Unity 透明窗体的创建

原文地址：https://alastaira.wordpress.com/2015/06/15/creating-windowless-unity-applications/

蛮牛地址：http://www.manew.com/thread-43230-1-1.html

该效果只针对Windows平台。结合摄像机的OnRenderImage事件和一些Windows底层API调用来实现该效果。

首先需要一个透明的Shader，我这直接使用系统的。

然后创建一个C#的脚本 TransparentWindow

using UnityEngine;
using System.Collections;
using System.Runtime.InteropServices;
using System;

public class TransparentWindow : MonoBehaviour
{
    [SerializeField]
    private Material m_Material;
    private struct MARGINS
    {
        public int cxLeftWidth;
        public int cxRightWidth;
        public int cyTopHeight;
        public int cyBottomHeight;
    }
    // Define function signatures to import from Windows APIs
    [DllImport("user32.dll")]
    private static extern IntPtr GetActiveWindow();
    [DllImport("user32.dll")]
    private static extern int SetWindowLong(IntPtr hWnd, int nIndex, uint dwNewLong);
    [DllImport("Dwmapi.dll")]
    private static extern uint DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS margins);
    // Definitions of window styles
    const int GWL_STYLE = -16;
    const uint WS_POPUP = 0x80000000;
    const uint WS_VISIBLE = 0x10000000;
    void Start()
    {
#if !UNITY_EDITOR
        var margins =new MARGINS() { cxLeftWidth = -1 };
// Get a handle to the window
var hwnd = GetActiveWindow();
// Set properties of the window
// See: https://msdn.microsoft.com/en-us/library/windows/desktop/ms633591%28v=vs.85%29.aspx
SetWindowLong(hwnd, GWL_STYLE, WS_POPUP | WS_VISIBLE);
// Extend the window into the client area
//See: https://msdn.microsoft.com/en-us/library/windows/desktop/aa969512%28v=vs.85%29.aspx
DwmExtendFrameIntoClientArea(hwnd,ref margins);
#endif
    }
    // Pass the output of the camera to the custom material
    // for chroma replacement
    void OnRenderImage(RenderTexture from, RenderTexture to)
    {
        Graphics.Blit(from, to, m_Material);
    }

}

上面的代码用到了InterOpServices命名空间，以便调用一些Windows底层API从而改变Unity应用在运行时的窗口属性。然后使用OnRenderImage事件将摄像机的输出应用到RenderTexture。将使用Shader的材质赋给脚本中的m_Material字段，这样我们就可以开始抠图了。

然后，重点来了：将摄像机的背景颜色改为与透明材质中_TransparentColourKey属性一样。

你可以随便设置该颜色，但两边必须一致。

最后就是生成和运行啦。因为用到了RenderTexture，所以如果使用Unity4.x必须为Pro版，而5.x任意版本均可。

效果：