup/bl_ui/space_image.py
index da752b5fe00..b624d024843 100644
--- a/release/scripts/startup/bl_ui/space_image.py
+++ b/release/scripts/startup/bl_ui/space_image.py
@@ -1537,9 +1537,12 @@ class IMAGE_PT_overlay_guides(Panel):
             row = col.row(align=True)
             sub = row.row(align=True)
             sub.prop(uvedit, "use_custom_grid", text="")
-            sub = sub.row(align=True)
-            sub.active = uvedit.use_custom_grid
-            sub.prop(uvedit, "custom_grid_subdivisions", text="")
+            if uvedit.use_custom_grid:
+                row = layout.row()
+                row.use_property_split = True
+                row.use_property_decorate = False
+                sub = sub.row(align=True)
+                sub.prop(uvedit, "custom_grid_subdivisions", text="")
 
             row = layout.row()
             row.use_property_split = True
diff --git a/source/blender/blenloader/intern/versioning_300.cc b/source/blender/blenloader/intern/versioning_300.cc
index e789cd66632..8f1f2fa2c17 100644
--- a/source/blender/blenloader/intern/versioning_300.cc
+++ b/source/blender/blenloader/intern/versioning_300.cc
@@ -2401,11 +2401,6 @@ void blo_do_versions_300(FileData *fd, Library *UNUSED(lib), Main *bmain)
               }
               break;
             }
-            case SPACE_IMAGE: {
-              SpaceImage *sima = (SpaceImage *)sl;
-              sima->custom_grid_subdiv = 10;
-              break;
-            }
           }
         }
       }
@@ -3426,5 +3421,21 @@ void blo_do_versions_300(FileData *fd, Library *UNUSED(lib), Main *bmain)
         }
       }
     }
+
+    /* Custom grids in UV Editor have separate X and Y divisions. */
+    LISTBASE_FOREACH (bScreen *, screen, &bmain->screens) {
+      LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+        LISTBASE_FOREACH (SpaceLink *, sl, &area->spacedata) {
+          switch (sl->spacetype) {
+            case SPACE_IMAGE: {
+              SpaceImage *sima = (SpaceImage *)sl;
+              sima->custom_grid_subdiv[0] = 10;
+              sima->custom_grid_subdiv[1] = 10;
+              break;
+            }
+          }
+        }
+      }
+    }
   }
 }
diff --git a/source/blender/draw/engines/overlay/overlay_grid.cc b/source/blender/draw/engines/overlay/overlay_grid.cc
index 71abcf91223..4a4d9ee6c19 100644
--- a/source/blender/draw/engines/overlay/overlay_grid.cc
+++ b/source/blender/draw/engines/overlay/overlay_grid.cc
@@ -31,6 +31,7 @@ void OVERLAY_grid_init(OVERLAY_Data *vedata)
   float *zplane_axes = pd->grid.zplane_axes;
   float grid_steps[SI_GRID_STEPS_LEN] = {
       0.001f, 0.01f, 0.1f, 1.0f, 10.0f, 100.0f, 1000.0f, 10000.0f};
+  float grid_steps_y[SI_GRID_STEPS_LEN] = {0.0f}; /* When zero, use value from grid_steps. */
   OVERLAY_GridBits grid_flag = OVERLAY_GridBits(0), zneg_flag = OVERLAY_GridBits(0),
                    zpos_flag = OVERLAY_GridBits(0);
   grid->line_size = max_ff(0.0f, U.pixelsize - 1.0f) * 0.5f;
@@ -68,7 +69,7 @@ void OVERLAY_grid_init(OVERLAY_Data *vedata)
     }
 
