MeshGenerationContext

Description

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

 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;
     }

     public TexturedElement()
     {
         generateVisualContent += OnGenerateVisualContent;
         m_Texture = AssetDatabase.LoadAssetAtPath<Texture2D>("Assets/tex.png");
     }

     Texture2D m_Texture;

     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);

         // Since the texture may be stored in an atlas, the UV coordinates need to be
         // adjusted. Simply rescale them in the provided uvRegion.
         Rect uvRegion = mwd.uvRegion;
         k_Vertices[0].uv = new Vector2(0, 0) * uvRegion.size + uvRegion.min;
         k_Vertices[1].uv = new Vector2(0, 1) * uvRegion.size + uvRegion.min;
         k_Vertices[2].uv = new Vector2(1, 1) * uvRegion.size + uvRegion.min;
         k_Vertices[3].uv = new Vector2(1, 0) * uvRegion.size + uvRegion.min;

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

Properties

Public Methods