iOS, RealityKit, Metal Shader APIs. Determine fragment's distance from the camera

Question

Using the new Metal Custom Shader API, I've created Grass models that move over time.

Is there a way to determine the distance between the model's fragment and the camera?

I've tried to search through surface_parameters.uniforms().

There are a few potential properties such as model_to_view, projection_to_view but I don't know what to do further.

Any tips appreciated.

Edit:: Here is the code for the grassGreenShader

[[visible]]
void grassGreenShader(realitykit::surface_parameters params)
{
    params.surface().set_base_color(half3(0.094, 0.697, 0.088));
    params.surface().set_opacity(1);
    respondToCameraDistanceShader(params);
}

Here is the code to change the base colour of the fragment. This part is wrong:

void respondToCameraDistanceShader(realitykit::surface_parameters params)
{
    float3 distanceToCamera = params.geometry().world_position();
    
    if (distanceToCamera.z < 0.3 && distanceToCamera.z > -0.3)
    {
        params.surface().set_opacity(distanceToCamera.z);
        params.surface().set_base_color(half3(0.934, 0.902, 0.355));
    }
}