     grid->zoom_factor = ED_space_image_zoom_level(v2d, SI_GRID_STEPS_LEN);
-    ED_space_image_grid_steps(sima, grid_steps, SI_GRID_STEPS_LEN);
+    ED_space_image_grid_steps(sima, grid_steps, grid_steps_y, SI_GRID_STEPS_LEN);
   }
   else {
     /* SPACE_VIEW3D */
@@ -197,6 +198,7 @@ void OVERLAY_grid_init(OVERLAY_Data *vedata)
   /* Convert to UBO alignment. */
   for (int i = 0; i < SI_GRID_STEPS_LEN; i++) {
     grid->steps[i][0] = grid_steps[i];
+    grid->steps[i][1] = (grid_steps_y[i] != 0.0f) ? grid_steps_y[i] : grid_steps[i];
   }
   pd->grid.grid_flag = grid_flag;
   pd->grid.zneg_flag = zneg_flag;
diff --git a/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl b/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl
index 54a4231590e..2c81966fe50 100644
--- a/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl
+++ b/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl
@@ -1,6 +1,6 @@
 /**
  * Infinite grid:
- * Draw antialiazed grid and axes of different sizes with smooth blending between Level of details.
+ * Draw antialiased grid and axes of different sizes with smooth blending between levels of detail.
  * We draw multiple triangles to avoid float precision issues due to perspective interpolation.
  **/
 
@@ -8,29 +8,33 @@
 #pragma BLENDER_REQUIRE(common_math_lib.glsl)
 
 /**
- * We want to know how much a pixel is covered by a line.
- * We replace the square pixel with acircle of the same area and try to find the intersection area.
- * The area we search is the circular segment. https://en.wikipedia.org/wiki/Circular_segment
- * The formula for the area uses inverse trig function and is quite complexe. Instead,
- * we approximate it by using the smoothstep function and a 1.05 factor to the disc radius.
+ * We want to know how much of a pixel is covered by a line.
+ * Here, we imagine the square pixel is a circle with the same area and try to find the
+ * intersection area. The overlap area is a circular segment.
+ * https://en.wikipedia.org/wiki/Circular_segment The formula for the area uses inverse trig
+ * function and is quite complex. Instead, we approximate it by using the smoothstep function and
+ * a 1.05 factor to the disc radius.
+ *
+ * For an alternate approach, see:
+ * https://developer.nvidia.com/gpugems/gpugems2/part-iii-high-quality-rendering/chapter-22-fast-prefiltered-lines
  */
 #define M_1_SQRTPI 0.5641895835477563 /* 1/sqrt(pi) */
 #define DISC_RADIUS (M_1_SQRTPI * 1.05)
-#define GRID_LINE_SMOOTH_START (0.5 - DISC_RADIUS)
-#define GRID_LINE_SMOOTH_END (0.5 + DISC_RADIUS)
+#define GRID_LINE_SMOOTH_START (0.5 + DISC_RADIUS)
+#define GRID_LINE_SMOOTH_END (0.5 - DISC_RADIUS)
 #define GRID_LINE_STEP(dist) smoothstep(GRID_LINE_SMOOTH_START, GRID_LINE_SMOOTH_END, dist)
 
-float get_grid(vec2 co, vec2 fwidthCos, float grid_scale)
+float get_grid(vec2 co, vec2 fwidthCos, vec2 grid_scale)
 {
-  float half_size = grid_scale / 2.0;
+  vec2 half_size = grid_scale / 2.0;
   /* Triangular wave pattern, amplitude is [0, half_size]. */
-  vec2 grid_domain = abs(mod(co + half_size, vec2(grid_scale)) - half_size);
+  vec2 grid_domain = abs(mod(co + half_size, grid_scale) - half_size);
   /* Modulate by the absolute rate of change of the coordinates
    * (make line have the same width under perspective). */
   grid_domain /= fwidthCos;
   /* Collapse waves. */
   float line_dist = min(grid_domain.x, grid_domain.y);
-  return 1.0 - GRID_LINE_STEP(line_dist - grid_buf.line_size);
+  return GRID_LINE_STEP(line_dist - grid_buf.line_size);
 }
 
 vec3 get_axes(vec3 co, vec3 fwidthCos, float line_size)
@@ -39,7 +43,7 @@ vec3 get_axes(vec3 co, vec3 fwidthCos, float line_size)
   /* Modulate by the absolute rate of change of the coordinates
    * (make line have the same width under perspective). */
   axes_domain /= fwidthCos;
-  return 1.0 - GRID_LINE_STEP(axes_domain - (line_size + grid_buf.line_size));
+  return GRID_LINE_STEP(axes_domain - (line_size + grid_buf.line_size));
 }
 
