Spiral ridge

avgcivilian · **Joined:** Oct 02, 2014 **Posts:** 14

I am trying to replicate a texture found on Marshall amplifier radio knobs (see picture below:

I can handle the colorization and conical reflection overlay, but I am having trouble figuring out how to draw a crisp, tight spiral. Would like to keep the width very narrow (~3 pixels), and then bump it just a tad so that it bears a raised effect.

I've tried doing gradients with several dozen bars, but the sender of the spiral doesn't quite look right (i.e., several lines come together for the center as opposed to a single line spiraling outwards).

Thanks in advance for any help.

molly · **Joined:** Apr 07, 2010 **Posts:** 14182

I think he is trying to make the texture that is shown on the radio knobs.

lylejk · **Joined:** Sep 24, 2010 **Posts:** 12516

Gave it a try using concentric circles generated using generate new paths python plugin and conical gradient target as a target displacement layer.

saulgoode · **Posted:** Mon Mar 30, 2015 9:50 am **(#4)**

I would not consider it a spiral, but instead a series of equally-spaced concentric rings.

For this I might suggest using the Blend Tool with settings such as the following (click on image to go to download page).

And then draw a short stroke of about 3 or 4 pixels on your image to create the gradient, followed by an application of the Bump Map filter (bump it to itself).

Attachment:

rings.png [ 70.91 KiB | Viewed 4653 times ]

Rod · **Joined:** May 16, 2010 **Posts:** 14709 **Location:** USA

There is a script here. It is actually fill selection with concentric selection.

viewtopic.php?f=9&t=6923

Works ok in GIMP-2.8.14

My settings

avgcivilian · **Joined:** Oct 02, 2014 **Posts:** 14

Thanks, all.

The notes in concentric circles are very helpful. Thank you!

I am trying to be fully authentic to the real-life dial. The texture is actually spiral and not concentric. If there isn't a way to do this, I can probably live with concentric circles. If I don't seen this out, the virtual dials (with concentric circles) will always silent mock me. :-).

MareroQ · **Posted:** Mon Mar 30, 2015 1:28 pm **(#7)**

Gimp shape creator

http://registry.gimp.org/node/32342
http://www.arakne.es/en/dessign/gimp-python-script-shape-creator-shapes/

avgcivilian · **Joined:** Oct 02, 2014 **Posts:** 14

Gold star to MareroQ. Cheers all!

molly · **Joined:** Apr 07, 2010 **Posts:** 14182

saulgoode wrote:

I would not consider it a spiral, but instead a series of equally-spaced concentric rings.

For this I might suggest using the Blend Tool with settings such as the following (click on image to go to download page).
[ Image ]

And then draw a short stroke of about 3 or 4 pixels on your image to create the gradient, followed by an application of the Bump Map filter (bump it to itself).

Attachment:

rings.png

Thats cool Saul... looks like a real metal disk with the raised ridges.

RobA · **Joined:** Jul 14, 2010 **Posts:** 697

Here is a crazy way!

Fill a layer with your base colour:

Attachment:

s1.png [ 1.28 KiB | Viewed 2361 times ]

Create a new layer, and set the blend (gradient) tool like so:

Attachment:

s2.png [ 18.33 KiB | Viewed 2361 times ]

then with the gradient tool, pull a 3 px horizontal line, and change the layer mode to overlay. Pretty cool, eh?

Attachment:

s3.png [ 331.47 KiB | Viewed 2361 times ]

but it gets even better.....

RobA · **Joined:** Jul 14, 2010 **Posts:** 697

Now right click on the overlay spiral, and pick "Add Layer Mask" and make it a greyscale copy of the layer:

Attachment:

s4.png [ 257.64 KiB | Viewed 1310 times ]

Looks worse? Never fear!

Now use the Move tool, set as Move the active layer and select the MASK in the layer palette, and use the cursors to nudge the mask around to get the effect you want...

Attachment:

s5.png [ 333.31 KiB | Viewed 1310 times ]

And you can keep duplicating the overlay spiral and nudge the mask around differently to build up different effects:

Attachment:

s6.png [ 454.88 KiB | Viewed 1310 times ]

-Rob A>

2-ton · **Posted:** Tue Mar 31, 2015 8:41 pm **(#12)**

...and you can scroll up and down this page and get some interesting movement effects, lol

avgcivilian · **Joined:** Oct 02, 2014 **Posts:** 14

Bravo, Rob! I'll post my finished product with this technique.

avgcivilian · **Joined:** Oct 02, 2014 **Posts:** 14

avgcivilian wrote:

Bravo, Rob! I'll post my finished product with this technique.

I realized I never posted my image. Thanks again to all for their help.

Rod · **Joined:** May 16, 2010 **Posts:** 14709 **Location:** USA

avgcivilian wrote:

Bravo, Rob! I'll post my finished product with this technique.

I realized I never posted my image. Thanks again to all for their help.

[ Image ]

Thanks for finally posting your results. lol. =)
Looks really good.