Simple Geometry (Labelled Triangle)

The smallest possible custom mesh - one triangle from three vertices - with each vertex labelled on screen so the relationship between the numbers in the code and the shape on screen is visible. The labels come from EntityTextComponent, whose renderer registers itself, and the ground gizmo shows which way the axes point. Useful as a scratchpad when a mesh comes out inside out or facing the wrong way.

The Program.cs file shows how to:

Building a single triangle from a vertex and index buffer
Choosing a vertex format: VertexPositionTexture and its Layout
Labelling vertices on screen to debug a mesh
Registering the label renderer with AddSceneRenderer(new EntityTextRenderer())
Orienting yourself with a named-axis ground gizmo
Using helpers: SceneSetup3D, UseSkybox, AddGroundGizmo, AddOrientationGizmo, CreateFlatMaterial

View on GitHub.

using Stride.CommunityToolkit.Bepu;
using Stride.CommunityToolkit.Engine;
using Stride.CommunityToolkit.Rendering;
using Stride.CommunityToolkit.Rendering.Gizmos;
using Stride.CommunityToolkit.Rendering.Text;
using Stride.CommunityToolkit.Skyboxes;
using Stride.Core.Mathematics;
using Stride.Engine;
using Stride.Graphics;
using Stride.Rendering;
using Buffer = Stride.Graphics.Buffer;

using var game = new Game();

game.Run(new SceneSetup3D { Profiler = true }.UseBepu().UseSkybox(), start: scene =>
{
    game.AddGroundGizmo(new(-4, 0, -4), showAxisName: true);

    // The world axes in the bottom left corner, turning with the camera
    game.AddOrientationGizmo();

    // Screen-space labels for the EntityTextComponents below
    game.AddSceneRenderer(new EntityTextRenderer());

    AddTriangleEntity(scene);
});

void AddTriangleEntity(Scene scene)
{
    const float startX = -4f;
    const float startZ = -1f;

    var vertices = new VertexPositionTexture[3];
    vertices[0].Position = new Vector3(startX, 0f, startZ);
    vertices[1].Position = new Vector3(startX + 0.5f, 1f, startZ);
    vertices[2].Position = new Vector3(startX + 1f, 0f, startZ);

    var vertexBuffer = Buffer.Vertex.New(game.GraphicsDevice, vertices, GraphicsResourceUsage.Dynamic);
    int[] indices = [0, 1, 2];
    var indexBuffer = Buffer.Index.New(game.GraphicsDevice, indices);

    var mesh = new Mesh
    {
        Draw = new MeshDraw
        {
            PrimitiveType = PrimitiveType.TriangleList,
            DrawCount = indices.Length,
            IndexBuffer = new IndexBufferBinding(indexBuffer, true, indices.Length),
            VertexBuffers = [new VertexBufferBinding(vertexBuffer, VertexPositionTexture.Layout, vertexBuffer.ElementCount)],
        }
    };

    var model = new Model { mesh, game.CreateFlatMaterial(Color.BlueViolet) };
    var entity = new Entity("Triangle", new Vector3(2f, 0, 2f)) { new ModelComponent(model) };

    AddVertexLabels(entity, [vertices[0].Position, vertices[1].Position, vertices[2].Position], "t");

    entity.Scene = scene;
}

// One label entity per local-space point, as children so they follow the parent
void AddVertexLabels(Entity parent, ReadOnlySpan<Vector3> localPositions, string labelPrefix = "v")
{
    for (var i = 0; i < localPositions.Length; i++)
    {
        var position = localPositions[i];
        var label = new Entity($"{labelPrefix}{i}")
        {
            new EntityTextComponent
            {
                Text = $"{labelPrefix}{i} ({position.X:0.##}, {position.Y:0.##}, {position.Z:0.##})",
                FontSize = 14,
                Offset = new Vector2(0, -18),
                TextColor = Color.White,
                // Anchor centres the label over its vertex; Alignment only arranges the lines of a block
                Anchor = Anchor.BottomCenter,
                EnableBackground = true,
                BackgroundColor = new Color4(0, 0, 0, 0.5f),
                Padding = new Vector2(2)
            }
        };

        // In the parent's local space, like the mesh vertices
        label.Transform.Position = position;
        parent.AddChild(label);
    }
}

Table of Contents

Simple Geometry (Labelled Triangle)