使用UGUI中的Mask的時候,如何正確裁減非預設材質的UI物件
阿新 • • 發佈:2018-12-26
http://blog.csdn.net/ykmzy/article/details/51366396
在Unity中的UGUI中實現區域裁剪可以使用Mask元件,但是當改變被裁剪物件的材質後,裁剪效果可能會失效,也就是說Mask對該UI失效,這是為什麼呢?
這我們得了解UGUI中Mask的工作原理。Mask得裁剪效果是使用Stencil計算來實現裁剪,關於Stencil(模板)可以仔細瞭解一下渲染管線得相關知識就可以知道是怎麼回事了,可參見維基百科,也可自行搜尋其它資料。
通過參考Unity中UGUI中的Mask.cs原始碼,可以管窺一二。
/// Stencil calculation time!
public virtual Material GetModifiedMaterial(Material baseMaterial)
{
if (graphic == null)
return baseMaterial;
var rootSortCanvas = MaskUtilities.FindRootSortOverrideCanvas(transform);
var stencilDepth = MaskUtilities.GetStencilDepth(transform, rootSortCanvas);
if (stencilDepth >= 8 )
{
Debug.LogError("Attempting to use a stencil mask with depth > 8", gameObject);
return baseMaterial;
}
int desiredStencilBit = 1 << stencilDepth;
// if we are at the first level...
// we want to destroy what is there
if (desiredStencilBit == 1)
{
var maskMaterial = StencilMaterial.Add(baseMaterial, 1, StencilOp.Replace, CompareFunction.Always, m_ShowMaskGraphic ? ColorWriteMask.All : 0);
StencilMaterial.Remove(m_MaskMaterial);
m_MaskMaterial = maskMaterial;
var unmaskMaterial = StencilMaterial.Add(baseMaterial, 1, StencilOp.Zero, CompareFunction.Always, 0);
StencilMaterial.Remove(m_UnmaskMaterial);
m_UnmaskMaterial = unmaskMaterial;
graphic.canvasRenderer.popMaterialCount = 1;
graphic.canvasRenderer.SetPopMaterial(m_UnmaskMaterial, 0);
return m_MaskMaterial;
}
//otherwise we need to be a bit smarter and set some read / write masks
var maskMaterial2 = StencilMaterial.Add(baseMaterial, desiredStencilBit | (desiredStencilBit - 1), StencilOp.Replace, CompareFunction.Equal, m_ShowMaskGraphic ? ColorWriteMask.All : 0, desiredStencilBit - 1, desiredStencilBit | (desiredStencilBit - 1));
StencilMaterial.Remove(m_MaskMaterial);
m_MaskMaterial = maskMaterial2;
graphic.canvasRenderer.hasPopInstruction = true;
var unmaskMaterial2 = StencilMaterial.Add(baseMaterial, desiredStencilBit - 1, StencilOp.Replace, CompareFunction.Equal, 0, desiredStencilBit - 1, desiredStencilBit | (desiredStencilBit - 1));
StencilMaterial.Remove(m_UnmaskMaterial);
m_UnmaskMaterial = unmaskMaterial2;
graphic.canvasRenderer.popMaterialCount = 1;
graphic.canvasRenderer.SetPopMaterial(m_UnmaskMaterial, 0);
return m_MaskMaterial;
}
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通過上面得程式碼我們得知Mask會對目標UI得材質使用StencilMaterial.Add方法來傳遞模板相關引數
StencilMaterial.Add(baseMaterial, desiredStencilBit - 1, StencilOp.Replace, CompareFunction.Equal, 0, desiredStencilBit - 1, desiredStencilBit | (desiredStencilBit - 1));
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繼續檢視StencilMaterial.Add方法,有如下程式碼
/// <summary>
/// Add a new material using the specified base and stencil ID.
