How to design a shader in Unity so it uses directions from the camera - unity3d

Question

I have found a few unique shaders from Shadertoy which I would like to impart an experience of 'sky' within models of buildings in Unity AR.
An example might be this one: https://www.shadertoy.com/view/4tdSWr which is just the sky looking up, or this one, https://www.shadertoy.com/view/4tdSWr which has some directional input from the mouse (click and drag) - the HLSL/unity version of this code except for changes to mouse input is at the end of this post.
Right now the clouds feel more like a green screen projection on the model, so there is no implication of direction or horizon if you are looking parallel to the plane the building is on. (ie, if I am standing with the clouds moving from right to left, as I turn left they don't appear to be moving from behind me and receding into the distance)
I have been trying to understand how to use the camera to 'rotate' the shader result so the direction of the camera is used to ensure the direction of the clouds movement. I would also like to use the angle of the camera with respect to the ground plane to impart a horizon when you are looking out towards the walls.
Any insight on how to do this would be great, especially if it is more than just a 'use _WorldSpaceCameraPos' or 'just add UNITY_MATRIX_MVP' as the results I found through excessive googling haven't really been that helpful so far.
The code for the second shader linked, adjusted for HLSL/Unity except for the mouse inputs is at the end of this post.
Shader "Unlit/skybox"
{
Properties
{
_MainTex ("Texture", 2D) = "white" {}
iChannel0 ("noise-image", 2D) = "noise-image.png" {}
}
SubShader
{
Tags { "RenderType"="Opaque" }
LOD 100
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog
#include "UnityCG.cginc"
struct appdata
{
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};
struct v2f
{
float2 uv : TEXCOORD0;
UNITY_FOG_COORDS(1)
float4 vertex : SV_POSITION;
};
sampler2D _MainTex;
sampler2D iChannel0;
float4 _MainTex_ST;
float random(in float2 uv)
{
return tex2D(iChannel0, uv / 64.).r;
}
float noise(in float2 uv)
{
float2 i = floor(uv);
float2 f = frac(uv);
f = f * f * (3. - 2. * f);
float lb = random(i + float2(0., 0.));
float rb = random(i + float2(1., 0.));
float lt = random(i + float2(0., 1.));
float rt = random(i + float2(1., 1.));
return lerp(lerp(lb, rb, f.x),
lerp(lt, rt, f.x), f.y);
}
#define OCTAVES 8
float fbm(in float2 uv)
{
float value = 0.;
float amplitude = .5;
for (int i = 0; i < OCTAVES; i++)
{
value += noise(uv) * amplitude;
amplitude *= .5;
uv *= 2.;
}
return value;
}
float3 Sky(in float3 ro, in float3 rd)
{
const float SC = 1e5;
// Calculate sky plane
float dist = (SC - ro.y) / rd.y;
float2 p = (ro + dist * rd).xz;
p *= 1.2 / SC;
// from iq's shader, https://www.shadertoy.com/view/MdX3Rr
float3 lightDir = normalize(float3(-.8, .15, -.3));
float sundot = clamp(dot(rd, lightDir), 0.0, 1.0);
float3 cloudCol = float3(1.,1.0,1.0);
//float3 skyCol = float3(.6, .71, .85) - rd.y * .2 * float3(1., .5, 1.) + .15 * .5;
float3 skyCol = float3(0.3,0.5,0.85) - rd.y*rd.y*0.5;
skyCol = lerp( skyCol, mul(0.85, float3(0.7,0.75,0.85)), pow( 1.0 - max(rd.y, 0.0), 4.0 ) );
// sun
float3 sun = mul(mul(0.25 , float3(1.0,0.7,0.4)) , pow( sundot,5.0 ));
sun += mul(mul(0.25 , float3(1.0,0.8,0.6)) , pow( sundot,64.0 ));
sun += mul(mul(0.2 , float3(1.0,0.8,0.6)) , pow( sundot,512.0 ));
skyCol += sun;
// clouds
float t = mul(_Time.y , 0.1);
float den = fbm(float2(p.x - t, p.y - t));
skyCol = lerp( skyCol, cloudCol, smoothstep(.4, .8, den));
// horizon
skyCol = lerp( skyCol, mul(0.68 , float3(.418, .394, .372)), pow( 1.0 - max(rd.y, 0.0), 16.0 ) );
return skyCol;
}
float3x3 setCamera( in float3 ro, in float3 ta, float cr )
{
float3 cw = normalize(ta-ro);
float3 cp = float3(sin(cr), cos(cr),0.0);
float3 cu = normalize( cross(cw,cp) );
float3 cv = normalize( cross(cu,cw) );
return float3x3( cu, cv, cw );
}
void mainImage( out float4 fragColor, in float2 fragCoord )
{
float2 uv = fragCoord.xy / _ScreenParams.xy;
uv -= 0.5;
uv.x *= _ScreenParams.x / _ScreenParams.y;
float2 mouse = iMouse.xy/_ScreenParams.xy;
float3 ro = float3(0.0, 0.0, 0.0);
float3 ta = float3(cos(mul(mouse.x , 6.28)), mul(mouse.y , 2.0), sin(mul(mouse.x , 6.28)));
float3x3 cam = setCamera(ro, ta, 0.0);
float3 rd = normalize(mul(cam , float3(uv, 1.0)));
float3 col = Sky(ro, rd);
fragColor = float4(float3(col),1.0);
}
v2f vert (appdata v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _MainTex);
UNITY_TRANSFER_FOG(o,o.vertex);
return o;
}
fixed4 frag (v2f i) : SV_Target
{
// sample the texture
fixed4 col = tex2D(_MainTex, i.uv);
// apply fog
UNITY_APPLY_FOG(i.fogCoord, col);
return col;
}
ENDCG
}
}
}