Creating a concave hull in 3DS max

[Wazanator]

I'm currently working on a tiny little modeling project, specifically lego like building blocks, my plan was to allow players to use a gravity gun like device to stack them on top of each other to get to a certain area.

Now the problem is whenever I compile the model it comes out with a collision hull like this:

As you can see it doesn't allow the holes to be filled as well as the upper pegs being converted into a pyramid shape so they don't exactly interlock

I'm using the same model for both the collision model and body model. I have the $concave keyvalue in my QC as well.

If someone could let me know how to get it to export and compile right I would be forever grateful.

-Wazanator

[Smurftyours]

You will have to create the collision mesh manually in max.

(This is just an example tailored to your model in specific.)

Each color in those pictures represents one specific smoothing group. If I was to export that model as a collision mesh and use it in hammer it would stay exactly how it looks now. Basically you use the least amount of convex objects to create the working collision mesh.

!WARNING!
There is a hard limit of how many smoothing groups you can use, unfortunately I do not know it.

Hope this helps!

[marks]

smurft nailed it. cant have concave collision hulls. no exceptions.

[shawnolson]

Actually you can do this straight from the root model without making a separate hull. It depends on how the main mesh is designed.

If each Element sub-object of your mesh has a unique smoothing group and you set $concave in the QC, you can get a concave hull from the mesh.

Attached below is a screen shot of a model that used its main mesh as the collision model and studiomdl.exe converted each Element too a convex part of the hull.

Of course, you may still want to make separate hulls so that the visible model has less vertices and polygons.

[Wazanator]

So if I understand correctly to make the collision mesh I'm going to need to make it out of a lot of tinier models then attach them all together give them the same smoothing group and export it, correct?

[marks]

yes thats correct.

[shawnolson]

So if I understand correctly to make the collision mesh I'm going to need to make it out of a lot of tinier models then attach them all together give them the same smoothing group and export it, correct?

Well if you want to make it concave, then each individual piece has to have its own unique smoothing group. Do not give them the same smoothing group.

[Smurftyours]

So if I understand correctly to make the collision mesh I'm going to need to make it out of a lot of tinier models then attach them all together give them the same smoothing group and export it, correct?

Read my example it explains it all.

[Wazanator]

So if I understand correctly to make the collision mesh I'm going to need to make it out of a lot of tinier models then attach them all together give them the same smoothing group and export it, correct?

Read my example it explains it all.

I did I just wanted to make sure that I was understanding it properly is all

[Smurftyours]

So if I understand correctly to make the collision mesh I'm going to need to make it out of a lot of tinier models then attach them all together give them the same smoothing group and export it, correct?

Well from what you said in this post it seems as though your not understanding what to do. Each convex shape must be its own object, with its own personal smoothing group.

[Sgt Frag]

The easy way to do it is make one cube. Make it edit poly. Select all polys, hit 1 on smoothing groups.

Clone it, select all polys, change 1 to 2... clone and make the next one 3...

You need to add the skin modifier to each also, and add them all to the same bone.

[shawnolson]

The easy way to do it is make one cube. Make it edit poly. Select all polys, hit 1 on smoothing groups.

Clone it, select all polys, change 1 to 2... clone and make the next one 3...

You need to add the skin modifier to each also, and add them all to the same bone.

Actually... the REALLY easy way is to use Wall Worm Model Tools... it has a couple hull utilities that just automate it. Select Hulls... click Process CM and all meshes (and each element sub-element of each mesh) are set to unique smoothing groups instantaneously!

[Smurftyours]

I understand the relevance of your tool set to this topic, but I always find that humans provide better results the programs. Also, in my personal opinion I find it rather unprofessional that you pop in to advertise your program after the topic was already solved.

[shawnolson]

I understand the relevance of your tool set to this topic, but I always find that humans provide better results the programs.

You may be correct.

Also, in my personal opinion I find it rather unprofessional that you pop in to advertise your program after the topic was already solved.

Advertising is one way to look at it. I'm pretty damn proud of the tool... and I only want to share with people what I've made. Perhaps he did not know there was a tool to do this... I don't get paid for this. Which, by definition, means I am not doing this professionally!

In any event, I have no intention of putting people off...