Revision: 41819
http://brlcad.svn.sourceforge.net/brlcad/?rev=41819&view=rev
Author: erikgreenwald
Date: 2010-12-28 21:58:38 +0000 (Tue, 28 Dec 2010)
Log Message:
-----------
MFC 41816
Modified Paths:
--------------
brlcad/branches/bottie/doc/deprecation.txt
brlcad/branches/bottie/doc/docbook/system/man1/en/rtarea.xml
brlcad/branches/bottie/doc/docbook/system/mann/en/search.xml
Modified: brlcad/branches/bottie/doc/deprecation.txt
===================================================================
--- brlcad/branches/bottie/doc/deprecation.txt 2010-12-28 21:52:14 UTC (rev
41818)
+++ brlcad/branches/bottie/doc/deprecation.txt 2010-12-28 21:58:38 UTC (rev
41819)
@@ -176,8 +176,6 @@
pre 7.0
-------
include/raytrace.h
- db_free_external -> bu_free_external [deprecated pre-7.0]
- RT_HIT_NORM -> RT_HIT_NORMAL [deprecated pre-7.0]
struct hit.hit_point -> RT_HIT_POINT [deprecated pre-7.0]
struct hit.hit_normal -> RT_HIT_NORMAL [deprecated pre-7.0]
@@ -186,6 +184,10 @@
* OBSOLETE *
************
+7.18.2
+------
+ RT_HIT_NORM -> RT_HIT_NORMAL [deprecated pre-7.0]
+
7.18.0
------
include/raytrace.h
@@ -320,6 +322,8 @@
have been identified in reverse chronological order. As expressions
are not extensively tested, use with caution.
+s/VAPPROXEQUAL(/VNEAR_EQUAL(/g
+ VAPPROXEQUAL() renamed to VNEAR_EQUAL() [7.18]
s/bu_vlb_getBufferLength(/bu_vlb_buflen(/g
bu_vlb_getBufferLength() remamed to bu_vlb_buflen() [7.18]
Modified: brlcad/branches/bottie/doc/docbook/system/man1/en/rtarea.xml
===================================================================
--- brlcad/branches/bottie/doc/docbook/system/man1/en/rtarea.xml
2010-12-28 21:52:14 UTC (rev 41818)
+++ brlcad/branches/bottie/doc/docbook/system/man1/en/rtarea.xml
2010-12-28 21:58:38 UTC (rev 41819)
@@ -63,18 +63,143 @@
<refsect1 id='description'>
<title>DESCRIPTION</title>
<para>
- <emphasis remap='I'>Rtarea</emphasis> calculates the exposed, presented
and centers of
+ The <emphasis remap='I'>rtarea</emphasis> command calculates the
exposed, presented and centers of
surface areas of specified geometry objects from a particular view. The
summary
output includes details for individual regions, assemblies (combinations
that contain
- regions), and summarized totals. The exposed area is the occluded 2D
- projection of the specified geometry. That is, if another
- object is in front, it will reduce the amount of exposed area. The
- presented area is the unoccluded 2D projection of the geometry, where
- hidden objects will report their presented area regardless of any
- objects that are in front.
+ regions), and summarized totals.
</para>
-
<para>
+ The <emphasis remap='B'>exposed </emphasis> area corresponds to what a
human observer would see looking at the object(s)
+ in question, if all the objects were non-transparent. For example, say
rays were cast towards two cubes, each one of which
+ is a region, one in front of the other, grouped into an assembly, with
the ray direction pointed into the page:
+ <screen>
+|----------------| Rear Cube
+| |
+| |
+| |--------------| Front Cube
+| | | |
+| | | |
+|--------|-------| |
+ | |
+ | |
+ |--------------|
+ </screen>
+
+ The exposed area of the Front Cube corresponds to the total area of the
sheet, since it is not
+ occluded by any other object:
+ <screen>
+|----------------| Rear Cube
+| |
+| |
+| |--------------| Front Cube
+| |**************|
+| |**************|
+|--------|**************|
+ |**************|
+ |**************|
+ |--------------|
+ </screen>
+
+
+
+ The Rear Cube, on the other hand, IS occluded by the Front Cube and
would thus report only a fraction
+ of its area as exposed:
+ <screen>
+|----------------| Rear Cube
+|****************|
+|****************|
+|********|--------------| Front Cube
+|********| | |
+|********| | |
+|--------|-------| |
+ | |
+ | |
+ |--------------|
+ </screen>
+
+
+
+ An object that combines both of these sheets would thus report as its
exposed area the
+ sum of the exposed areas of the individual sheets:
+ <screen>
+|----------------| Rear Cube
+|****************|
+|****************|
+|****************|------| Front Cube
+|***********************|
+|***********************|
+|--------|**************|
+ |**************|
+ |**************|
+ |--------------|
+ </screen>
+
+
+ </para>
+ <para>
+ <emphasis remap='B'>Presented</emphasis> area, unlike exposed area, does
not take occlusion into account. It is the
+ equalivent of taking each object and considering it in isolation. So
for the previous
+ case of two sheets of metal, the Front Cube would report the same area:
+
+ <screen>
+|----------------| Rear Cube
+| |
+| |
+| |--------------| Front Cube
+| |**************|
+| |**************|
+|--------|**************|
+ |**************|
+ |**************|
+ |--------------|
+ </screen>
+
+
+
+ the Rear Cube, on the other hand, ALSO reports its full area:
+ <screen>
+|----------------| Rear Cube
+|****************|
+|****************|
+|****************-------| Front Cube
+|****************| |
+|****************| |
+|--------|-------| |
+ | |
+ | |
+ |--------------|
+ </screen>
+
+
+ When reporting the presented area of the group, there is a subtle point
- rtarea does not count area covered
+ by multiple regions multiple times when totaling the presented area. So
for the group containing both cubes,
+ the presented area is NOT the cumulative area of both regions' presented
areas but the area of the union of those
+ two areas. In this case, that works out to be the same as the exposed
area.
+ <screen>
+|----------------| Rear Cube
+|****************|
+|****************|
+|****************|------| Front Cube
+|***********************|
+|***********************|
+|--------|**************|
+ |**************|
+ |**************|
+ |--------------|
+ </screen>
+
+
+ </para>
+
+ <para>
+ It should be noted that rtarea only counts surfaces with a surface
normal that
+ has a component looking back in the direction of the ray. So, for
example, a
+ cube with only one face looking "back toward" the ray will not report
area from
+ other faces as "presented", since their surface normals will indicate
they are
+ not surfaces being presented to the ray.
+ </para>
+
+ <para>
WARNING: <emphasis remap='I'>Rtarea</emphasis> may not correctly report
area or
center when instancing is done at the group level. Using
<command>xpush</command>
can be a workaround for this problem.
Modified: brlcad/branches/bottie/doc/docbook/system/mann/en/search.xml
===================================================================
--- brlcad/branches/bottie/doc/docbook/system/mann/en/search.xml
2010-12-28 21:52:14 UTC (rev 41818)
+++ brlcad/branches/bottie/doc/docbook/system/mann/en/search.xml
2010-12-28 21:58:38 UTC (rev 41819)
@@ -129,7 +129,7 @@
<term><emphasis remap='B' role='bold'>-mindepth</emphasis> <emphasis
remap='I'>n</emphasis></term>
<listitem>
<para>
- True if the depth of the object in the gree is greater than
+ True if the depth of the object in the tree is greater than
or equal to <emphasis remap='I'>n</emphasis>.
</para>
</listitem>
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