This tutorial is very much based on EK22's air bubbles technique.
My initial idea was to create text made of bubbles, but that would not have been possible without Rononour's fantastic 'Pack sprites' G'MIC filter.
So a big thank you to both of you !
create your canvas, i used 800x600px white
type and align your text, a rounded bold font works probably best
i used Valken 300px
alpha select your text and save to a channel for future use, then delete the text layer
with the selection still on, activate the background layer and press delete – this will be our mask
next fill the mask with a few big bubbles
use a round brush in a medium 50 grey (#808080)
make sure the dots dont overlap the mask and position them in a way, so smaller bubbles will have enough space around the big dots
create a new transparent layer on top of your mask and fill it with one smaller dot, i used a 25 brush size
go to G'MIC → Pattern → Pack Sprites
i used all the default values, except for 'Masking', that has to be set to 'Mask as bottom layer'
set 'Input layers...' to 'All' and 'Output' to 'New Layer'
we now want to get rid of the white mask, so with the new layer active, call up the basetext selection from the channel, Shrink by 1, Invert, then hit Delete
also add a (blue) background
alpha select your packed bubbles and save the selection to a channel
(deselect) then activate the channel and blur by 5
(if you dont like bumpmapping with a channel for some reason: duplicate the packed bubbles layer, lock the alpha channel, drag white over it, unlock the alpha channel and blur by 5 – that gives you the same bumpmap)
Bump-map your grey bubbles layer with the blurred channel as the bumpmap
i set the Azimuth to 90°, because im going to make underwater bubbles, so the sun/light is above the water
set the Elevation to a value that gives a strong highlight (i used 20)
a Depth of 4 was enough for my taste but the shadow was bit strong so, i changed the 'Ambient' to 65 (btw, this is all stuff i learned from ChrisF's Cookie tutorial)
as a backup, alpha select the bubbles, save to a channel, then apply a 'Colour to Alpha' with the medium 50 grey to your bubbles layer – we want the shadows and highlights isolated
now we work on the 3D effect
duplicate the packed bubbles layer
we want one layer with the shadows only, and the other layer with the highlights only
so we apply a 'Colour to Alpha' with white on one layer and another one with black to the other
duplicate the highlight layer, blur by 3 and tighten it with an alpha curve, for a nice crisp light
set the shadow layer Mode to 'Grain Merge', then duplicate and invert the colour of the upper layer
reduce the opacity of the dark shadow to 70% and the light to 83%, or whatever you think looks good
depending of what effect you are going for, you can change to Mode of the original (non tightened) highlight, to 'Soft Light', 'Grain merge' or leave it at 'Normal'
In 'Normal' Mode you get a very strong white. In 'Soft Light' Mode it looks all very soft and picks up the background colour. In 'Grain Merge' Mode you get a stronger white, but still with the blue being integrated.
I liked the 'Soft Light' best, but duplicated the tightened highlight to make it stronger
depending on what you want, you can also add a dropshadow, that is knocked out by the layer
so add a new transparent layer on top of the BG
activate the saved bubbles selection and fill it with a dark colour (#072666)
deselect, then blur (i used 5)
maybe offset 1px down, then apply an inverted layermask from the bubbles channel
i set the mode to 'Burn' and reduced the Opacity to 15%
thats it for the 3D shaping
now comes the decorating part
add a gradient black (or very dark blue) to transparent, from the bottom of the canvas to the bottom of the text
repeat until happy or manipulate with an alpha-curve
duplicate the BG and put it on top of the dark gradient layer
go to G'MIC → Light & Shadow → Light patch
i used default values except for the 'Density' → 10
set the Mode to 'Soft Light' reduce Opacity to 40% and apply a white layermask
paint a gradient from black to white on that mask, to make the Light Patch fade out into the darkness
for some lightrays i duplicated the white shadow layer, put it on top of all layers, then applied G'MIC → Light & Shadows → Light Rays
set the mode to 'Screen' (with Opacity at 20%), then dragged the center of the rays to the top of the canvas and smudged the visible border with the Smudge Tool
you can add Solid Noise on top of the layers at default values, then apply G'MIC → Deformations → Rain Drops and set the Mode to 'Soft Light' for some water texture
14. or you can add some different bubbles
ChrisF has posted a video on how to create liquid and bubbles here, but its in german....
....basically you paint bubbles with the sparks brush, then desaturate (luminosity) and apply an alpha-curve
change Mode to 'Grain Merge' and reduce Opacity to 30%
Thats the basic underwater effect.
As you can see, you can do a lot more with that basic effect:
Filling the bubbles with a colour changes them to shiny pearls.
Here i tried to go for a daylight version with iridescent highlights made with a rainbow gradient on repeat.
If you want to study what i did, here is the XCF
If you want to study what i did, here is the XCF