MeshDataTool: edit vertices and recompute normals

using Reckfell;

public static class GeometryStage3D
{
    public static StandardMaterial3D Material(bool vertexColors = false, bool unshaded = false)
    {
        return new StandardMaterial3D
        {
            AlbedoColor = vertexColors ? Colors.White : new Color(0.24f, 0.44f, 1),
            VertexColorUseAsAlbedo = vertexColors,
            ShadingMode = unshaded ? BaseMaterial3D.ShadingModeEnum.Unshaded : BaseMaterial3D.ShadingModeEnum.PerPixel,
            Roughness = 0.8f
        };
    }

    public static void Setup(Entity3D root, string ru, string en)
    {
        root.AddChild(new WorldEnvironment { Environment = new Reckfell.Environment
        {
            BackgroundMode = Reckfell.Environment.BGMode.Color,
            BackgroundColor = new Color(0.035f, 0.04f, 0.05f),
            AmbientLightSource = Reckfell.Environment.AmbientSource.Color,
            AmbientLightColor = Colors.White, AmbientLightEnergy = 0.5f
        }});
        root.AddChild(new DirectionalLight3D { RotationDegrees = new Vector3(-55, -25, 0), LightEnergy = 1.2f });
        root.AddChild(new MeshInstance3D
        {
            Mesh = new BoxMesh { Size = new Vector3(8, 0.05f, 6) }, Position = new Vector3(0, -0.12f, 0),
            MaterialOverride = new StandardMaterial3D { AlbedoColor = new Color(0.10f, 0.11f, 0.13f), Roughness = 1 }
        });
        var camera = new Camera3D { Position = new Vector3(4, 4.8f, 6), Current = true, Fov = 45 };
        root.AddChild(camera); camera.LookAt(new Vector3(0, 0.35f, 0), Vector3.Up);
        var canvas = new CanvasLayer(); root.AddChild(canvas);
        var label = new Label { Position = new Vector2(24, 20), Text = TranslationServer.GetLocale().StartsWith("ru") ? ru : en };
        label.AddThemeFontSizeOverride("font_size", 22); canvas.AddChild(label);
    }
}

using Reckfell;

public partial class ArrayQuadLab3D : Entity3D
{
    public ArrayMesh Generated { get; private set; } = null!;

    public static ArrayMesh CreateQuad()
    {
        Vector3[] vertices = [new(-1, 0, -1), new(1, 0, -1), new(1, 0, 1), new(-1, 0, 1)];
        Vector3[] normals = [Vector3.Up, Vector3.Up, Vector3.Up, Vector3.Up];
        Vector2[] uv = [new(0, 0), new(1, 0), new(1, 1), new(0, 1)];
        int[] indices = [0, 1, 2, 0, 2, 3];
        using var arrays = new Reckfell.Collections.Array();
        arrays.Resize((int)Mesh.ArrayType.Max);
        arrays[(int)Mesh.ArrayType.Vertex] = vertices;
        arrays[(int)Mesh.ArrayType.Normal] = normals;
        arrays[(int)Mesh.ArrayType.TexUV] = uv;
        arrays[(int)Mesh.ArrayType.Index] = indices;
        var mesh = new ArrayMesh();
        mesh.AddSurfaceFromArrays(Mesh.PrimitiveType.Triangles, arrays);
        return mesh;
    }

    public override void _Ready()
    {
        GeometryStage3D.Setup(this, "ArrayMesh: 4 вершины, 2 треугольника", "ArrayMesh: 4 vertices, 2 triangles");
        Generated = CreateQuad();
        AddChild(new MeshInstance3D { Mesh = Generated, MaterialOverride = GeometryStage3D.Material() });
    }
}

using System;
using Reckfell;

public partial class MeshEditLab3D : Entity3D
{
    public ArrayMesh Generated { get; private set; } = null!;

    public static Error RaiseFarEdge(ArrayMesh mesh, float height)
    {
        if (mesh.GetSurfaceCount() != 1 || mesh.SurfaceGetPrimitiveType(0) != Mesh.PrimitiveType.Triangles ||
            !float.IsFinite(height) || height < 0 || height > 2) return Error.InvalidParameter;
        using var data = new MeshDataTool();
        Error error = data.CreateFromSurface(mesh, 0);
        if (error != Error.Ok) return error;
        for (int i = 0; i < data.GetVertexCount(); i++)
        {
            Vector3 point = data.GetVertex(i);
            if (point.Z > 0) point.Y = height;
            data.SetVertex(i, point);
        }
        Vector3[] normals = new Vector3[data.GetVertexCount()];
        for (int face = 0; face < data.GetFaceCount(); face++)
        {
            int a = data.GetFaceVertex(face, 0), b = data.GetFaceVertex(face, 1), c = data.GetFaceVertex(face, 2);
            Vector3 normal = (data.GetVertex(c) - data.GetVertex(a)).Cross(data.GetVertex(b) - data.GetVertex(a));
            normals[a] += normal; normals[b] += normal; normals[c] += normal;
        }
        for (int i = 0; i < normals.Length; i++)
        {
            if (normals[i].IsZeroApprox()) return Error.InvalidData;
            data.SetVertexNormal(i, normals[i].Normalized());
        }
        Material material = data.GetMaterial();
        mesh.ClearSurfaces();
        error = data.CommitToSurface(mesh, compressionFlags: 0);
        if (error == Error.Ok) mesh.SurfaceSetMaterial(0, material);
        return error;
    }

    public override void _Ready()
    {
        GeometryStage3D.Setup(this, "MeshDataTool: новая форма и нормали", "MeshDataTool: updated shape and normals");
        Generated = ArrayQuadLab3D.CreateQuad();
        Error error = RaiseFarEdge(Generated, 0.9f);
        if (error != Error.Ok) throw new InvalidOperationException("Mesh edit failed: " + error);
        AddChild(new MeshInstance3D { Mesh = Generated, RotationDegrees = new Vector3(0, 180, 0), MaterialOverride = GeometryStage3D.Material() });
    }
}