Creating dynamic mud effect using soft body

Our goal in this tutorial is to make effect that one dynamic sphere make trail on surface while moving over it’s surface, similar like some ball moving over mud.

So first lets explain how this works and then we’ll go step by step.

Upper picture is whole scene rig. You can see that we have 2 planes ( NURBS ) gravity and drag field, Rigid body sphere that makes trail in plane.

We use two planes because one is soft body and other one ( lower) is collision object that sphere will collide on move over. Trick is to make upper plane a soft body which particles will collide with sphere, gravity field will pull them down and drag field will make them stop when they reach some distance from starting point, basically you changing with drag field how deep trail will be.

 So lets start making the scene.

First make one NURBS plane 40x40 in length and width and 40x40 subdivisions. More subdivisions means better solving and better look. But solver calculation. Basically on every subdivision square you got one particle that collides with sphere.

Duplicate that plane and move it one unit lower.

Make a NURBS sphere with scale 3x3x3 and move it to corner of upper plane and move it just a bit above surface so surfaces don’t intersect.

Something like this :

Now lets make sphere to collide with lower copy of plane. Select sphere and make it active rigid body. In dynamics panel :

And plane that is lower make passive rigid body. That means that object can collide with that object but fields or momentum from other objects don’t affect his position and movement. But sphere is active rigid body so gravity and other fields affect more or less on his motion.

Now make in scene one gravity and one drag field.

For now leave field as is.  If you play animation your sphere should collide with plane! Bounce a bit and stop.

Lets change some parameters for sphere:

First select sphere and in rigid body properties change next few settings like in picture:

Now select plane that is rigid body and just change Bounciness to 0 so sphere don baunce from it. We changed spin impulse for sphere so now sphere rotates and should go over plane diagonally. Mass is set to 50 so its heavier and  there be more friction with plane surface.

Now if you play animation sphere should fall on surface and go over it by diagonal. From one cornet to another.

Now lets make soft body and it’ settings.

Select upper NURBS plane and go to soft/rigid body’s pull down menu and click on box next to Make soft body:

New window should appear for initial settings for soft body:

Press apply button when you set like in picture above.

Options are:

Duplicate, make copy soft is that MAYA will duplicate that surface, hide initial and make it goal object and give us new on with particles that are dynamic and can collide with sphere.

Weight 0.5 is how hard particles trying to stay on initial place from goal object.

If you look in outliner and expand under  plane surface you should see particles node!

Now from outliner select particles than shift select sphere and from particles manu take option Make collide. So now particles will collide with sphere.

But if you play animation you’ll see that particles are moving on start position when sphere is moving away from them. That is not effect what we want! But can give you nice effect if you want to make some water ripples or something like that.

So we need to tweak some settings.

First we need to connect drag field to particles coz initially it’s not connected.

Open dynamic relationship editor which is in: Window/relationship editors/dynamic relationship

Open that window and you’ll get something like in picture below :

In left part of window you need to select particles and all forces in scene will appear in right part which are able to connect to particles. You click just once to Drag field and you should get some yellow color around it. That means that those two are connected now.

                Drag field we need because we want particles to stop on some point. Otherwise particles will go and follow it’s movement vector to infinity, and we sure don’t want that!

Now play animation. Still not what we want. Select drag field and change it’s magnitude to 100.

Than select particles from outliner and set goal weight to 0 and play animation.

Now all should work fine!

This is what I get with this settings.

Posted in Maya 3D