Revision: 72264
http://sourceforge.net/p/brlcad/code/72264
Author: starseeker
Date: 2019-01-25 14:14:35 +0000 (Fri, 25 Jan 2019)
Log Message:
-----------
Fixed multiple issues interfering with generating raytraced images using long
object lists in MGED and other tools calling libged's rt command.
The problem manifests when MGED or another tool working through libged's API
wants to generate a raytrace image of a scene with a large number of objects.
libged's approach to performing this without blocking is to launch an rt
command as a subprocess, which means it is necessary to communicate to that
subprocess all the details of the view and scene to be raytraced. However, if
the scene description is too large it can result in an rt command invocation
that exceeds the length allowed by operating systems for command invocation
(observed in practice on Windows.)
The rt command already supports a command-driven execution mode that was being
used for view communication, and expanding the supported command set to allow
for scene object specification by piped command avoids the need for crazy long
command argument lists. libged was adjusted to used this method for all
platforms.
This new approach exposed a different limitation of the MGED/rt interaction
model, in that rt will not process standard input commands until it has
finished its fb_open call. This is not a problem if rt is creating it's own
framebuffer, but when it is rendering to an existing MGED framebuffer fb_open
doesn't complete until after the libged command execution is done and MGED's
callbacks can finalize the fb_open. This causes a hanging condition for long
objects lists - libged fills up the stdin pipe and waits for rt to clear it
before continuing, but rt doesn't clear it because it is waiting for MGED to
finalize the fb_open before it starts processing. Of course, the fb_open
finalization won't occur until the libged command completes. The fix for this
was to postpone the fb_open call in rt until just before an actual render needs
to take place, to allow rt to do most of the stdin processing up front.
These issues are things to watch out for in other cases where libged uses
subprocess invocation, since such communication is a standard feature of that
execution model...
Modified Paths:
--------------
brlcad/trunk/NEWS
Modified: brlcad/trunk/NEWS
===================================================================
--- brlcad/trunk/NEWS 2019-01-25 13:48:42 UTC (rev 72263)
+++ brlcad/trunk/NEWS 2019-01-25 14:14:35 UTC (rev 72264)
@@ -14,6 +14,7 @@
--- 201X-XX-XX Release 7.30.0 ---
----------------------------------------------------------------------
+* fixed rt support for specifying large object lists - Cliff Yapp
* new 'gex' tool for low-level .g file exploration - Tom Browder
* added support for command-line editing of metaballs - Sean Morrison
* added manual page for the 'get' command - Cliff Yapp
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