pyglpainter

Minimalistic, modern OpenGL drawing library for technical applications, teaching or experimentation. It is implemented in Python 3 with Qt 5 bindings (it inherits from QOpenGLWidget).

It provides a simple Python API to draw raw OpenGL primitives (LINES, LINE_STRIP, TRIANGLES, etc.) as well as a number of useful composite primitives (see classes Grid, Star, CoordSystem, Text, Circle, Arc, HeightMap, OrthoLineGrid).

All objects/items can either be drawn as real 3D world entities (which optionally support "billboard" mode), or as a 2D overlay.

The user can interactively navigate using the mouse via the classical Pan-Zoom-Rotate paradigm implemented via a virtual trackball (using quaternions for rotations).

Background

This code was originally written for a CNC application, but then split off and made more general.

This library was developed to produce simple technical visualizations and minimalistic line drawings in 3D space; it does not implement a hierarchical scene graph. To be extensible, shader code has to be supplied by the application.

It uses the "modern", shader-based, OpenGL API rather than the deprecated "fixed pipeline".

Qt has been chosen not only because it provides the GL environment, but also vector, matrix and quaternion math. A port of this Python code into native Qt C++ would therefore be trivial.

Installation

pip install pyglpainter

Usage

The test directory of the source repository provides a full integration example, which can also be run for testing.

Most of the time, calls to item_create() are enough to build a 3D world with objects in it (the name for these objects here is "items"). Items can be rendered using different shader programs.

Mouse Navigation

Left Button drag left/right/up/down: Rotate camera left/right/up/down

Middle Button drag left/right/up/down: Move camera left/right/up/down

Wheel rotate up/down: Move camera ahead/back

Right Button drag up/down: Move camera ahead/back (same as wheel)

One particular choice was to hold the camera's field of view constant; "Zooming" can be achieved by moving the camera forward along its look axis.

Requirements

• The Python version specified in the file .python-version
• OpenGL version 2.1 (with GLSL version 1.20)

Development

Dependencies are managed using pipenv:

pip install pipenv --user
pipenv install

To run the example:

PYTHONPATH=src pipenv run python ./test/example.py

Building

pipenv run make build_deps
pipenv run make dist