Re: [Therion] Scale and Base-scale and font sizes

[Martin Budaj]

On Thu, 18 Aug 2005 00:10:01 +0100, Wookey wrote
> I used to have 
>  scale 1 2000
>  base-scale 1 1000
> 
> in my layout. That worked OK, but the symbols were very small and 
> the text was microscopic.

They were printed in 1/2 size because of base-scale setting.
 
> So I added 
>  code metapost
>  fonts_setup(10,16,20,24,28)
> 
> And that made the text a sensible size.
> 
> I just changed base scale to read
> base-scale 1 2000
> 
> which makes the symbols a much more sensible size, but makes the 
> text too big.

If the base-scale is equal the scale, it has no effect (such as 1:1 photocopy)
. The text was large because of your fonts_setup setting.
 
> My understanding of these two values is that scale sets the scale of 
> the output (i.e how big the final PDF sheet is in map mode, or how 
> many sheets in atlas mode) , whilst base-scale 'has the same effect 
> as if the map printed in base-scale would be photreduced to the 
> scale' (quote from thbook)

You may forget the base-scale if the default settings work well. We introduced 
the base-scale to make it possible to do simple adjustments to the size of 
symbols used without the need of metapost programming (e.g. when symbols 
appear too big in the 1:400 scale, but OK in 1:200 scale, it's enough to set 
base-scale 1 200 and scale 1 400 and I get map in 1:400 scale with symbols 
proportionally as large as on 1:200 map)

> But if it was photoreduced then the fonts and symbol size shouldn't change.

I think photocopy 1:2 changes everything to be 1/2 smaller

> So I am confused about how this should work. When would I ever want scale
> and base-scale to be different? Why does changing base-scale effect 
> the size of symbols and text?

See above. If therion gives you suitable symbol sizes, use only scale setting. 
If not, experiment with base-scale or redefine metapost.

> On a related point I tried doing an atlas version with the defaults (i.e.
> 1:200) and get loads of 'number too big errors' from metafont.
>
> I can see why such a scale is a problem in map mode (page larger 
> than PDF can manage), but in atlas mode the page size is limited to 
> A4 (or whatever) - so why can I not print an atlas (with a lot of 
> sheets) showing the system in high detail? Is it a fundamental 
> problem of the way the PDFs are generated or can it be fixed?

An additional limitation is the size of a picture, which can metapost process 
-- it's about 2.8 m. Each scrap is processed separately in one picture, so it 
means, that each scrap must be smaller than 2.8 * 2.8 m _in the output scale_. 
I don't think it's a big issue unless you try to draw the whole cave in one 
scrap. (At 1:100 scale a scrap can contain 280*280 m section of the cave). 

Atlas size (and SVG map size) is unlimited.

Martin

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