Stunt Playground v1.0 released!!

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Postby Sascha Willems » Tue Jan 03, 2006 1:54 pm

As I said above, the new version acts very strange on my PC. I did a clean boot and removed any overclock from my graphics cards and it's still there, and as other current games and demos work it may be a problem with the Stuntplayground or Ogre :

The cars jitter depending on speed and current framerate. It's a bit like lag in an onlinegame where your car get's warped back and forth a bit. Besides this, physics feel very strange. I drove against those small red/white "huts" (dunno their name in englisch) with a racing car and it flow in the air. If needed I can get a video of the strange behaviour uploaded.
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Postby walaber » Tue Jan 03, 2006 2:02 pm

Delfi- you need to un-install the old one before re-installing.

kallaspriit- the latest uploaded version does not have this problem, you need to uninstall the current one, re-download, and re-install.

Sascha- I'm not sure what it causing the jitter... it's very, very, light on my machine... what OS and processor are you running?
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Postby Sascha Willems » Tue Jan 03, 2006 2:04 pm

It's an Athlon XP2600+ running on Windows XP (with SP2) and a GeForce 6800 (vanilla, 256 MBytes). Graphicsdrivers are 81.98 (rather new) and it's no difference between the OpenGL renderer or the D3D-renderer.

And as I said above, box stacks (theres one very complex arena, that seems to be missing in the most recent release. Did you remove it?) that shouldn't move at all with no interaction start to fall sideways. All those things get more noticeable with lower framerates.
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Postby JernejL » Tue Jan 03, 2006 2:06 pm

the latest package will not install on my pc whatsoever, the one you had up half a hour ago installed but the sp.exe didn't work...

can we just get a zip or rar file?

if you really want it to be installer use inno setup or NSIS..
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Postby Sascha Willems » Tue Jan 03, 2006 2:15 pm

Here is a video of the jitter problem (1.5 MBytes, WMV). Note that the problem is now very visible, because FRAPS drags down the framerate to 25 FPS. Also the vehicle seems to act strange when crashing into the wall, though that might come from the huge wheels too?
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Postby _Tux_ » Tue Jan 03, 2006 2:15 pm

i can confirm the jitter as well. i used to have this once when testing a smooth following camera and interpolating the position with the time.

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Postby Julio Jerez » Tue Jan 03, 2006 2:29 pm

Sascha Willems wrote:Here is a video of the jitter problem (1.5 MBytes, WMV). Note that the problem is now very visible, because FRAPS drags down the framerate to 25 FPS. Also the vehicle seems to act strange when crashing into the wall, though that might come from the huge wheels too?
I had that jitter in the first demo too, and I thought it was because Walaber is running at a fix time step, and some how it was mess up with the car super sampling.
The engine will call transform callback more than once, so I fix that problem.
I test the old game with the new SDK and it did not fixed.
I think that the problems are the discrepancy between running the physics at a fix rate and the rendering a display rate.
To verify if that is the problem Walaber you can try running but physics and render at the same rate and if this is the problem than what it the vehicle nee is interpolation display.
It is easy to do that by keeping track of the last tow physics frame and display the interpolated matrix that correspond to the last render frame.
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Postby walaber » Tue Jan 03, 2006 2:30 pm

Delfi - i have to use the .msi installer to install components for MSVC++ 8.0, there is no other way to install them.

have you completely un-installed the previos version? do it from Control Panel -> add/remove programs. then try again. VERY little has changed between the previous installer and this one.

