Proj4WebGL is an experiment in implementing a PROJ.4-compatible geographic projection system which can be used from within WebGL shaders in a WebGL-compatible browser. It is designed to be used in combination with the already existing Proj4js port of PROJ.4 to JavaScript.
Like Proj4js it supports automatically fetching projection information from spatialreference.org.
See this project's GitHub pages site for a demo.
This project requires Python 3, HAML and CoffeeScript to be installed on your computer to re-generate the JavaScript and resource files. A Makefile is provided.
Note that the jsresource.py script is the reason for the Python dependency.
It is a simple script to wrap the GLSL source files up into a single JSON file
for use by JavaScript.
For the moment, the Proj4WebGL API is in flux since it is a playground for my own experimentation. At a high level:
- Initialise a Proj4js
Proj4.Projobject as-per-normal. - Pass the object to
Proj4Gl.projectionShaderSourcewhich will return a string containing GLSL source code to implement the projection. - See
coffee/mapviewer.coffeefor an example.
As an experimental project, only a very small number of projections have been implemented.
aea(to/from lat/lng)cea(to/from lat/lng)eqc(to/from lat/lng)laea(to/from lat/lng)lcc(to/from lat/lng)merc(to/from lat/lng)stere(to/from lat/lng)tmerc(to/from lat/lng)