Need advice on collision conflict with trimesh

[Siger Wang]

Hello,

I am new to ODE and I am trying to simulate the motion of human teeth.

I've got the trimeshes of all the 28 teeth. Each teeth has almost
30000 triangles. In the simulation,

the teeth are going to collide with their neighbours. And the head of
each tooth is full of irregular

features.

Currently, I get a PC with CPU: Intel Corel2 Quad CPU Q8400 @2.66GHz
2.67GHZ, RAM: 4G

DDR2 800MHz. Is the PC strong enough to accomplish the job in hours?
What things should I pay

attention particularly?

Hope to get your advice. Thank you.

Siger

[Danny Price]

Interesting project! I'm not ODE is the best tool however. Would need to know more about what you're trying to accomplish.

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[Siger Wang]

Thank you for your interesting!

My project moves forward these days. It's mainly about computer-aided
orthodontics. A lot of people suffers from tooth problems, the project
is designed to re-establish the occlusion of the patient according to
the medical laws.
I use an opengl engine to render the teeth in my PC. Unfortunately, I
am only able to render 1 frame/s, this is miserable. I try to shrink
the mesh to its 30% orginal size. Now I am able to render 5 frame/s,
much better.

Still, there is problem left. I don't implement the collision code
yet. I am planning to try hashspace, what's your opinion?



Danny Price 写道：

[Dimitris Papavasiliou]

> My project moves forward these days. It's mainly about computer-aided
> orthodontics. A lot of people suffers from tooth problems, the project
> is designed to re-establish the occlusion of the patient according to
> the medical laws.
> I use an opengl engine to render the teeth in my PC. Unfortunately, I
> am only able to render 1 frame/s, this is miserable. I try to shrink
> the mesh to its 30% orginal size. Now I am able to render 5 frame/s,
> much better.
>
> Still, there is problem left. I don't implement the collision code
> yet. I am planning to try hashspace, what's your opinion?

Make sure that your graphics drivers are set up properly and you're not
getting software rendering. Having to render 28 * 30K = 840K triangles
per frame shouldn't result is framerates that low, at least not on
relatively modern hardware. In any case since your meshes are evidently
very detailed and you'll probably only be looking at one at a time close
up you might want to look into some sort of level-of-detail scheme like
progressive meshes or something like that.

Regarding the collision detection, what exactly do you intend to do? If
you only need collision detection then using a simulator might be more
trouble than it's worth. If you need to simulate too, then what exactly
will you me simulating?

D.

[Siger Wang]

Thank you for reply again!

The collision issue is detailed in :
https://groups.google.com/forum/?fromgroups=#!topic/ode-users/la75-lxb4vw

Currently I think that when one tooth is collided with its neighbour, there is no bouncing, just like two very smooth surface slides from each other.
I don't test it yet. But if there is bouncing in the contact points, the teeth will bounce which dis-obeys my expection.

Fankly speaking, I am a fresh man in opengl. I do the render job in the drawStuff's style using drawTriangle. I checked my video card, it's ATI Radeon HD 4300/4500 Series with its abilty in the picture, could you give any detail advice on how to render the scene quicker? Thank you.

在 2013年5月21日星期二UTC+8下午5时36分55秒，Dimitris Papavasiliou写道：

[Dimitris Papavasiliou]

> Fankly speaking, I am a fresh man in opengl. I do the render job in the
> drawStuff's style using drawTriangle. I checked my video card, it's ATI
> Radeon HD 4300/4500 Series with its abilty in the picture, could you
> give any detail advice on how to render the scene quicker? Thank you.

It's not a very good idea to use DrawStuff for your rendering. I can't
explain why exactly because I haven't studied its code but it hasn't
been designed for that kind of usage and it's therefore reasonable to
assume that it might be responsible for the very low frame-rates you're
experiencing.

Since your needs in terms of rendering aren't particularly big I'd
suggest just following a couple of tutorials about how to set up an
OpenGL context and window and how to render a triangle mesh which you
can evidently already import. You can stick with the "compatibility
profile" (which is old-style OpenGL and a bit simpler) to avoid having
to concern yourself with shaders and other modern stuff like that. It's
pretty simple really.

Also make sure that your drivers are running properly and you have
accelerated rendering. I'm not sure how to do that on Windows but a
sure-fire way is to simply try to run a relatively demanding 3D
application like a game. If it's _very_ slow you're running on software.

D.

[Siger Wang]

3Q.

I'll keep your words in mind.

在 2013年5月22日星期三UTC+8下午5时23分17秒，Dimitris Papavasiliou写道：