Online Geometry

This page contains the design document for an enhancement or feature. The design should be considered a work in progress and may not represent the final design. As this is a collaborative design, contributions and participation from other developers and users is encouraged. Use the discussion page for providing comments and suggestions.

Aim of Project

The aim of this project is to provide an online service to users of BRL-CAD to view and share their geometric files (BRL-CAD's native .g file) on browser. Currently in initial development stage, project aimed to have more advanced features in near future with ultimate goal to provide geometry editing features by leveraging BRL-CAD's existing code to maximum extent.

Current Implementation

Brief workflow

JavaScript 3D library, ThreeJS is used for drawing 3D models in browser. But ThreeJS doesn't support .g format. However, it can read obj files. obj is plain text format that can represent 3D geometry. It stores position of vertices, vertex normals and faces etc. You can read more about obj at: http://en.wikipedia.org/wiki/Wavefront_.obj_file

BRL-CAD has converter called g-obj that simply converts specified object(s) from BRL-CAD database .g file to obj file(s). So, right now g-obj plays fundamental role in the working of this project but there are lot of possibilities to replace this with some robust method.

In the end, obj file is given to ThreeJS and it draws entity on browser.

Detailed workflow

Here is the flow diagram of OGV: Media: Flow_diagram_of_online_geometry_viewer.jpeg. We can divide the whole process in following four operations:

• Upload .g file
• Extracting data
• Conversion
• Display

Above four operations are performed by following four files:

upload.php:	It provides a web interface for user to upload .g file.
upload_file.php:	It extracts data that includes name of .g file and that of its entities and pass it to model_display.php.
model_display.php:	It provides list of entities for user to choose from. When user clicks the "view" button corresponding to any entity, request is sent to create_obj.php for creating obj file.
create_obj.php:	As name suggests, when request received from model_display.php, it run g-obj converter that creates obj and respond with appropriate status. If success, entity is displayed on browser.

Extracting name of .g file and that of its entities:

Name of file is extracted using PHP's $_FILES variable and list of entities of .g file are copied to PHP variable using BRL-CAD's "ls" command.

Conversion

When .g file is uploaded, user is redirected to model_display.php. When user clicks on "view", add_entitiy() method is called that sends an AJAX request to create_obj.php. In create_obj.php, create_obj() method runs g.obj converter that creates obj file.

Languages used

PHP	74.3%
CSS	13.6%
JavaScript	12.1%

Third party libraries

ThreeJS:	3D JavaScript webGL library
BootStrap:	Front-end framework used for CSS work
pace.js:	Automatic page load progress bar
jquery:	For AJAX work
Swift Mailer:	For sending emails

Top level directories

accounts:	Sign-in signup module, swift mailer
css:	images, pace.js
doc:	html, latex
images
js:	ThreeJS
user_accounts:	Parent directory for user directories.

Other files

config.php:	A global configuration file.
doxyfile:	Doxygen file.
functions.php:	PHP functions
geo_viewer.sql:	Database schema file (.sql)
header.php:	Common file for header of webpage. (TODO: There are two header.php files, one in root directory and other in accounts/include. One of these duplicate files need to be removed)
README.md
variables.php:	Contain variables.

Further, detailed comments are written in the source code itself. If you still have doubts, questions etc., please contact at brlcad-devel@lists.sourceforge.net or at IRC at #brlcad channel on freenode network.

Status of Development

See the TODO page to get involved or check on the status of development.

History

This effort was initiated in 2013 by Harmanpreet Singh as a Google Summer of Code project.