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Geometry LOD

I recommend using the component convex hull (CCH) function geo LODs - it's under the structure/convexity menu. Geo LODs require all the objects to have convex shapes (ie no concave angles to the faces) and for the objects to be named properly. This function does it all for you.

A simple example. If you make a L shaped block all in one piece, the 90 degree angle is concave so will not work. What you need to do is take the top part of the L and separate it from the lower part so that you have two square blocks, one sitting on top of the other. (note: you need to do this manually before you run the CCH function, if you do not, then it will join the top part with the lower right to make a convex shape.)


Geometry LODs

Invisible LODs for engine calculation. Textures are used for special surface characteristics.

Each Geometry LOD must contain named selections of all components. If there are any animated parts, they should keep the names as in other LODs. You can automatically select components by menu Structure→Topology→Find Components.

Geometry components must be closed convex objects

some help tools are in menu structure→convexity

Convexity→Find non-convex and “find non-convexities” - checking tools

Component Convex Hull will try to decompose object in convex components

Convex Hull makes one convex object

use Make convex and Convexity Fine Tune if previous tool fails (different algorithm)

Collision Geometry

Used for physical collision detection Must contain also information about object MASS (gray boxes) and center of gravity (blue cross).

The model should be very simple, defining the basic model shape. Thinner parts than 15cm cannot collide in faster speeds. Better if the geometry is larger than the model shape.

CTRL-A select all. Use MASS dialog to assign total mass. If you want to move the center of gravity, select vertices and change their individual mass. Keep an eye on the “total mass” check box.

It is not a problem, if some components do not have any mass. The mass of the whole model is used for collision, gravity and momentum. BUT, the component will not be simulated, if it has no named selection set.

1 mass = 1kg


Just like the gates / doors in the Resolution LODs, you have to make block/wall in the Geometry LOD similar to the door, and NAME them the same as your animated doors. This will animate the block/door in the Geometry LOD so your “invisible wall” opens as well.


In the Geometry LOD you have to use blocks/cubes to match your walls / floors / roof / doors. If you want open space inside the building, it must not filled inside with “blocks” except where walls are.

To make your Geometry LOD, I suggest;

  • Start with blank GEO LOD
  • Add a “Box” (F7)
  • Stretch box to be similar to one of your walls or floor or roof or door. Doesn't to have to match exactly to Resolution LOD.
  • 1 Box can be for several walls. Example, whole side of building could be 1 box.
  • Keep doing this until you have a box for every wall etc
  • When you need no more boxes, select STRUCTURE > TOPOLOGY > FIND COMPONENTS
ofp/modeling/geometry_lod.txt · Last modified: 2009-09-12 19:33 by snakeman