ScriptReference/UIElements.VisualElement-generateVisualContent

[giscus[bot]]

ScriptReference/UIElements.VisualElement-generateVisualContent

https://docs.unity3d.com/ScriptReference/UIElements.VisualElement-generateVisualContent.html

[vertxxyz]

If nothing is being drawn, check that:

• Vertices are drawn at the correct depth. The helper Vertex.nearZ provides this z depth for you.
• The correct triangle winding order is used. This is clockwise¹.
• Colours used for vertices are not transparent.
• Your triangles have area. If you are drawing lines, two vertices isn't enough, you will have to manually give them volume as triangles.
• Your element isn't hidden behind others.

If these are not your problem, start with the simple case (drawing a large triangle/quad) in a basic element and work your way upwards to drawing complex content.

Footnotes

1. The coordinate space starts in the top left of the element, with positive coordinates trending to the bottom right ↩

[vertxxyz]

As of 2022.1 you should generally use painter2D to draw content. You do not need to call Clear on it before usage.
It has a much more straight forward API, is harder to abuse, and has fairly good error reporting.

/// <summary>
/// Draws a 1px wide circle aligned in the center of the element.
/// </summary>
private static void GenerateVisualContent(MeshGenerationContext obj)
{
	const int pixelWidth = 1;
	Rect dimensions = obj.visualElement.contentRect;
	float radius = Math.Min(dimensions.width, dimensions.height) * 0.5f - pixelWidth ;

	Painter2D p2d = obj.painter2D;
	p2d.lineWidth = pixelWidth;
	p2d.strokeColor = Color.white;
	p2d.BeginPath();
	p2d.Arc(dimensions.center, radius, 0, Angle.Turns(1));
	p2d.Stroke();
}