Imaging in Chaotica - Part 2: Response Curves

7 min read
tatasz's avatar
By tatasz
25 Favourites
Today, a bit more about imaging in Chaotica.
Mostly curves <3


Lets take a closer look at curves:

1 Curves by tatasz


Curves basically re-map the brightness values: for example, make bright pixels brighter or darker by just adjusting the curve.

3 What by tatasz

The horizontal axis is the original brightness (before editing), while the vertical is the new brightness. The tones are distributed as follows: dark tones closer to the origin, and light tones far from the origin.
The image above shows the curves before any changes. See that before and after values are equal, since no changes were made yet. 

Basically, if you drag a node up, lets say, it will make the corresponding tones brighter. For example, dragging up the top node (light tones) will make highlights brighter, and dragging down the bottom node (dark tones) will darken the dark areas. On the example below, we will brighten up the midtones too:

Curves by tatasz

See how editing the overall curve increases the contrast of the fractal and hightlights the cloudy shapes.

That is the Overall curve. You can also edit the RGB and Alpha curves (use the channel menu to select one). If you want to remove all changes, use the Reset button.

5 Other Colors by tatasz

Red, Green and Blue curves work in a similar manner. For example, the green curve can be used to add (or remove) green from your image - or just from the highlights or dark tones. The alpha curve will controle opacity (if "save alfa" checkbox ticked in render settings).


Lets just play around a bit, starting with this image:

01 by tatasz

We can add some red:

02 by tatasz 01red by tatasz

Play a little bit with green, adding some to highlights and removing some from darker tones to create purple shadows:

03 by tatasz 02green by tatasz

Or do something crazy with blue:

04 by tatasz 04blue by tatasz

The best is to edit them all ;)


The curves range is not limited by the window. In fact, you can zoom in and out. Press Alt and right mousebutton and drag up (to zoom in) and down (to zoom out).

2 Curves by tatasz

Now you can go wild and set some crazy values if you feel like =)


To add a node, click on any point of the line.
To remove a node, drag it through an existing node: they will merge into one.

Move by tatasz


You can change the background color in the background box under the curves:

Apply before by tatasz

The combination 0, 0, 0 corresponds to black, and 1,1,1 to white. Those are not limits though, try using negative colors and values above 1 for very interesting effects.

R=0.0 G=0.0 B=0.0                    R=1.0 G=1.0 B=1.0
000 by tatasz White by tatasz

R=0.05 G=0.3 B=0.3                    R=0.0 G=-1.0 B=0.0 
005 03 03 by tatasz Negative by tatasz

By default, curves will not affect the background color. You can change it by ticking the "Apply before curves" box.

For example, below, i used curves to increase contrast of the flame. See how the background darkens as soon as i apply background before curves.

unticked                                       ticked
005 03 03 by tatasz Checked by tatasz

See you soon with Part 3 and a bit of World Editor magic.

anonymous's avatar
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margotd1's avatar
margotd1Hobbyist Photographer
In what way does the alpha curve control opacity?  I always save the alpha, as I prefer a transparent background.  However, the background isn't totally transparent, and I would like to know if I adjust the curve up or down for complete transparency?
CopperColour's avatar
I didn't see this before. Thank you for explaining a few things I didn't know.
MiniaKrn's avatar
MiniaKrnHobbyist Digital Artist
Lovely tutorials.
Is there any tutorial on anti-aliasing, blur, gamma and noise? Love 
metafrost's avatar
metafrostHobbyist Digital Artist
Out of curiosity can a color change be made as a key frame? Working on some animation and would love to know. So far no luck. Perhaps there's a perimeter in the world editor? It would be interesting to morph rgb during an animation but I have to imagine you pay for it in render time. These tutorials are excellent!
triptychaos's avatar
ZOOMING IN AND OUT for curves... always learning, thanks super tatasz... :D
IgorDa's avatar
I use this program :)
 Thank you very much,
 very interesting!!!
Gerda1946's avatar
Gerda1946Hobbyist Digital Artist
Very interesting! Thanks!!
piethein21's avatar
piethein21Hobbyist Digital Artist
how much your fractal responds to the curves depend on the gamma (i think?)
maybe mention that :)
lyc's avatar
:nod: the gamma (it's actually 1/gamma that is applied, so it's a misnomer in apo) has the effect of flattening the brightness range, so there's more "shaping" by the response curve.
piethein21's avatar
piethein21Hobbyist Digital Artist
I see I see its not just me ^^
thanks for the answer :)
tatasz's avatar
tataszHobbyist Digital Artist
Hmmm yeah sounds like a good addition...
Will do
piethein21's avatar
piethein21Hobbyist Digital Artist
^^ k cool :highfive:
fractal2cry's avatar
tutorial queen
tatasz's avatar
tataszHobbyist Digital Artist
=D just procastinating hehe
anonymous's avatar
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