Unity Shader #2.1 Basic Commands

#UnityShader #GameEngine #TechnicalArt

In the process of the render pipeline we do have several other commands for some options.

Face Culling

The backside of a surface is by default culled during the process.

By adding Cull Off before CGPROGRAM, we can turn off the backside face culling.

Pass
{
    Cull Off
    CGPROGRAM
    //...
    ENDCG
}

The other options here:

- Cull Off: turn off the backside face culling.

- Cull Back: [Default] cull the backside of a face.

- Call Front: cull the frontside of a face.

If we want to set the cull mode in the inspector, we can add a line in the Properties{} part, and then use Cull[_CullMode].

Properties
{
    [Enum(UnityEngine.Rendering.CullMode)]_CullMode("CullMode", float) = 2
}

Pass
{
    Cull [_CullMode]
    CGPROGRAM
    //...
    ENDCG
}

CullMode:

- 0: Off

- 1: Front

- 2: Back

Time

We can use the _Time parameter to use the time value.

_Time.x/y/z/w: t/20, t, 2t, 3t

_SinTime.w: the cos value of the time

_CosTime.w: the cos value of the time

Alpha Test

In the fragment shader, the clip(n) function has the following behavior:

n < 0: hide the fragment

n >= 0: show the fragment.

We can use the clip() function to realize some resolution/blend/wave effect, and we will do that in future notes.

For blending/semi-transparency, we need to add a Blend command like the Cull above before the CGPROGRAM.

Pass
{
    Blend SrcAlpha OneMinusSrcAlpha
    CGPROGRAM
    //...
    ENDCG
}

Besides OneMinusSrcAlpha, we do have other blending modes. Another frequently used mode is the Blend SrcAlpha One.

---

Also, remember to turn off ZWrite. Otherwise there might be some obvious and serious issues with sorting/rendering order.

Pass
{
    ZWrite Off
    Blend SrcAlpha OneMinusSrcAlpha
    CGPROGRAM
    //...
    ENDCG
}

In some cases we probably need ZWrite to be on, and we will cover these cases in later notes.

---

Recall the semi-transparent objects should be after 2500 in Render Queue(by default 3000), so we add a Tags{} in SubShader{} part before any Pass{}'s.

SubShader
{
    Tags{"Queue" = "Transparent"}
    Pass
    {
        ZWrite Off
        Blend SrcAlpha OneMinusSrcAlpha
        CGPROGRAM
        //...
        ENDCG
    }
}

---

Just one more thing to add, if you want to manually set the alpha value of a color (or a float), always make sure that the alpha value does fall in the range of (0,1). You can always use the saturate() function as a safe guard. saturate() makes sure that it does not return any value out of range(0,1).

half alpha = saturate(tex2D(_MainTex, i.uv).r * _Color.a * _Emiss);