Dynamics - Rigid Bodies
To begin the next set of tutorials we are now looking at rigid body dynamics.
In this first example I've created a chain, that swings down with the force of gravity. The chain links collide with each other as solid objects to create the swinging chain. Stand-in objects of lower density of polygons were used in the simulation an higher quality chains were used for rendering.
This next example is of an earring that swings much like the chain, except that the objects are attached to each other via Pin constraints instead, because they don't collide in the same way.
The next example is of a catapult throwing a rock at a brick wall. This one was slightly more complex to setup, but was quite fun to watch in simulate.
First the ground plane was set to be a rigid object that isn't moved by dynamics. (Passive Rigid Body) Then the bricks, catapult and rock were set to be dynamic objects. (Active Rigid Body)
To propel the catapult, a spring constraint was used. Dynamics done the rest.
Lastly is the Cradle. The idea is the end metal balls are supposed to bounce off the pack. This seemed to require more luck than anything else, but basically the balls are Active Rigid Bodies and are held up by a pair of Nail constraints. It was then a matter of tweaking with the properties of the balls and gravity field to get it to work. Even then it only managed a swing or two.
Here is a video of the examples above.
Match Moving - Still Camera
This is matching a filmed shot in 3D for the purpose of adding in CG elements.
Well not exactly match moving yet as the camera is still, but this is sometimes the scenario. That also means that you can't use software to calculate the 3D space in the image so in this example the camera had to be positioned manually with trial and error.
Anyway, I had to use what is in the scene as visual cues to work out approximately the 3D space. One of the first things to work it is the focal length. This can partially be figured out but how much objects shrink into the distance. First of all the camera had to be roughly positioned, then a few cubes were added to the scene a positioned where the buildings were. From then on it was a matter of tweaking the camera position, the focal length and the models until the whole set was mapped out in 3D space.
A few spheres were added into the scene to test how things fitted in and then an orrery was put on top of the bricks in the center.
Lastly the lighting was figured out (approximately) by looking at the shadows in the scene.
Next week we look at a moving shot.
Oh and here is the progress on the high res body modelling tutorial which I started during the holidays. Not finished yet, but getting there.
A Flock of Pixels