Animating blood spatter

There quite a few forum topics about blood. And there is lots of information on getting it to look right, texturally anyhow. But I am clueless as to how to animate a nice stream of blood spurting out. Something like a really big knife blow in a slasher flick or something equally outrageous. You know where the person strikes and a nice stream of blood spurts out and hits the camera. Of course hitting the camera is optional the important thing here is the fluid dynamics. Somthing which I hear is going to have a new tool in 2.4. Until 2.4 comes out how do you get decent spurts of liquid?

The way I would do it is have the blood modeled in a line splater and have it hit the wall or surface really fast in the IPO. I did this a while back with jelly. Let me see if I can find it.

The spatter will simply be a layer that will be composited in. It’s inherently flat. There’s really no reason to model such a thing three-dimensionally…

No, I’m not talking about the spatter that is left on the wall that the CSI team decomposes to find out everything. I am talking about an absolutely 3D splash that come out of someone and travels somewhere else after a particularly violent blow. It sounds as if the jar of jelly might be very close to what I am talking about. If you have the .blend around it would be much appreciated.

If you’re talented you can fake-model the bloodstreams as if it came from a simulation. Honestly, I just can’t think a workaround for this. Even the director of Shrek commented that the pouring of a glass of milk was the single most difficult shot in the entire movie.

Yes fluid dynamics has to be one of the most difficult thing to simulate. I am really excited about the 2.4 release that splashing dropping cube was amazing. If you haven’t seen it:

So until then you have to painstakingly move every vertice so that your estimation of a splash looks right? Wow, no wonder they are implementing a tool for this.

Yes! These are very exiciting times indeed. And according to the author of the fluid dynamics system, it can be extended to animate smoke and objects (like leaves) in the wind. I hope that will be the ideal showcase for other developers who are thinking about developing next gen goodies in a stable open source enviroment.

Anyway… Maybe another way to animate liquids is by using meta object. Maybe you should try something involving meta balls and meta cilinders +particle deflection?

P.S. I highly doubt it that the fluid simulation will be ready for the 2.4 realese. I think much has to be tested, much code has to be cleaned up to make it in a stable release. Perhaps 2.41 or 2.42?

Typically, in CGI when you wanna do a blood squirt or a bullet exit wound, you would just use metaballs or particles. Obviously thats not gonna cut for a really detailed, fluid splash of blood. But its a start.

One thing that I thing would be really neat, is if blender had the option to paint by particles.

Imagine the following scene. A robber is standing against a wall, he gets shot by the cops, the blood splatters onto the wall.
As far as I know, the only way to get the blood splat onto the wall, texturewise, is to have an animated texture map, where the blood splat appears at the correct moment in time. But wouldnt it be much easier if you could have it so that when particles penetrate the relevant part of the wall, they paint it as well. Either with a pure color or a pre-defined texture.

That would make splat or paint effects really easy.

Hey, is it possible to emit softbody meshes in a particle stream and have them splat? Hmmm - Could be a good thing to test.

Seems to me the entire essence of the splat will be fluid dynamics. Maybe I’m wrong and it sure would be cool for someone to show us some cool trick, but we might have to wait for the next release or whenever the integrate these fluid dynamics in.

This is also a thing that is pretty complicated to do in one render pass, but when you use compositing it’s ridiculously simple. Just render your character alone in the scene and two versions of the background empty. Other one with the splatter and other one without. Then just swap the two in composition phase when the blood hits the wall, and add your character on top as a separate layer.

You can do this in Blender’s sequence editor.