Getting Around trueSpace Page 12

Tutorials

Getting Around in trueSpace 5 and 6

Page 12

Quick-jump to topics in this tutorial:

11. Simulations

TrueSpace from versions 3 upwards supports physical simulation. TrueSpace 6.6 greatly enhanced the simulation capabilities to include the likes of tornados, electrostatic properties (magnetism) and glued objects breaking apart when they collide with other objects. (However, we have to note that unfortunately there seems to be a bug with planes in simulations in trueSpace 6.6. In those cases, substitute a cube for the plane and things will work better.) This section of the introduction to trueSpace will only cover the basic simulation properties found in versions 5 and upwards. Users who want more in depth material should consult the manual. The easiest way to understand and explain the simulation capabilities in trueSpace is to jump right in and play around. So let's make and run a few simple simulations and explain things as we go.

Tutorial 1 - Bouncing Ball

Create a new scene and create a default size sphere on the grid. From the simulation toolbar, navigate your way to the rubber properties icon (Fig. 11.1).

Fig. 11.1

Selecting this assigns the properties of rubber to our sphere. Next we need to raise the sphere up in the Z axis so that it is off the ground. TrueSpace treats the grid or Z axis height of 0 as the ground. Click on the green run simulation button

and with any luck the sphere will bounce up and down and eventually come to a rest. (The run simulation button is in the top toolbar in tS6.5 and above, but in the bottom right toolbar in tS5 and 6 - see Fig. 11.2.) To stop the simulation, hit the Esc key on your keyboard.

Fig. 11.2

You can play back the animation that has been generated by clicking on the Play animation button.

Let's play around with the simulation some more before we move on. By default trueSpace runs simulations for 60 seconds. This is often far too long, so right click on the run simulation button to bring up the simulation properties. Change the time to 10 seconds. The other thing we usually need to do is to check the erase script button. Doing this erases the script and records new animation. Not doing so allows you to stop the simulation, maybe change a few things around and then carry on with the simulation. The other thing to enable is auto rewind so that every time you start a simulation the frame count is reset to 0. (Fig. 11.3)

Fig. 11.3

Okay, so change the simulation to 10 seconds and try assigning new properties to the sphere. Different materials will make the sphere bounce in different ways.

Tutorial 2 - Bouncing Ball with rotation

Let's move on. In tutorial 1 the sphere would have bounced up and down on the spot. In the real world the sphere probably would have started to roll off to one side and eventually roll away. Using the same setup as in tutorial 1 now go and click on the initial rotation vector toolbar button. This assigns some rotation to the sphere. Tip: having grid snapping enabled is a big help when working with the initial rotation vector tool. Once you have selected this tool you will see a white arrow coming out of the sphere. You can increase the amount of rotation by dragging on this arrow if you want. Usually the arrow will not be pointing in the direction of spin that you want. An easy way to get the arrow pointing correctly is to leave the length (amount of rotation) at default and go into a side view. With grid snapping enabled, use the move tool and move the arrow so that it is pointing as shown in this diagram. (Fig. 11.4) You can now increase the rotational strength if you wish.

Fig. 11.4

Run the simulation and with any luck the sphere will bounce up and down plus roll away in the direction of the initial rotation vector arrow. You may find you have too much rotation and the sphere rolls away too quickly. Here, just drag the arrow downwards towards the centre of the sphere to reduce the amount of spin. Play back the animation a few times and admire your handiwork. Because this is a simple simulation it should calculate very quickly. One thing to be wary of when creating simulations is they can quickly become complicated and takes hours to generate a simulation. Users contemplating working a lot with simulations should upgrade to trueSpace 6.6 as the simulation engine was greatly enhanced.

Tutorial 3 - Pendulum

Often in a simulation you want part of an object fixed to some point like a pendulum in a clock with the weight swinging backwards and forwards. To start with, create a default size cylinder. Next copy it and rotate the original cylinder by 90 degrees in the X axis as in the diagram. Resize the copy so that it looks something like the diagram. (Fig. 11.5) Glue the 2 cylinders together with the "Glue as Sibling" tool. Raise the combined object off the grid slightly or 1m so that when it swings it doesn't come into contact with the imaginary ground plane.

