Friday, April 09, 2010

What an Evil Disaster

After about a week of on and off hacking, I have finally knocked down one of the major stumbling blocks to getting WED 1.1 up to beta quality: exporting UV-mapped (texture mapped) bezier polygons that cross DSF borders. It works! Well, sort of.

If you have tried to program polygon cutting algorithms, you can appreciate the difficulty of an algorithm that:
  • Clips polygons robustly (including holes and other weird topology) and
  • Maintains a UV mapping while doing this and
  • Works with bezier curves and not just line segments.
WED now does all three! This was the ugliest and hardest part of the DSF exporter, and a big missing piece from going beta.

Of course, there is one problem: X-Plane can't read the bezier curves.

The problem is a simple defect in how X-Plane manages DSFs.
  • A valid bezier polygon, fully inside the DSF tile, may have control handles that go outside the tile.
  • X-Plane can't handle any DSF coordinates outside the tile.

I am not sure what I will do about this, but in the short term, I fear X-Plane will remain limited. Probably the best short term option is to have WED at least flag such problematic bezier polygons; it is possible to approximate them or edit them to make the export work.

There is still a little bit more exporter code to write, including the line segment exporter (which is separate from the polygon exporter), but with luck the whole DSF export path should be cleaned up in the next few days.

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