How to add tiling and transparency to this shader? - unity3d

Question

I don't know much about shaders, so I am struggling to add transparency to a shader I already use.
So basically I used the shader below to display 360 videos on a sphere. It flipps the normals so it is displayed on the inside.
However, I would like to add an alpha value to it so I can make the sphere (and therefore the video) as transparent as I need it to be. What should I change?
Shader "Custom/Equirectangular" {
Properties {
_Color ("Main Color", Color) = (1,1,1,1)
_MainTex ("Diffuse (RGB) Alpha (A)", 2D) = "gray" {}
}
SubShader{
Pass {
Tags {"LightMode" = "Always"}
Cull Front
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma fragmentoption ARB_precision_hint_fastest
#pragma glsl
#pragma target 3.0
#include "UnityCG.cginc"
struct appdata {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct v2f
{
float4 pos : SV_POSITION;
float3 normal : TEXCOORD0;
};
v2f vert (appdata v)
{
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.normal = v.normal;
return o;
}
sampler2D _MainTex;
#define PI 3.141592653589793
inline float2 RadialCoords(float3 a_coords)
{
float3 a_coords_n = normalize(a_coords);
float lon = atan2(a_coords_n.z, a_coords_n.x);
float lat = acos(a_coords_n.y);
float2 sphereCoords = float2(lon, lat) * (1.0 / PI);
return float2(1 - (sphereCoords.x * 0.5 + 0.5), 1 - sphereCoords.y);
}
float4 frag(v2f IN) : COLOR
{
float2 equiUV = RadialCoords(IN.normal);
return tex2D(_MainTex, equiUV);
}
ENDCG
}
}
FallBack "VertexLit"
}
EDIT
I have also noticed that texture tiling and offset does not work on this shader. Any ideas how to make that work?

Answer 1

Short story: this is going to be really difficult
Not the shader, the shader's easy. All you have to do is modify this line:
return tex2D(_MainTex, equiUV);
The Long story:
Or: what to modify this line to.
Video formats, due to their very nature, do not natively contain an alpha channel. You'll be hard pressed to find one that does (I looked into this briefly back in 2015 when "interviewing" for a "job" where they needed something similar).
Once you figure out how you're going to encode the alpha, then you can modify the shader to look for that data and convert it to an alpha value, and bam you're done.
I think the place that I was "interviewing" at did it by splitting the video into an upper and lower sections, the upper half was just the alpha channel (black/white) and the lower half was the color data. The player would split the video horizontally and treat the two halves differently. I didn't have to mess with it, they'd already done it, so I'm not sure how it was done programmatically, I can only speculate.

Answer 2

You forgot blending for transparency. And it is better to provide corresponding shader tags as well.
Tags { "LightMode"="Always" "Queue"="Transparent" "RenderType"="Transparent" }
Blend SrcAlpha OneMinusSrcAlpha
Cull Front