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

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

namespace Lib.mesh.generate;

[Guid("1b9977be-70cf-4dbd-8af1-1459596b6527")]
internal sealed class NGonMesh : Instance<NGonMesh>
{
    [Output(Guid = "9c949c29-9dc1-4ded-94ce-1e86317a5233")]
    public readonly Slot<MeshBuffers> Data = new();

    public enum TextureModes
    {
        Planar,
        Circular,
        CircularScaled
    }

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

    private void Update(EvaluationContext context)
    {
        try
        {
            var radius = Radius.GetValue(context);
            var stretch = Stretch.GetValue(context);
            var rotation = Rotation.GetValue(context);

            var yaw = rotation.Y.ToRadians();
            var pitch = rotation.X.ToRadians();
            var roll = rotation.Z.ToRadians();

            var textureMode = (TextureModes)(int)TextureMode.GetValue(context).Clamp(0, Enum.GetValues(typeof(TextureModes)).Length);

            var rotationMatrix = Matrix4x4.CreateFromYawPitchRoll(yaw, pitch, roll);

            var center = Center.GetValue(context);

            var center2 = new Vector3(center.X, center.Y, center.Z);
            var segments = Segments.GetValue(context).Clamp(1, 10000);
            var verticesCount = segments + 1; // +1 for center

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

            if (_indexBufferData.Length != segments)
                _indexBufferData = new Int3[segments];

            var normal = Vector3.TransformNormal(VectorT3.ForwardLH, rotationMatrix);
            var tangent = Vector3.TransformNormal(VectorT3.Right, rotationMatrix);
            var binormal = Vector3.TransformNormal(VectorT3.Up, rotationMatrix);

            // center
            {
                float uCenter = 0;
                float vCenter = 0;
                switch (textureMode)
                {
                    case TextureModes.Planar:
                        uCenter = 0.5f;
                        vCenter = 0.5f;
                        break;

                }

                _vertexBufferData[0] = new PbrVertex
                                           {
                                               Position = center2,
                                               Normal = normal,
                                               Tangent = tangent,
                                               Bitangent = binormal,
                                               Texcoord = new Vector2(uCenter, vCenter),
                                               Selection = 1,
                                               ColorRgb = Vector3.One
                                           };
            }

            // the other points are on a circle
            for (var segmentIndex = 0; segmentIndex < segments; ++segmentIndex)
            {
                var phi = 2 * MathF.PI * segmentIndex / segments;
                var p = new Vector3(radius * MathF.Sin(phi) * stretch.X, // starts at top
                                    radius * MathF.Cos(phi) * stretch.Y,
                                    0);
                float u0 = 0f, v0 = 0f;

                switch (textureMode)
                {
                    case TextureModes.Planar:
                        u0 = MathF.Sin(phi) / 2 + 0.5f;
                        v0 = MathF.Cos(phi) / 2 + 0.5f;
                        break;
                    case TextureModes.Circular:
                        u0 = phi / (2 * MathF.PI);
                        v0 = 1;
                        break;
                    case TextureModes.CircularScaled:
                        u0 = phi / (2 * MathF.PI);
                        v0 = radius;
                        break;
                }

                var uv0 = new Vector2(u0, v0);
                var posRotated = Vector3.TransformNormal(p, rotationMatrix);
                _vertexBufferData[segmentIndex + 1] = new PbrVertex
                                                          {
                                                              Position = posRotated + center2,
                                                              Normal = normal,
                                                              Tangent = tangent,
                                                              Bitangent = binormal,
                                                              Texcoord = uv0,
                                                              Selection = 1,
                                                              ColorRgb = Vector3.One
                                                          };
                _indexBufferData[segmentIndex] = new Int3(0,
                                                          (segmentIndex + 2) > segments ? 1 : segmentIndex + 2,
                                                          segmentIndex + 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 * segments, 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 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 = "33921c65-61bc-4229-af8c-c89db9a874bf")]
    public readonly InputSlot<int> Segments = new();
        
    [Input(Guid = "9dbf0c3d-4762-41f6-94b8-26acbd1531c1")]
    public readonly InputSlot<float> Radius = new();
        
    [Input(Guid = "deee0efc-949e-41da-bdb1-d80dbb6ac6e2")]
    public readonly InputSlot<Vector2> Stretch = new();

    [Input(Guid = "69a2e8c2-2c88-4969-8beb-66fe8ff4af18")]
    public readonly InputSlot<Vector3> Center = new();

    [Input(Guid = "b819ad07-6229-4b8d-b8b6-a2a89b7c81d8")]
    public readonly InputSlot<Vector3> Rotation = new();

    [Input(Guid = "d85761fb-3c82-4785-a2a2-4b111230e4ee", MappedType = typeof(TextureModes))]
    public readonly InputSlot<int> TextureMode = new();
}