Based on my work on ADE_GP (ground polys), I think I have found a definitive method for avoiding both flickering shadows and autogen suppression when using FS8-style ground polys with FS9 or FSX that I wanted to share.
Autogen suppression by ground polys is unavoidable! But, it is controllable.
There are (at least) two types of autogen suppression by ground polys.
Don
Autogen suppression by ground polys is unavoidable! But, it is controllable.
There are (at least) two types of autogen suppression by ground polys.
- The first and easiest to understand is suppression within the bounding box. Whenever a scenery object is placed in FlightSim, autogen is suppressed within its bounding box, that is, the smallest rectangle - oriented in the cardinal directions - that can contain the object. In this context, the object is one or more ground polys. Obviously, if your ground polys are not oriented in cardinal directions, the bounding box will be larger than if they were and extra autogen will be suppressed. To minimize this type of autogen suppression, subdivide your ground polys into groups covering smaller areas - thus creating several much smaller bounding boxes. These groups may be placed in separate files (probably easiest if you are hand-placing the ground polys using FS8 MakeMdl) or by having multiple groups within each layer in the same file.
- The other type of autogen suppression is less well understood. It can result in wide swaths of missing autogen in areas not even bordered by ground polys. But it is definitely caused by the ground polys; remove the ground polys and the autogen returns. This type of autogen suppression can be avoided with the judicious use of the "dummy Scale" command, i.e., a SCALE_AGL command with all its fields set to 0. (For further information on dummy Scale commands and some history on the topic, please refer to this thread. To avoid this type of autogen suppression, a dummy Scale command should be placed at the end of the code block called by each ADDCAT command, just before the BGL_RETURN statement. Unfortunately, use of dummy scale commands can lead to flickering of ground shadows. To avoid flickering, add a block of data and code as you would to place additional ground polys. The associated latitude and longitude references should reflect the entire area covered by ground polys. The layer argument of the ADDCAT command must be a number higher than any layer used by the ground polys. (This implies 62 as the maximum useable GP layer.) The code block called by the ADDCAT command should contain nothing but a BGL_RETURN statement, i.e., no dummy scale command. This autogen suppression prevention block may be placed in the same file as the ground polys or in a separate file. What's important is that it specify a layer number higher than any used by the ground polys.
Don