Editing Geometry Viewer Application for BRL-CAD

From BRL-CAD

Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.

The edit can be undone. Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.
Latest revision Your text
Line 10: Line 10:
 
== Outline ==
 
== Outline ==
  
The idea is to build a geometry viewer application that generates a standalone double-clickable file that views a given model. The approach is to concatenate the contents of a given “.g” file with the function calls from librt and display a “.g” file, in a standard brlcad setup.
+
The idea is to build a geometry viewer application that generates a standalone double-clickable file that views a given model. The approach is to concatenate the contents of a given “.g” file with the function calls from librt, libdm that parse and display a “.g” file, in a standard brlcad setup.
 
 
Our source code will generate an executable, we will then separately concatenate a ".g" file into this executable:
 
 
 
This executable is capable of:
 
 
 
# Finding the start of ".g" file bytes/headers
 
# Populating the g file database for librt
 
# Plotting the items in the g file using [http://www.glfw.org/docs/latest/pages.html glfw3].
 
 
 
  
 
Our motivation is to introduce portability and ability to share results of brlcad via email with users who don’t have brlcad setup in their environments. First we will develop a standalone application but later this can be integrated into mged or any other tool as a brlcad feature.
 
Our motivation is to introduce portability and ability to share results of brlcad via email with users who don’t have brlcad setup in their environments. First we will develop a standalone application but later this can be integrated into mged or any other tool as a brlcad feature.
  
== Status (15.08.2016) ==
 
  
Our source code takes an embedded .g file and locates it's header bytes from there on it calls db_open() by writing the gbytes into a temporary file and populates struct db_i. The source also calls db_ls to get a count of objects in the database and calls db_walk_tree on one of the objects. Then work a list of all top level objects is fetched via db_ls and then db_walk_tree is called on each of them. The next step is to plot these zones, for this purpose we have decided to choose [http://www.glfw.org/docs/latest/pages.html glfw3]. Currently the work is being done to generate a simple window from our application using glfw.
 
 
== Task Breakdown ==
 
== Task Breakdown ==
  
Line 37: Line 26:
 
• [http://brlcad.org/docs/doxygen-r64112/d4/de4/group__libdm.xhtml '''Libdm'''] is BRL-CAD's primary graphics display manager (dm) library. It is used to display geometry in GUI. This will be utilized by our source to visualize model files.
 
• [http://brlcad.org/docs/doxygen-r64112/d4/de4/group__libdm.xhtml '''Libdm'''] is BRL-CAD's primary graphics display manager (dm) library. It is used to display geometry in GUI. This will be utilized by our source to visualize model files.
  
This resulting draw result will then be bundled into an executable (Linux) and later into packages for Mac & Windows.
+
This resulting draw result will then be bundled into an “.exe” (windows) and later into packages for Mac & Linux.
  
 
== Task list ==
 
== Task list ==
  
; 1. Evaluate technology to be used
+
# Evaluate technology to be used
* <s>Develop initial project design draft</s> [DONE]
+
** Develop initial project design draft
* <s>Setup development environment</s> [DONE]
+
** Setup development environment
 
+
** Evaluate programming language choice (C decided, for GUI may use some Python)
** ''' Installing BRLCAD:''' ([http://svn.code.sf.net/p/brlcad/code/brlcad/trunk/INSTALL '''Install Instructions'''])
+
# Evaluate and look into current viewer applications:
 
+
** Mged / archer
:: '''System Specs:''' CentOS 7, Dual Core, 4G RAM, 40 G Storage
+
** Isst, it doesn’t use libdm.  
 
+
** Geometry viewer [https://github.com/BRL-CAD/geometry_viewer]
<source lang="bash">
+
# Create application interface to brlcad libraries [http://brlcad.org/w/images/3/3d/Application_Development.pdf]
# Fetch the STABLE version of BRLCAD (7.24.4):
+
** Interface with librt
svn checkout http://svn.code.sf.net/p/brlcad/code/brlcad/branches/STABLE/ brlcad-stable
+
** Interface with libdm
 
+
# Create application interface with model file:
cd brlcad-stable
+
** Create input interface to parse “.g” file
 
+
** Create output interface to parse output from libdm.  
mkdir brlcad-build
+
# Develop front end
 
+
* Develop Single window view
cd brlcad-build
+
* Develop File Input
 
+
# Write Functional testing test cases.
cmake ../ -DBRLCAD_BUNDLED_LIBS=ON -DCMAKE_BUILD_TYPE=Release -BRLCAD_ENABLE_STRICT=OFF
 
 
 
# Without enable strict we get an error: "array subscript is above array bounds" during make
 
 
 
make -j6
 
 
 
make install
 
 
 
vim ~/.bash_profile
 
 
 
# Add "/usr/brlcad/rel-7.24.4/bin" to PATH.
 
 
 
vim brlcad-7.24.4.conf
 
 
 
# Add "/usr/brlcad/rel-7.24.4/lib"
 
 
 
ldconfig
 
 
 
</source>
 
 
 
 
 
* Evaluate programming language choice (C decided, for GUI may use some Python)
 
; 2. Evaluate and look into current viewer applications:
 
* Mged / archer
 
* Isst, it doesn’t use libdm.  
 
