# Difference between revisions of "Community Publication Portal"

(→Cristina Precup: Visualizing Directed Acyclic Graphs) |
(→Chris Dueck: Calculating 2D Sketch Surface Area) |
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==== Chris Dueck: Calculating 2D Sketch Surface Area ==== | ==== Chris Dueck: Calculating 2D Sketch Surface Area ==== | ||

+ | |||

+ | Calculating the surface area of a 2D Sketch primitive is not a trivial task. Sketches are created interactively by the user, and can contain straight line segments, circular arc segments (and full circles), as well as Bezier and NURBS curves. | ||

+ | |||

+ | The method used to approximately compute the area of a 2D sketch is as follows: | ||

+ | |||

+ | 1.) Approximate the sketch by a polygon | ||

+ | 2.) Compute the area of the polygon exactly using Green's Theorem | ||

+ | 3.) Add the areas of any circular arc segments that were created during (1) | ||

+ | |||

+ | To approximate the sketch by a polygon, each possible curve type of a sketch must be considered. | ||

+ | |||

+ | If the curve is a straight line, it need not be approximated. | ||

+ | |||

+ | If the curve is a circular arc, it must be determined if it is a full circle (in which case its area can be computed easily) or if it is a circular arc segment. If it is a circular arc segment, the line segment from the beginning of the arc to the endpoint is added to the polygon, and the excess area of the circular arc segment itself can be calculated easily (https://en.wikipedia.org/wiki/Circular_segment) | ||

+ | |||

+ | If the curve is a Bezier curve, it can be approximated by a series of circular arcs. The algorithm used can be found here (http://itc.ktu.lt/itc354/Riskus354.pdf). The algorithm recursively subdivides the Bezier until it is approximated to tolerance by a biarc and uses the curvature value of the Bezier at a point to determine the depth of subdivision. Then each circular arc in the approximation of the Bezier curve is treated as above. | ||

+ | |||

+ | Finally, the area of the polygon can be efficiently calculated using Green's Theorem (http://www.softsurfer.com/Archive/algorithm_0101/algorithm_0101.htm#3D%20Standard%20Formula) using cross products. | ||

==== Cliff Yapp: NURBS Ray Tracing in BRL-CAD ==== | ==== Cliff Yapp: NURBS Ray Tracing in BRL-CAD ==== |

## Revision as of 20:42, 7 November 2012

Welcome to the BRL-CAD community publication portal. This page is dedicated to the preparation and editing of BRL-CAD announcements. Proposed and upcoming topics are listed. Anyone is **welcome and encouraged** to share news about any activity related to BRL-CAD. Community editing and review are encouraged.

## Contents

- 1 Ready for Publication
- 2 Final Editorial Review
- 3 Initial Drafts
- 3.1 Anurag Murty: Voxelizing Geometry
- 3.2 Cristina Precup: Visualizing Directed Acyclic Graphs
- 3.3 Ksenija Slivko: Reducing Code
- 3.4 Laijiren: NURBS Tessellation: What, Why, How?
- 3.5 Suryajith Chillara: Benchmark Performance Database
- 3.6 Wu Jianbang: NURBS surface-surface intersections
- 3.7 Andrei Popescu: Network Performance Testing
- 3.8 Chris Dueck: Calculating 2D Sketch Surface Area
- 3.9 Cliff Yapp: NURBS Ray Tracing in BRL-CAD
- 3.10 Erik Greenwald: Bolting ADRT's libtie under the hood

- 4 Idea Hopper
- 4.1 BRL-CAD's Evolutionary API
- 4.2 Introduction to new .deb and .rpm builds
- 4.3 2010 End Of Year Review
- 4.4 Erik Greenwald: ADRT/ISST Visualization
- 4.5 Bob Parker: Alpha Archer: Working Towards Next Generation MGED
- 4.6 Finding the Hot Spots
- 4.7 Point Clouds
- 4.8 bn_mat_inv: singular matrix
- 4.9 Model Showcase: Goliath
- 4.10 Model Showcase: Chumaciera
- 4.11 Model Showcase: Proyecto Catapulta
- 4.12 Model Showcase: Union Coupling Tool
- 4.13 Geometry Service FAQ
- 4.14 BRL-CAD's 3rd Generation Build System
- 4.15 BRL-CAD's Open Source Vision
- 4.16 BRL-CAD Primitives Showcase
- 4.17 BRL-CAD Geometry Converter Showcase
- 4.18 Release Schedule
- 4.19 RTGL
- 4.20 BRL-CAD Quick Reference Card
- 4.21 BRL-CAD Bibliography
- 4.22 Revolve Primitive
- 4.23 Parametrics and Constraints
- 4.24 Converting Implicit to Explicit: CSG to BREP NURBS
- 4.25 Online Model Repository
- 4.26 Project Statistics for 2010
- 4.27 Next Generation BRL-CAD

**Formatting & Editing Standards:**

- Quotations are italicized and placed between double quotes (
*"Like This"*).

