Join Joel Bradley for an in-depth discussion in this video Planning out the shot, part of Blender: Creating Rigid Body Simulations (2013).
By this point in our course, we have already armed ourselves with all of the basic information we need in order to set about creating our own straightforward rigid body simulations. Of course, the problem we may run into is that very little in life remains straightforward for long. And so sooner or later we will probably find ourselves called upon to create simulations that have a number of extra complexities added into the mix. For this reason then we're going to use our second chapter to walk through another rigid body scenario. But one that this time has a number of additional considerations or requirements attached to it.
The idea being that we can introduce ourselves to a couple of important concepts and work flow approaches that we will need to be aware of as we begin to create our more complex shots. In fact, what we will tackle in this video is the need to analyze, breakdown and plan the shot or effect that we are wanting to create in our simulation. The biggest mistake in my humble opinion that any technical artist can make is to try and dive straight into the creation process without first outlining very clearly exactly what it is we're trying to accomplish.
Even taking the time to create as many notes as possible regarding just how our stated goal might be accomplished. To skip this planning stage is to force ourselves down a very difficult path. Where every ounce of success and quality we are able to drag out of our work, will come at a price in terms of time, frustration and ultimately a measure, perhaps of dissatisfaction with the quality of our final result. Obviously all we will be able to accomplish in this shot video is to give ourselves a quick overview of the process.
But we need to be aware that it should be given as much time as necessary in order to get everything we need from it. If our project is simple and straightforward, then it could well be that an hour or two will be more than sufficient for that. For extremely complex scenarios however, we could conceivably be at this stage of the process for a few days or even weeks in extreme cases. Whilst that may (LAUGH) initially sound a little crazy. Especially when we are waiting to get going on the actual creation of our project.
And the point of what we will do here, is that, once we are into the creation phase, everything we need to do, the steps we need to take. Which problems will need to be solved. Should all, for the most part have been taken care of and (INAUDIBLE) because we took out time for the planning stage. To that end then, let's take a look at what we have going on in our stat scene so that we can start to plan things out. If I just press the Play button on our animation controls, we can see that our refuse bot here already has some basic key frame motion applied to it.
The idea is that he will be pushing all of these bits of waste. Which just happen to look like geometric primitives, along this (UNKNOWN) and then if we just switch over to the catch camera, we can see the idea is that they will be dropped into this waiting recycle tank. That itself will then be collected and taken to a recycling plant, probably located in a district far away. With this scenario in mind, then, we are already able to note down that we will need to make use of a number of rigid body types in the simulation.
The robot itself, because of the key frame animation will obviously need to be an animated rigid body. Whilst the objects it will be pushing, given that they will need to collide with the bot, the gantry and fall through space will need to be active. If the pieces of refuse are going to be active rigid bodies then it instantly becomes obvious that we are going to want the gantry geometry to be a passive rigid body that they can sit on the slider. Once the objects go over the edge. We have two possibilities that need to be taken into account.
If we just switch to the catch camera again, we can see that our objects, depending on how they fall, could be caught by this receptacle geometry. But we need to allow for the fact that they might miss it. And so have to collide with the flow geometry itself. For the floor, I think we can safely say that a passive rigid body will be the best choice. And whilst we could use the same option for the tank, I would actually like to see a little bit of reaction movement from this as the objects tumble into it. So, in this instance, I think I will try an active rigid body first.
Now, both this tank geometry and the scoop on the front of our butt here introduce a dynamics concept regarding mesh types that we will need to get to grips with if we want to produce successful accurate rigid body simulations. This would be the difference between a convex and a concave piece of geometry. Along with an understanding of how those defenses will affect the dynamics options we have available to us. We will also in this chapter introduce the idea of using a proxy mesh as a collision object.
For situations where we may find the density of our graphical meshes slowing our simulation calculations down just a little too much. And then, finally, just add a little bit more complexity to our senerios. We will take a look about how we can go about using force fields to interact with, and even massively affect the behavior of our ridgy bodies in a simulation. Giving us aspects of a whole range of effects possibilities. With the planning faze very quickly taken care of, then we could move on and start to put our simulation together. Just to reiterate, we do ourselves and our creative a work a great disservice if we simply dive right in and skip this phase all together.
The carpenter's adage, measure twice and cut once holds true even in the realm of digital effects.
- Setting up objects for simulation
- Setting up the physics world
- Choosing a collision type
- Applying a collision shape
- Creating an animated rigid body
- Baking to keyframes
- Working with the mesh collision shape
- Adding a force field to the mix
- Understanding constraints
- Creating fracture patterns