How do I create multiple lines vanishing in a spiral

[jond]

I've looked through several twist and spiral discussions, but most are so old that all the pictures and links are long gone.

 

I am trying to create an image like looking down a gun barrel or the spiral in the movie "Vertigo".

 

Here's an example of what I'm trying to do that I found online:

 

And advice?

 

Thanks in advance!

 

[Ego Eram Reputo]

1. Make sure your canvas is larger than the finished image, as you 'll probably want to crop the edges later on.
2. Run this plugin [Light Rays] over a blank canvas. When installed it resides in Effects > Texture > Light Rays. You'll want to reduce the number of light rays to 20 or less.
3. Run Effects > Distort > Twist with size and Amount/Direction setting to suit what you want. NB this is a built in effect - not a plugin.
4. Crop the image to remove the ends of the rays where they begin to 'flatten out' (red box is a guide)

 

[frio]

For more precise control over the amount and style of twisting, you can get mathematical with G'MIC-Qt and its Polar Transform filter.

 

After rendering some Light Rays as above:

Run Advanced->G'MIC-Qt->Deformations->Polar Transform. Choose Custom Transform with Radius=0.8*r and Angle=a+3*(w/r)^0.5, Boundary=Nearest. This gives you a twist that gets "tighter" towards the middle than the built-in Twist filter.

By adjusting the angle formula, you can create other kinds of twists - you can try changing the multiplier (3) or the power (0.5) to change how the angle evolves away from the center. As an example, Angle=a+16*(w/r)^-2 (left) and Angle=a+-3*(w/r)^0.25 (right):

Using power -0.5 appears to mostly match how the built-in Twist filter works, for the record.

Edited October 22, 2023 by frio

[G'MIC]

Super cool @frio, well done.

I think the whole process would make a cool new filter in the G'MIC-Qt plug-in !

Edited October 23, 2023 by G'MIC

[jond]

Thanks a bunch. This is exactly what I was looking for.

[G'MIC]

Here it is, I've added a new filter in the G'MIC-Qt plug-in, named Rendering / Twisted Rays.

It should cover most of the case @frio described in his post.

 

And with a bit of scripting, you can render nice animations too 😁

 

I hope this will be useful for someone!

[BDP]

Just done an update to my G'MIC filters - the interface for the Twisted Rays looks very different to the one posted above - a lot more options, and multi-language! Just not the same at all . . .

 

Brian

 

[G'MIC]

24 minutes ago, BDP said:

Just done an update to my G'MIC filters - the interface for the Twisted Rays looks very different to the one posted above - a lot more options, and multi-language! Just not the same at all . . .

 

Brian

 

 

That's because there were already a filter named "Twisted Rays" by someone else, which has been renamed to "Twisted Rays [Samj]".

Press the "Filter Update" button to get my newest version.

[BDP]

Thanks for replying - pressing Filter Update just leaves the filter by 'samj, which is called Twisted Rays - no new one

 

Brian

 

[null54]

18 minutes ago, BDP said:

Thanks for replying - pressing Filter Update just leaves the filter by 'samj, which is called Twisted Rays - no new one

 

That is because the Paint.NET G'MIC plugin is outdated, it is still on 3.3.0. I will have an updated version out soon.

I missed the release notification post for version 3.3.1 on the G'MIC forum.

[BDP]

Thank you. It's not important to my life - I just like to try the new stuff!

 

Brian

[G'MIC]

2 hours ago, null54 said:

 

That is because the Paint.NET G'MIC plugin is outdated, it is still on 3.3.0. I will have an updated version out soon.

I missed the release notification post for version 3.3.1 on the G'MIC forum.

 

Hello Nicholas,

Is there something I can do to help passing the info more easily?

[null54]

42 minutes ago, G'MIC said:

Is there something I can do to help passing the info more easily?

 

I was looking for the 3.3.x release updates in the Release of G’MIC 3.3, not the On the road to G’MIC 3.4 thread by mistake.

 

Would it be possible for you create a GitHub release with the specified tag when releasing a new version?

That would also let you use GitHub as one of the download mirrors for the various G'MIC binaries.

 

GitHub does not (yet) send notifications for new tags that are pushed to a repository, it only sends them when the developer creates a release for a specified tag.

I subscribed to GitHub's RSS feed for the GMIC repository tags, so that will make it easier to see when a new tag has been pushed.

[G'MIC]

52 minutes ago, null54 said:

 

I was looking for the 3.3.x release updates in the Release of G’MIC 3.3, not the On the road to G’MIC 3.4 thread by mistake.

 

Would it be possible for you create a GitHub release with the specified tag when releasing a new version?

That would also let you use GitHub as one of the download mirrors for the various G'MIC binaries.

 

GitHub does not (yet) send notifications for new tags that are pushed to a repository, it only sends them when the developer creates a release for a specified tag.

I subscribed to GitHub's RSS feed for the GMIC repository tags, so that will make it easier to see when a new tag has been pushed.

 

OK, I will do that from now.

The issue with github "releases" is that it requires a tag, and for G'MIC, the code in the github repository is not exactly the same as the .tar.gz file we provide on the website (in it, we add additional generated files that are actually required to compile G'MIC properly).

[null54]

4 minutes ago, G'MIC said:

The issue with github "releases" is that it requires a tag, and for G'MIC, the code in the github repository is not exactly the same as the .tar.gz file we provide on the website (in it, we add additional generated files that are actually required to compile G'MIC properly).

 

Interesting, what are the generated files?

I build G'MIC-Qt from the tagged GitHub releases of G'MIC, but I have to generate the G'MIC-Qt translation files using a separate pre-build step.

[G'MIC]

1 minute ago, null54 said:

Interesting, what are the generated files?

 

For instance, src/gmic_stdlib.h and src/gmic_stdlib_community.h, and also all the gmic-qt folder that is present in our .tar.gz archive

(will the translation files auto-generated).

 

[null54]

13 minutes ago, G'MIC said:

For instance, src/gmic_stdlib.h and src/gmic_stdlib_community.h, and also all the gmic-qt folder that is present in our .tar.gz archive

(will the translation files auto-generated).

 

That makes sense, my pre-build setup also handles downloading those G'MIC headers.

I think that most people who would download the automatically-generated 'Source Code' files from GitHub's releases will understand that it is the same code you get when cloning the repository, and that some additional setup may be required before building the code.