MeshGenerationContext

Description

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

Visual content is generated by first allocating a mesh, using Allocate, and then filling the vertices and indices.

If a texture is provided during the allocation, you can use the Vertex.uv vertex values to map it to the resulting mesh. To improve performance, the renderer can store the texture in an internal atlas. In that case, you must remap the UVs inside the MeshWriteData.uvRegion rectangle. If you do not remap the UVs, the texture may display incorrectly when atlassed. The following example demonstrates the correct way to generate UVs.

//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