Caligari trueSpace3 3D graphics implements fully integrated simulation of the physical behavior of real-world objects, including gravity, inter-object collisions, linear and rotational velocity and acceleration, wind, and even atmospheric density upon which an airplane or other flying objects can glide.
In this animation there is no movement of objects except for simulation on the part of the tS3 program. I used and will demonstrate to you:
1. Atmospheric density
2. Gravity
3. Physical behavior [Physical Attributes]
4. Inter object collision

I changed the density and created a floating sphere by assigning the physical attributes of styrofoam [bubble]. The fish on the other hand had the physical property of iron so in the same density it sinks. As the fish sinks it collides and bounces off the bubbles.

Move to a front view in tS3 with a small window of top side and perspective, and we will get started.
1. Atmospheric density: This is change by bringing up the properties panel,/ Global Physical Properties/Global pop-up/ right click on sky and clouds icon/ set Density to 100,000 [do not use coma]and Thinning to 300/ Enter both settings.
2. Gravity; On the previous Global pop-up set gravity but do not change the settings
3. Physical behavior: Create an object and be sure that it is glued and sized with out Inverse Kinematics or Plastic Form. I glued my fish together after I had already assigned attributes to the fish body and the body move away from the after glued parts during simulation. An interesting molting effect, but not what I wanted. I also resized a sphere smaller after assigning the Local Physical Attribute of Styrofoam [and buoyant with the changed gravity]. Making the sphere smaller created a denser object and it was no longer buoyant but sank. Then I did the opposite and made a sphere larger after assigning the Local Physical Attribute of Styrofoam. The sphere became much more buoyant than one the same size with the same L.P.A. that had not been altered after assignment.
To assign and object Local Physical Attributes select; the object/Local Physical Attributes tool/pick attribute,[Styrofoam for bubbles or iron for fish].
4. Interobject collision; Move the Styrofoam spheres to the bottom of the window but not below the horizon. Take the iron fish above the bubbles and start the simulation. Start simulation is found on the Animation Controls Group and in the Global pop-up.

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I found that the more bubbles I created colliding with the fish the slower the decent. Depending on the placement of the fish there would be different movements. If I placed the fish just above the bubbles then the collisions would tumble the fish upside down. If I raised the fish up so as to get more speed before collisions then there was not the tumbling effect. This is just a touch of the creativity waiting for you in Caligari trueSpace3 and Physical Simulation.

TrueSpace2 Tutorial	2D Page