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Refining the simulation on the colliders

From: Creating Simulations in MassFX and 3ds Max

Video: Refining the simulation on the colliders

Having run through a refining pass on our launchers and ironed out a number of simulation problems there, it's time now to step through the rest of our rigid body simulation and take care of any further issues that we maybe running into. The first thing we would probably want to do of course is run our simulation once again, just to get a clear idea of the issues that may exist. If we just go into MassFX toolbar, we can hit the Start Simulation button and as we examine the simulation, you can see, well, that there does appear to be quite a number of issues that we will need to deal with.

Refining the simulation on the colliders

Having run through a refining pass on our launchers and ironed out a number of simulation problems there, it's time now to step through the rest of our rigid body simulation and take care of any further issues that we maybe running into. The first thing we would probably want to do of course is run our simulation once again, just to get a clear idea of the issues that may exist. If we just go into MassFX toolbar, we can hit the Start Simulation button and as we examine the simulation, you can see, well, that there does appear to be quite a number of issues that we will need to deal with.

Our stacks of cans for instance are dropping straight through the stand, which as a static rigid body ought to be colliding with, or more accurately, catching them. It is also clear that our launch spheres are not in actual fact getting anywhere near they cans themselves. In fact, it looks as though they are running into some kind of invisible force field. Finally, if we look carefully at the cans upon the shelves, we can see that they too appear to be behaving in a very odd manner indeed.

In truth, these noted behaviors are in fact symptoms of the same basic problem. If we just select our standard geometry and come over to the Modifier options, you can see, if we come down to the Physical Shapes rollout, that we have mistakenly left this option set to Convex when we're clearly dealing with a concave object. If you remember, with static rigid bodies that have a concave graphical mesh we need to actually switch our collision shape over to using the Original option, so let's do that.

Our shelves, too, if I just select one, although having had a physical mesh type of box automatically set, which would seem entirely appropriate, do also need switching over to a different physical shape type. In this instance Convex will work nicely for us. Indeed, if we just run the simulation once more, we can see that things are definitely improved. Whenever we run into misbehaving dynamic rigid bodies in a simulation it is always a good idea to check our Physical Shape options, maybe even experiment with them a little bit.

We still of course have a number of other issues that we need to tackle before we can say that we're happy with this simulation. In fact, what we really do need at this point to take a close look of what is going on with our stacks of cans. To move in a little closer, let's hit C key on the keyboard and switch over to our Target CloseUp Camera. If we now run the simulation from this particular viewpoint, we can clearly see that our stacks of cans are simply collapsing of their own accord. Now, this unwanted behavior is caused by the initial drop that the objects are making once the simulation starts and the rigid bodies come under the influence of gravity.

To solve this problem we can again make use of some MassFX global controls. Before we do that, however, we may want to just correctly set the physical properties for our cans, as this is certainly going to help them behave in a more realistic manner. So let's select one of our cans and come over to the Command panel. In the Physical Material Properties rollout you'll notice that the Mass for this object has been automatically set somewhat higher than an empty tin can ought to be. Really, we should have a mass of about 75-90 gm or so applied here.

Now in MassFX, the mass values for rigid bodies are measured in kilograms, so for 75 grams we should have a setting here of 0.075. You'll notice that as I apply the setting our object's Density value is automatically calculated and updated for us. We do also need to set the physical Ss down to Shapes rollout, you can see we are currently using the Capsule option, which given the shape of our geometry, is not nearly accurate and not for what we want to accomplish.

So let's switch this over to Convex. If we run the simulation now, we can see our stacks of cans do still collapse, but they do so much less violently. For the final part of the solution to our collapsing stacks, we needs to work a little bit in the MassFX Tools dialog. In the World Parameters tab, let's first of all copy the existing earth gravity value to the clipboard, so let's just select it and use Ctrl+C. Then we want to reset this value to -0.1, so a much reduced gravity effect.

Now we need to select all of the cans in our stacks, so let's open up 3ds Max's Layer Manager and using the tools in here, we can make certain that all of those objects are indeed selected. What we want to do now is run the simulation, but this time without animation, and we just want to do this until our cans touch down on the stand and on one another, and when they do, we want to quickly stop the simulation. Making certain that the cans remain selected in the Simulation Tools tab of the Tools dialog, we want to click the Capture Transform button and set the current location of our cans as the starting position in the simulation.

