I want to convert the function in the first image to the form of libfive::Tree, but there is a problem now.

The texelFetch() function actually takes an index id as input and retrieves the value of pixels[id]. We know that id is an integer, so how can we convert libfive::Tree to an integer index id to retrieve the value of pixels[id]?

pixels is a known array of type std::vector. The method I can think of is to traverse each element of pixels as shown in the third image, but I think this would make the final libfive::Tree very large.

Do you have any good methods or tips?

I am very grateful for your patience in addressing my questions time and again. Wishing you a pleasant day.