411 REFERENCE · Wikibooks
Paint.NET/Realistic Fire
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
This tutorial is a simple, but effective way to make a realistic fire.
Make a new image with dimensions 1000x500
Draw a gradient like so (with white at the bottom and black at the top):
Image:Layer1firetut.png
Make a new layer.
Double-click Layer 2 to edit its properties
Set the Blending Mode to 'Overlay', then hit OK.
Image:Paint.net - Layer Properties dialog box.png
Go to the 'Effects' menu under 'Render' and choose 'Clouds'. Change the blending mode to 'Difference', then hit OK.
Image:Paint.net - Clouds dialog box.png
Push CTRL+F to repeat the effect. Do this about a dozen times.
On the 'Image' menu, choose 'Flatten'. This will give you a single layer with some nice black-and-white clouds.
On the 'Adjustments' menu, choose 'Curves...'.
Choose 'RGB' under 'Transfer map', then uncheck the 'Red' and 'Green' checkboxes so you're only modifying the blue channel, add a control point as shown below. Do the same for the green channel so you have the curves shown below.
Image:Paint.net - Curves dialog box.png
Voila!
Other things to try
Use different shapes for the Layer 1 Gradient. Round gradients make neat looking explosions
Tweak with the Curves, the general shape of them should be preserved to keep good saturation, but the channels don't need to go in the above order. *Try Green, Red, Blue (instead of Red, Green, Blue) for a copper flame (copper burns green).
Play with the 'scale' setting of Clouds for finer or Coarser clouds
Play with the Roughness setting for clouds for softer or sharper fire
Just try things out, you never know what you'll get.