paging system much more robust when position change is very rapid and sporadic.
Recall that we must load 3d models in the main render thread because model
loading can trigger opengl calls (i.e. with texture loading) and all opengl
calls *must* happen in the main render thread.
To accomplish this we load the base tile in the pager thread and build a work
queue of external models that need to be loaded. We never allow a tile to be
paged out of the tile cache until all it's pending model loads are complete.
However, when changing position very rapidly, we can quickly create a huge
backlog of pending model loads because we are changing positions faster than we
can load the associated models for the existing tiles. The end result is
that tiles that are long out of range can't be removed because there is still
a huge backlog of pending model load requests and memory blows up.
This change being committed allows the tile paging system to remove tiles
if they are out of range, even when there are pending models to load. The
model loading code in the render thread can now check to see if the tile
exists and discard any model load request for tiles that no longer exist.
This situation should never occur in normal operation, but could occur in
"contrived" situations where an external script was rapidly changing
the simulator position to then be able to query FG terrain height, and doing
this for a large number of points that are distributed across a large area.
configure and compile out-of-the-box on a MinGW target:
Use -lSDL instead of -lglut32 on windows builds when --enable-sdl
is set.
Link against alut.dll in addition to openal32.dll.
Replace BSD bcopy() with ANSI C memmove() in a few places. This is
simpler than trying to abstract it out as a platform dependency in a
header file; bcopy() has never been standard.
The ENABLE_THREADS handling has changed to be set to 0 when threads
are not in use. This breaks expressions like #ifdef ENABLE_THREADS.
Replace with a slightly more complicated expression. It might have
been better to fix the configure.ac script, but I didn't know how and
this whole setting is likely to go away soon anyway.
The MinGW C runtime actually does include snprintf, so only MSVC
builds (and not all WIN32 ones) need _snprintf in JSBSim/FGState.cpp
Building on a platform with no glut at all exposed some spots where
plib/pu.h was being included without a toolkit setting (it defaults to
glut). Include fg_os.hxx first.
And when still using glut, glut.h has a bizarre dependency on a
_WCHAR_T_DEFINED symbol. It it's not defined, it tries to redefine
(!!) wchar_t to disasterous effect.
The message 'Alert: catching up on tile delete queue'
comes from the fact that 48 tiles are scheduled and
added to the cache at startup before the plane location
is initialized. My proposed patch is to initialize
SGLocation with an invalid position and detect this
fact before scheduling tiles. I prefer to do that
rather than testing for lon and lat being 0,0 because
it is a valid position and someone could want to fly
near Accra.
account for variation in lighting alignment, but it's more useful than the
previous attempt which was based on a misunderstanding of how environment
mapping worked.
are cosmetic, but we now have a combination of code that seems to work
very robustly. I was able to land the yf23 at about 130 kts on the lower
level of the bay bridge and then taxi the entire length.
from the rest of the runway lighting. VASI/PAPI lights are generally
always on. Also, the red/white VASI coloring has never worked right.
This is also a step towards fixing that problem.
This patch is there to correct a problem that prevent to load static objects when specifying a relative fg-root or a different, relative, fg-scenery. It appears that there is a mix between fg-root, fg-scenery and PLIB's model-dir.
It has been reported on the list that users are not able to see the buildings, especially those running the win32 builds because they run 'runfgfs.bat' that set FG_ROOT=./DATA.
I decided not to use model-dir because it just add confusion and to build a valid path earlier.
scene management code and organizing it within simgear. My strategy is
to identify the code I want to move, and break it's direct flightgear
dependencies. Then it will be free to move over into the simgear package.
- Moved some property specific code into simgear/props/
- Split out the condition code from fgfs/src/Main/fg_props and put it
in it's own source file in simgear/props/
- Created a scene subdirectory for scenery, model, and material property
related code.
- Moved location.[ch]xx into simgear/scene/model/
- The location and condition code had dependencies on flightgear's global
state (all the globals-> stuff, the flightgear property tree, etc.) SimGear
code can't depend on it so that data has to be passed as parameters to the
functions/methods/constructors.
- This need to pass data as function parameters had a dramatic cascading
effect throughout the FlightGear code.
a tile boundary. (Potentially imposes a slight performance penalty, but
getting the correct answer needs to be higher priority than getting the
wrong answer really quickly.)
are now working. A runway light is defined by a point and a direction. The
point and direction are combined with the local up vector to create a small
triangle orthogonal to the direction. The two ficticous corners of the
triangle are given an alpha value of zero, the orignal corner is given an
alpha of one. The triangle is drawn in glPolygonMode(GL_FRONT, GL_POINT)
mode which means only the corner points are drawn, and since two have alpha=0
only the original point is drawn. This is a long way to go to draw a point,
but it ensures that the point is only visible within 90 degrees of the light
direction, behind the light it is not visible. This is still a long way
to get to drawing a point, but we use an environement map, with the direction
vector as the normal to mimic a light that is brightest when viewed head
on and dimmest when viewed perpendicularly or disappears when viewed from
behind.
- warning, there is a bug in how the current runway light direction vector
is calculated which will adversely effect runway lighting. The airports
should be regenerated in order to fix this problem.
fgLoad3DModel() throws an exception if it fails to load the requested model.
This causes FGTileMgr::update(...) to exit. So I've added a try/catch block
to catch the exception and display an error message instead.
Animations are now contained within the scene graph itself and are
updated whenever the graph is traversed -- that saves time by not
updating animations not currently in sight, and it allows animations
to be used for static objects and random objects as well.
