Precise Collisions for imported meshes

[Art Vandelay]

Hi,

I realize this is a topic that was covered before but I couldn't find a solution and wasn't sure if there was one now.

I have several imported meshes in a scene (relatively complex ones) and I can drag and drop one at a time. I want to check whether the mesh I am dragging has collided with a different one. In that case it is blocked and can't be dragged further. The problem is I would like to check this precisely, meaning exactly when two meshes touch each other, and not just by using a bounding box. Is there any way to do this?

Thanks for your help!

[GameMonetize]

Hello, the only way would be via physics engine

The MeshImpostor is certainly the way to go (http://doc.babylonjs.com/how_to/using_the_physics_engine)

[Art Vandelay]

Thanks @Deltakosh! Will try it out.

[Art Vandelay]

Quick question. I noticed in the table in the documentation it says that for impostor type "mesh" oimo.js uses a box. Does this mean what I want to do is impossible with oimo.js?

 

Thanks

[RaananW]

yes, that's what it means

Only cannon has a mesh impostor, and it only collide against spheres, so I am not sure it will work anyhow.

I think the only way to really do that is to check for intersections constantly, but I am not sure how CPU-intensive that is.

[Art Vandelay]

Checking for intersections doesn't use impostors as well?

[Wingnut]

Hi guys.  Sorry for interrupting in the middle of a pending clarification question.

I just wanted to remind of the "surround with simple impostors" trick.  On mesh that aren't too complex, you can add (invisible) boxes along the edges of the mesh, and put a box impostor on each one.

In the below playground, I didn't add any physics to my "ridge boxes" yet, or ever.  But, in theory, it COULD work.  The ridge/edge boxes would need to be parented to something, so they wouldn't fly away-from mesh... upon impact.  But, in theory, 2-20 of these edge-physics "shapes"... could do physics reactions off-of one-another... fairly well.  No meshImpostors, no spheres-only limitations, but some meticulous ridge-box placements.

https://www.babylonjs-playground.com/#1UHFAP#195

Here, you can see the ridge/edge boxes in white... un-parented-ly positioned upon/around the plotted mesh.

Two of the ridge-positionings... are broken.  Dunno why.  Anyway, perhaps this is a good starter playground for doing some physics tests on "ridge-physics" shapes.  Turn-on the physics, impostor the ridge-boxes, parent them to something (inside makeThing() func).   Then generate 5-10 "things", put them in a box or tumble them across a ground... see how well they work... if wanted.  Tell/show results, if you please.

Note: Avoid impostor overlap at places where multiple ridge-boxes come together, if possible (I think).

Ok, now, back to the question at-hand, for-which I am curious about the answer.    Party on!

[GameMonetize]

For intersections: Nope it uses mesh bounding info and geometry directly

[Wingnut]

Aww, what the heck... I'll ask something, too.

Doesn't Art lose "precise collisions" by using boundingInfo?

http://playground.babylonjs.com/#HE5NZP

[GameMonetize]

precise means "use the mesh" so I would say yes

[Wingnut]

I'm confused. 

I'm not an intersect pro... sorry.

Ok, single mesh drinking glass.  No extra collision-sensor mesh.

Drop marble into glass.

Can we detect collision with bottom of glass?

Or will collision trigger when marble passes glass-lip?

*scratch scratch*  I should test. 

"precise" parameter... and we get bottom-of-glass collision? If so, cooooool.

[Art Vandelay]

Sorry, I'm still a little confused too (but greatly appreciate the answers). @Deltakosh When you say mesh bounding info and geometry directly, I understand there is no impostor used, but is the bounding info accurate? Meaning not just a box or a sphere etc...

Thanks again

[GameMonetize]

BoundingInfo is the combination of a bounding box and a bounding sphere