compositegeom objects are very similar to the Basic Shapes objects, with a couple of crucial differences and a few "quirks".

The basics of a compositegeom are most easily explained with a short video.

Whilst you can add as many children as you like to a compositegeom, and build a something fantastically complicated, it is still a single object, and it will move and act as such. Like other geometry objects it can have a material, tags and an image, and the compositegeom passes on these properties to all of its children.

So why is that useful?

The main uses of these objects are:

  • Moving Objects which are 'complex' shapes
    The Third Wheel in "Third Wheel" is a compositegeom object, as are the fingers in Genetic Sorting Machine.
  • Grouping a number of basic shapes together so that they share certain attributes.
    Most of the platforms in "Alice and Bob" are parts of the same object, and all the walls and ledges in "Grape Vine Virus" are one big compositegeom.

Another crucial difference between compositegeom and other geometry objects is that compositegeom objects do not have a mass attribute. Their mass (and centre of gravity) are calculated from the masses and positions of all their child objects.
NB: This only matters when you are using [Dynamic objects].


compositegeom objects also have a few "quirks" (steming from bugs in the game engine):

  • Incorrect handling of deadly and mostlydeadly tags with "sticky" Goo Balls - see note in tag attribute
  • Incorrect handling of nocontacts attribute with "sticky" Goo Balls - see note in [Making Geometry less Solid]
  • Unexpected Displacement of Rotated, Dynamic compositegeom objects - [link TBA]