tooll3--t3/Operators/Lib/mesh/generate/TorusMesh.cs

using T3.Core.Rendering;
using T3.Core.Utils;

namespace Lib.mesh.generate;

[Guid("a835ab86-29c1-438e-a7f7-2e297108bfd5")]
internal sealed class TorusMesh : Instance<TorusMesh>
{
    [Output(Guid = "f8f17f87-56f2-4411-b9bf-b9193b9aa90d")]
    public readonly Slot<MeshBuffers> Data = new();

    public TorusMesh()
    {
        Data.UpdateAction += Update;
    }

    private void Update(EvaluationContext context)
    {
        try
        {
            var majorRadius = Radius.GetValue(context);
            var tubeRadius = Thickness.GetValue(context);

            var segments = Segments.GetValue(context);
            var radiusSegments = segments.Width.Clamp(1, 10000) + 1;
            var tubeSegments = segments.Height.Clamp(1, 10000) + 1;

            var spin = Spin.GetValue(context);
            var radiusSpin = spin.X * MathUtils.ToRad;
            var spinMinorInRad = spin.Y * MathUtils.ToRad;

            var fill = Fill.GetValue(context);
            var fillRadius = fill.X / 360f;
            var tubeFill = fill.Y / 360f;

            var smoothAngle = SmoothAngle.GetValue(context);
                
            var useFlatShading = fillRadius / tubeSegments > smoothAngle / 360 || tubeFill / radiusSegments > smoothAngle / 360;
            var faceCount = (tubeSegments -1)  * (radiusSegments - 1) * 2;
            var verticesCount = tubeSegments * radiusSegments;

            // Create buffers
            if (_vertexBufferData.Length != verticesCount)
                _vertexBufferData = new PbrVertex[verticesCount];
                
            if (_indexBufferData.Length != faceCount)
                _indexBufferData = new Int3[faceCount];


            // Initialize
            var tubeAngleFraction = tubeFill / (tubeSegments -1) * 2.0 * Math.PI;
            var radiusAngleFraction = fillRadius / (radiusSegments -1) * 2.0 * Math.PI;

            for (int tubeIndex = 0; tubeIndex < tubeSegments; ++tubeIndex)
            {
                var tubeAngle = tubeIndex * tubeAngleFraction + spinMinorInRad;
                    
                double tubePosition1X = Math.Sin(tubeAngle)*tubeRadius;
                double tubePosition1Y = Math.Cos(tubeAngle)*tubeRadius;
                double tubePosition2X = Math.Sin(tubeAngle+ tubeAngleFraction)*tubeRadius;
                double tubePosition2Y = Math.Cos(tubeAngle+ tubeAngleFraction)*tubeRadius;

                var v0 = tubeIndex / (float)(tubeSegments-1);
                var v1 = (tubeIndex + 1) / (float)(tubeSegments-1);

                for (int radiusIndex = 0; radiusIndex < radiusSegments; ++radiusIndex)
                {
                    var vertexIndex = radiusIndex + tubeIndex * radiusSegments;
                    var faceIndex =  2 * (radiusIndex + tubeIndex * (radiusSegments-1));
                        
                    var u0 = (radiusIndex ) / (float)(radiusSegments-1);
                    var u1 = (radiusIndex +1)/ (float)(radiusSegments-1);

                    var radiusAngle = radiusIndex * radiusAngleFraction + radiusSpin;

                    var p = new Vector3((float)(Math.Sin(radiusAngle) * (tubePosition1X + majorRadius)),
                                        (float)(Math.Cos(radiusAngle) * (tubePosition1X + majorRadius)), 
                                        (float)tubePosition1Y);
                        
                    var p1 = new Vector3((float)(Math.Sin(radiusAngle + radiusAngleFraction) * (tubePosition1X + majorRadius)),
                                         (float)(Math.Cos(radiusAngle + radiusAngleFraction) * (tubePosition1X + majorRadius)), 
                                         (float)tubePosition1Y);
                        
                    var p2 = new Vector3((float)(Math.Sin(radiusAngle) * (tubePosition2X + majorRadius)),
                                         (float)(Math.Cos(radiusAngle) * (tubePosition2X + majorRadius)), 
                                         (float)tubePosition2Y);
                        
                    var uv0 = new Vector2(u0, v1);
                    var uv1 = new Vector2(u1, v1);
                    var uv2 = new Vector2(u1, v0);

                    var tubeCenter1 = new Vector3((float)Math.Sin(radiusAngle), (float)Math.Cos(radiusAngle), 0.0f) * majorRadius;
                    var normal0 = Vector3.Normalize(useFlatShading 
                                                        ? Vector3.Cross(p - p1, p - p2) 
                                                        : p - tubeCenter1);
                        
