MeshGenerationContext

Description

Provides methods for generating a visual element's visual content during the VisualElement.generateVisualContent callback.

Visual content is generated by using the Painter2D object, or manually by allocating a mesh using the MeshGenerationContext.Allocate method and then filling the vertices and indices.

To use the painter object, access the MeshGenerationContext.painter2D property, and then use it to issue drawing commands. You can find an example in the Painter2D documentation.

If you manually provide content with MeshGenerationContext.Allocate and also provide a texture during the allocation, you can use the Vertex.uv vertex values to map it to the resulting mesh. UI Toolkit might store the texture in an internal atlas.

//This example creates a custom element that dynamically renders a textured rectangle 
//based on the element’s size. 

using UnityEngine;
using UnityEngine.UIElements;

public class TexturedElement : VisualElement
{
    static readonly Vertex[] k_Vertices = new Vertex[4];
    static readonly ushort[] k_Indices = { 0, 1, 2, 2, 3, 0 };

    static TexturedElement()
    {
        k_Vertices[0].tint = Color.white;
        k_Vertices[1].tint = Color.white;
        k_Vertices[2].tint = Color.white;
        k_Vertices[3].tint = Color.white;

        k_Vertices[0].uv = new Vector2(0, 0);
        k_Vertices[1].uv = new Vector2(0, 1);
        k_Vertices[2].uv = new Vector2(1, 1);
        k_Vertices[3].uv = new Vector2(1, 0);
    }

    Texture2D m_Texture;

    public TexturedElement()
    {
        //This element grows to fill the available space.
        style.flexGrow = 1.0f;
        
        //Subscribes the OnGenerateVisualContent method to the generateVisualContent delegate.
        generateVisualContent += OnGenerateVisualContent;

        //Create a simple 2x2 checkerboard texture.
        m_Texture = new Texture2D(2, 2);
        m_Texture.SetPixels(new Color[] {
            Color.white, Color.black,
            Color.black, Color.white
        });
        m_Texture.Apply();

        //You can also load a texture from a file.
        //m_Texture = AssetDatabase.LoadAssetAtPath<Texture2D>("Assets/tex.png");
    }

    //This method is called when the element needs to render its content.
    void OnGenerateVisualContent(MeshGenerationContext mgc)
    {
        Rect r = contentRect;
        if (r.width < 0.01f || r.height < 0.01f)
            return; // Skip rendering when too small.

        float left = 0;
        float right = r.width;
        float top = 0;
        float bottom = r.height;

        k_Vertices[0].position = new Vector3(left, bottom, Vertex.nearZ);
        k_Vertices[1].position = new Vector3(left, top, Vertex.nearZ);
        k_Vertices[2].position = new Vector3(right, top, Vertex.nearZ);
        k_Vertices[3].position = new Vector3(right, bottom, Vertex.nearZ);

        MeshWriteData mwd = mgc.Allocate(k_Vertices.Length, k_Indices.Length, m_Texture);

        mwd.SetAllVertices(k_Vertices);
        mwd.SetAllIndices(k_Indices);
    }
}

Properties

Public Methods