My CAD software has two render modes, Perspective and Orthogonal. Perspective renders the lines to a point on the horizon, like you'd expect a photograph of the object to look. Orthogonal renders the lines in parallel, so that a view of the model from one of the major directions (top, bottom, left, right, front, back) looks like a 2D drawing. Nothing better to do on a Saturday night, made two screenshots of the render modes:
Perspective. Note that you can see the front of the tender and air tank:
Orthogonal. No depth, just a planar view of the left-hand side, like you'd see in a drawing:
Now, back to hoppers...