Revision: 78102
http://sourceforge.net/p/brlcad/code/78102
Author: starseeker
Date: 2021-01-21 22:50:53 +0000 (Thu, 21 Jan 2021)
Log Message:
-----------
Lay out an example that requires parent comb redefinition. Still not sure how
to implement this yet, but there are clearly cases where it can be necessary.
Modified Paths:
--------------
brlcad/trunk/doc/docbook/system/mann/npush.xml
Modified: brlcad/trunk/doc/docbook/system/mann/npush.xml
===================================================================
--- brlcad/trunk/doc/docbook/system/mann/npush.xml 2021-01-21 21:47:45 UTC
(rev 78101)
+++ brlcad/trunk/doc/docbook/system/mann/npush.xml 2021-01-21 22:50:53 UTC
(rev 78102)
@@ -275,9 +275,99 @@
<para>
Note that neither option alters the parameters of primitive shapes.
</para>
+
+ <para>
+ Worse still is a case where multiple copies of identical objects are
referenced at multiple levels.
+ Consider the following example:
+ </para>
+ <literallayout>
+sph_016/
+ u [M1] sph16a/R
+ u [M2] sph16_1/
+ u sph16.c/
+ u sph16.s
+ u sph16_1/
+ u sph16.c/
+ u sph16.s
+ u [M3] sph16a/R
+ u [M4] sph16_1/
+ u sph16.c/
+ u sph16.s
+ u sph16_1/
+ u sph16.c/
+ u sph16.s
+ </literallayout>
+ <para>
+ If we push to depth 3, we end up with four different versions of the
sph16.c tree:
+ </para>
+ <literallayout>
+sph_016/
+ u sph16a/R
+ u sph16_1/
+ u [M12] sph16.c/
+ u sph16.s
+ u sph16_1/
+ u [M1] sph16.c/
+ u sph16.s
+ u sph16a/R
+ u sph16_1/
+ u [M34] sph16.c/
+ u sph16.s
+ u sph16_1/
+ u [M3] sph16.c/
+ u sph16.s
+ </literallayout>
+ <para>
+ The first stage of the answer is to create three new combinations and
redefine the sph16a tree:
+ </para>
+ <literallayout>
+sph_016/
+ u sph16a/R
+ u sph16_1_01/
+ u [M12] sph16.c/
+ u sph16.s
+ u sph16_1/
+ u [M1] sph16.c/
+ u sph16.s
+ u sph16a/R
+ u sph16_1_02/
+ u [M34] sph16.c/
+ u sph16.s
+ u sph16_1_03/
+ u [M3] sph16.c/
+ u sph16.s
+ </literallayout>
+ <para>
+ That addresses sph16_1, but the tree updates to sph16a created a new
problem: now we have
+ two different versions of the sph16a tree. To resolve that problem, we
must create a new
+ comb to replace one of the conflicting sph16a instances and redefine the
sph_016 tree:
+ </para>
+ <literallayout>
+sph_016/
+ u sph16a/R
+ u sph16_1_01/
+ u [M12] sph16.c/
+ u sph16.s
+ u sph16_1/
+ u [M1] sph16.c/
+ u sph16.s
+ u sph16a_01/R
+ u sph16_1_02/
+ u [M34] sph16.c/
+ u sph16.s
+ u sph16_1_03/
+ u [M3] sph16.c/
+ u sph16.s
+ </literallayout>
+ <para>
+ Unlike sph16a and sph16_1, sph_016 has not seen any changes to its
volumetric definition. sph_016
+ is the "top level" object specified for this push, and as such constitutes
a reliable termination point for
+ any need to propagate tree changes. Even if any combs elsewhere in the
database reference sph_016,
+ they will not see any volumetric changes as a consequence of the operation
and do not need to redefine
+ their trees to preserve original sph_016 trees for external use in copies
of sph_016.
+ </para>
+ </refsection>
- </refsection>
-
<refsection xml:id="search_options"><title>OPTIONS</title>
<variablelist remap="TP">
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