1. ## March Challenge Entry - Map of Canada

Wow, I hadn't even noticed my challenge suggestion had been selected. Well, it just so happens I began work on a map that fits the theme without realizing it. I did actually start after the challenge was announced, I just didn't notice it until now.

### Latest WIP ###

Yes, there's a bunch of colour now, but that's just for for while I work in QGIS.

2. This is a completely different symbolization from How I'll be doing it in the end, but for now, here it is in pure black and white.

### Latest WIP ###

There seems to be a bit of a glytch wit the mountain symbol when it goes through the print composer, but it doesn't really matter as I'll be redoing the symbols later anyway.

3. Here's a test run of the stippling algorithm with 20000 points and 20 iterations. It took several hours. I may have to come up with a more efficient way to do this.

4. Originally Posted by Hai-Etlik
Here's a test run of the stippling algorithm with 20000 points and 20 iterations. It took several hours. I may have to come up with a more efficient way to do this.

What algorithm is that? That looks very interesting to me in regards TreeThing.

5. Originally Posted by Ramah
What algorithm is that? That looks very interesting to me in regards TreeThing.
Seed the space with points
Compute a voronoi diagram from the points
Clip the diagram to a mask polygon
Find the centroids of the voronoi cells
Use the new points to generate a new voronoi diagram
Repeat

You can substitute in a weighted centroid function based on a density function (Like a greyscale image) to vary the density. I've implemented that as well, but it's even slower still.

An earlier thread on the topic is here: http://www.cartographersguild.com/sh...ling-using-JTS

6. Have you ever played with a program called "scree painter". I haven't actually tried using it but it might give a similar effect.

http://www.screepainter.com/index.html

7. Originally Posted by cereth
Have you ever played with a program called "scree painter". I haven't actually tried using it but it might give a similar effect.

http://www.screepainter.com/index.html
Not sure I could get quite what I'm after out of that, but it does look interesting. Switching to an error diffusion algorithm like they use might be better in the long run than my current centroidal voronoi algorithm.

I'm currently running it for all forested biomes with trees spaced at 7km. Over the whole map that's over 150,000 tree symbols eventually.

I've switched my initial seeding from random to a triangular lattice with some jitter. That sped up the seed phase and hopefully won't need as many iterations of the voronoi algorithm. I'm going with 5 iterations this time.

8. I see from your other thread you were working on using this method to make a program that places trees etc. Very interesting.

9. I love your sense of experimentation, Hai. I hope you get the stippling program sorted soon!

10. Originally Posted by ravells
I love your sense of experimentation, Hai. I hope you get the stippling program sorted soon!
Thanks. It's not any faster, but I have made some code improvements. In particular, the codebases for weighted and unweighted stippling are now combined.

Here's the latest output loaded into QGIS

### Latest WIP ###

I've tossed together some better looking symbols, though ultimately this is going to need a whole bunch of different ones. The mountains also need to be sorted by y coordinate.

A large area of forest around the great lakes disappeared while I was trying to clean up my geometry a bit and I didn't notice until I was several hours into a run through the stippler. I've run with it for now to see how things are looking.

I probably need to increase the size of the buffer around lakes and rivers a tad, and reduce it around mountains.

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