x1000 times slower bug - millisecond pulsar freeze part 2...

Malenfant · Post #1by **Malenfant** » 02.09.2006, 01:57

I think this was reported previously sometime earlier...

I just downloaded and fired up Cham's pulsar addon and slowed it down to 1000x slower, and it stopped completely. That part at least was known to be a problem.

The weird thing is that I've got Celestia open as a window with the pulsars frozen at 1000x slower, and this web page as another window in front of it, but when I start loading a page or doing anything here, I can see the Pulsars start to move in the background! They only move a few frames at a time, for as long as a page is loading it seems. I'm not sure if anyone's noticed that before.

So what the heck could be going on here?? Why would it only start moving when I'm loading a webpage?!

Johaen · Post #2by **Johaen** » 02.09.2006, 03:03

If I had to guess, it might have something to do with the CPU usage. Is there a framerate drop when you refresh a webpage?

Chuft-Captain · Post #3by **Chuft-Captain** » 02.09.2006, 03:20

Yes, this was reported earlier, and you commented on it then too.
Here's the answer...

Chris wrote:Much to my surprise, this problem turns out to be a precision limitation of double precision floating point arithmetic. The faster your frame rate, the smaller the per frame time increment, and the more susceptible it is to being treated as effectively zero. I'm not sure what was happening in earlier versions that kept the problem from appearing. There's no simple fix for the problem now.

EDIT: ... and here's the original thread, which has some other peoples insights: http://celestiaproject.net/forum/viewtopic.php ... ght=#72920

Malenfant · Post #4by **Malenfant** » 02.09.2006, 03:45

Yeah, but was it reported earlier on that it started moving again when you reloaded a webpage? Or for that matter even when you move another window around on the screen...?!

Hm, now I think of it I wonder if this has something to do with the fact I have a dual-core CPU...

Looking at the performance in Task Manager, I see it's hovering around 15% when I'm not doing anything (I've got winamp playing in the background too). If I move a window around that isn't Celestia, and just keep moving it, the frames move on and the CPU goes up tro about 65-70%. (keep in mind, 50% means one CPU is being fully used). If I move a window and then let go after a second it goes up to about 20-30%. If I actually move the Celestia window around, the CPU use goes up the same way, but the scene shown in the window jumps forward a few frames in time after it's stopped moving.

As I'm typing, I'm noticing the beams of the pulsar are ocassionally stepping forward a few frames. When I had Task Manager open it was moving quite a bit, presumably because the screen was updating or something when the graphs were changing?

It's all a bit strange.

Here's the system I've got:

Dualcore AMD64 3800 CPU
2 GB DDR2 RAM
250 GB SATA HDD
Nvidia 7600 GT 256 MB Video (PCI-E)
Asus M2N32 SLI-Deluxe motherboard
Windows XP Home SP2
Dual monitors (Viewsonic VX2025WM LCD and Samsung Syncmaster 753DF CRT)
Celestia 1.4.1