Vertex Effect Example

Shadow.cs

using System.Collections.Generic;

namespace UnityEngine.UI
{
	[AddComponentMenu ("UI/Effects/Shadow", 14)]
	public class Shadow : BaseVertexEffect
	{
		[SerializeField]
		private Color m_EffectColor = new Color (0f, 0f, 0f, 0.5f);

		[SerializeField]
		private Vector2 m_EffectDistance = new Vector2 (1f, -1f);
		
		[SerializeField]
		private bool m_UseGraphicAlpha = true;

		protected Shadow()
		{}

#if UNITY_EDITOR
		protected override void OnValidate()
		{
			effectDistance = m_EffectDistance;
			base.OnValidate ();
		}
#endif

		public Color effectColor
		{
			get { return m_EffectColor; }
			set
			{
				m_EffectColor = value;
				if (graphic != null)
					graphic.SetVerticesDirty ();
			}
		}

		public Vector2 effectDistance
		{
			get { return m_EffectDistance; }
			set
			{
				if (value.x > 600)
					value.x = 600;
				if (value.x < -600)
					value.x = -600;
	
				if (value.y > 600)
					value.y = 600;
				if (value.y < -600)
					value.y = -600;

				if (m_EffectDistance == value)
					return;

				m_EffectDistance = value;

				if (graphic != null)
					graphic.SetVerticesDirty ();
			}
		}

		public bool useGraphicAlpha
		{
			get { return m_UseGraphicAlpha; }
			set
			{
				m_UseGraphicAlpha = value;
				if (graphic != null)
					graphic.SetVerticesDirty ();
			}
		}

		protected void ApplyShadow(List<UIVertex> verts, Color32 color, int start, int end, float x, float y)
		{
			UIVertex vt;

			var neededCpacity = verts.Count * 2;
			if (verts.Capacity < neededCpacity)
				verts.Capacity = neededCpacity;

			for (int i = start; i < end; ++i)
			{
				vt = verts[i];
				verts.Add (vt);

				Vector3 v = vt.position;
				v.x += x;
				v.y += y;
				vt.position = v;
				var newColor = color;
				if (m_UseGraphicAlpha)
					newColor.a = (byte)((newColor.a * verts[i].color.a) / 255);
				vt.color = newColor;
				verts[i] = vt;
			}
		}

		public override void ModifyVertices(List<UIVertex> verts)
		{
			if (!IsActive ())
				return;

			ApplyShadow (verts, effectColor, 0, verts.Count, effectDistance.x, effectDistance.y);
		}
	}
}