 #define linearstep(p0, p1, v) (clamp(((v) - (p0)) / abs((p1) - (p0)), 0.0, 1.0))
@@ -106,49 +110,30 @@ void main()
       grid_res = grid_buf.zoom_factor;
     }
 
-    /* From biggest to smallest. */
-    vec4 scale;
-#define grid_step(a) grid_buf.steps[a].x
-#if 0 /* Inefficient. */
-    int step_id = 0;
-    scale[0] = 0.0;
-    scale[1] = grid_step(0);
-    while (scale[1] < grid_res && step_id != STEPS_LEN - 1) {
-      scale[0] = scale[1];
-      scale[1] = grid_step(++step_id);
-    }
-    scale[2] = grid_step(min(step_id + 1, STEPS_LEN - 1));
-    scale[3] = grid_step(min(step_id + 2, STEPS_LEN - 1));
-#else
-    /* For more efficiency, unroll the loop above. */
-    if (grid_step(0) > grid_res) {
-      scale = vec4(0.0, grid_step(0), grid_step(1), grid_step(2));
-    }
-    else if (grid_step(1) > grid_res) {
-      scale = vec4(grid_step(0), grid_step(1), grid_step(2), grid_step(3));
-    }
-    else if (grid_step(2) > grid_res) {
-      scale = vec4(grid_step(1), grid_step(2), grid_step(3), grid_step(4));
-    }
-    else if (grid_step(3) > grid_res) {
-      scale = vec4(grid_step(2), grid_step(3), grid_step(4), grid_step(5));
-    }
-    else if (grid_step(4) > grid_res) {
-      scale = vec4(grid_step(3), grid_step(4), grid_step(5), grid_step(6));
-    }
-    else if (grid_step(5) > grid_res) {
-      scale = vec4(grid_step(4), grid_step(5), grid_step(6), grid_step(7));
-    }
-    else if (grid_step(6) > grid_res) {
-      scale = vec4(grid_step(5), grid_step(6), grid_step(7), grid_step(7));
-    }
-    else {
-      scale = vec4(grid_step(6), grid_step(7), grid_step(7), grid_step(7));
+/** Keep in sync with `SI_GRID_STEPS_LEN` in `DNA_space_types.h`. */
+#define STEPS_LEN 8
+    int step_id_x = STEPS_LEN - 1;
+    int step_id_y = STEPS_LEN - 1;
+
+    /* Loop backwards a compile-time-constant number of steps. */
+    for (int i = STEPS_LEN - 2; i >= 0; --i) {
+      step_id_x = (grid_res < grid_buf.steps[i].x) ? i : step_id_x; /* Branchless. */
+      step_id_y = (grid_res < grid_buf.steps[i].y) ? i : step_id_y;
     }
-#endif
-#undef grid_step
 
-    float blend = 1.0 - linearstep(scale[0], scale[1], grid_res);
+    /* From biggest to smallest. */
+    float scale0x = step_id_x > 0 ? grid_buf.steps[step_id_x - 1].x : 0.0;
+    float scaleAx = grid_buf.steps[step_id_x].x;
+    float scaleBx = grid_buf.steps[min(step_id_x + 1, STEPS_LEN - 1)].x;
+    float scaleCx = grid_buf.steps[min(step_id_x + 2, STEPS_LEN - 1)].x;
+
+    float scale0y = step_id_y > 0 ? grid_buf.steps[step_id_y - 1].y : 0.0;
+    float scaleAy = grid_buf.steps[step_id_y].y;
+    float scaleBy = grid_buf.steps[min(step_id_y + 1, STEPS_LEN - 1)].y;
+    float scaleCy = grid_buf.steps[min(step_id_y + 2, STEPS_LEN - 1)].y;
+
+    /* Subtract from 1.0 to fix blending when `scale0x == scaleAx`. */
+    float blend = 1.0 - linearstep(scale0x + scale0y, scaleAx + scaleAy, grid_res + grid_res);
     blend = blend * blend * blend;
 
     vec2 grid_pos, grid_fwidth;
@@ -165,9 +150,9 @@ void main()
       grid_fwidth = fwidthPos.xy;
     }
 
