Hi Massimo, Thanks for the pictures. Moving slow is a walking pace, not at 360km/h.. that's pretty fast in my book. The streaks are motion blurr on the particles as when you are moving fast the particle moves relative to the eye point between frames will be stretched out. As the particle is stretched out the alpha value also gets reduced so it becomes more transparent particle to make sure the overall coverage of the background is the same. So the "slow" case it looks like things are working correctly to me.
For the fast case the motion blur support in PrecipitationEffect is failing as the camera is moving so fast between the particle cells that their is no previous frame position recorded for it to compute the motion blur for. This is a limitation/bug in PreciptationEffect. I wrote this class originally for a driving sim so it works well for driving speeds, but at jet aircraft speeds this particle cell issue rears it's head. These cells are virtual cells, which are in fact a single osg::Geometry that is transformed many times in the view in front of you, these virtual cells are reassigned on the fly to give you the effect of having an infinite particle system. I can think of two solutions - to better compute the previous frame position of a virtual cell that is newly coming into the view, or the more hacky solution, increase the depth of cells further out from camera so that the first frame that they become in view are miss out on the motion blur is far away enough from the camera as to not be seen. The former of the two solution really has to be the right way to go. Now fixing this bug will lead to motion blur at both your "slow" and fast speeds, which I can't say how you'll react to, as you picked out the "slow" viz as the one in error, rather than the fast speed. One could possible offer the option of removing the motion blur effect or scaling it down, but this itself might lead to other artifacts such as strobe like effect as you will find it easier to spot patterns in the particles as you go from cell to cell. Robert. On Mon, Dec 21, 2009 at 8:12 PM, Massimo Tarantini <[email protected]> wrote: > >> From your description it sounds like an issue that occurs when the >> camera moves very fast relative to the particle system, rather than >> very slow. My only guess is that you've model units that aren't in >> meters so the velocities are out. >> > > > Now i have also posted the 3 images to imageshack: > > http://img189.imageshack.us/img189/5565/static594.jpg > http://img189.imageshack.us/img189/9955/movingslow526.jpg > http://img189.imageshack.us/img189/5372/movingfast976.jpg > > Anyway, the problem is in movingslow526.jpg at 360kmh, while > movingfast976.jpg at 1800kmh is better, and static594.jpg (stopped) is > perfect. > My terrain is generated with osgdem (non Geogentric), and is in UTM33/WGS84. > The Geographics coordinates are in meters. > > Thanks.[/list] > > ------------------ > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=21746#21746 > > > > > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
