How to change generated mask by texture mask? - unity3d

Question

I have a shader which generates opacity mask and rotate it.
This is how it looks:
Generated mask looks like this:
I generate a mask via code, but I want to take mask just from a texture2D.
How can I do that?
How do I change mask generating by only texture2D?
Code of my shader:
Shader "Custom/RadialOpacity" {
Properties {
[PerRendererData]_MainTex ("MainTex", 2D) = "white" {}
_Color ("Color", Color) = (1,1,1,1)
_OpacityRotator ("Opacity Rotator", Range(-360, 360)) = -360 // 2 full circles
[HideInInspector]_Cutoff ("Alpha cutoff", Range(0,1)) = 0.5
[MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
}
SubShader {
Tags {
"IgnoreProjector"="True"
"Queue"="Transparent"
"RenderType"="Transparent"
"CanUseSpriteAtlas"="True"
"PreviewType"="Plane"
}
Pass {
Name "FORWARD"
Tags {
"LightMode"="ForwardBase"
}
Blend One OneMinusSrcAlpha
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma multi_compile _ PIXELSNAP_ON
#include "UnityCG.cginc"
#pragma target 3.0
uniform sampler2D _MainTex;
uniform float4 _MainTex_ST;
uniform float4 _Color;
uniform float _OpacityRotator;
static const float TAU = float(6.283185); // это 2 * PI
struct VertexInput {
float4 vertex : POSITION;
float2 texcoord0 : TEXCOORD0;
};
struct VertexOutput {
float4 pos : SV_POSITION;
float2 uv0 : TEXCOORD0;
float3 normalDir : TEXCOORD2;
};
VertexOutput vert (VertexInput v) {
VertexOutput o = (VertexOutput)0;
o.uv0 = v.texcoord0;
o.pos = mul(UNITY_MATRIX_MVP, v.vertex );
#ifdef PIXELSNAP_ON
o.pos = UnityPixelSnap(o.pos);
#endif
return o;
}
float4 frag(VertexOutput i) : COLOR {
i.normalDir = normalize(i.normalDir);
float4 _MainTex_var = tex2D(_MainTex,TRANSFORM_TEX(i.uv0, _MainTex));
float2 oStart = (i.uv0 - 0.5);
float2 oVector = float2(-1, -1);
float oRotatorNormalized = _OpacityRotator / 360.0;
float oRotator_ang = oRotatorNormalized * -TAU;
float oRotator_cos = cos(oRotator_ang);
float oRotator_sin = sin(oRotator_ang);
float2x2 oRotationMatrix = float2x2(oRotator_cos, -oRotator_sin, oRotator_sin, oRotator_cos);
float2 oRotatorComponent = mul(oVector * oStart, oRotationMatrix);
/* generating opacity mask BEGIN_SECTION */
float2 oMaskHorizOrVert = atan2(oRotatorComponent.g, oRotatorComponent.r);
float oAtan2MaskNormalized = (oMaskHorizOrVert / TAU) + 0.5;
float oAtan2MaskRotatable = oRotatorNormalized - oAtan2MaskNormalized;
float oWhiteToBlackMask = ceil(oAtan2MaskRotatable);
/* generating opacity mask END_SECTION */
float oFinalMultiply = _MainTex_var.a * max(oAtan2MaskNormalized, ceil(oWhiteToBlackMask));
/*** (Emissive) ***/
float3 finalColor = _MainTex_var.rgb * _Color.rgb * oFinalMultiply;
return fixed4(finalColor, oFinalMultiply);
}
ENDCG
}
}
FallBack "Diffuse"
}
And I want to get something like that:
Properties {
...
_OpacityMask ("OpacityMask", 2D) = "white" {}
...
}
...
float oWhiteToBlackMask = ceil(OpacityMask);
float oFinalMultiply = _MainTex_var.a * max(oAtan2MaskNormalized, ceil(oWhiteToBlackMask));
...

Answer 1

https://forum.unity3d.com/threads/rotation-of-texture-uvs-directly-from-a-shader.150482/
Ok if I understand your question correctly, you want to add a texture 2D parameter and have it rotate. You'll need to rotate the UV coordinates over time, which you can probably accomplish using the code in the link above.
I'm not sure how you get that exact fade at the end with a texture 2D but maybe some clever usage of time you can figure out the animation.