- AA (All Acronyms) need to be defined upon first use, don't abbrev. words.

- Section headings uppercase the major words and are in bold (
**Like This**)

- Use the serial comma: one, two, and three; not one, two and three.

- Cite references, include hyperlinks.

- Keep it brief.

**Distribution Channels:**

For release publications, follow HACKING. For everything else, distribute to the following:

- brlcad-news@lists.sourceforge.net
- http://brlcad.org/d/node/add/story
- https://sourceforge.net/news/?group_id=105292
- (optional) https://brlcad.org/wiki/
- (optional) http://www.tenlinks.com/NEWS/tl_daily/submit_news.htm
- (optional) http://upfrontezine.com

## Ready for Publication

These articles are ready for publication. Release notes should be posted after tarballs, ideally the last or first week of a month. Other publications should be scheduled one or two weeks later, ideally on the second or third week of the month.

Note: if you see a comment indicating that a section is FROZEN, any changes you make in that section may go unnoticed as the article is being prepared for distribution. If you find errors in a FROZEN article, go ahead and correct the article but contact Sean (brlcad on freenode IRC) who may be able to incorporate changes during final publication.

#### Move from Final Review to Here When Ready

## Final Editorial Review

These should be "complete" articles. The author is done. All that remains is a structure, grammar, voice, punctuation, and spelling review. Images welcome.

#### Kyle Bodt: Ronja

Ronja (Reasonable Optical Near Joint Access) is an innovative piece of equipment that utilizes reliable optical data links to create a current communication range of 1.4 km and a speed of 10Mbps full duplex that can be used as a general purpose wireless link for virtually any networking project. This is a very important project for Twibright Labs, a small group of computer science graduate students operating out of Charles University in Prague in the Czech Republic. The group specializes in the usage of Free Software and User Controlled Technology Development.

The primary output for the Ronja project is a design. The lab does not intend to manufacture and sell the hardware that is being designed but wants to engage in open source development of the technology. The philosophy surrounding User Controlled Technology is the ideal that the end-user is provided with unrestricted access to the intellectual property surrounding the technology, including the tools that are being used to create it. One tool playing an integral part in the development of the Ronja designs is BRL-CAD. All of the models that Twibright labs use to display the different variants of their Ronja concept were created with the help of BRL-CAD. BRL-CAD has allowed the members of Twibright labs to create instructional diagrams so that the users and builders of their open source technology will be able to have the latest information with regard to the proper construction of a Ronja unit. The interactive geometry editor and ray-tracers in BRL-CAD are an integral part in the communication of design plans for Twibright labs and enables them to connect with the users, who are the driving force behind the User Controlled Technology ideal.

## Initial Drafts

These are incomplete articles being worked on. Short 250 to 500-word articles (not counting tables, images, etc) are usually perfect.

#### Anurag Murty: Voxelizing Geometry

Given a set of primitives as input, the voxelize command uses the data obtained from BRL-CAD's raytracer to represent the input in the form of voxels(Volumetric Picture Elements). A uniform grid of rays is uniformly shot on the given input and an approximation of the volume filled in each voxel region is made from the raytracing data. Depending on the approximate volume of the voxel filled, a voxel is classified as IN or OUT of the voxelized output. The voxels are represented as RPPs. Such voxelized outputs have applications in Volumetric rendering and finite element analysis.

SYNTAX : voxelize [-s "dx dy dz"] [-d n] [-t f] new_obj old_obj [old_obj2 old_obj3 ...]

ARGUMENTS-

-d - Specifies the level of detail(precision in approximation of volume) required. An input of n means that n * n rays will be shot through each row, and an approximation of volume filled is reached averaging these n * n values

-s - Specifies the voxel size in each direction.

