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This course introduces basic physics simulation principles in Autodesk 3ds Max using MassFX, a system that makes it cost effective to animate rigid body objects, cloth, and particle systems. Author Brian Bradley introduces basic concepts such as gravity, drag, volume, and density, and how Newton's Laws of Motion can help you understand the interaction of objects with these unseen forces. Using the purpose built scene, Brian walks through the tools and features of the MassFX (PhysX) system, applying the principles discussed as he goes. Along the way, discover how to combine rigid bodies and constraints, mCloth fabrics, and mParticles geometry to create fairground-style effects.
For anyone accustomed to the workflow of 3ds Max's previous dynamic simulation tool Reactor, which of course has been replaced by MassFX since 3ds Max 2012, working with MassFX may seem a little odd at first, as the workflows are quite different in a number of respects. The first big difference is that everything in our simulation now takes place, or is viewable, inside the 3ds Max viewport rather than in a dedicated viewer window, as was the case with reactor.
This could create a little initial confusion as, with our MassFX toolbar enabled, we now have two sets of controls in the 3ds Max interface that use standard VCR-type button icons. One set of course can be found on the MassFX toolbar itself; the other would be our standard 3ds Max Animation Playback controls, found in the bottom-right corner off the Max UI. Of course we can easily dispel any confusion by taking a look at a simple demonstration scene designed to show us the difference between the two.
As you can see, we have a sphere set up as a MassFX rigid body object ready to be simulated and we have a keyframe animated object in the form of a teapot. Now, if we come down and use the play button on our animation controls, we see the motion of playback of our animated teapot in the viewport. Notice though, that nothing happens to our sphere. This is exactly the behavior we would expect, as only the teapot object in the scene has been animated and is therefore the only object controlled by the Animation Playback options.
In contrast, if we come up and use the Start Simulation control on our MassFX toolbar, by default we will now see both the animated teapot and the stimulated sphere reacting or moving in the scene. Just as a side note, you will notice throughout this course that I will refer to this particular button on the MassFX toolbar as the Start Simulation control rather than calling it a play button. Now, whilst this is not a hugely important point to get stuck on, the difference in this choice of words is deliberate.
Hopefully, it will help reinforce in our minds the difference regarding animation playback and the running of a live simulation in the viewport. Going back to our scene, the cool thing here of course with this default behavior is that we can quickly and easily create very precise interaction between animated and dynamic objects live in the viewport. Of course we can, if we need to, modify this default behavior in our start button a little. If you will closely, you will notice that it is indeed a flyout.
And if we click and hold, you can see we have two options available. One is Start Simulation. The other Start Simulation Without Animation. If we choose the second option, as you might expect, the sphere simulates and drops to the floor, but we get no motion from our teapot. This of course means we could focus our attention on just the simulated objects in the scene without any potentially distracting keyframe-animated objects moving around.
One thing we do need to remember is that animation will only play for the duration set in our animation timeline options, whist of course our MassFX simulation because it is running live in the viewport, will continue to run and simulate even after timeline playback has ended. We will need to click the MassFX start button a second time to specifically end a simulation. To have our simulation stop automatically once the timeline limit has been reached, we can come into the Simulation tools top of our MassFX tools dialog, come to the Simulation Settings rollout, and set the required behavior using this On Last Frame option.
Another big difference between MassFX and the old Reactor tools comes in the way that objects are added to a simulation. In Reactor, geometry had to be add into very specific collections such as rigid body collection, a cloth collection, a rope collection, and so on before the simulation could be run. In MassFX things are much simpler. If I just select our rigid body sphere and come over to the Command panel in the Modify tab, you can see the only thing applied to sphere is a MassFX rigid body modifier.
This modifier houses all of the local parameters that will determine how this object behaves inside a simulation. With the modifier applied, as soon as we start a simulation from the MassFX toolbar, everything works as it should. Of course if we were working with soft bodies rather than rigid bodies, we would simply add the mCloth modifier as opposed to a rigid body modifier. Unlike Reactor then, working with MassFX tools settings inside 3ds Max is a streamlined process that is very easy to work with.
The neat thing here is that rigid and soft body objects can not only exist inside the same simulation, but as MassFX is a unified dynamics framework, they have no problem at all interacting with each other.
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