Problem with Custom Render Texture Shader Graph in Built-In Render Pipeline

[Bentzge]

I made a shader graph to dilate a custom render texture, but when using it with the built-in render pipeline it doesn’t quite work anymore.

Here’s the graph.

This is the code from the custom node.

void UVDilate_float(UnityTexture2D Tex, UnitySamplerState Sampler, float2 TexelSize, float2 UV, float MaxSteps, out float4 Out)
{
    float2 texelsize = TexelSize;
    float2 offsets[8] = { float2(-1, 0), float2(1, 0), float2(0, 1), float2(0, -1), float2(-1, 1), float2(1, 1), float2(1, -1), float2(-1, -1) };

    float4 sample = SAMPLE_TEXTURE2D_LOD(Tex, Sampler, UV, 0);
    Out = sample;
    
    bool Break = false;
        
    int i = 0;
    
    while (i < MaxSteps)
    {
        i++;
        
        int j = 0;
        while (j < 8)
        {
            float2 curUV = UV + offsets[j] * texelsize * i;
            float4 offsetsample = SAMPLE_TEXTURE2D_LOD(Tex, Sampler, curUV, 0);

            if ( !offsetsample.a < 1.0)
            {
                Out = offsetsample;
                Break = true;
                break;
            }
                
            j++;
        }  
        
        if (Break)
            break;

    }
}

And this is what I’m doing to invoke the dilation.

/// <summary>
/// Method used to dilate a texture based on its alpha channel.
/// </summary>
/// <param name="tex">The original texture.</param>
/// <param name="steps">Dilation distance in pixels.</param>
/// <returns>A dilated version of the original texture as a CustomRenderTexture </returns>
public CustomRenderTexture DilateTexture(RenderTexture tex, int steps = 16)
{
    var RT = new CustomRenderTexture(tex.width, tex.height, tex.graphicsFormat);
    RT.material = new Material(dilationShader);
    RT.material.SetTexture("_MainTex", tex);
    RT.material.SetFloat("_MaxSteps", steps);
    RT.updateMode = CustomRenderTextureUpdateMode.OnDemand;
    RT.Update();

    return RT;
}

I’m having trouble getting to the root of the issue, since the texture is obviously being sampled (see replies), just not dilated.

Any help is appreciated.

[Bentzge]

Expecterd result in URP.

[Bentzge]

Observed result in Built-In.

[Bentzge]

For future reference.
After spending a bit more time on debugging I found the error. The problem wasn’t the shader but the image I fed to it. I didn’t realize because everything was generated at runtime and I used the same settings as with the URP version, but somehow the image to dilate didn’t contain any alpha values when rendered with the Built-In pipeline.