-t - Specifies the threshold volume to decide if voxel is to be included in the voxelized output.

new_obj - Name for resultant primitive that is a region containing the resulting voxels.

old_obj - Name of source primitive or collection.

NOTES-

1. A greater level of detail usually implies a much better approximation of fill volumes at the cost of more computations.

2. Lesser voxel sizes give a more precise representation of the input at the cost of more memory requirements.

3. Threshold value (the argument of -t) should be a value between 0 and 1, and not a percentage.

#### Cristina Precup: Visualizing Directed Acyclic Graphs

**Visualizing Constructive Solid Geometry** is a project meant to illustrate in an intuitive and interactive manner the hierarchical structure of .g geometry databases.

For the representation of the hierarchies, the **Adaptagrams** graph library has been used. This made possible organizing the objects contained within the database into directed acyclic graphs.

Following, are the steps that have been taken in developing the graph layout API:

- Integrate the Adaptagrams library into BRL-CAD.
- Traverse the geometry database and distinguish different types of objects (
*primitive*,*combination*,*non-geometry*) within it, as well as, establish the operations between them (*union*,*difference*, ...). Add all this data to the graph structure constructed with Adaptagrams. - Display the objects using a Tk Canvas widget inside a window.
- Develop a
*decorative routine*that sets different colors for different types of objects, correspondingly. - Create a name label for each represented object.
- Develop a layout algorithm that aligns the nodes of the graph in a hierarchical way.
- Introduce the
**graph**command in both**MGED**and**Archer**. It has two subcommands:**show**which displays a list with the name and type of the objects along with the nodes' and edges' positions;**positions**that lists the names, types and positions of the corresponding nodes within the graph;

- Introduce the
**igraph**command in both MGED and Archer. This command pops up a graph based visualization window of the currently opened .g database. Its documentation can be found in*brlman*.

As an example, here is how the graph for the *share/db/axis.g* database looks like now:

Further work that can extend the *interactive* trait of the graph layout API includes adding user actions upon the graph such as *move* (dragging a node) or *delete* functionalities.

#### Ksenija Slivko: Reducing Code

#### Laijiren: NURBS Tessellation: What, Why, How?

#### Suryajith Chillara: Benchmark Performance Database

##### Abstract

The main idea is to store the data both in the database and the log files stored in the archive. The storage in the database enables the content to be searched via the parameters such as machine descriptions, versions, results and could be compared. The storage as a file in the archive is to maintain a back up of the file and whenever a developer needs a specific bunch of benchmark logs, he could get them from the archive with or without the help of the database.

##### Main Components

**Log Parser :**The data of the log file needs to be parsed and the relevant and important information has to be logged in the database so as to make the data access for the graphic display through the frontend could be made possible.**Web API :**Implemented via the bottle framework so as to submit the logs from the brlcad installation via scripts.**Web backend :**A backend has been implemented as a MVC framework from scratch using the python bottle framework.**Frontend :**The website that can offer multiple mechanisms for adding new performance run data into the database and provide multiple graphical and non-graphical visualizations of aggregate performance data (i.e., graphs, charts, tables, etc). Graphs, tables and charts are generated with the help of Google Charts via wrapper which generates the javascript code to interact with the Google Charts service.

Plumbing between these components is via the python scripts.

##### Tool & Service dependancies

- Python 2.7 and libraries
- Bottle web framework
- MySQL
- Google Charts

#### Wu Jianbang: NURBS surface-surface intersections

I focused on the "NURBS surface-surface intersections" project after the mid-term evaluation of this year's GSoC, before which I worked on converting implicit primitives to NURBS B-rep forms.

The function calculating NURBS surface-surface intersection curves is surface_surface_intersection() which is declared in include/nurbs.h and implemented in src/libnurbs/opennurbs_ext.cpp. It outputs intersection curves in 3d space and in both surfaces' UV parameter spaces.

The approach of the algorithm originates from:

Adarsh Krishnamurthy, Rahul Khardekar, Sara McMains, Kirk Haller, and Gershon Elber. 2008. Performing efficient NURBS modeling operations on the GPU. In Proceedings of the 2008 ACM symposium on Solid and physical modeling (SPM '08). ACM, New York, NY, USA, 257-268. DOI=10.1145/1364901.1364937 http://doi.acm.org/10.1145/1364901.1364937

It can be divided into several steps:

- Generate the bounding box of the two surfaces.
- If their bounding boxes intersect:
- Split the two surfaces, both into four parts, and calculate the sub-surfaces' bounding boxes
- Calculate the intersection of sub-surfaces' bboxes, if they do intersect, go deeper with splitting surfaces and smaller bboxes, otherwise trace back.