* Geometry viewer [https://github.com/BRL-CAD/geometry_viewer]
 
; 3. Create Compiler Application:
 
 
 
First step is to merge .g file into executable and then read it's contents. This is achieved by simply concatenating .g file with executable using the Linux "cat" command e.g., '''cat viewer moss.g > exec'''.
 
  
Then we locate the header bytes (hex) of the embedded .g file from within the executable. From "hexdump" command we can conclude that .g files have the bytes '''(76 01 00 00 00 00 01 35)''' in common:
 
  
<source lang="bash">
 
hexdump -C build/share/db/wave.g | head
 
00000000  76 01 00 00 00 00 01 35  76 02 00 00 00 00 0a 00  |v......5v.......|
 
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
 
*
 
00000050  00 00 00 00 00 00 00 35  76 02 00 00 00 00 02 00  |.......5v.......|
 
00000060  00 00 00 00 00 00 00 35  76 20 00 20 01 04 1a 06  |.......5v . ....|
 
 
 
00000070  62 61 73 65 31 00 c0 40  82 c0 00 00 00 00 00 c0  |base1..@........|
 
</source>
 
 
Once the bytes have been located we have the option of either:
 
 
** Populating [http://brlcad.org/docs/doxygen-r64112/d2/d66/structdb__i.xhtml '''struct db_i''' ] manually
 
** Getting a file descriptor of bytes in memory and passing it on to [http://brlcad.org/docs/doxygen-r64112/d3/d9b/group__dbio.xhtml#gaa9eb8edb99fa1da5d188587e07d8dacc '''db_open'''].
 
 
; 4. Create application Interface with librt
 
Librt is used to open brlcad geometry files and edit them. It reads a .g file by calling the function [http://brlcad.org/docs/doxygen-r64112/d3/d9b/group__dbio.xhtml#gaa9eb8edb99fa1da5d188587e07d8dacc '''db_open'''] and populates a [http://brlcad.org/docs/doxygen-r64112/d2/d66/structdb__i.xhtml '''db_i structure''' ]. To view the geometry files we need [http://brlcad.org/docs/doxygen-r64112/d4/de4/group__libdm.xhtml '''Libdm'''] which takes this db_i structure as input to do so.
 
 
As we have located the g file bytes, we simply write out these bytes onto a temporary file and pass this file onto db_open(). db_open then populates the database structure db_i. An [http://brlcad.org/wiki/Example_db_walk_tree '''example'''] is already available that shows the usage of db_open. We are utilizing the skeleton of this example to populate the struct db_i. A cleaner approach would be to directly populate the struct db_i and I am working on that.
 
 
The next step is to identify the top level objects of a g file. These can be listed by issuing a [http://brlcad.org/wiki/MGED_CMD_tops "tops"] command on mged after opening a g file. In code this can be achieved by following db_ls and/or DB_LS_TOPS in src/libged/*.c.
 
 
After these top level objects have been identified we need to call [http://brlcad.sourceforge.net/doxygen/d3/d9b/group__dbio.html#ge69d8a8eb90d514e554e1b84bbb7018f db_walk_tree] on each of them.
 
 
;5 Plot the Model using GLFW
 
 
GLFW is basically a library to use with OpenGL, to aid in the creation of graphical windows and some other stuff. The plan is to use this library to open up a simple window and then plot all the members of the g file into this window.
 
 
; 6. Develop front end
 
* Develop Single window view
 
* Develop File Input
 
; 7. Write Functional testing test cases.
 
  
 
== Project Workflow ==
 
== Project Workflow ==
  
 
* This design document will be updated regularly to include the status of tasks as well as any changes in project scope and/or approach.  
 
* This design document will be updated regularly to include the status of tasks as well as any changes in project scope and/or approach.  
* The source will be uploaded on: [https://github.com/asadpiz/brlcad-viewer]
+
* The source will be upload on: [https://github.com/asadpiz/brlcad-viewer]
 
* There will also be occasional weekly status meetings on irc '''#brlcad''' (Fridays 16:00 GMT+2)
 
* There will also be occasional weekly status meetings on irc '''#brlcad''' (Fridays 16:00 GMT+2)
  
Line 138: Line 63:
 
[http://brlcad.sourceforge.net/doxygen/modules.html]
 
[http://brlcad.sourceforge.net/doxygen/modules.html]
 
[http://brlcad.org/docs/doxygen-r64112/index.xhtml]
 
[http://brlcad.org/docs/doxygen-r64112/index.xhtml]
[http://brlcad.org/docs/doxygen-r64112/d2/d66/structdb__i.xhtml]
 
[http://brlcad.org/docs/doxygen-r64112/d3/d9b/group__dbio.xhtml#gaa9eb8edb99fa1da5d188587e07d8dacc]
 
[http://brlcad.org/docs/doxygen-r64112/d0/d0a/ged_8c_source.xhtml#l00420]
 
[http://brlcad.org/docs/doxygen-r64112/dc/ddd/osg-test_8cpp_source.xhtml#l00588]
 
[http://en.flossmanuals.net/contributors-guide-to-brl-cad/appendix-iii-further-references-and-resources/]
 
[http://svn.code.sf.net/p/brlcad/code/brlcad/trunk/HACKING]
 

Please note that all contributions to BRL-CAD may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here.
You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see BRL-CAD:Copyrights for details). Do not submit copyrighted work without permission!

To edit this page, please answer the question that appears below (more info):

Cancel Editing help (opens in new window)