Fast&easy quasi-fractal lines in Photoshop?

[Blacky]

I'm looking to draw things like natural cave walls and such, with a mouse, but with a quasi low fractal effect between mouse points. i.e. the ability to draw something like this:
Carto.png
without spending a huge amount of time (and yet controlling the general shape of it, no purely random generator that I do know how).

I'm sure it should be fast and easy, and I'm pretty sure I saw that somewhere, but can't find it now nor can I find the right wording to do a meaningful Google search.

Any ideas?

[madcowchef]

A popular way of going about drawing continents is to do fractal clouds and a threshold layer above it for the purely random look, just adding another, mostly clear, layer above this to draw black and white onto. This will allow you to lay it out yourself or alternately you can just add noise to your initial drawing and then use the threshold adjustment layer to get what you are looking for but I find this not messy enough for me most times. It you aren't familiar with either of those techniques I can point you to one of the tutorials that outline them. Hope that helps.

[Blacky]

Thanks but that's not it. Thresholded clouds are what I used in the image above, I know how to do something purely random like that.

What I would like is to be able to draw lines&curves with the mouse then somewhat “randomize” this drawing, or to place a few point and then fractalize or randomize the drawing between those points. Something akin to the zigzag or the roughen filters in Illustrator (only, better).

Imagine a tactical underground map, where I need to dig several natural-ish tunnels; for example.

[madcowchef]

Here's an example:
Threshcave.jpg
There's the end result
threshcave2.jpg
there's what I drew

All of it took only a couple of minutes and didn't lead too to much mess, but that depends on how quickly you nail the balance (mine is simple 50% on both the fractal and the drawn layer over a black).

[madcowchef]

I'm saying you can use a layer over the fractal layer to draw in your tunnels as simple white lines then use the cloud to act as a randomizer for the edges by adjusting thresholds and transparency. Once you get the balace of fractal/whitelayer/threshhold any line you draw will appear with highly natural edges.

[Blacky]

Yup, still stuck. If you have your psd around I'll appreciate it, and as offered if you know about a few detailed tutorial URLs.

I'm sure I'm missing one stupid step somewhere.

[Blacky]

Ahhhh… Ok!

I understand the theory, seems like a good idea, but I just did a few tests and it seems there's always an issue with the clouds not being precise enough or just at odds with my lines to fully integrate once thresholded.

Do you have an example? Maybe I'm missing something (well, probably ).

Edit: too slow Blacky, too slow

Edit2: gosh, I really need to buy a new brain an eBay. This seems like a very good process, but for the life of me, can't reproduce it. Could you send me the psd you made?

[madcowchef]

If you have too much mess, just draw over in black on the same layer with the white to get rid of the messy parts, the joy of it is its super quick and requires almost no precision.

[Blacky]

Hope that helps

Yes, mostly got it thanks a lot!

My biggest mistake was no using enough softness for my brush, made it a whole lot better. A lot of alpha around the edge, lot of “softness” is required.

A small things, but your clouds are much better than mines (basic clouds or difference clouds). Do you use a plugin for those?

[madcowchef]

threshcave.psd

Hope that helps, I'd begun cleaning up a couple of the stray white sections. Oh and the top layer is just a copy of all the layers merged. Don't know why I even made it, force of habit I guess.