Lock 3D physics on a 2d Axis Issue

Hello everyone,
I am having this problem
You can scroll down (almost at end) to see pictures and a description.
I just created this project for testing purposes so you can see it for yourselves.

Just push crate to left and as soon as it lands continue pushing it to left until end of level and you will see that crate is moving (slightly)in Y axis .
In my case is more severe than here but this will give a good idea of what is going on.
Thank you!

I want to post a short video with my problem.As you can clearly see although crate is at Y=(0) and trees are at Y=(-0.1) when i move it around it moves in Y axis although i have it locked.
https:// (please download and watch.Preview in dropbox is horrible )
And since i am here could someone help me with making crate move smoothly without all this friction and rotation?I know almost nothing on how to make a sprite move around with physics interactions to “ON”

Has anyone from Unreal stuff checked this out yet?

Hey ,

I followed along with various comments in thread you linked to, and it seemed like asked a few questions regarding this issue:

Were you able to resolve this issue by pushing items further forward or back on Z axis? Or is this still an issue? If so, could you answer questions asked in that thread here on this post, so I can forward it to him? Thanks!

Hello ,
judging by pictures we can see clearly that physics object moves inside its locked Axis.Both floor and crate are at Y=0. tree is at Y=-1.At last picture we can clearly see crate being above floor and beneath tree.

Hey ,

Okay, I see some slight movement in Y for PhysicsActor, despite Locked Axis of Y being set in Sprite. I have entered a bug report for developers to look over (TTP# 347496) and I will let you know when I see any update on it.

In meantime, I was able to see that Y doesn’t seem to change any more than 0.1 in either direction. That’s not supposed to happen, but it does mean that you can work around it for now by moving trees or other background sprites a little further back. I would recommend a minimum of -1 if at all possible. Using very small values ( trees in test project you uploaded, for example, were set at -0.01) will run into some known floating point precision issues.

Hope that helps! Thanks for report!

Any chance to see this fixed in 4.7?

I am now facing an even bigger problem with above “bug” . I have created some big boulders (they have physics locked in Y axis and they have a round collision box ) that fall from sky as he enters a trigger volume.If they are higher than lets say 600 pixels then second they collide with my floor they get stuck inside my tiles since they move in Y axis enough for this to cause problems.This is affected by other factors as well (maybe angle ?) so i cannot reproduce it every time but it happens quite often destroying any chance of me creating a seamless game experience.

Hey ,

developers looked into it and unfortunately are not going to be able to fix it. In bug report, it was stated:

axis lock option uses constraints
to lock, and due to way solver
works, there can sometimes be slight
violation of constraints. Maybe in
future PhysX will give us another way
to fix this, but right now there isn’t
much we can do…

So you’ll need to stick with making sure your sprites are separated on Y by a large enough amount, as mentioned above.

For new issue you’ve discovered, it does appear to be related, but I believe fix will be similar. What is Collision Thickness on your floor and boulder sprites? default is 100, but if I recall correctly yours is much smaller. I tested this all way down to a Thickness of 20 with no problem. When I tried 10, however, I encountered same problem. If you raise boulder and/or floor sprites, do you have same issue? I would expect raising collision thickness on boulder should be enough.

What you are saying is partially true since a bigger thickness number prevents my boulder from getting stuck but it does not prevent Y axis movement of my sprite resulting in all sort of weird things aesthetically speaking . Try to imagine a thin paper with a drawing moving back and forth when wind blows.This is what is happening to my sprites when above criteria are met and sometimes it stays rotated in Y axis like pictures i have send you above.It is not pretty … :frowning:

angle in Y shouldn’t be big enough to see from player’s perspective, and there shouldn’t be any overlap like you have in pictures above if there’s enough Y distance between background, foreground, and main sprites. Having a wider collision thickness should aid in avoiding that problem as well. Is there an additional problem or substantial rotation occurring? Can you post some new images, with settings adjusted as recommended? Thanks!

Nope, everything is handled on CPU in a cross-platform manner so there should be no difference.

I will try your suggestions and report back!

I have an all AMD build. Maybe this why i am having this problem ? Phys-x is Nvidia only so maybe it does not work on my rig.Is this case?