Inu Games - Modular Snap System Runtime

Tomarr_Sovai · October 14, 2019, 7:58pm

Thanks. I will test it.

scha · November 3, 2019, 4:12pm

Hi everybody,

I remade the example project to have all examples in one demo, with a menu to navigate between levels.

Fixed couple of issues: missing mesh and UE4.23 compatibility. Project is 4.22, as before, but now it should work with 4.23 too.

Please check it out: **MSSR Examples by Inu Games **

MSSRExamples.zip contains the playable demo with all example levels, and MSSRExamples_Project.zip contains the corresponding project files. VR demo is the same as before, no changes yet.

Please let me know it works fine for you.

Arkhemor · November 10, 2019, 7:46pm

Hello @ . I’ve recently bought your MSSR plugin. Thanks for creating it, it’s really functional and easy to use.

I’m using it for a VR project, and the modified BP_MotionController somehow disables the hand grip animation in the default VR Template. Hand grip animation plays only if you are grabbing an object in MSSR, but it should play whenever GrabLeft or GrabRight is triggered. Do you happen to know that where the blueprint flow breaks, or does enabling the animation (grabbing nothing) contradict with the MSSR functionality?

Thanks.

Original VR template (4.23): GrabRight plays MannequinHand_Right_Grab

MSSRVR_Project (4.22, Jun 27, 2019): GrabRight doesn’t play MannequinHand_Right_Grab unless a cube is grabbed

Question 2: What exactly do “MotionControllerPawnDetach” do? Does it replace “MotionControllerPawn” as the player pawn? Mechanics I put into MotionControllerPawn don’t work with MSSR at the moment.

scha · November 11, 2019, 1:55pm

Hi @Arkhemor

It seems I forgot to set bWantsToGrip, you can fix it easily if you edit BP_MotionControllerDetach Grab and Relase events, which are located in the “Grabbing” event graph. It should be like on the screenshots below:

[ATTACH=JSON]{“data-align”:“none”,“data-size”:“medium”,“data-tempid”:“temp_176801_1573479701464_17”}[/ATTACH]
https://forums.unrealengine.com/core/image/gif;base64

[ATTACH=JSON]{“data-align”:“none”,“data-size”:“medium”,“data-tempid”:“temp_176802_1573479703039_844”}[/ATTACH]
https://forums.unrealengine.com/core/image/gif;base64

Yes it replaces MotionControllerPawn, but it mostly the same. It uses BP_MotionControllerDetach instead of BP_MotionController. BP_MotionControllerDetach is where the bulk of MSSR code is located. in the Grabbing event graph. Basically, I modified the way objects are grabbed and releaed, but the rest of the blueprints are the original ones from the VR template.

And the “Detach” in the name is because in the beginning there was 2 VR examples. Another example simply used the DetachFromActor function, which was not really doing a good job keeping things realistic. In this version of the example there is a more complex algo that you can see in the BP_MSSRHelpers:: Detach function.

Please let me know if you have more questions

Arkhemor · November 11, 2019, 9:27pm

Hey,

I get Invalid File Specified error from the BP screenshots you uploaded. Can you upload them again please?

Thanks for the explanation about the Motion Controller Pawn.

I would like to use the plugin for a modified/custom VR pawn, so is there any documentation about how to implement it into a blank project or VR Template from scratch?

Thanks for your support.

scha · November 11, 2019, 9:46pm

I hope it works now.

VR example is basically the default UE4 VR template modified a little bit. The modified part is in those Grab and Release events mostly. You can check how they are done, they are not very complex. If there is something not clear feel free to ask.

Arkhemor · November 13, 2019, 2:07pm

Yes, the hands are working. Thanks a lot! Now I’m working on the other implementations.

MSSR works well while grabbing the default BP_PickupCube, but it won’t work with new grabbable objects. Here, I create one duplicate and one child from the default PickupCube. What could be the issue? The created new objects (child or duplicate) are grabbable in the default VR Template.

scha · November 13, 2019, 2:26pm

In most of the MSSR examples, the “Grab” event checks if the actor has a tag, usually “pickup”. Here, in the VR example, the check is in the “GetActorsNearHand” method (see pic). You can check one of the cubes, look for Actor Tags array in the properties. So you have to add a tag like that to your actor.
You can also change the code of the Grab to check some other criteria, like just grab anything which is a physics actor. The original example used an Interface PickupActorInterface to see what you can pick, but I don’t like this approach, because it forces you to use a custom actors. A tag can be added to any actor, including basic static mesh actors.

And to “snap” you need to have sockets defined on those meshes, but I suppose you know that already. If not, check Overview level in the example project and the tutorial video.

Arkhemor · November 13, 2019, 6:53pm

I didn’t realize that actor tag wasn’t embedded in the blueprint. Sorry for the confusion, fixed it and it works like a charm now. Thanks again!

Another question: Do I set the global snap search distance from the Structure Variable under BP_MotionController? I couldn’t get it to work.

scha · November 13, 2019, 7:33pm

Under BP_MotionControllerDetach if you are using MotionControllerMap2. There are 2 example maps, MotionControllerMap and MotionControllerMap2. The “2” uses more advanced algorithm to detach things, so it uses BP_MotionControllerDetach and MotionControllerPawnDetach.

