通道遮罩 ColorMask可以让我们制定渲染结果的输出通道，而不是通常情况下的RGBA这4个通道全部写入。可选参数是 RGBA 的任意组合以及 0， 这将意味着不会写入到任何通道，可以用来单独做一次Z测试，而不将结果写入颜色通道
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 {}
}
}
实现如图效果，前面的cube改为DepthMask的shader，实现在前面的cube透明，但是仍然挡住了后面cube的效果
fdd904b67e934e24b10e5c9c84392fc2[1].jpg
