Imaging in Chaotica - Part 2: Response Curves

7 min read

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tatasz's avatar
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.

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margotd1's avatar
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?