Chapter 4: Terrain Objects

Positioning Terrain Objects

For a ship or ground object, x and y (horizontal) center point should be in the middle of the model, as viewed from above. The y (vertical) center point should be at the waterline/groundline. You could model it at a different location, and use the offset = x,y,z command to tell the game how far back/forward/up/down/left/right it needs to move the model to get it in the place it expects it to be, but it's better to get it right from the start.

Negative Altitude Considerations

You may have noticed from the previous illustration that the building in question extended down beneath the ground level. At first glance, this might seem silly, since it's a flight sim and not a mole simulator. But the reason for it becomes obvious the first time you try to place a building or other large terrain object onto any piece of real estate that isn't perfectly flat. If you don't want your object to seem to be hovering ove the ground, you need to extend it down an appropriate amount beneath the ground level. Ideally, this "foundation" will never be seen. But if someone does place your object on a slope, it will make it look a little more realistic. You'll probably want to spend a minimum of polygons and texture map space on this part.

Another factor to be aware of when building objects that sit on the ground or sea is the terrain itself. If you build an object with an exposed compartment the floor of which is lower than ground/sea level, the polygon that makes up the terrain will be drawn over (and above) your floor. If it is an open-air boat, for example, it might appear to be full of water. If it is a crater, it will just flatten out right at the level of the surrounding terrain. There is no way around this issue at the current time, so plan wisely.