A simple utility for playing with offset surfaces and convex polytopes.

Installation

This is a python script with the following dependencies: - Python 2.7 - numpy - scipy (0.19) - PyQt4 - PyQt4-OpenGL

Help for satisfying dependencies

sudo apt-get install python-qt4 python-qt4-gl sudo apt-get install python-pip sudo pip install numpy scipy sudo pip install --upgrade numpy scipy

Running

In the root of the repository, simply execute:

python offset_surface.py

A window will appear.

Workflow

Camera manipulation

The camera uses an "orbiting" model. Alt + Left Mouse Button -- Orbit the camera around its current target Alt + Middle Mouse Button -- Move the camera and its target parallel with the view plane. Alt + Right Mouse BUtton -- Zoom in/out. Move the camera closer and farther from the target.

Manipulating the camera causes an icon to appear reflecting the nature of the operation. These can be disabled, via the View menu (i.e., View -> Show Camera Movement Widgets).

Offset Surface Manipulation

First load an OBJ file through File -> Open Obj (or Ctrl+o). If successful, a colored polyhedron should appear with the edges highlighted in white.

As you pass the mouse over the facets of the polyedron, a yellow line should appear in the face under the mouse (centered on the face and point outward in the face's normal direction). This indicates the "active" face.

Changing offset

By default, the offset surface has a distance of 0. This can be changed by dragging on faces.

• Left dragging in the visible normal direction of the active face will change that face's offset value. Moving away from the face increases the offset. Moving toward the polyhedron will decrease the offset (the value will not fall below zero.)
• Holding shift while dragging will cause all faces to be offset the same amount.