[FS2004] Polygon concave

[Buite]

Is FS2004 able to use concave Polygon?

All my convex polygon are good in TmfViewer but all my concave polygon are bad, so I think probably FS2004 doesn't use concave Polygon.

[Buite]

It's ok I've fund my problem.

[hcornea]

Always good to share the solution, having asked a question.

It might just help someone else.

I'm still unsure about what convex vs concave polygons might be.


Sent from my mobile .. words substituted by iPhone at will.

[Golf-HotelDelta]

Originally Posted by hcornea

I'm still unsure about what convex vs concave polygons might be.

Think of a "V" shape (concave) versus an "O" shape (convex).

[Buite]

I had just forgive one point, so I hadn't the right number of point and TmFViewer want the right point's number.

[hcornea]

Originally Posted by Golf-HotelDelta

Think of a "V" shape (concave) versus an "O" shape (convex).

Yes, I believe I know what the words mean, having more than a rudimentary understanding of optics (!) just not sure how they relate to land polygons (which in my brain are either sloped or flat -- this may, of course, be an FSX thing)

[rhumbaflappy]

All polys in FS2004 should be convex, otherwise the edges of the poly might fold over on itself. Ideally, all polys would be triangles, thereby forcing convexity.

http://en.wikipedia.org/wiki/Convex_...ambiguation%29

Dick

[hcornea]

Interesting Dick. I guess I had considered all poly's to be flat / triangulated things.

Since you can only define an "edge" i hadn't really considered any other shape.


Sent from my mobile .. words substituted by iPhone at will.

[Golf-HotelDelta]

In FSX, vector polygons need be neither flat nor convex.

[hcornea]

So ... a concave polygon is defined by having a point lower than its two neighbouring points ... the induced depression producing (at least in theory) a concavity.

Hmm ... it is a moot point for me as I don't develop for FS9 at all.

It seems to me that this is the only concave shape that you could define by edge-vertices alone.

[rhumbaflappy]

Concavity was quite an issue when drawing VTP or LWM polys for FS9. Luis Sa spent a bit of time coming up with code in SBuilder to triangulate the polys so they would not have concave shapes. I don't believe Luis' code is 100% all the time. FS9 doesn't allow holes either. I do note that there are some default concave shapes in the default LWM polys... but nothing complicated. The assembly code doesn't prevent it, but the display engine can get "confused" by it.

In FSX, Shp2Vec handles the code, and does a great job of eliminating the problem.

Dick

[Golf-HotelDelta]

Originally Posted by hcornea

So ... a concave polygon is defined by having a point lower than its two neighbouring points ... the induced depression producing (at least in theory) a concavity.

No.

It seems to me that this is the only concave shape that you could define by edge-vertices alone.

How about this top-down view? It is a 'concave' shape with different heights at each vertex.