Okay, so, I’m planning out a short film currently, very much a horror film. There is one scene in particular that I need help with on the vfx though. I have a shot where a chainsaw would be seen digging through a man’s arm. I plan on shooting a clean background plate, and a shot of the character in front of a greenscreen so I have a good matte for removing the character’s arm and replacing it with a cg element. The only problem I have however, is I don’t know how I’d go about with the whole cutting part. I’m experienced with blender and wouldn’t have a problem compositing, modeling the arm or adding particle blood, so this is my only snag, and any help would be appreciated c:
Damn, 56 views and no replies? Anyone? 
Nope, but I (like several others I’m sure) am waiting to see if someone else will come up with a good answer. I suspect it will involve having two different versions of the arm, one normal and one cut apart, then strategically switching between them in the animation. But there’s probably a more elegant method that I’m not thinking of.
I’m sure you could do something like Horseman mentioned and use blenders masking features to go from the “good” arm and revealing the sliced arm. You would have to model the sliced arm. In terms of blood squirting out fluid particles are an option, or just compositing real squirting blood footage (that has an alpha) coming out of the wound.
But I’ll be watching this too, to see what other ideas people come up with.
do you follow filmriot? They do a lot of practical effects explanations – with a propensity towards gore
http://revision3.com/filmriot/episodes
here’s one that may have some insight:
Thanks for the film riot recommendation daren… looks like a fun channel for vfx
Yes, Film Riot is amazing, I’ve followed them since pretty much their start. And the masking idea was something I hadn’t really thought of, and it’d definitely help in making the cut come across as more gradual. I think I might use a mix between particles and composited blood alphas for the gore, and really just see which suits it better, but considering how good blender’s particle effects have been advancing, I’m excited to see how it’ll turn out.
If you watch the “sparks” tutorial from andrew price yo might get an idea how to do the cutting.
Yeah, I just watched that the other day. I’m glad cycles has motion blur now, might do quite well to make particles look more like real blood. Especially when it’s spurting that fast.