Revision: 68869
http://sourceforge.net/p/brlcad/code/68869
Author: brlcad
Date: 2016-09-20 22:38:27 +0000 (Tue, 20 Sep 2016)
Log Message:
-----------
include a high-level introduction to the overall approach being taken which
affords an opportunity to introduce opennurbs, libbrep, and a few other details.
Modified Paths:
--------------
brlcad/branches/brep-debug/doc/docbook/system/implementation/en/bool_eval_development.xml
Modified:
brlcad/branches/brep-debug/doc/docbook/system/implementation/en/bool_eval_development.xml
===================================================================
---
brlcad/branches/brep-debug/doc/docbook/system/implementation/en/bool_eval_development.xml
2016-09-20 21:27:16 UTC (rev 68868)
+++
brlcad/branches/brep-debug/doc/docbook/system/implementation/en/bool_eval_development.xml
2016-09-20 22:38:27 UTC (rev 68869)
@@ -143,9 +143,40 @@
</caption>
</figure>
<section>
- <title>Major Algorithms</title>
+ <title>Technical Approach</title>
<section>
<para>
+ The technical approach used for evaluating Boolean
+ operations on NURBS entities involves calculating geometric
+ intersections, trimming surfaces accordingly, and stitching
+ together a resulting object. Boundary representation (BREP)
+ NURBS objects are composed of faces, edges, and vertices;
+ and these topologically describe how surfaces, curves, and
+ points are joined together to represent geometry. The
+ geometry is used to find intersections. The topology is
+ used in the application of Boolean logic. This is
+ oversimplified as there are also trimming curves, loops,
+ orientations, and other details involved, but this is
+ nonetheless a useful foundation for understanding the basic
+ approach employed.
+ </para>
+ <para>
+ BRL-CAD heavily integrates and extends the OpenNURBS Toolkit
+ by Robert McNeel & Associates, developers of the
+ proprietary Rhinoceros freeform NURBS modeling software.
+ BRL-CAD heavily uses OpenNURBS for trimmed NURBS geometry
+ representation (both in-memory and on-disk) and implements
+ functionality not included with OpenNURBS such as ray
+ tracing and Boolean evaluation. <footnote><para>While their
+ license is permissive, the OpenNURBS Toolkit is only
+ intended for and McNeel only supports it being using for
+ reading and writing 3DM files.</para></footnote> Additional
+ functionality implemented for BRL-CAD is primarily contained
+ within the boundary representation and ray trace libraries
+ (LIBBREP and LIBRT).
+ </para>
+
+ <para>
The overall NURBS Boolean Evaluation algorithm is based on
the paper <emphasis>BOOLE: A System to Compute Boolean
Combinations of Sculptured Solids.</emphasis> (S. Krishnan
@@ -157,10 +188,10 @@
The NURBS surface-surface intersection algorithm is based on
the "NURBS Intersection Curve Evaluation" section of the
paper <emphasis>Performing Efficient NURBS Modeling
- Operations on the GPU</emphasis> (A. Krishnamurthy et
- al., 2008). A detailed outline of the algorithm, as
- implemented, appears in the main implementation file for the
- NURBS Surface-Surface intersection algorithm,
+ Operations on the GPU</emphasis> (A. Krishnamurthy et al.,
+ 2008). A detailed outline of the algorithm, as implemented,
+ appears in the main implementation file for the NURBS
+ Surface-Surface intersection algorithm,
<filename>src/libbrep/intersection.cpp</filename>.
</para>
</section>
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