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Ok, after a few more days and tons of bad language it actually works now!
See the video:
Bullet physics in Godot 4.
z80 Great ! It would be nice to add some tests using the concave mesh issue discussed a while ago as well as your unstable joints issue.
By the way, regarding this issue, Unity also suffer from weird issues (looks like some force gain momentum with time then grow exponentially and makes everything explode in KSP), I think it would be much better to automatically "weld" parts together into a single collider mesh so the physics engine only have to deal with a single entity and not a bunch of parts stuck together with bad glue and duck tape. Especially regarding the gameplay added value for such poor model, IMHO, it doesn't add much but cost a lot of annoyance and performance issues.
Finally, do you have some compile editor ready to use ? It would be great (don't forget to tweak the version as well !)
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JusTiCe8 Great ! It would be nice to add some tests using the concave mesh issue discussed a while ago as well as your unstable joints issue.
Yes, that's in the nearest TODO list.
JusTiCe8 looks like some force gain momentum with time then grow exponentially and makes everything explode in KSP
That's side effect of using speed-based constraints and simulating bodies separately via Newton/Euler equations. Bullet actually has generalized coordinates-based Largrange equations to solve this issue perfectly. It's called Featherstone method. It's located in \godot\thirdparty\bullet\BulletDynamics\Featherstone. It's not yet supported by Godot though.
The poor man's today alternative is simulating all connected pieces as a single rigid body 
JusTiCe8 Finally, do you have some compile editor ready to use ? It would be great (don't forget to tweak the version as well !)
Sure, here you go (the url leads to the game page, I couldn't come up with anything better to hosting it there): 
.
For now version is the commit SHA256:
z80 It could be interesting, if interface to both Bullet and new Godot native physics engine are the same or very compatible, to provide both implementations of Ignition so it could help comparing both and devs could also identify what they need to do to at least reach Bullet level engine.
For the download, why not use release on github directly ? I've never used it yet myself so I can't help.
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JusTiCe8 why not use release on github directly ?
Ah, it's dumb as usual. I wasn't able to find "draft a new release" button. Github says "At the top of the page, click Draft a new release".
It turned out, it's not at the top, it's on the right Here is the github release download url godot.windows.editor.x86_64_7aca0f70.zip.
Ok, just tried it in the real game.
First, on positive side, when switched to Bullet, the physics doesn't blow up anymore! That's a win!
On the negative side
1) Even though concave mesh collision shape is created, I can see it with Debug/Visible Collision Shapes check box. But for some reason collisions don't happen. Bodies fly right through.
2) Even though joints are created, they don't work for now. Constructions just fall apart when pushed.
Ok, new update: godot.windows.editor.x86_64_b49f801f3.zip.
Fixes:
- Joints work
- Concave polygon shape works.
The return of bullet physics in Godot 4 is one of the biggest achievements along with the introduction of Vulcan. Is it possible to make a module for Godot? This will please many developers. Not everyone will want to install a separate build or compile it, a module will allow you to distribute your work throughout the community. In any case, I want to thank you. This gave hope to our studio to stay on Godot in the future, as we decided to switch to another engine due to physics.
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Engardium Is it possible to make a module for Godot? This will please many developers. Not everyone will want to install a separate build or compile it, a module will allow you to distribute your work throughout the community. In any case, I want to thank you.
Great idea, thank you! I know they've changed binary modules design process a lot but didn't look into it yet. I'll check what it takes to make a module out of Bullet physics server...
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Engardium Bad news.
I've been trying to convert it to GDextenstion. I've checked out godot_cpp.git 4.0.2-stable tag which corresponds to 4.0.2-stable godot current version.
The obstacle I've encountered is G6DOFJointAxisFlag enum in Godot : : PhysicsServer3D and godot_cpp : : PhysicsServer3D do not correspond to each other. G6DOF_JOINT_FLAG_MAX is not defined in godot_cpp as well as a few other enums.
So, I guess having Bullet physics as a GDextension binary plugin is delayed... For now only the built-in version is available.
I've created an issue: https://github.com/godotengine/godot-cpp/issues/1104. Will see what happens...
If it matters, I've created a separate github repo for porting Bullet to GDextension.
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Maybe then suggest a merge into the main repository? To include your work in the engine? The developers did not want to waste time implementing Bullet, but since a good person did everything for them, maybe they will take it as the basis of the engine?
I've added the suggestion to the discussions.
https://github.com/godotengine/godot-proposals/discussions/6687#discussioncomment-5602799
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Engardium My personal favorite quote in the conversation is "By giving Godot users no other way, it's forcing evolution for the best, with some pain along the way."