The difference between two is how they manage the “Detach” operation.(Grip+Trigger). The first map will just call UE’s DetachFromActor. The problem is that you can easily end up holding something with a hole in the middle.

Second map will rebuild attachment trees to avoid this situation. It will use MSSR’s snap sockets to find which cube is logically attached to which one then use that to make new trees without holes. The algorithm is in BP_MSSRHelpers Detach function.

Arkhemor · November 13, 2019, 8:33pm

Thanks for the explanation, now it works alright.

I noticed a glitch with the parent objects. If you attach multiple attachment trees, some of the attached objects lose their physics. It really compromises the gameplay I am trying to implement. Can you replicate this, and any idea on how to avoid it?

Sorry for asking too much questions, but I loved your plugin and unfortunately I’m quite new to UE4.

Edit: Console log: Blueprint Runtime Error: “Accessed None trying to read property AttachedComp”. Blueprint: BP_MotionControllerDetach Function: Execute Ubergraph BP Motion Controller Detach Graph: Grabbing Node: Set Simulate Physics

scha · November 13, 2019, 8:39pm

No prob. I will try to reproduce that tomorrow. Physics in UE are tricky, because underlying PhysX library represents things differently, there no trees in PhysX.

scha · November 14, 2019, 11:08am

I can’t reproduce it. I watched your video and tried to do exactly the same few times and it works correctly.
But I noticed something. You spawn new cubes right? Do you spawn them with all the right parameters?
Show me your spawning code please.

edit: I spawned cubes too and I have the same error. I will try to find why

scha · November 14, 2019, 11:46am

I think I found it. The problem is the “auto weld” physics parameter of the BP_PickupCube. Usually it’s enabled by default, but in the PickupCube bp it was disabled. So I enabled it back and now it seems to work also with the cubes you spawn on runtime.
To enable it, you need to open the BP_PickupCube, disable “SimulatPhysics”, check “Auto Weld”, then enable simulate physics again. Otherwise it’s grayed out.

Arkhemor · November 14, 2019, 11:16pm

Would have never guessed Auto Weld, thanks! It fixed other attaching/detaching problems I haven’t mentioned too. Here’s the actor spawner BP, in case anyone needs it.TP_Cube_Spawner posted by anonymous | blueprintUE | PasteBin For Unreal Engine

Two more questions:

How do you modify the “force” preview material?
I want front face of a gemoetry to attach with the other one’s back only. Currently, two front or two back faces can be attached. Is there any socket implementation that I can use to avoid same-face snaps?

scha · November 15, 2019, 8:09am

Some of physics parameters are very obscure. I try to understand how they work by studying the source of the engine and by trial and error. I think there are bugs i the engine too

>How do you modify the “force” preview material?

You can set it on the preview actor, it’s a variable.

> I want front face of a gemoetry to attach with the other one’s back only. Currently, two front or two back faces can be attached. Is there any socket implementation that I can use to avoid same-face snaps?

I’m not sure I understand, maybe you can show some example?

Did you tried +/- sockets? You can add a sign to the socket name, like “Socket+” or “Socket+_0” or “Socket-” etc. Those signed sockets will only snap to sockets with the same name and opposite sign, or to a socket with the same name and no sign.

There is also the “snap open only” parameter.

Those points are explained in the long tutorial and overview example, check that.

scha · November 15, 2019, 10:53am

Btw, i think I understand what you mean. You should ensure that your sockets are pointing outside of the geometry. The X-axis (red one) should point outside, like the normals, not up or sideway. Because, by default, MSSR aligns things respecting this direction. Check where is the X axis on the pickup cube mesh sockets for example. This is explained in the tutorial too.

Arkhemor · November 15, 2019, 7:51pm

> Some of physics parameters are very obscure. I try to understand how they work by studying the source of the engine and by trial and error. I think there are bugs i the engine too

Well done on the good job then. Very much appreciated.

Looking at the extended tutorial now. Mine looks like pretty much a positive/negative pole issue. Here’s a scheme of my socket setup, the only snap that I want to enable, and two snaps that I want to avoid:

scha · November 15, 2019, 8:09pm

Yes, that can be solved with socket polarity. Call them something like Socket+ and Socket- and they will only snap in the right way, “plus” with “minus” only. There is an example with a hat and a “head”, and the sockets are called “hat+” on the head and “hat-” on the hat.

scha · November 16, 2019, 2:59pm

I added another example to the example project. It shows how to make a user-friendly physics handle with MSSR.
Some parts don’t even require the plugin (grab speed ease-in, depenetration, etc.)

You can see a little video preview here:

https://twitter.com/games_inu/status…14829933334529

and download it on itch as usual: MSSR Examples by Inu Games

Features :

Setup phys.handle with MSSR.
Realistic detach
Mix between simulated and static actors.
Physics handle Interpolation Speed ease-in. It helps to grab things more “gently”, example video: https://twitter.com/games_inu/status…45301538443264
Max depenetration speed on the physics actors. Setting this will limit forces applied to separate overlapping actors.