事情是這樣的,之前呢,用Sprite Mask做了遮罩效果,但是,老闆想要月球來回轉動,就不能用圖片轉動,只能用UI了,那相應的,遮罩怎麼辦呢,老闆也是神人,給我指了一條新的思路,就是將3D遮罩轉化成2D遮罩,不過放在手機上卡成狗,幸好群裡大佬ific指點了一下遮罩的shader,效果不錯,在此將兩種方法都分享出來~

一.使用RenderTexture渲染成Sprite,然後使用Sprite Mask進行遮罩

1.為要遮罩的模型單獨建立layer,新建一個攝像機只看該層

 2.將攝像機的畫面渲染到sprite上

public class MoonMask : MonoBehaviour {
    public Camera ModelMaskCamera;
    public Texture2D CamTexture;
    public RenderTexture renderTexture;
    public SpriteRenderer spriteRenderer;

    // Use this for initialization
    void Start () {
        //注意這裡的第三個引數
        renderTexture = new RenderTexture(Screen.width, Screen.height, 24, RenderTextureFormat.ARGB32);
        ModelMaskCamera.targetTexture = renderTexture;
        ModelMaskCamera.Render();
        RenderTexture.active = renderTexture;
        spriteRenderer.transform.localPosition = new Vector3(-(float)Screen.width / 100, -(float)Screen.height/100,0);
        CamTexture = new Texture2D(Screen.width, Screen.height, TextureFormat.RGB24, false);
    }
	
	// Update is called once per frame
	void Update ()
    {
            getScreenTexture();
    }
    void getScreenTexture()
    {
        Rect r = new Rect(0, 0, Screen.width, Screen.height);
        RenderTexture.active = renderTexture;
        CamTexture.ReadPixels(r, 0, 0);
        CamTexture.Apply();
        Sprite sprite = Sprite.Create(CamTexture, new Rect(0, 0, Screen.width, Screen.height), Vector2.zero);
        spriteRenderer.sprite = sprite;
    }
}
 

這裡踩了挺多坑,因為攝像機看到的只有模型時會有殘影出現,所以要在後面加一層背景,當時我不能加UI,因為加UI會覆蓋在模型上面,透明度又不能設定為0,設定為0了殘影還是會出現,不設定為0會影響模型顯示效果

好吧,加了Sprite,使它的Z軸在模型後面,擴大攝像機的far值, 使其能看到該Sprite,但是神奇的是還是覆蓋在模型上面,偶然發現將RenderTexture的Depth Buffer賦值為At least 16 bit depth或者At least 24 bit depth的時候能夠讓sprite顯示在模型後面,雖然不知道什麼原理~

上面程式碼中的第三個引數就是設定這個的 : 傳16是At least 16 bit depth,傳24是At least 24 bit depth

官方API : https://docs.unity3d.com/ScriptReference/RenderTexture-depth.html

3.遮罩實現

unity內建了sprite的遮罩 : 

被遮罩物體上:

 遮罩的原理 : 顯示遮罩圖片不透明部分與被遮罩圖片的不透明部分相交部分

二.使用shader中的ColorMask屬性進行遮罩

1.建立遮罩模型(比如我的需求是一塊麵板中間挖個洞)

2.新建一個shader,將下面程式碼賦值過去

Shader "DepthMask" {

	SubShader{
		// Render the mask after regular geometry, but before masked geometry and
		// transparent things.

		Tags {"Queue" = "Geometry-10" }

		// Turn off lighting, because it's expensive and the thing is supposed to be
		// invisible anyway.

		Lighting Off

		// Draw into the depth buffer in the usual way.  This is probably the default,
		// but it doesn't hurt to be explicit.

		ZTest LEqual
		ZWrite On

		// Don't draw anything into the RGBA channels. This is an undocumented
		// argument to ColorMask which lets us avoid writing to anything except
		// the depth buffer.

		ColorMask 0

		// Do nothing specific in the pass:

		Pass {}
	}
}
 

3.新建一個材質,選擇該shader,並拖拽到遮罩模型上

4.將被遮罩物體作為該物體的子物體,並且Z軸在它之下