Again, with the object still selected, let's go into the Multi-Object Editor and set our cans to Start Simulation in Sleep mode. This tells our dynamic rigid bodies to ignore everything in the simulation, such as gravity, until another rigid body collides with them. Do remember of course we need to paste the correct value for gravity back in before we run the simulation again, so let's do that. Now we can switch over to our main camera view and then again run the simulation. And as you can see, things appear to be working exactly as we would like them.

So with the refinement phases having seemingly yielded good results, we need to now check just what this simulation will look like when it is played back at its final render speed. Before we can do that, however, we are going to have to create animation keyframe data for all of our currently simulated objects; this means taking a look at MassFX's Simulation Baking options.

Show transcript

This video is part of

Image for Creating Simulations in MassFX and 3ds Max
Creating Simulations in MassFX and 3ds Max

51 video lessons · 2431 viewers

Brian Bradley
Author

 
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  1. 3m 27s
    1. Welcome
      58s
    2. Working with the exercise files
      46s
    3. Setting up the 3ds Max project structure
      1m 43s
  2. 39m 20s
    1. Why simulate and not animate?
      3m 38s
    2. A look at gravity and drag
      3m 55s
    3. Understanding volume, mass, and density
      3m 45s
    4. What are Newton's laws of motion?
      3m 20s
    5. Finding believable frames per second and substeps
      3m 5s
    6. Understanding the difference between rigid and soft bodies
      3m 28s
    7. More about rigid body types
      3m 32s
    8. How collisions are calculated
      4m 35s
    9. Learning the difference between concave and convex meshes
      6m 24s
    10. What is a constraint and how do we use it?
      3m 38s
  3. 24m 20s
    1. A look at the MassFX and the 3ds Max user interfaces
      5m 52s
    2. Exploring the MassFX workflow
      5m 14s
    3. Discovering ground collision and gravity
      4m 49s
    4. Adjusting substeps and solver iterations
      3m 43s
    5. Using the Multi-Editor and the MassFX Visualizer
      4m 42s
  4. 44m 11s
    1. Breaking down the shot
      4m 51s
    2. Setting up the launchers
      3m 59s
    3. Setting up the drop system
      4m 30s
    4. Prepping the cans
      3m 33s
    5. Refining the simulation on the launchers
      5m 9s
    6. Refining the simulation on the colliders
      6m 5s
    7. Baking out the simulation for rendering
      5m 37s
    8. Reviewing the simulation with an animation sequence
      5m 3s
    9. Adding an animation override
      5m 24s
  5. 33m 32s
    1. Adding a rigid constraint and creating breakability
      8m 3s
    2. Creating a moving target with the Slide constraint
      4m 47s
    3. Creating springy targets with the Hinge constraint
      5m 59s
    4. Spinning targets using the Twist constraint
      4m 57s
    5. Creating crazy targets with the Ball & Socket constraint
      4m 58s
    6. Constructing a MassFX Ragdoll
      4m 48s
  6. 36m 51s
    1. Applying the mCloth modifier and pinning the hammock
      5m 55s
    2. Setting up the hammock's physical properties
      5m 39s
    3. Working with the mCloth interaction controls
      6m 14s
    4. Attaching the hammock to animated objects
      4m 5s
    5. Putting a rip in mCloth
      6m 14s
    6. Using mCloth to create a rope object
      4m 53s
    7. Creating a soft body object
      3m 51s
  7. 14m 47s
    1. Adding forces to a simulation
      5m 27s
    2. Putting forces to practical use
      5m 33s
    3. Using forces with mCloth
      3m 47s
  8. 35m 27s
    1. Walking through mParticles
      4m 38s
    2. Using fracture geometry
      6m 0s
    3. Creating breakable glue: Part 1
      4m 19s
    4. Creating breakable glue: Part 2
      5m 19s
    5. Creating a gloopy fluid: Part 1
      4m 14s
    6. Creating a gloopy fluid: Part 2
      4m 41s
    7. Adding forces to mParticles
      6m 16s
  9. 1m 5s
    1. What's next?
      1m 5s

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