NGUI根据图片是否透明来决定是否可以点中

该博文介绍了如何在Unity3D中实现一个名为UIHitAlphaTest的脚本，用于根据图片的透明度决定UI元素是否响应点击事件。脚本通过检查像素的alpha值与预设阈值进行比较，从而确定点击是否有效。

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using UnityEngine ;
using System.Collections ;
using System.Collections.Generic ;
[RequireComponent ( typeof (UIWidget ) ) ]
public class UIHitAlphaTest : MonoBehaviour
{
[Range (0 .01f,1f ) ]
public float threshold = 0 .5f ;
List <UIWidget > childs = new List <UIWidget > ( ) ;
void Start ( )
{
UIWidget w = GetComponent <UIWidget > ( ) ;
w . hitCheck = HitCheck ;
childs . Add (w ) ;
childs . AddRange (w . GetComponentsInChildren <UIWidget > ( ) ) ;
}
Vector3 t1p1 = Vector3 . zero ;
Vector3 t1p2 = Vector3 . zero ;
Vector3 t1p3 = Vector3 . zero ;
Vector3 t2p1 = Vector3 . zero ;
Vector3 t2p2 = Vector3 . zero ;
Vector3 t2p3 = Vector3 . zero ;
Vector2 t1uv1 = Vector2 . zero ;
Vector2 t1uv2 = Vector2 . zero ;
Vector2 t1uv3 = Vector2 . zero ;
Vector2 t2uv1 = Vector2 . zero ;
Vector2 t2uv2 = Vector2 . zero ;
Vector2 t2uv3 = Vector2 . zero ;
bool HitCheck (Vector3 worldPos )
{
for ( int widgetIndex = 0 ; widgetIndex < childs . Count ; widgetIndex ++ )
{
UIWidget widget = childs [widgetIndex ] ;
Vector3 localPos = widget . cachedTransform . InverseTransformPoint (worldPos ) ;
Texture2D tex = widget . mainTexture as Texture2D ;
for ( int i = 0 ; i < widget . geometry . verts . size ; i += 4 )
{
t1p1 = widget . geometry . verts . buffer [i ] ;
t1p2 = widget . geometry . verts . buffer [i + 1 ] ;
t1p3 = widget . geometry . verts . buffer [i + 2 ] ;
t2p1 = widget . geometry . verts . buffer [i + 2 ] ;
t2p2 = widget . geometry . verts . buffer [i + 3 ] ;
t2p3 = widget . geometry . verts . buffer [i ] ;
t1uv1 = widget . geometry . uvs . buffer [i ] ;
t1uv2 = widget . geometry . uvs . buffer [i + 1 ] ;
t1uv3 = widget . geometry . uvs . buffer [i + 2 ] ;
t2uv1 = widget . geometry . uvs . buffer [i + 2 ] ;
t2uv2 = widget . geometry . uvs . buffer [i + 3 ] ;
t2uv3 = widget . geometry . uvs . buffer [i ] ;
bool t1 = CheckTriangle
(localPos,
t1p1, t1p2, t1p3,
t1uv1, t1uv2, t1uv2,
tex ) ;
bool t2 = CheckTriangle
(localPos,
t2p1, t2p2, t2p3,
t2uv1, t2uv2, t2uv3,
tex ) ;
if (t1 || t2 )
{
return true ;
}
}
}
return false ;
}
bool CheckTriangle (Vector3 pos, Vector3 v1, Vector3 v2, Vector3 v3, Vector2 uv1, Vector2 uv2, Vector2 uv3, Texture2D tex )
{
// Normal of triangle
Vector3 normal = Vector3 . Cross ( v3 -v1, v2 -v1 ) ;
if ( normal . sqrMagnitude < 0 .01f )
return false ;
pos = pos - Vector3 . Dot ( pos -v1, normal ) * normal ; // Project point onto plane
float xScale = (pos . x - v2 . x ) / (v3 . x - v2 . x ) ;
float yScale = (pos . y - v1 . y ) / (v2 . y - v1 . y ) ;
Vector2 finalUV = new Vector2 (uv2 . x + (uv3 . x - uv2 . x ) * xScale, uv1 . y + (uv2 . y - uv1 . y ) * yScale ) ;
Color pixel = tex . GetPixel ( ( int ) (finalUV . x * tex . width ), ( int ) (finalUV . y * tex . height ) ) ;
return pixel . a >= threshold ;
}
}