void Start()
{
Material material = renderer.material;
Texture2D texture = new Texture2D(512,512, TextureFormat.RGB24, false);
texture.wrapMode = TextureWrapMode.Clamp;
material.SetTexture(0, texture);
texture.DrawFilledRectangle(new Rect(0, 0, 120, 120), Color.green);
texture.DrawRectangle(new Rect(0, 0, 120, 60), Color.red);
texture.DrawCircle(256, 256, 100, Color.cyan);
texture.DrawFilledCircle(256, 256, 50, Color.grey);
texture.DrawCircle(0, 0, 512, Color.red);
texture.DrawLine(new Vector2(120, 60), new Vector2(256, 256), Color.black);
texture.Apply();
}