I would just add "Or it makes Godot users switch to Unreal and give up Patreon support" Which is indeed evolution for the best in some sense
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Awesome, thanks for making the integration! I, for one, can't wait for an additional Physics library option other than Godot's Physics for 3D.
Also be sure to check Godot Jolt which is a GDExtension in progress for Jolt in Godot. It's almost fully working. So you also might get ideas from the code, if needed: https://github.com/godot-jolt/godot-jolt
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alfredbaudisch Also be sure to check Godot Jolt which is a GDExtension in progress for Jolt in Godot. It's almost fully working. So you also might get ideas from the code, if needed: https://github.com/godot-jolt/godot-jolt
Yea, thanks for the hint! I'm aware of Godot-jolt. It's absolutely great!
In the case of making a GDextension out of Bullet it seems like it's a bug in the command "godot --dump-extension-api extension_api.json" which is supposed to generate all the API. Specifically for PhysicsServer3D it doesn't export several enums which are needed for Bullet to work. The devs have already assigned it a bug flag, see https://github.com/godotengine/godot-cpp/issues/1104.
@"alfredbaudisch"#p110287 oh but notice how I just said "with Bullet/Jolt" and not Godot's Physics itself
Absolutely! IMHO it's much less of a pain to rely on something tested. Despite of all the arguments the devs' position 1) claim lack of contributors and at the same time 2) developing custom physics engine from scratch still does not line up in my head
ive also found physics unreliable in godot 4. some collisions just dont get correctly detected.
is this because of godot physics? if so, is bullet physics so much better?
DJM is this because of godot physics? if so, is bullet physics so much better?
Bullet is battle-proven, with many shipped titles.
GTAIV and Read Dead between them:
Bullet is an open-source 3D physics library produced by Erwin Coumans, featuring rigid and soft body physics, 3D collision detection and multiple 3D modelling/animation software plugins. The library has been incorporated into the Rockstar Advanced Game Engine, which has been used by Grand Theft Auto IV and Red Dead Redemption.
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Given the position of the developers, I see the only way to make a module from Bullet. We are waiting for the correction of the error that does not allow this. I hope they fix this at least soon. Until this happens, I beg the Z80 to support us with new versions with corrections and not give up this good cause. You are saving the community at this difficult time.
a month later
Hello everyone!
I've just fixed a bug in Bullet physics support for Godot4 and upgraded to the most recent 4.0.3-stable except two files viewport.h/viewport.cpp which in some of my projects make viewport texture to not work.
Please find the code snapshot and windows-64bit binaries here https://github.com/z80/ignition/releases/tag/commit_cd4f85694.
3 months later
z80 Hi appreciate you working on this, I've managed to pull out the Bullet Physics stuff from your repo into the latest builds for Godot for my own project however I noticed an odd issue with the implementation.
The capsule colliders seem to not be working correctly, They seem to apply an additional invisible barrier that doesn't seem to show in the debug collisions. It was pretty easy to get this to repeat I also built your instance of the engine just in case it was limited to just my version and it seems like the issue is present in both. I'm guessing this is something to do with margins since the collision debug seems to show the capsule scaled correctly etc.
Steps I did to see this issue:
- Create a basic scene with some cubes that fall and can be pushed by a character body.
- Create a basic character movement script to move left right back forwards.
- Move around the scene and you will see that the cubes are pushed by an invisible force, attached to the capsule.
- You can also see its limited to just capsules as by simply changing the collision shape to something else such as cylinder the issue is gone.
- Swap to using Godot Physics, Issue is not present and collision applies normally and as expected with capsule collider.
Any ideas on how to solve this issue? Also is there any updates on moving this stuff to GDExtensions it seems like your bug report hasn't been updated in awhile?
Xanz I actually managed to fix this issue but posting the solution in case anyone else is attempting to use the implementation.
So there is two issues, In Godot 4 the default capsule orientation is upright rather than aligned along the Z axis. Since the implementation uses the code from Godot 3.5 the alignment is still aligned to the Z axis instead of upright. You can fix this in the bullet code so that instead of creating and returning a BtCapsuleShapeZ you return a BtCapsuleShape, This will fix the alignment issues and the strange invisible force.
Alongside this another issue encountered is that the capsule height is no longer aligned with the debug widgets heights and just the general capsule height as it seems like Godot 4 expects that to be the exact height. This causes an issue as bullet expects a half height(This is just knowledge from implementing bullet in a custom engine so could be slightly incorrect but seems to resolve this issue).
This will cause issues with capsules appearing like they are floating or just general strange height related issues. To solve this simply divide the height received in the CapsuleBulletShape::setup method by 2(You could do this earlier in the callstack but it seems like a sensible place to do it as it keeps it within the bullet module). This will give you the half height which is what bullet expects.
Good luck to anyone else using this!