sbox-public/engine/Sandbox.Engine/Resources/Textures/Generators/RadialGradientTextureGenerator.cs

using System.Text.Json.Serialization;
using System.Threading;

namespace Sandbox.Resources;

[Title( "Gradient - Radial" )]
[Icon( "vignette" )]
[ClassName( "gradientradial" )]
[Expose]
public class RadialGradient : TextureGenerator
{
	public Vector2Int Size { get; set; } = 128;

	[Range( 0, 2 )]
	public bool IsHdr { get; set; } = false;

	[Range( 0, 2 )]
	public float Scale { get; set; } = 1;

	[Range( 0, 1 )]
	public Vector2 Center { get; set; } = 0.5f;

	[KeyProperty]
	public Gradient Gradient { get; set; } = new Gradient( new Gradient.ColorFrame( 0.0f, Color.Cyan ), new Gradient.ColorFrame( 0.2f, Color.Red ), new Gradient.ColorFrame( 1.0f, Color.Yellow ) );

	[Header( "Normal Map" ), Title( "Height to Normal" )]
	public bool ConvertHeightToNormals { get; set; }

	[ShowIf( "ConvertHeightToNormals", true )]
	public float NormalScale { get; set; } = 1;

	[Hide, JsonIgnore]
	public override bool CacheToDisk => true;

	protected override ValueTask<Texture> CreateTexture( Options options, CancellationToken ct )
	{
		var w = Size.x.Clamp( 1, 1024 * 4 );
		var h = Size.y.Clamp( 1, 1024 * 4 );

		using var bitmap = new Bitmap( w, h, IsHdr && !ConvertHeightToNormals );
		bitmap.Clear( Color.Transparent );

		bitmap.SetRadialGradient( bitmap.Rect.Size * Center, Scale * bitmap.Width, Gradient );
		bitmap.DrawRect( bitmap.Rect );

		if ( ConvertHeightToNormals )
		{
			using var normalMap = bitmap.HeightmapToNormalMap( NormalScale );
			return ValueTask.FromResult( normalMap.ToTexture() );
		}

		return ValueTask.FromResult( bitmap.ToTexture() );
	}
}