54 lines
2.3 KiB
C#
54 lines
2.3 KiB
C#
using Unity.Collections.LowLevel.Unsafe;
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using UnityEngine.Experimental.Rendering;
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namespace UnityEngine.InputSystem.Utilities
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{
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internal static class SpriteUtilities
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{
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public static unsafe Sprite CreateCircleSprite(int radius, Color32 colour)
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{
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// cache the diameter
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var d = radius * 2;
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var texture = new Texture2D(d, d, DefaultFormat.LDR, TextureCreationFlags.None);
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var colours = texture.GetRawTextureData<Color32>();
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var coloursPtr = (Color32*)colours.GetUnsafePtr();
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UnsafeUtility.MemSet(coloursPtr, 0, colours.Length * UnsafeUtility.SizeOf<Color32>());
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// pack the colour into a ulong so we can write two pixels at a time to the texture data
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var colorPtr = (uint*)UnsafeUtility.AddressOf(ref colour);
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var colourAsULong = *(ulong*)colorPtr << 32 | *colorPtr;
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float rSquared = radius * radius;
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// loop over the texture memory one column at a time filling in a line between the two x coordinates
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// of the circle at each column
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for (var y = -radius; y < radius; y++)
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{
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// for the current column, calculate what the x coordinate of the circle would be
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// using x^2 + y^2 = r^2, or x^2 = r^2 - y^2. The square root of the value of the
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// x coordinate will equal half the width of the circle at the current y coordinate
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var halfWidth = (int)Mathf.Sqrt(rSquared - y * y);
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// position the pointer so it points at the memory where we should start filling in
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// the current line
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var ptr = coloursPtr
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+ (y + radius) * d // the position of the memory at the start of the row at the current y coordinate
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+ radius - halfWidth; // the position along the row where we should start inserting colours
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// fill in two pixels at a time
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for (var x = 0; x < halfWidth; x++)
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{
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*(ulong*)ptr = colourAsULong;
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ptr += 2;
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}
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}
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texture.Apply();
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var sprite = Sprite.Create(texture, new Rect(0, 0, d, d), new Vector2(radius, radius), 1, 0, SpriteMeshType.FullRect);
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return sprite;
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}
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}
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}
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