Bullet physics implementation and other stuff
307805 385 4- omegan
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- cybermax
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VictorG:
not much:
- completely new layout, where I can create, delete and modify objects in time, as in DOP.
- add some new example scene.
- weariness and refracturing.
- solver output(collision and objects info)
- low/high geometry output
- new source objects for fluids
- visualization of density for fluids
omegan:
thx, speed is very important, because in production We can simulate multiple situation and choose the right
I moved the release of the next version in December , It has few bugs and I have a lot of other work at school.
not much:
- completely new layout, where I can create, delete and modify objects in time, as in DOP.
- add some new example scene.
- weariness and refracturing.
- solver output(collision and objects info)
- low/high geometry output
- new source objects for fluids
- visualization of density for fluids
omegan:
thx, speed is very important, because in production We can simulate multiple situation and choose the right
I moved the release of the next version in December , It has few bugs and I have a lot of other work at school.
https://vimeo.com/user3251535 [vimeo.com]
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- curveU
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It's awesome cybermax! Will you release a Linux version? and is it possible to go Opensource with this project? I beileve some smart people in houdini community might make it even better.
cybermax
VictorG:
I moved the release of the next version in December , It has few bugs and I have a lot of other work at school.
- Vladislav Tushevskiy
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cybermax
update:
ok, I made some changes in btCompoundShape and now its more stable, faster and with any errrors(what I know). It can use different(random) max_force attribute which creating nice destruction effects - for concrete looks better than classic constraint.
what is it changes? did you mean changes in source of native bullet code?
- cybermax
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almateaNO, btCompoundShape I use for new hard constraint system (something like btFractureBody). I described it wrong, sorry.
what is it changes? did you mean changes in source of native bullet code?
However, I changed native bullet source code, due to plugin higher speeds. But these are small changes.
curveU:
linux version will come later, but Its in my plane.
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- Vladislav Tushevskiy
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cybermaxalmateaNO, btCompoundShape I use for new hard constraint system (something like btFractureBody). I described it wrong, sorry.
what is it changes? did you mean changes in source of native bullet code?
thanks for answer
do you use a constraints for same purpose? (i mean a using constraints for imitation a glue)
do you use only convex bodies or use a concave also (is it Gimpact or compound of convex bodies?)?
- cybermax
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almateaNew “hard” constraint system dont use constraint, Its using btCompoundShape because Its more stable for many “merge” objects than using constraints. But plugin still support spring constraint.
do you use a constraints for same purpose? (i mean a using constraints for imitation a glue)
almateaFor concave body I am using my convex decomposition algoritm(so Its using compound convex bodies), because concave bullet body has bad behavior after collision according my research.
do you use only convex bodies or use a concave also (is it Gimpact or compound of convex bodies?)?
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- Vladislav Tushevskiy
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cybermax
For concave body I am using my convex decomposition algoritm(so Its using compound convex bodies), because concave bullet body has bad behavior after collision according my research.
do your algorithm safe a shape of body? i mean - is it approximate algorithm or not? this algorithm for any body with arbitrary form?
i use representation of shape as set of tetrahedrons.
- cybermax
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almateaIts not approximate algorithm and It dont use tetrahedrons.
do your algorithm safe a shape of body? i mean - is it approximate algorithm or not? this algorithm for any body with arbitrary form?
i use representation of shape as set of tetrahedrons.
And Its run for all shape form.
I dont public more detail, but Try searching some about BSP with PVS. I worked with this algoritms before few years, when I programming my raytrace render, so I made some changes and convex decomposition was done
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- Vladislav Tushevskiy
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- mrice
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- cybermax
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mriceI dont remember exactly but I think that problem was If I have many object collision with others, like a column formation. Firstly I saw little vibration then reaction forces were increase … in other words, It wasnt stable.
Just curious, what's the issue with gimpact?
The only downside I see is an approx. 3x performance penalty, but I'd think the complexity of decomposition would become prohibitive for large amounts of geo/objects.
I have similar instability with many constraint, this is reason why I am creating my “hard” constraint system with btCompound object.
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- Vladislav Tushevskiy
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- mrice
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cybermax
I dont remember exactly but I think that problem was If I have many object collision with others, like a column formation. Firstly I saw little vibration then reaction forces were increase … in other words, It wasnt stable.
.
Could be that gimpact is configured by default to use a SAT algorithm which doesn't appear to work very well. This test [audenmedia.com] has many stacked concave gimpact shapes.
almateaYou'd have to work around that..
and it seems that gimpact body can not be a part of btCompound
- Vladislav Tushevskiy
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mrice
Could be that gimpact is configured by default to use a SAT algorithm which doesn't appear to work very well. This test [audenmedia.com] has many stacked concave gimpact shapes.
I did uncomment “#define BULLET_TRIANGLE_COLLISION 1” in btGImpactCollisionAlgorithm.h - then concave bodies have correct collision, but in high stack have penetration after some time even if I use a big fixedTimeStep parameter (about 240 or 480).
And convex bodies as compound shares work mush faster than gImpacts (I mean perfomance of bullet).
Please give more details about your scene - it very interest!
- cybermax
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Concave body works fine in my system. After I release next version I will make some test with gimpact again and compare the speed. If gimpact will be quicker, but there will be high stack penetration, I can make option in GUI and users decide what they want
mrice: I see your video and its cool, can you give us more info(sim time, object,constraints count etc…). Do you have problem with many constraints - unstable, object vibration????
mrice: I see your video and its cool, can you give us more info(sim time, object,constraints count etc…). Do you have problem with many constraints - unstable, object vibration????
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- Vladislav Tushevskiy
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- cybermax
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almateaMy current system with convex decomposition you can try, because my plugin is free … so feel free If you find problem, let me know.
it would be nice to see a video demonstration about this, especially with high stack of gimpacts.
Gimpacts I will test later, now I implement more important features(concave body works fine)
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- mrice
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cybermax
mrice: I see your video and its cool, can you give us more info(sim time, object,constraints count etc…). Do you have problem with many constraints - unstable, object vibration????
About 50k explicit objects and 250k constraints. Sim time averaged 2 minutes/frame, but could be alot faster, gimpact collisions were used much more than needed (due to laziness)
I havent seen any instability with constraints. I'm mostly on linux, but the only difference I know of is that bullet on linux doesn't use the Sony vector math library.
- slegrand
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