Added new FGModelLoader and FGTextureLoader classes. These are intern
tables for models, to guarantee (mostly) that no model is loaded more
than once. FGTextureLoader is not yet used anywhere, but
FGModelLoader is now in place everywhere that ssgLoad* used to be
used (thus adding the ability to use animations).
In the future, FGModelLoader will add some interesting functionality,
including the ability to reload 3D models on the fly.
the tile cache it's ssg elements are disconnected from the main ssg scene
graph, and then the tile is thrown on the end of a delete queue. The
tilemgr->update() routine runs every frame. It looks at this queue and if
it is non-empty, it incrementally frees the compents of the first tile
on the queue. When the tile is completely free it is removed from the queue.
The amount of time to free the memory for even a single tile can be quite
substantial, especially with the increased overhead of dynamic/random
ground objects. This change allows the system to spread the work of freeing
tile memory out over many frames so you don't get a noticable single frame
hit or stutter.
This is a small fix for what turned out to be a major bug. Ground elevation
was calculated incorrectly when distant from one of the view locations. This
resulted in several problems including bizarre gear trimming, mid air
"crashes" (as in thinking we hit the ground) and so on when close to or on the
ground.
Unfortunately it does require a second ssg traversal when in tower view
(only), but the increased load isn't all that noticable. For the time being
this really is the best solution. In a future update I will be eliminating
the unecessary per frame traversals for the static views (without having to
maintain multiple ssgRoots).
When we go to multiple FDM instances we will perhaps need to put the ssg
traversal and ground elevation queries for the FDMs into an event timer that
updates the FDMs ground elevation in a round robin fashion (maybe every 1/n
seconds where n is the number of FDM instances running).
This is a new improved patch for the previous tile manager fixes.
Rather than building dependencies between FGlocation or the viewer or fdm with
tilemgr what I ended up doing was linking the pieces together in the Mainloop
in main.cxx. You'll see what I mean...it's been commented fairly well. More
than likely we should move that chunk somewhere...just not sure where yet.
The changes seem clean now. As I get more ideas there could be some further
improvement in organizing the update in tilemgr. You'll note that I left an
override in there for the tilemgr::update() function to preserve earlier
functionality if someone needs it (e.g. usage independent of an fdm or
viewer), not to mention there are a few places in flightgear that call it
directly that have not been changed to the new interface (and may not need to be).
The code has been optimized to avoid duplicate traversals and seems to run
generally quite well. Note that there can be a short delay reloading tiles
that have been dropped from static views. We could call the tile scheduler on
a view switch, but it's not a big deal and at the moment I'd like to get this
in so people can try it and comment on it as it is.
Everything has been resycned with CVS tonight and I've included the
description submitted earlier (below).
Best,
Jim
Changes synced with CVS approx 20:30EDT 2002-05-09 (after this evenings updates).
Files:
http://www.spiderbark.com/fgfs/viewer-update-20020516.tar.gz
or
http://www.spiderbark.com/fgfs/viewer-update-20020516.diffs.gz
Description:
In a nutshell, these patches begin to take what was one value for ground
elevation and calculate ground elevation values seperately for the FDM and the
viewer (eye position). Several outstanding view related bugs have been fixed.
With the introduction of the new viewer code a lot of that Flight Gear code
broke related to use of a global variable called "scenery.cur_elev".
Therefore the ground_elevation and other associated items (like the current
tile bucket) is maintained per FDM instance and per View. Each of these has a
"point" or location that can be identified. See changes to FGLocation class
and main.cxx.
Most of the problems related to the new viewer in terms of sky, ground and
runway lights, and tower views are fixed.
There are four minor problems remaining. 1) The sun/moon spins when you pan
the "lookat" tower view only (view #3). 2) Under stress (esp. magic carpet
full speed with max visibility), there is a memory leak in the tile caching
that was not introduced with these changes. 3) I have not tested these
changes or made corrections to the ADA or External FDM interfaces. 4) The
change view function doesn't call the time/light update (not a problem unless
a tower is very far away).
Details:
FDM/flight.cxx, flight.hxx - FGInterface ties to FGAircraftModel so that it's
location data can be accessed for runway (ground elevation under aircraft)
elevation.
FDM/larsim.cxx, larcsim.hxx - gets runway elevation from FGInterface now.
Commented out function that is causing a namespace conflict, hasn't been
called with recent code anyway.
FDM/JSBSim/JSBSim.cxx, YASim/YASim.cxx - gets runway elevation from
FGInterface now.
Scenery/newcache.cxx, newcache.hxx - changed caching scheme to time based
(oldest tiles discard).
Scenery/tileentry.cxx, tileentry.hxx - added place to record time, changed
rendering to reference viewer altitude in order to fix a problem with ground
and runway lights.
Scenery/tilemgr.cxx, tilemgr.hxx - Modified update() to accept values for
multiple locations. Refresh function added in order to periodically make
the tiles current for a non-moving view (like a tower).
Main/fg_init.cxx - register event for making tiles current in a non-moving
view (like a tower).
Main/location.hxx - added support for current ground elevation data.
Main/main.cxx - added second tilemgr call for fdm, fixed places where viewer
position data was required for correct sky rendering.
Main/options.cxx - fixed segfault reported by Curtis when using --view-offset
command line parameter.
Main/viewer.cxx, viewer.hxx - removed fudging of view position. Fixed numerous
bugs that were causing eye and target values to get mixed up.
graph as the terrain, except for internal cockpit view. The SSG
scene-graph variables (except for the lighting root -- I'll get that
later) are now held in globals.hxx.
FGModelMgr::draw() is obsolete; I'll remove it in a future revision.
