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Illusion and Photoshop tutorials:

Creating a particle shape

Making things go boom


Hello folks. Today we will create a little mayhem in Illusion, which is a great, affordable 2D particle app from Impulse.

The result will hopefully be a cool smokey explosion.

You should have a basic understanding of both Illusion and Photoshop before attempting this tutorial.

We will start by creating a cloudy particle shape in Photoshop.

This is a cloud image included in Adobe's Photoshop CD. I used this image as the starting point for this tutorial because it is available to every owner of photoshop, but for any serious work i prefer to roll my own ;-)

If you wish to use this as your base cloud image, i would suggest using the original cloud.psd, as it's free of the jpg compression artifacts you may find in the above copy.

We will begin by cropping a suitable sized section (try to pronounce that!) with the crop tool. As illusion's particle shape size is restricted to 128 X 128 pixels, we can set cropping to these settings:

This will cause our cropping area to be the same as illusion particle size. I decided to use a cloud in the lower left corner.

Note that the image is actually enlarged a bit. Photoshop's cubic resampling does this quite well, but we would have had sharper result if the cropping area was significantly larger than the result.

Yet another reason to use your own photos!

As there's decent amount of contrast between the blue sky and the white cloud, we can isolate the sky area with magic wand tool.

This is a good starting point for the alpha channel of our particle image. Next, in the select drop down menu, expand selection [alt+s, alt+m, alt+e] by one pixel. This will ensure that there won't be a blue edge in our cloud shape. Then invert the selection [Ctrl+shift+i] and save it to a new alpha channel [alt+s, +s].

Yes! You are right! The stuff in [these] is the ultimate productivity secret - shortcut keys!

Activate the visibility (eye icon) for the alpha channel to see how your matte looks so far.

Wait a minute! I can still see some semitransparent clouds in the areas that weren't selected! What's up?

- No problemo, just double click the alpha channel to open the cannel settings dialogue, and set the masked area opacity to 100%. This will cause transparent areas to be in full color. The default red is ok, as it's quite opposite from our bluish image. If you were creating the matte for, say, autumn leaves, you should set the color to blue, as it is opposite to the red leaves...

Mmmm... it's starting to look like something, ain't it? But if we were to use this image as the particle shape, we would have a very boxy look, which is not desirable...

Time to do some alpha channel manipulation! Select the alpha channel as the active channel, and using the gradient tool draw a gradient (surprise!) to fade the transparency of the bottom of the cloud.


 

Use default black and white colors, and set the tool to multiply mode:

The edges are still harsh, so use the tool twice again to draw gradients to the sides of the shape.

(I always draw the gradient in the wrong direction... luckily there's undo [Ctrl+z] ;-)

Now let's look at all the channels again.

Yep. Looks really good!

Well, it would look even better if you use the soft brush tools to make the gradients a bit less constant - again, roll your own.

Ok, the last thing to do is to rotate the image (canvas) 90 clockwise [alt+i, +e, +9], and add some levels correction [Ctrl+l].

Rotation thingy is because Illusion assumes the shape's forward motion to be from left to right, and we will want to move the cloud edge first. You could rotate the shape in illusion, but this will save an extra step each time you use the shape in illusion.

Levels correction was done because i think it just looked cooler with a bit more contrast ;-)

Ok! We are done with Photoshop for now. Lets throw some particles around!!

WHOOOOPS!!! We almost forgot to save the image! Save it as 32 bit tga with whatever name you wish.

Next we will create an emitter in illusion.


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