How to choose the best type of controls to use in a toolbar?

I have a 3D view displaying two objects. One is the reference object, the other the user object. Displaying the two objects together allows the user to compare its own object to a reference object (these objects are gamuts).

Each object have three display modes (smooth, wireframe and flat) and an opacity selector (a slider ranging from 0 to 100).

There also are controls that are "gamuts independent" : a selector to chose from 2D to 3D, a "Top View" and a "Bottom View" buttons and a slider, called Gamut Slice on the following picture.

The picture represents what we have today, but we wish to redesign this window.

(The two check boxes "New Profile" and "Reference Profile" are not useful and will be deleted.)

I'd like to integrate all the control elements in a toolbar, but I don't know which criterion are the best to determine the controls I should be using.

Especially, I would like to somehow regroup the display modes Smooth, Wireframe, and Flat together. I thought of two possible solutions : using three separate buttons (one for each mode), or using a combo box with the three modes. There are probably plenty of other possible solutions.

On what criterion should I make my choices ?