Fig. 11.5

So that our object swings properly it is helpful (although not essential) to change the axis location of the combined object. So, change to a side view and show the pendulum objects axis. With grid snapping enabled move the axis upwards until it reaches the end of the narrow cylinder. The pendulum now rotates around this axis.

Let's give the pendulum the properties of iron just as we did when applying rubber properties earlier. Next select the "Object Fixation Point 1" tool. You will see a white cross hair. If you don't see it, change to wire frame mode for easier viewing. Change to a side view. Raise the cross hair to the top of the upright cylinder. Next move it outwards to your left. Select the "Object Fixation Point 2" tool and repeat what you did for the first point, except this time move the fixation point out to the right.. We need 2 points to create 2 pivot points so that the pendulum only swings in the Y axis and not in both the X and Y axes. It helps to have grid snapping turned on, so that the two object fixation points will be at the same height. (Fig. 11.6)

Fig. 11.6

Select the object tool to take you out of fixation point editing, then select and rotate the pendulum 45 degrees in the Y axis. Set up the simulation to run 10 seconds with erase script enabled. Run the simulation. In a little while you will have an animation where the pendulum swings back and forth several times. You may be wondering why the pendulum swings so slowly. The reason is trueSpace is calculating the simulations based upon the size of the objects. In this case, the weight is 2m in all 3 axes. Imagine a real pendulum 2m in size swinging. Users of 6.5 and above can test this out by changing the scene units to cm from metres. Try this and run the simulation again. This time the pendulum will swing much quicker.

Tutorial 4 - Wind

There's 2 basic types of wind in trueSpace. Local wind and global wind. The differences are quite easy to understand. Local wind is like an electric fan. You only feel the wind when you are near it whereas the global wind is like the wind outside so that no matter where the objects are in your scene, they are still affected by the wind. By default the wind object is placed in the centre of the grid. You can increase or decrease the strength of the wind by right clicking on the icon. Start a new scene and create about 6 cubes in a row. Assign different physical properties to each cube. Create a global wind by clicking on the global wind tool. It doesn't matter where you place the wind in the scene. The wind will flow in the direction of the arrow on the object. (Fig. 11.7)

Fig. 11.7

Run the simulation over 10 seconds and see what happens. It's very likely nothing will happen. There's 2 reasons why, the first the wind isn't strong enough and secondly the cubes are on the ground and the wind strength isn't enough to overcome the friction of the object interacting with the imaginary ground plane. Increase the wind strength to 10 and run the simulation again. If nothing much happens try raising the cubes off the ground. This will make the lighter objects in particular begin moving sideways before they hit the ground. Play around with this then carry on with the last tutorial where we alter the friction of the cubes.

Tutorial 5 - Modified Wind tutorial

Start a new scene and set up the 6 cubes just like in the previous tutorial with them all along the ground plane. This time when you assign the physical properties, right click on each parameter e.g. set parameters of wood tool. This brings up an options dialog where you can fine tune the properties of each material that you use in your simulations. For each material reduce the amount of friction to 0 then run the simulations again. (Fig. 11.8) This time, with a wind strength of 10, you should see the lighter objects go whizzing off as there's no friction to keep them stationary.

Fig. 11.8

Tech tip: If you've ever run a simulation with a car model and wondered why the back wheels always lift off the ground, it's caused by friction. TrueSpace doesn't know it's a car and treats the car model like it would with a sphere and the car object will begin to roll. The cure here is to reduce the amount of friction so as to give the illusion that the wheels are turning. This will keep it firmly on the ground.

You can have quite a bit of fun by making 4 low walls and placing a few cubes inside the 4 walls and reduce the friction on all objects. Either have a global wind or give each object some initial motion and watch the cubes carry on like dodgem cars at a fair ground.

So that brings us to the end of this section. We've only just scratched the surface of what's possible in trueSpace. As mentioned trueSpace 6.5 and 6.6 have a greatly enhanced toolset. Things like tornados are incredibly fun to play with!!

This section was written by Nigel Doyle.