Can I use ripple to create 2 point wave interference

[ravel]

Hi Everyone,

As above.

Can I make a 2 point wave interference pattern using the ripple filter? I tried to attach an to this but so far haven't been able to.

Thanks for any help,
Tim

[Hoogo]

Something like this?

[ravel]

Yes!! It's very close

My idea is to have an image appear as though looking down through water to the ocean floor below of which the photographer's feet have JUST penetrated the surface and created said interference pattern. The ripple filter / effect is precisely what I want except it has a single wave orign instead of two, creating the interference pattern.

Tim

[Hoogo]

What about applying the ripple-filter twice? You can select the center yourself, but unfortunately not the size.

I'm thinking about "Shape tools > distort image with image". Copy a gauss-blurred version of the 2 circles into the clipboard, call the filter, paste it there and play with the sliders.

But there should be more realistic solutions with "Shape tools > distort image with image". But I have to think a little more about it.

[bkh]

The ripple filter / effect is precisely what I want except it has a single wave orign instead of two, creating the interference pattern.

In principle, you only have to apply the ripple filter twice, with different center points. (After all, you are just dealing with a superposition of two waves.)

(EDIT: Deleted)

"Distort Image With Image …", as suggested by Hoogo, would also work — you'd have to create a circular gradient representing the height of one wave pattern (128 = normal waterline). Fill two layers with that gradient and put them on top of each other with the center points at the right positions and set the intensity of the top layer to 50 %. Merge the layers (or just make a merged copy) and use that layer for "Distort Image With Image …"). The advantage here is that you could use a relief filter on the merged waves layer to create a layer to simulate light or reflections.

Cheers

Burkhard.

[Hoogo]

The only problem is that the ripple filter doesn't allow you to set the center point of the ripple effect.

There's a little crosshair beneath the preview of the ripple filter. That's for setting the center.

[bkh]

The only problem is that the ripple filter doesn't allow you to set the center point of the ripple effect.

There's a little crosshair beneath the preview of the ripple filter. That's for setting the center.

Thanks, that makes things a lot easier … didn't see it because it's only visible if you switch the preview on (but even if the preview is off, you can click into the main image to set the center). I should have checked the manual

Cheers

Burkhard.

[Hoogo]

I think I've got it. But you need some manual steps, the relief only works for small spirals, and I have not found a way to solve that.

-Place the spirals as you need them
-Ctrl+Shift+C, Ctrl+Shift+E. You now have a new document with a map
-"layer > rescale layer", rescale it to the needed size using bilinear interpolation
-Ctrl+C to copy the result into the clipboard.
-Use it in the "distort picture with picture".

I've chosen slightly different scalings for the 2 spirals, that gives a cooler effect.

[ravel]

That's AWESOME!!!

You've created a real physics phenomena of the spider effect which happens when the wave source/s are accelerating. I JUST read about it in doing my image search for the project.

I hadn't yet found the distort with image, but I assume it's like a "bump map" in 3D? In any case that would allow me to take an actual wave interference photo and use it as the distortion image over the based image.

Thank you so much for nailing it so fast, now I have to find / render a mermaid swimming up towards me to put under the waves

Tim

[Hoogo]

I hadn't yet found the distort with image, but I assume it's like a "bump map" in 3D? In any case that would allow me to take an actual wave interference photo and use it as the distortion image over the based image.

At least it's like the bump mapping we used in the 90's on our 8Bit Commodore64. Looks quite 3D, but is only 2D with some variable offset for each pixel. Don't know what real bump map is.

Creating this map of offsets from a real photo could be difficult, but maybe using the relief like I did should look good enough.

[bkh]

You've created a real physics phenomena of the spider effect which happens when the wave source/s are accelerating. I JUST read about it in doing my image search for the project.

Similar phenomenon, but a different cause – in this case, it happens because Hoogo used spirals instead of concentric circles …

waves-height map.jpg

waves-light.jpg

In any case, here's my version of the simulation – in the PLD, grab the "second wave source" layer and move it around …

EDIT: works best in 16 bit mode.

Cheers

Burkhard.

[Hoogo]

Similar phenomenon, but a different cause – in this case, it happens because Hoogo used spirals instead of concentric circles …

I think it's because I've scaled the 2 spirals differently.

In any case, here's my version of the simulation – in the PLD, grab the "second wave source" layer and move it around …

But how to convert the height map into a map for the distort filter?

[ravel]

This is great, now I have virtually everything I need.

Hoogo, I suspect it's because yopirals. A moving wave source will create a series of concentic rings, but displaced in the direction of motion and so resembling a spiral.

A real wave source is exactly as bkh did in his version. The waves from a single source can probably never cross a previously emitted wave, but i think two spirals OR moving sources both produce the spider effect.

Wrt a bump map, it's any image who's pixel values are used to control the displacement amplitude of the surface of a 3d model. So adding a gray scale image of wood grain to a 3d model would give it actual grain perpendicular to the model's surface, so I think it has the same effect visually use image to distort in Photoline.

[Hoogo]

Hoogo, I suspect it's because yopirals. A moving wave source will create a series of concentic rings, but displaced in the direction of motion and so resembling a spiral.
A real wave source is exactly as bkh did in his version. The waves from a single source can probably never cross a previously emitted wave, but i think two spirals OR moving sources both produce the spider effect.

Maybe I don't know exactly what the spider effect means. Is it the asymmetry in the interferences? That goes away when you have a look at the scaling in the attributes-dialog for the spirals. I've used ~130% and ~140%, and if you set both to the same value, the interferences are symmetric again.

I had tried gradient and curves first, as Burkhard did, but then I had the idea that a spiral would be close enough to a circle, and that the topic is mainly about the frequencies and not about the exact positions.

Wrt a bump map, it's any image who's pixel values are used to control the displacement amplitude of the surface of a 3d model. So adding a gray scale image of wood grain to a 3d model would give it actual grain perpendicular to the model's surface, so I think it has the same effect visually use image to distort in Photoline.

Is it the same as a displacement map? I have seen a bump map as kind of fake height map. Different heights would not create any effect when you look in a right angle onto the suface.

Another idea about the lighting and the height map:
The layer effect "special emboss" can use a pattern as a height map for lighting. Move the picture with the height map into the pattern list, and you can use it in the effect.

Too bad that you can't load that xy-map into a liqify-layer.

[bkh]

But how to convert the height map into a map for the distort filter?

You don't have to convert it – when using a simple 3D model, a pixel h units above the plane is displaced in x and y direction by factors proportional to h, where the factors depend only on the viewing direction. So you just use the height map directly in the "Distort Image With Image …" dialogue and set the x and y scaling factors according to the viewing direction.

Cheers

Burkhard.