Re: [Rails-devel] Tile Database API & route calculation

[John A. T. <ja...@ja...>]

Ok, after looking at Iain's code, I propose the following:

Extend the tile XML file to show additional exclusive track use and add 
necessary drawing data:

<Tile id="62" colour="green" category="NY">
    # position/rotation can be defaulted
    <Station id="1" type="City" slots="2" value="80" position="90,.4" rotation="0" />
    <Station id="2" type="City" slots="2" value="80" position="270,.4" rotation="0" />
    # gauge and level are defaulted, use shorter labels for size and parsing speed
    <Track from="1" to="A" />
    <Track from="1" to="F" />
    <Track from="2" to "E" />
    <Track from="2" to "D" />
</Tile>
<Tile id="Map-1841-Milano" colour="yellow" category="M">
    <Annotation text="Milano" size="12pt" position="270,.7" justify="b" rotation="0" />
    <Station id="1" type="City" slots="1" value="60" position="210,.6" />
    <Track from="1" to "A">
        <Excludes from="1" to "B" />
    </Track>
    <Track from="1" to "B">
        <Excludes from="1" to="A" />
    </Track>
</Tile>
<Tile id="23" colour="green">
    <Track from="A" to="D" />
    <Track from="D" to="B" />
</Tile>
<Tile id=16 colour="green">
    <Track from="A" to "C" level="0"/>
    <Track from="B" to "D" level="2"/>
</Tile>
<Tile id="Map-1830-Altoona" colour="fixed">
    <Station id="1" type="City" slots="1" value="10" reservedtoken="PRR" />
    <Track from="E" to="1" />
    <Track from="B" to="1" />
    <Track from="B" to="E">
	 <Draw from="E" to="[210,.25]" radius="-.25" />
	 <Draw from="[210,.25]" to="[300,.25]" radius=".25" />
	 <Draw from="[300,.25]" to="B" radius="-.25" />
    </Track>
</Tile> 

Tile code defaults to the id if it is numeric, otherwise it defaults to 
"", can be overriden with code="603" etc.

Note that for the #23 tile the excludes are automatically picked up 
since the edges overlap.  Since 90% of the gauge will be normal, it 
makes sense to default that attribute (as well as level, which is only 
needed for tiles with overpasses).  The Milano tile shows how extra 
excludes that wouldn't be known just from looking at the connectivity 
information are specified.  The last tile shows how you can specify how 
to draw a particular piece of track if the default choices won't work (a 
negative radius means curving away from the center of the tile, positive 
means curve towards the center; leaving radius out means a straight 
line).  If you are worried about intialization time (and automatically 
positioning elements that don't have a position specified is not a 
trivial task), this file could be built from a master file that contains 
all the tile definitions and filling in all the drawing and other 
defaulted information.  Once you do that, this needs to be considered a 
generated file, but that is a good thing since otherwise you will have 
multiple copies of the same tile data that have to be updated and we 
know that means they won't be exactly the same.

In addition to text annotations, we need to support other annotations as 
well, which would be used to show additional building costs or graphics 
added to the tile.  In my perl code, I just supply arbitrary postscript 
code for them, but that won't work here.  I suggest having something 
like <Annotation shape="xxx" position="a,r" scale="s"/> which references 
shape xxx defined elsewhere, either SVG to draw it or perhaps even 
custom code.

It will be a lot less work to add the excludes that can't be deduced 
automatically than to do all the splitting of junctions into junction 
exits, and the resulting datastructure will be simpler as well.

-- 
John A. Tamplin					ja...@ja...
770/436-5387 HOME				4116 Manson Ave
                		 		Smyrna, GA  30082-3723