Unity Shader _Time

_Time是个4维向量，跟Unity3D中的deltaTime（这是个一维的，数值）不同。

float4 _Time : Time (t/20, t, t*2, t*3), use to animate things inside the shaders。

fixed x= Speed * _Time;  等价于 fixed x= Speed * _Time.x;

Time	float4	Time (t/20, t, t*2, t*3), use to animate things inside the shaders.
_SinTime	float4	Sine of time: (t/8, t/4, t/2, t).
_CosTime	float4	Cosine of time: (t/8, t/4, t/2, t).
unity_DeltaTime	float4	Delta time: (dt, 1/dt, smoothDt, 1/smoothDt).
_ProjectionParams	float4	x is 1.0 (or –1.0 if currently rendering with a flipped projection matrix), y is the camera’s near plane, z is the camera’s far plane and w is 1/FarPlane.
_ScreenParams	float4	x is the current render target width in pixels, y is the current render target height in pixels, z is 1.0 + 1.0/width and w is 1.0 + 1.0/height.

参考： https://docs.unity3d.com/462/Documentation/Manual/SL-BuiltinValues.html