- After getting the intersecting bboxes, approximate the surface inside the bbox with two triangles, and calculate the intersection points of the triangles (both in 3d space and two surfaces' UV space)
- Fit the intersection points into polyline curves, and then to NURBS curves. Points with distance less than max_dis are considered in one curve.

It needs to be mentioned here that the value max_dis can be provided by the user or generated automatically.

Besides, after calculating the intersection curves, the next steps towords evaluated NURBS are splitting the surfaces into sub-surfaces with the intersection curves as their boundaries, and some inside-outside tests to decide which sub-surfaces should be included in the final object. Some work on splitting has been done, generating some b-rep faces that can pass IsValid(), but still further work is needed.

#### Andrei Popescu: Network Performance Testing

The project that I have been working on during the summer, as part of the Google Summer of Code program,

can be broken down into three independent parts and it consisted in running various tests for the BRL-CAD

networking library(Libpkg) .

- Speed testing and investigations to uncover any potential performance bottleneck.
- Unit tests and code review to find and cover any untreated exceptions(crashes) in the Libpkg library.
- Eliminate the assumption of globals in the API.

For the first part, I have run two types of tests :

Local ones, both the "sender" and the "receiver" were located on localhost.
The script gathered data

regarding the transmission speed for each set of package sizes (Here, package refers to the package

created by networking library, not networking packages) respectively file sizes.

Remote ones, where the "sender" and the "receiver" were on separate machines, connected using SSH.

The script ran and the data gathered was done in the same way as the localhost one.Using the data

obtained from the tests, two 3D graphs were drawn.However, the tests were inconclusive, I could not find

an "ideal" package size to use regardless of file size.

After Mid-term I focused mostly on second part. I used test units from libbu(Utility library) as an example

for the unit test type and design.
When the mentioned tests were run, several exceptions that caused

crashes were discovered. Lastly, I have written fixes for the discovered crashes.

The third part of the project has not been covered yet, so more work is needed.Although, I am doing my

best to finish it in the following weeks.

#### Chris Dueck: Calculating 2D Sketch Surface Area

Calculating the surface area of a 2D Sketch primitive is not a trivial task. Sketches are created interactively by the user, and can contain straight line segments, circular arc segments (and full circles), as well as Bezier and NURBS curves.

The method used to approximately compute the area of a 2D sketch is as follows:

1.) Approximate the sketch by a polygon 2.) Compute the area of the polygon exactly using Green's Theorem 3.) Add the areas of any circular arc segments that were created during (1)

To approximate the sketch by a polygon, each possible curve type of a sketch must be considered.

If the curve is a straight line, it need not be approximated.

If the curve is a circular arc, it must be determined if it is a full circle (in which case its area can be computed easily) or if it is a circular arc segment. If it is a circular arc segment, the line segment from the beginning of the arc to the endpoint is added to the polygon, and the excess area of the circular arc segment itself can be calculated easily (https://en.wikipedia.org/wiki/Circular_segment)

If the curve is a Bezier curve, it can be approximated by a series of circular arcs. The algorithm used can be found here (http://itc.ktu.lt/itc354/Riskus354.pdf). The algorithm recursively subdivides the Bezier until it is approximated to tolerance by a biarc and uses the curvature value of the Bezier at a point to determine the depth of subdivision. Then each circular arc in the approximation of the Bezier curve is treated as above.

Finally, the area of the polygon can be efficiently calculated using Green's Theorem (http://www.softsurfer.com/Archive/algorithm_0101/algorithm_0101.htm#3D%20Standard%20Formula) using cross products.

#### Cliff Yapp: NURBS Ray Tracing in BRL-CAD

Over the past year, an intense development effort by BRL-CAD's development team has successfully implemented raytracing of Non-Uniform Rational BSpline (NURBS) geometry within the BRL-CAD Computer-Aided Design (CAD) package. NURBS surfaces are very general, very complex mathematical shapes used by virtually all modern commercial CAD software packages. Because BRL-CAD did not originally support this type of geometry, commercial models could only be imported into BRL-CAD after a labor-intensive and difficult conversion process from NURBS form to triangle-base geometry (referred to in BRL-CAD as Bags-of-Triangles or BoTs). The new NURBS raytracing capability builds on work by many developers over a period of years, who in turn built on the open source library OpenNURBS. Support for this primitive type means BRL-CAD can now store and raytrace data from commercial models without requiring preliminary conversion to another type of geometry.

