Making Mountains in GIMP

[waldronate]

What Photoshop calls an angular gradient is exactly that: a gradient where the intensity represents the angle around the center point. It's basically the other half of the 2D polar coordinate representation (radial gradient is the first).

What GIMP is calling an "angular gradient" is what image processing folks would call an EDM (Euclidean distance metric) filter. It returns the distance from the edge of the shape.

There are plugins for Photoshop that will do what GIMP does, but the ones that I could find all seem to be part of expensive image processing plugin suites.

Wilbur will do this sort of thing (draw your selection, then use Select>>Modify>>Distance to calculate the gradient and Select>>Save Selection to save it as an image), but if you're going to involve an external tool you might as well just use GIMP.

[ravells]

Thanks a million Waldronate. This is an incredibly useful tool. I tried to replicate it using Drawplus (a Xara type vector drawing proggie) and posted a request on their BB, but no dice so far except for an approximate fix by making a smaller contour of the object and then feathering the result.

[RobA]

Yep. Like Waldronate says.

In Gimp, what photoshop calls angular is called COnical (and there are two.. your example would be asymmetrical. There si also symmetrical, which uses the gradient over 180 degrees and its mirror on the other half).

I was clear in one or two places, then started to shorthand. The fill for the mountains was "Shaped (Angular)" There is also "Shaped (Spherical)" and "Shaped (Dimpled)". ALl three of these have the gradient painted perpendicular to the selection outline.

A way that mmight work to manually do it in PS (at least in greyscale) would be to determine the maximum distance across the selection (perpendicular) call it D. Start with a black background, set paint to white with an opacity of 1.

Shrink the selection by (D/255) and fill the selection... repeat until no selection left....

Try it as an action....
-Rob A>

[su_liam]

Nice. Very useful now. I've been playing with a little java app that does the distance filter thing. I'll rep you if it lets me.

edit:
Yay. It let me.

I'd move over to gimp altogether except for three things:
a)8-bit. I work a lot with 16-bit greyscale. I'd rather have double-precision float, but hey, reality.
b)Pen support. I can use my pen and tablet with gimp, but I can't get pressure sensitivity to work. This may be an issue with Apple's implementation of X11, but that's what I have...
c)Photoshop's more sophisticated brush attributes.
d)I know enough about Photoshop to make it dance. Learning curve is an issue.
e)Large-window greyscale erode and dilate. Only works on selections and they call it Grow and Shrink or some such, but a radius 3 Shrink is the same as a 7x7 dilate. Gimp only has 3x3 erode and dilate filters. Prettier, ultimately, but slower.

Hmm... I guess that works out to five.

[RobA]

And gimp also has:

Mathmap and Gluas to write your own (albeit slow running) filters!

-Rob A>