How can I demonstrate human bone fractures?


I’m a complete newb when it comes to 3D content creation. To date I’ve used google sketchup with the sketchyphysics plugin to make some simple demonstrations, but I don’t think that software will suit my next task.

I’ve been asked to make a simple 3D demonstration of several simple types of long bone fractures. In short, I don’t know where to begin and whether blender will allow me to do this.

I found a similar video online:

I would need to make a video similar to the sequence starting at 1:00 in the above link.

So I guess my questions are whether I came to the right place, and if so, how should I begin?

Thanks in advance…

Blender surely is the software to go with…
To me this is a rather trivial matter and done quite quick, but I work with Blender for years. I really can´t judge how long it would take to learn that.

You´d need to get a model of a skeleton, either buy one cheap, look for a free one, or make one yourself. If you only need to illustrate the breaking bones, it´s really easy.

You´d need knowledge of the animation basics, keyframing and shapekeys in Blender, along with the basic modelling tools and render, scene and lighting setup.
Depending on the requirements, stylized, photo realistic for instance the whole learning and creation process will vary.

I´d say you´d need around 3 months for that wihtout any prior blender knowledge if you spend 2-3h a day with Blender. 5 days a week.

Is it a commercial, educational or just a hobby project?

The accrual bone fracture sequence can be made quickly and simply or as difficult as you like.

Simple one involves modeling the bone, and model the broken one. Sequence them one after other so that it appear to brake. The brake is instantaneous you know.

Thank you for your response.

This is an educational project. I have a skeleton model I downloaded from the google sketchup repository. I read that those files can be converted and imported to Blender, but haven’t investigated that process in detail.

I would need to model the bone breaking in slow motion, with the fragments moving relative to one another in real time. So I think the simple solution offered by ridix where I’d show the intact bone and broken bone in sequence wouldn’t quite be what I’m going for.

So if I successfully import the intact bone model into Blender, would an experienced Blender user be able to divide the model into the respective fragments and make the fragments move relative to one another? I anticipate the answer to this is yes.

If that’s possible, what would be the best way for me to acquire the necessary skills to do this? I bought “Blender for Dummies” by Jason van Gumster over the weekend and have been reading through some of the sections. I having the hard copy reference may be better for a beginner rather than reading through forums that usually deal with rather specific questions. Is this a reasonable reference for a beginner, or would you recommend something else?

Is the three month estimate based on modeling the skeleton myself? How long do you think it’d take if I can use the model I already have?

Thanks again.

The bender guru video is very similar to what I’m envisioning for making the various fracture fragments. Is it possible to make an oblique crack through a cylinder that doesn’t necessarily follow any one of the various vertices?

You said you are new to 3D content creation, or better 3DCG, not just to Blender.
You not only have to learn the tool, you also have to learn basics, which your last post shows.

It is impossible to break a mesh apart without following any vertices. If you´re good enough, you could most likely code a plugin with python that generates the crack, meaning, create vertices and edges.

The only way is to pre-break the bone with edges, also fill the geometry. The bone is hollow, it is a mesh after all, so you would have to “fill” the sites of fracture. Imagine the bone a toilet paper roll with closed ends. If you cut it in half, you got to close the two emerging holes. So you´d have to pre-break the bone, most likely texture it, as I guess you´d like to show the bone marrow for a complete fracture. Also chips of bone need to be generated seperately.
And then you start the animation, keying the position of the boneparts while the bone is intact, and then hand-animating the fracture setting keys. There really is no good way to do this automated.
You might also want to work with softbodies or shapekeys, as a bone is not completely rigid, it will deform quite a bit before finally breaking which should give a very nice effect for the slow motion animation.

The only way to get from Sketchup to Blender is collada (.DAE)
You can also check out, they should have free skeleton models and bone models as well, and already in formats blender can import (keep an eye open for .3ds and .obj, they work with the least problems)

Well, yes, there is. What you need to do is have a couple of beers, then get on your cafe racer with indy profile tires that you can lay down to the pegs, and do about 95 MPH on a twisty-turny 25 MPH road. When you wake up in the hospital have a look at the x-rays. This is not really for the faint of heart. Trust me, I know… .

So today I began working on the project and feel like I learned quite a bit. First off, Blender crashed every time I tried to import my .DAE file, so I was able to convert the model to .OBJ using a different piece of software called Meshlab.

It took me a bit to figure out how to manipulate the model, but things really took off once I figured out tabbing and the fact that right clicking selects objects.

I was able to break apart the model using the boolean difference function. That allowed me to make a break that didn’t follow previously existing vertices. After that I did some keyframing and made a little 12 frame video that shows the bone pieces “breaking” over the first 10 frames. If you watch the following video, don’t blink because you’ll miss the actual break.

This gave me a neat little demonstration, but as arexma suggested, I’m not nearly there yet. I still need to “fill in the ends of my toilet paper roll”, and I’d like to show some deformation before the crack appears. I understand that shapekeys can be used to accomplish this.

If I use shapekeys to show some deformation before cracking, how could I set things up so that both bone pieces are deforming uniformly? I think it would be difficult to set up two separate shape keys for the individual fragments such that they overlap perfectly whey they are both set to 1.000. Is it possible to shape the two objects simultaneously near the fracture site?

Also, I’d like to show the fracture gradually traversing the diameter of the bone, so that in any given frame only a certain percentage of the fracture has actually occurred. It isn’t immediately obvious to me how I’d accomplish this using keyframing and shapekeying. Is this possible, or is there another technique I should know about?

Finally, I had planned on waiting to fill in and texture the end of the bone until I had satisfactorily demonstrated the break. But if someone would like to advise me on how to proceed there, I’d like to start thinking about that aspect of the project as well.

Thank you all again for your previous replies. I hope this isn’t too tedious for you. I do think that if I manage to finish the project, this thread will be a useful reference for other beginners.