Sascha and tux- I'm pretty sure the jitter is just my shitty camera control code. Sacha- the way to test this, is to drive the car very fast, and record with F7. then hit the space bar to switch to playback mode. watch the playback in slow-motion, and see if the car drives smoothly. if it drives smoothly, it means it was just the camera jumping around. if the actual car jitters, it's a physics problem. I will look into it.
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Postby JernejL » Tue Jan 03, 2006 2:34 pm

i also get all this crazy jittering, and some of the vehicles act like crazy, for example the monster truck running over a plank starts to spin like crazy, the monster truck has very high mass centre which also doesn't work good, the mass centre for monster trucks is in the same level as wheel axes, the the monster truck chassis are made of carbon fibers, and all the machinery is in the suspension-bottom-part.

i made two videos of the juttering using my mobile phone but as the videos are already availible i decided not to upload them, pleae work on the mass centre issuse, as the cars will behave much better.
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Postby Sury » Tue Jan 03, 2006 2:54 pm

If you move some prop very high it stops and remains there., and as the camera is following it and freezes there too. Body leaves the NewtonWorld ?
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Postby walaber » Tue Jan 03, 2006 3:07 pm

Sury- I thought I had fixed that in the latest build... I will try to re-create here as well. I also fixed what happens if a vehicle leaves the track (try jumping over the fence now). I cannot recreate this on the latest beta.

in other news, the jitter bug was due to my camera update code. I fixed it by only updating the camera when the physics is updated, and it works perfectly now, very smooth. I haven't updated the public beta yet though.

one bug I have found with the Monster Truck is that when the tires hit other props, they seem to "affect" the truck to much. for example, drive the Monster Truck tires into a barrel or something, and it will stop the entire truck. if you instead drive the truck body into a barrel, the (much heavier) truck will push it aside easily. this seems to be an error in the force calculated on the tires vs. dynamic objects. it's only noticable on the Monster Truck because of it's oversized open wheels. Julio, any thoughts? right now the Monster Truck tires are set at 15kg each, I will try increasing this to something more like 50kg.
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Postby Julio Jerez » Tue Jan 03, 2006 3:19 pm

walaber wrote:in other news, the jitter bug was due to my camera update code. I fixed it by only updating the camera when the physics is updated, and it works perfectly now, very smooth. I haven't updated the public beta yet though.

Good I am glad you found that. I was thinking that discrepancy between physics updates and render updates are not so severe and that is why I though it might be related to the physics super sampling, but is was not.
Anyway that was a bug and it is fied now please download the SDK again, when you have time, and use the new dll. It won’t call transform update more than once per update.
walaber wrote:one bug I have found with the Monster Truck is that when the tires hit other props, they seem to "affect" the truck to much. for example, drive the Monster Truck tires into a barrel or something, and it will stop the entire truck. if you instead drive the truck body into a barrel, the (much heavier) truck will push it aside easily. this seems to be an error in the force calculated on the tires vs. dynamic objects. it's only noticable on the Monster Truck because of it's oversized open wheels. Julio, any thoughts? right now the Monster Truck tires are set at 15kg each, I will try increasing this to something more like 50kg.

This is definitely a bug in the tire physics, it needs diffrent material softness with different body types.
I hardcoded one-value fix all, and it is very high for the floor, but the relative velocity between the tire and the floor is usually low.
I did not have many different vehicle types for better calibration, and it is possible the this may need user setup in per type bases.
I will play your game tonight and see what tweak can be made to the engine to control that.
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Postby JernejL » Tue Jan 03, 2006 3:50 pm

Julio Jerez wrote:I hardcoded one-value fix all, and it is very high for the floor, but the relative velocity between the tire and the floor is usually low.
I did not have many different vehicle types for better calibration, and it is possible the this may need user setup in per type bases.
I will play your game tonight and see what tweak can be made to the engine to control that.


it would really make more sense if we can define materials and shape for wheels in our own apps, custom wheels would be awesome :)
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Postby walaber » Tue Jan 03, 2006 4:22 pm

Okay Julio, let me konw that you come up with. I'm very excited I was able to fix the jitter problem, that made the game hard to play, and unprofessional-looking. :D
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Postby JernejL » Sun Jan 08, 2006 12:18 pm

the camera jitter is now fixed, but the monster truck centre of mass is still too high, if you drive a real monster truck they don't have so high mass centre, in SP if you drive monster truck at high speed and suddently steer it will start to roll and that shouldn't happen, in reality monster trucks are very stable vehicles.
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