I have an animated scene I'm working on where two fantasy characters are fighting and one rips the arm off the other and tosses it away.  What's the best way to go about animating this?  I have the fight done to this point and it looks good, but I'm unsure how to do the arm-rip.  I thought I might just dupe the victim and then make just the duplicate's arm visible and make the arm of the original not visible.  Or is there an easier way?

Quote - I thought I might just dupe the victim and then make just the duplicate's arm visible and make the arm of the original not visible.  Or is there an easier way?

I'm pretty sure that is the easiest way.

You will get a missing area where the arm attaches to the shoulder.  Exporting the arm and hand (by selecting the subset) and using one of the prop endcaps might be better. It depends if the arm needs to bend after being ripped off .  There were some amputation props at renderotica freestuff, and maybe freestuff here.

Quote - You will get a missing area where the arm attaches to the shoulder.

That's really a seperate issue, and using parented end caps or magneting closed will need to be done whatever method is used to achieve the original objective. The real challenge is how to do the spurting blood.

Gratuitous plug for my freebie prop at sharecg.

http://www.sharecg.com/v/50442/view/5/3D-Model/water-prop

:)

The hiding could-would be the best way to do it.

The tear -off area's can be plugged with a prop... that, depending on the visibility of it, you would have to build.
Otherwise, you could play with texture and displacement on the tear-of area's.
It is an animation?
Change view angle, during tear -off?
Depends on the script?

* Exporting the arm and hand (by selecting the subset) and using one of the prop endcaps might be better.*

I'm not familiar with this process (or many others) - how would I go about doing this?

pose the arm how you want it and select File , Export, Wavefront obj and follow the prompts. You should get a display to select what gets exported so select the parts you want (probably shoulder, lower arm, hand and all fingers) . Then import that obj (Figure, Import, etc) and that will be your ripped off arm.

If the camera angles are good, and the missing bit at the shoulder looks ok then you are done.

I did not find the props to close off the arm openings.  :(

You could use a ball to endcap the openings.
With the morphtool and some textures-displacement, it could work.
Or, open the exported arm hand-fingers obj in a 3D app, and close the remaining gap?
You'd still need some trick to close the gap on the collar :-)

Thanks everyone!  I'll post a frame when I'm finished.

Quote - You could use a ball to endcap the openings.
With the morphtool and some textures-displacement, it could work.
Or, open the exported arm hand-fingers obj in a 3D app, and close the remaining gap?
You'd still need some trick to close the gap on the collar :-)

I did something similar to this, doing the old lightsaber cutting off the forearm trick. Camera angle and the clothing hid the missing parts. I also did the duplicate character thing. Makes the render drag out a bit, though.