[mapguide-users] Re: MgCooker: bad performance, I can't use it. Help!!!

[Jackie Ng]

I was not the original author of MgCooker, so I cannot explain why the
"official method" is not (you know) the default method.

Anyway, the meters-per-unit value is important because it factors into scale
calculations and rendering. A bad or incorrect meters-per-unit value will
cause serious distortion in rendered images, and will throw the number of
tiles needed to be rendered into disarray.

Now why do you have to manually put this value into MgCooker? Because
MapGuide not expose an API to calculate MPU over the http mapagent! So you
have to calculate this value by yourself, or you can just download this MPU
calculator script I just uploaded.

http://trac.osgeo.org/mapguide/wiki/CodeSamples/PHP/MPUCalculator

Using the Sheboygan tiled map as an example:

Default method: 375k tiles @ approx 4hrs
Official method with MPU of (111319.49079327 calculated by the script): 20k
tiles @ approx 10 mins

As to what the official method actually is? I see references to this thread
in the MgCooker source code:

http://osgeo-org.1560.n6.nabble.com/Pre-Genererate-tiles-for-the-entire-map-at-all-pre-defined-zoom-scales-td4207405.html

This is probably the math for the "official" method.

Note that there's a UI bug in MgCooker where the MPU field has maximum
allowed value set to 10000 meaning you can't enter an MPU greater than this
value. I'll put up a patched MgCooker exe soon for 4.0.1 that fixes this.
The next 5.0 beta will have this fixed as well.

- Jackie

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