-    float gridA = get_grid(grid_pos, grid_fwidth, scale[1]);
-    float gridB = get_grid(grid_pos, grid_fwidth, scale[2]);
-    float gridC = get_grid(grid_pos, grid_fwidth, scale[3]);
+    float gridA = get_grid(grid_pos, grid_fwidth, vec2(scaleAx, scaleAy));
+    float gridB = get_grid(grid_pos, grid_fwidth, vec2(scaleBx, scaleBy));
+    float gridC = get_grid(grid_pos, grid_fwidth, vec2(scaleCx, scaleCy));
 
     out_color = colorGrid;
     out_color.a *= gridA * blend;
diff --git a/source/blender/editors/include/ED_image.h b/source/blender/editors/include/ED_image.h
index ef75277b1ea..da303f3552b 100644
--- a/source/blender/editors/include/ED_image.h
+++ b/source/blender/editors/include/ED_image.h
@@ -32,7 +32,8 @@ struct wmWindowManager;
 
 float ED_space_image_zoom_level(const struct View2D *v2d, int grid_dimension);
 void ED_space_image_grid_steps(struct SpaceImage *sima,
-                               float grid_steps[SI_GRID_STEPS_LEN],
+                               float grid_steps_x[SI_GRID_STEPS_LEN],
+                               float grid_steps_y[SI_GRID_STEPS_LEN],
                                int grid_dimension);
 /**
  * Calculate the increment snapping value for UV/image editor based on the zoom factor
diff --git a/source/blender/editors/space_image/image_draw.c b/source/blender/editors/space_image/image_draw.c
index 37a6e6dfcb1..8a934396229 100644
--- a/source/blender/editors/space_image/image_draw.c
+++ b/source/blender/editors/space_image/image_draw.c
@@ -585,18 +585,19 @@ float ED_space_image_zoom_level(const View2D *v2d, const int grid_dimension)
 }
 
 void ED_space_image_grid_steps(SpaceImage *sima,
-                               float grid_steps[SI_GRID_STEPS_LEN],
+                               float grid_steps_x[SI_GRID_STEPS_LEN],
+                               float grid_steps_y[SI_GRID_STEPS_LEN],
                                const int grid_dimension)
 {
-  if (sima->flag & SI_CUSTOM_GRID) {
-    for (int step = 0; step < SI_GRID_STEPS_LEN; step++) {
-      grid_steps[step] = powf(1, step) * (1.0f / ((float)sima->custom_grid_subdiv));
+  const int flag = sima->flag;
+  for (int step = 0; step < SI_GRID_STEPS_LEN; step++) {
+    if (flag & SI_CUSTOM_GRID) {
+      grid_steps_x[step] = 1.0f / sima->custom_grid_subdiv[0];
+      grid_steps_y[step] = 1.0f / sima->custom_grid_subdiv[1];
     }
-  }
-  else {
-    for (int step = 0; step < SI_GRID_STEPS_LEN; step++) {
-      grid_steps[step] = powf(grid_dimension, step) *
-                         (1.0f / (powf(grid_dimension, SI_GRID_STEPS_LEN)));
+    else {
+      grid_steps_x[step] = powf(grid_dimension, step - SI_GRID_STEPS_LEN);
+      grid_steps_y[step] = powf(grid_dimension, step - SI_GRID_STEPS_LEN);
     }
   }
 }
diff --git a/source/blender/editors/space_image/space_image.c b/source/blender/editors/space_image/space_image.c
index 096ae4fd328..2b65267644a 100644
--- a/source/blender/editors/space_image/space_image.c
+++ b/source/blender/editors/space_image/space_image.c
@@ -112,7 +112,8 @@ static SpaceLink *image_create(const ScrArea *UNUSED(area), const Scene *UNUSED(
   simage->tile_grid_shape[0] = 1;
   simage->tile_grid_shape[1] = 1;
 
-  simage->custom_grid_subdiv = 10;
+  simage->custom_grid_subdiv[0] = 10;
+  simage->custom_grid_subdiv[1] = 10;
 
