Post by iconPost by Vigilante | 2009-06-08 | 18:02:30

I wonder if you might say a few words about comparing accuracy of maps used by VORG, VRTools, and Zezo? I'm sure ZeZo's are the most accurate, and VRTools' are the least. But a relevant question is how safe are Zezo's coast lines as far as how VORG renders its coastlines?

commenticon 3 Comments
Post by iconPost by zezo | 2009-06-08 | 18:33:59
I use the GSHHS shoreline data provided by noaa.gov.

The game and VRtool probably use the same or similar dataset, with what you see in the game interface being converted from straight lines to curves and probably less accurate.

Now the differences. GSHHS comes in 5 different resolutions, ranging from few meters to few kilometers. The better resolution you use, the slower things get. VRtool and the game use vector charts and can not afford the full resolution data. The display charts at zezo.org are rasterized from the full data as one-time operation that takes half hour and 4 Gigs of RAM, and should be the most accurate indeed.

The ground collision detection is different story. You can not afford using vector data for that, so it's always raster. I don't know what the game uses, but I've decided on 4 minutes of arc/pixel. That makes a 1620000-byte 1-bit bitmap file.

The different vector and raster resolutions explain the ghost islands in the game.

There is one related issue. The optimizer will suggest different distances to ground in different winds. Game and simulation are run in steps, and the VOR(G) boats can make between 0 and 5 miles in the 10-minute step in different winds.

The algorithm checks every possible position against the bitmap, and discards it if it finds it's on land.

There is another reason for not having too fine collision raster. You can jump over anything smaller than few miles in the 10-minute step - that leads to all the 'boat with wheels' accusations in the game. That can be easily avoided with few intermediate position checks, but one additional check will slow the optimizer down 2 times, and is therefore impossible for the online version.
Post by iconPost by Vigilante | 2009-06-08 | 18:59:23
Extremely helpful! More than I expected!
Post by iconPost by zezo | 2009-06-08 | 19:08:10
There is a series of articles on the game physics and the optimizer itself waiting to be written or copied from private emails. That was one more reason for creating this 'blorum'.
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