UI: Improve circle drawing of cursor for uv sculpting

Calculate segments based on radius.

Differential Revision: https://developer.blender.org/D15591

release/scripts/modules/gpu_extras/presets.py

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-def draw_circle_2d(position, color, radius, *, segments=32):
+def draw_circle_2d(position, color, radius, *, segments=None):
     """
     Draw a circle.
 
@@ -11,10 +11,11 @@ def draw_circle_2d(position, color, radius, *, segments=32):
     :arg radius: Radius of the circle.
     :type radius: float
     :arg segments: How many segments will be used to draw the circle.
-        Higher values give besser results but the drawing will take longer.
-    :type segments: int
+        Higher values give better results but the drawing will take longer.
+        If None or not specified, an automatic value will be calculated.
+    :type segments: int or None
     """
-    from math import sin, cos, pi
+    from math import sin, cos, pi, ceil, acos
     import gpu
     from gpu.types import (
         GPUBatch,
@@ -22,6 +23,12 @@ def draw_circle_2d(position, color, radius, *, segments=32):
         GPUVertFormat,
     )
 
+    if segments is None:
+        max_pixel_error = 0.25 # TODO: multiply 0.5 by display dpi
+        segments = int(ceil(pi / acos(1.0 - max_pixel_error / radius)))
+        segments = max(segments, 8)
+        segments = min(segments, 1000)
+
     if segments <= 0:
         raise ValueError("Amount of segments must be greater than 0.")
 

release/scripts/startup/bl_ui/space_toolsystem_toolbar.py

@@ -1889,7 +1889,7 @@ class _defs_image_uv_sculpt:
                 if brush is None:
                     return
                 radius = brush.size
-            draw_circle_2d(xy, (1.0,) * 4, radius, segments=32)
+            draw_circle_2d(xy, (1.0,) * 4, radius)
 
         return generate_from_enum_ex(
             context,