Transparency working in editor but not in play mode

I have been testing writing shaders for 3D UI purposes. I made an unlit, cutoff shader that will render only what is inside a box with a fading effect before clipping.
I have issues with the transparency effect, which works in the editor but not in play mode.

The transparency works well when seen from the editor :

But it doesn’t look the same when viewed from the camera :

These pictures were taken with a _Transparency value of 0.25, from the following shader :

Shader "Custom/HoloProj_RenderInVisibleVolumes"
        _Color("Color", Color) = (1, 1, 1, 1)
        _MainTex ("Texture", 2D) = "white" {}
        _Transparency("Transparency", Range(0.0, 1)) = 0.5
        Tags { "RenderType" = "Transparent" }

            Blend SrcAlpha OneMinusSrcAlpha
            Cull Off


            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;

            struct v2f
                float2 uv : TEXCOORD0;
                float3 wpos : TEXCOORD1;
                float4 vertex : SV_POSITION;
                fixed4 color : COLOR0;

            float4x4 _WorldToBox;
            sampler2D _MainTex;
            float4 _MainTex_ST;
            float4 _Color;
            float _Transparency;

            float max3 (float3 v) {
                return max (max (v.x, v.y), v.z);

            v2f vert (appdata v)
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.wpos = mul(unity_ObjectToWorld, v.vertex);
                o.color = _Color;

                return o;

            fixed4 frag (v2f i) : SV_Target
                // Computes visibility volume position relative to vertex.
                float3 boxPosition = mul(_WorldToBox, float4(i.wpos, 1));

                // Prevents vertex outside of the visibility volume to be drawn.
                clip(boxPosition + 0.5);
                clip(0.5 - boxPosition);

                float closest_to_threshold = max3(abs(boxPosition));

                // Compute fade out transparency value.
                // Smooth function : 256 = (1/0.5^8) ; pow(x, 8) is equivalent to 3 multiplications. 
                // Function smoothly reduces transparency from the initial _Transparency value down to 0 as vertex gets closer to the boundaries of the visiblity area.
                float transparency = (-256 * pow(closest_to_threshold, 8) + 1) * _Transparency;

                if (transparency < 0)
                    transparency = 0;   // Hopefully, we may expect optimization static branching.

                fixed4 col = tex2D(_MainTex, i.uv);
                col.a = _Transparency;
                return col * i.color;


You can ignore all cutoff/fading calculations as only _Transparency is applied to the color’s alpha component, which is what I use to get the transparency effect (wrongfully I guess).

In play mode, this forces me to go with much lower values, here 0.015, to get the same result I had in the editor with 0.25. The surface flickers slightly as well.

How do I properly make this transparence effect work?

Figured it out : this is an issue with improper queuing. The shader needs to be queued in Transparent or above with the tag “Queue” = “Transparent”.