/// </summary>
public static Material Add(Material baseMat, int stencilID, StencilOp operation, CompareFunction compareFunction, ColorWriteMask colorWriteMask, int readMask, int writeMask)
{
if ((stencilID <= 0 && colorWriteMask == ColorWriteMask.All) || baseMat == null)
return baseMat;
if (!baseMat.HasProperty("_Stencil"))
{
Debug.LogWarning("Material " + baseMat.name + " doesn't have _Stencil property", baseMat);
return baseMat;
}
if (!baseMat.HasProperty("_StencilOp"))
{
Debug.LogWarning("Material " + baseMat.name + " doesn't have _StencilOp property", baseMat);
return baseMat;
}
if (!baseMat.HasProperty("_StencilComp"))
{
Debug.LogWarning("Material " + baseMat.name + " doesn't have _StencilComp property", baseMat);
return baseMat;
}
if (!baseMat.HasProperty("_StencilReadMask"))
{
Debug.LogWarning("Material " + baseMat.name + " doesn't have _StencilReadMask property", baseMat);
return baseMat;
}
if (!baseMat.HasProperty("_StencilReadMask"))
{
Debug.LogWarning("Material " + baseMat.name + " doesn't have _StencilWriteMask property", baseMat);
return baseMat;
}
if (!baseMat.HasProperty("_ColorMask"))
{
Debug.LogWarning("Material " + baseMat.name + " doesn't have _ColorMask property", baseMat);
return baseMat;
}
for (int i = 0; i < m_List.Count; ++i)
{
MatEntry ent = m_List[i];
if (ent.baseMat == baseMat
&& ent.stencilId == stencilID
&& ent.operation == operation
&& ent.compareFunction == compareFunction
&& ent.readMask == readMask
&& ent.writeMask == writeMask
&& ent.colorMask == colorWriteMask)
{
++ent.count;
return ent.customMat;
}
}
var newEnt = new MatEntry();
newEnt.count = 1;
newEnt.baseMat = baseMat;
newEnt.customMat = new Material(baseMat);
newEnt.customMat.hideFlags = HideFlags.HideAndDontSave;
newEnt.stencilId = stencilID;
newEnt.operation = operation;
newEnt.compareFunction = compareFunction;
newEnt.readMask = readMask;
newEnt.writeMask = writeMask;
newEnt.colorMask = colorWriteMask;
newEnt.useAlphaClip = operation != StencilOp.Keep && writeMask > 0;
newEnt.customMat.name = string.Format("Stencil Id:{0}, Op:{1}, Comp:{2}, WriteMask:{3}, ReadMask:{4}, ColorMask:{5} AlphaClip:{6} ({7})", stencilID, operation, compareFunction, writeMask, readMask, colorWriteMask, newEnt.useAlphaClip, baseMat.name);
newEnt.customMat.SetInt("_Stencil", stencilID);
newEnt.customMat.SetInt("_StencilOp", (int)operation);
newEnt.customMat.SetInt("_StencilComp", (int)compareFunction);
newEnt.customMat.SetInt("_StencilReadMask", readMask);
newEnt.customMat.SetInt("_StencilWriteMask", writeMask);
newEnt.customMat.SetInt("_ColorMask", (int)colorWriteMask);
newEnt.customMat.SetInt("_UseAlphaClip", newEnt.useAlphaClip ? 1 : 0);
m_List.Add(newEnt);
return newEnt.customMat;
}
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通過對StencilMaterial.Add方法得檢視我們知道該方法在對目標材質得_StencilOp,_StencilComp等等屬性進行操作,這樣操作後才可以實現它得模板裁剪。我們自定義的Shader一般沒有這幾個屬性,所以我們在自己的shader中新增如下程式碼便可以實現自定義材質得正確Mask了
_StencilComp ("Stencil Comparison", Float) = 8
_Stencil ("Stencil ID", Float) = 0
_StencilOp ("Stencil Operation", Float) = 0
_StencilWriteMask ("Stencil Write Mask", Float) = 255
_StencilReadMask ("Stencil Read Mask", Float) = 255
............................................................................
Stencil
{
Ref [_Stencil]
Comp [_StencilComp]
Pass [_StencilOp]
ReadMask [_StencilReadMask]
WriteMask [_StencilWriteMask]
}