unity探索者之UGUI图片描边

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自从UGUI出现之后，我就已经放弃使用NGUI了，原因不多说，毕竟是亲爹产的

不过即使如此，UGUI也存在不少问题，很多组件也不完善

今天要说的就是Outline这个组件，相信不少朋友都使用过，也相信不少朋友都和我一样，对于这个组件十分恶心

比如，我们给下面这张图添加一个描边

诶，效果还不错哦，我们再换一张

  

 恩，我觉得应该没有美工能接受这样的描边，就算你叫他美术都不好使

这个问题要解决，怎么办好呢？我们先来分析分析UGUI中Outline的源码

    public class Outline : Shadow
    {
        protected Outline()
        {}

        public override void ModifyMesh(VertexHelper vh)
        {
            if (!IsActive())
                return;

            var verts = ListPool<UIVertex>.Get();
            vh.GetUIVertexStream(verts);

            var neededCpacity = verts.Count * 5;
            if (verts.Capacity < neededCpacity)
                verts.Capacity = neededCpacity;

            var start = 0;
            var end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, effectDistance.x, effectDistance.y);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, effectDistance.x, -effectDistance.y);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, -effectDistance.x, effectDistance.y);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, -effectDistance.x, -effectDistance.y);

            vh.Clear();
            vh.AddUIVertexTriangleStream(verts);
            ListPool<UIVertex>.Release(verts);
        }
    }

代码很简单，也很好理解，通俗点说，就是把图片复制4份，然后叠在图片下方，每一张复制的图片都进行偏移，偏移量就是我们设置的描边的尺寸

既然原理是这样的，那问题简单了，我们增加复制的数量，将缺口补上就好了

    public class Outline : Shadow
    {
        public float bevelAngleCoefficient = 0.7071f; //1除以根号2

        public override void ModifyMesh(VertexHelper vh)
        {
            if (!IsActive())
                return;
            if (effectDistance.x == 0 && effectDistance.y == 0)
                return;

            var verts = ListPool<UIVertex>.Get();
            vh.GetUIVertexStream(verts);

            var neededCpacity = verts.Count * 9;
            if (verts.Capacity < neededCpacity)
                verts.Capacity = neededCpacity;

            float bevelAngleX = effectDistance.x * bevelAngleCoefficient;
            float bevelAngleY = effectDistance.y * bevelAngleCoefficient;

            var start = 0;
            var end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, effectDistance.x, effectDistance.y);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, bevelAngleX, 0);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, effectDistance.x, -effectDistance.y);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, 0, bevelAngleY);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, -effectDistance.x, effectDistance.y);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, -bevelAngleX, 0);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, -effectDistance.x, -effectDistance.y);

            start = end;
            end = verts.Count;
            ApplyShadowZeroAlloc(verts, effectColor, start, verts.Count, 0, -bevelAngleY);

            vh.Clear();
            vh.AddUIVertexTriangleStream(verts);
            ListPool<UIVertex>.Release(verts);
        }
    }

bevelAngleCoefficient是斜角系数，这个值的设定是为了满足不同类型的图片，边缘较圆滑的图片，使用默认值就可以，对于上面的叉，值设置为2最为合适，效果如下

对于边缘圆滑的图片，修改bevelAngleCoefficient值也能达到比较好的效果