Trouble with Vertex selection in big shapes

Hi!

I am drawing huge shapes by loading measures with a lot of vertices (over 5 million). Given the amount of vertices, instead of generating a face for every triangle, I am using a function like this one:

//Build face/shape from triangulation
const Handle(Poly_Triangulation) aTris = new Poly_Triangulation(Nodes, Triangles);
auto aBuilder = new BRep_Builder();
aBuilder->MakeFace(TopoDS::Face(mShape), aTris);

With this method, I generate a mShape (TopoDS_Shape) that only contains 1 face from a triangulation with all my vertices.
Right now, if I want to hilight or "select" a group of vertices, the process follows these steps:

- Create a rectangle in 2D viewer
- Generate a Prism using the rectangle as a face ( BRepPrimAPI_MakePrism(face, viewDir) )
- Intersect my model with the prism by checking if my model vertices belong IN or ON the generated prism (cannot use Boolean Intersection from the API)
- Every vertex inside the Prism volume is considered a "selected" vertex, so these will be painted in a different color

This approach fits quite well with my needs... Until now. This method allows me to select vertices even when they are not visible in the viewer (maybe behind other vertices).
But now I would like to modify it. Instead of selecting every vertex inside the prism, I would like to select ONLY those vertices that are visible by me in the viewer.
In other words, I want to create a rectangle to select my vertices, but only the first ones that are "hit" by the intersection prism.
For example, in a closed cylinder, I would like to create my rectangle and only find the vertices in the part of the cylinder I can see, and avoid the vertices in the back of the cylinder.

I have tried some things, but the result always detects all vertices, even if they are behind others.
Could anyone give me some advice to do this?