   /* header */
   region = MEM_callocN(sizeof(ARegion), "header for image");
diff --git a/source/blender/editors/transform/transform.c b/source/blender/editors/transform/transform.c
index eb46da3579a..95aa48efd84 100644
--- a/source/blender/editors/transform/transform.c
+++ b/source/blender/editors/transform/transform.c
@@ -1719,11 +1719,17 @@ static void initSnapSpatial(TransInfo *t, float r_snap[2])
     int grid_size = SI_GRID_STEPS_LEN;
     float zoom_factor = ED_space_image_zoom_level(v2d, grid_size);
     float grid_steps[SI_GRID_STEPS_LEN];
+    float grid_steps_y[SI_GRID_STEPS_LEN];
 
-    ED_space_image_grid_steps(sima, grid_steps, grid_size);
+    ED_space_image_grid_steps(sima, grid_steps, grid_steps_y, grid_size);
     /* Snapping value based on what type of grid is used (adaptive-subdividing or custom-grid). */
     r_snap[0] = ED_space_image_increment_snap_value(grid_size, grid_steps, zoom_factor);
     r_snap[1] = r_snap[0] / 2.0f;
+
+    /* TODO: Implement snapping for custom grid sizes with `grid_steps[0] != grid_steps_y[0]`.
+     * r_snap_y[0] = ED_space_image_increment_snap_value(grid_size, grid_steps_y, zoom_factor);
+     * r_snap_y[1] = r_snap_y[0] / 2.0f;
+     */
   }
   else if (t->spacetype == SPACE_CLIP) {
     r_snap[0] = 0.125f;
diff --git a/source/blender/makesdna/DNA_space_types.h b/source/blender/makesdna/DNA_space_types.h
index a974330a2ac..44d4cef53a6 100644
--- a/source/blender/makesdna/DNA_space_types.h
+++ b/source/blender/makesdna/DNA_space_types.h
@@ -1236,11 +1236,10 @@ typedef struct SpaceImage {
 
   int tile_grid_shape[2];
   /**
-   * UV editor custom-grid. Value of `N` will produce `NxN` grid.
+   * UV editor custom-grid. Value of `{M,N}` will produce `MxN` grid.
    * Use when #SI_CUSTOM_GRID is set.
    */
-  int custom_grid_subdiv;
-  char _pad3[4];
+  int custom_grid_subdiv[2];
 
   MaskSpaceInfo mask_info;
   SpaceImageOverlay overlay;
diff --git a/source/blender/makesrna/intern/rna_space.c b/source/blender/makesrna/intern/rna_space.c
index bf25e3214f8..e2a3fcc367e 100644
--- a/source/blender/makesrna/intern/rna_space.c
+++ b/source/blender/makesrna/intern/rna_space.c
@@ -1886,6 +1886,15 @@ static void rna_SpaceUVEditor_tile_grid_shape_set(PointerRNA *ptr, const int *va
   }
 }
 
+static void rna_SpaceUVEditor_custom_grid_subdiv_set(PointerRNA *ptr, const int *values)
+{
+  SpaceImage *data = (SpaceImage *)(ptr->data);
+
+  for (int i = 0; i < 2; i++) {
+    data->custom_grid_subdiv[i] = CLAMPIS(values[i], 1, 5000);
+  }
+}
+
 /* Space Text Editor */
 
 static void rna_SpaceTextEditor_word_wrap_set(PointerRNA *ptr, bool value)
@@ -3611,9 +3620,12 @@ static void rna_def_space_image_uv(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Custom Grid", "Use a grid with a user-defined number of steps");
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_IMAGE, NULL);
 
-  prop = RNA_def_property(srna, "custom_grid_subdivisions", PROP_INT, PROP_NONE);
+  prop = RNA_def_property(srna, "custom_grid_subdivisions", PROP_INT, PROP_XYZ);
   RNA_def_property_int_sdna(prop, NULL, "custom_grid_subdiv");
+  RNA_def_property_array(prop, 2);
+  RNA_def_property_int_default(prop, 10);
   RNA_def_property_range(prop, 1, 5000);
+  RNA_def_property_int_funcs(prop, NULL, "rna_SpaceUVEditor_custom_grid_subdiv_set", NULL);
   RNA_def_property_ui_text(
       prop, "Dynamic Grid Size", "Number of grid units in UV space that make one UV Unit");
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_IMAGE, NULL);