The last major feature needed to make import of commercial models in BRL-CAD straightforward is conversion support for ISO’s "Standard for the Exchange of Product model data" or STEP file format. STEP uses NURBS geometry in its definition, making support for NURBS geometry a necessary prelude to support for STEP import. Most commercial CAD modelers support this file format as an output option, hence STEP support in BRL-CAD would allow a direct path for moving geometric descriptions from a variety of commercial modelers to BRL-CAD. Considerable progress has already been made on STEP import support, but more work is need to bring the code and feature set to "production quality". If anyone would like to join the BRL-CAD open source development effort and has a little familiarity with C++, the step-g converter and its supporting libraries have some simple-yet-useful tasks that would be an excellent and very useful way to explore the project - join BRL-CAD's IRC channel or development email list if you are interested!

#### Erik Greenwald: Bolting ADRT's libtie under the hood

Initial progress on the integration of ADRT's libtie "triangle intersection engine" with LIBRT.

## Idea Hopper

These are ideas for interesting or useful publications. We need someone to at least write a draft.

#### BRL-CAD's Evolutionary API

Talk about BRL-CAD deprecation process.

#### Introduction to new .deb and .rpm builds

Brief article overviewing the efforts by jordisayol for Debian, Ubuntu, Fedora, and openSUSE. Included are new icons, menu items, mime type associations, and more.

#### 2010 End Of Year Review

Article giving an overview of the past year's highlight developments with hints at what 2011 may bring. Alternatively, may be the annual statistics review if we switch from fiscal to calendar year reporting.

#### Erik Greenwald: ADRT/ISST Visualization

Article introducing ADRT/ISST core capability.

#### Bob Parker: Alpha Archer: Working Towards Next Generation MGED

Article introducing Archer's core new features that will be "coming" to MGED. Undo, interactive editing, tree view, and info panels come to mind.

#### Finding the Hot Spots

Article on the rt lighting model Stephen Kennedy developed that visualizes the time spent per-pixel.

#### Point Clouds

Article introducing the new point cloud primitive.

#### bn_mat_inv: singular matrix

Article on the v4 format and binary compatibility.

#### Model Showcase: Goliath

Article talking about the making of the Goliath model.

#### Model Showcase: Chumaciera

Article on Pedro Baptista's bearing model.

#### Model Showcase: Proyecto Catapulta

Article on a model developed by André Santos, António Almeida, and Pedro Ferreira.

#### Model Showcase: Union Coupling Tool

Article on a model developed by Inês de Matos under teacher Luís Ferreira. The project focuses on a tool, union coupling, based on the book, http://purl.pt/14352 , page 122 of the original book and page 128 of the file, figures 108 and 109.

#### Geometry Service FAQ

FAQ summarization of the GS as it pertains to the wider open source community.

#### BRL-CAD's 3rd Generation Build System

Article on the new CMake build system.

#### BRL-CAD's Open Source Vision

Article introducing the Project Priorities diagram and overall project vision.

#### BRL-CAD Primitives Showcase

Article summarizing all of BRL-CAD's primitives and their current status.

#### BRL-CAD Geometry Converter Showcase

Article summarizing all of BRL-CAD's geometry converters.

#### Release Schedule

Explain our release schedule and versioning system.

#### RTGL

Article on Nick's point-based visualization mode.

#### BRL-CAD Quick Reference Card

Article on a BRL-CAD QRC similar to the existing MGED QRC.

#### BRL-CAD Bibliography

After the .bib gets published to the website, an article announcing it and soliciting additions.

#### Revolve Primitive

Article on Timothy Van Ruitenbeek's work implementing 'revolve'.

#### Parametrics and Constraints

Article on Dawn Thomas' work to integrate parametric equation and constraint evaluation support.

#### Converting Implicit to Explicit: CSG to BREP NURBS

Article on the work by Cliff Yapp, Joe Doliner, and Ben Poole converting primitives with an implicit representation into an explicit NURBS representation.

#### Online Model Repository

Article on Elena Băutu's work developing the model repository website.

#### Project Statistics for 2010

Article on our current stats similar to previous years.

#### Next Generation BRL-CAD

Article on our super secret awesome new GUI.