                    MeshUtils.CalcTBNSpace(p, uv0, p1, uv1, p2, uv2, normal0, out var tangent0, out var binormal0);

                    _vertexBufferData[vertexIndex + 0] = new PbrVertex
                                                             {
                                                                 Position = p,
                                                                 Normal = normal0,
                                                                 Tangent = tangent0,
                                                                 Bitangent = binormal0,
                                                                 Texcoord = uv0,
                                                                 Selection =1,
                                                                 ColorRgb = Vector3.One,
                                                             };

                    if (tubeIndex >= tubeSegments - 1 || radiusIndex >= radiusSegments - 1)
                        continue;
                        
                    _indexBufferData[faceIndex + 0] = new Int3(vertexIndex + 0, vertexIndex + 1, vertexIndex + radiusSegments);
                    _indexBufferData[faceIndex + 1] = new Int3(vertexIndex + radiusSegments , vertexIndex + 1, vertexIndex + radiusSegments+1);
                }
            }
                
            // Write Data
            ResourceManager.SetupStructuredBuffer(_vertexBufferData, PbrVertex.Stride * verticesCount, PbrVertex.Stride, ref _vertexBuffer);
            ResourceManager.CreateStructuredBufferSrv(_vertexBuffer, ref _vertexBufferWithViews.Srv);
            ResourceManager.CreateStructuredBufferUav(_vertexBuffer, UnorderedAccessViewBufferFlags.None, ref _vertexBufferWithViews.Uav);
            _vertexBufferWithViews.Buffer = _vertexBuffer;
                
            const int stride = 3 * 4;
            ResourceManager.SetupStructuredBuffer(_indexBufferData, stride * faceCount, stride, ref _indexBuffer);
            ResourceManager.CreateStructuredBufferSrv(_indexBuffer, ref _indexBufferWithViews.Srv);
            ResourceManager.CreateStructuredBufferUav(_indexBuffer, UnorderedAccessViewBufferFlags.None, ref _indexBufferWithViews.Uav);
            _indexBufferWithViews.Buffer = _indexBuffer;

            _data.VertexBuffer = _vertexBufferWithViews;
            _data.IndicesBuffer = _indexBufferWithViews;
            Data.Value = _data;
            Data.DirtyFlag.Clear();
        }
        catch (Exception e)
        {
            Log.Error("Failed to create torus mesh:" + e.Message);
        }
    }

    private Buffer _vertexBuffer;
    private PbrVertex[] _vertexBufferData = new PbrVertex[0];
    private readonly BufferWithViews _vertexBufferWithViews = new();

    private Buffer _indexBuffer;
    private Int3[] _indexBufferData = new Int3[0];
    private readonly BufferWithViews _indexBufferWithViews = new();

    private readonly MeshBuffers _data = new();

    [Input(Guid = "608DE038-6C7A-43FC-BA89-374C7B1A318E")]
    public readonly InputSlot<float> Radius = new();

    [Input(Guid = "FDBAD44A-2504-453B-BFAE-976828372CC0")]
    public readonly InputSlot<float> Thickness = new();

    [Input(Guid = "99F5D952-8490-4930-B8AB-9D8E968183C6")]
    public readonly InputSlot<Int2> Segments = new();

    [Input(Guid = "770A164B-10E7-4145-B1C9-DAD1F564EC6B")]
    public readonly InputSlot<Vector2> Spin = new();

    [Input(Guid = "F3E7341C-0C81-42AF-BA48-B43D345188C1")]
    public readonly InputSlot<Vector2> Fill = new();

    // [Input(Guid = "1457EDC2-5F9B-4F72-9CB2-4CA40066F177")]
    // public readonly InputSlot<System.Numerics.Vector4> Color = new InputSlot<System.Numerics.Vector4>();

    [Input(Guid = "2D083DC4-1576-4A44-8744-E0896424A6A9")]
    public readonly InputSlot<float> SmoothAngle = new();
}