Making a frog go "poof".    11 Aug 00


Click here to watch the MOV if you haven't seen it yet.


(Note: an Illusion project file containing all of the emitters and the background image used here can be found at the end of the tutorial, and CAN be loaded by the demo version of Illusion.)


I've said it before -- one of the things I like to do most with Illusion is "blow stuff up". In my last tutorial I showed how to convert "any" emitter into an "explosion" emitter; this tutorial will focus more on the entire process of "blowing up" a frog, from initial image to final animation.

Disclaimer: I do not condone the use of violence against frogs or any other animals. Well, mosquitoes yes. Ants too. Spiders as well when they get into the house. But that's it. Definitely not frogs, no matter how annoying they get.


Why Blow up a Frog? (This must be Fate)

So how did I decide to animate a frog? It must have been fated to happen. A friend sent me an image of a frog that (I believe) had gotten into his brother's house when he was visiting. Shortly after I got the image, I was in a lengthy conversation on many different topics. The conversation would eventually make its way back to Illusion, and in the course of this talk I was challenged to make a frog explode.

Do you see the evidence of "cosmic forces" working here? Frog gets into the house (a rare occurrence I'm sure) on the *one* night my friend was visiting, he happened to have his digital camera with him (he doesn't carry it everywhere), then the challenge from somebody who knew nothing about the frog. It's almost spooky. I just had to do it.

(By the way, anybody who can identify the type of frog and the country it lives in will win a "special prize". Send me email with your guesses.)

Okay, let's get to it. Here's the image I started with (resized smaller):






Step 1: Free the Frog!

The first thing we need to do is isolate the frog so we can make a particle shape image from it. (I use Paintshop Pro for my image manipulation, but you can use whatever paint app you prefer. The steps I give are using Paintshop Pro terminology though.) The basic steps are:

1) Create a mask to make the non-frog parts of the image transparent and the frog parts non-transparent.
2) Save the mask to an alpha channel.
3) Resize the image to 128x128.
4) Save the image as TGA.

Now in detail: Create a new mask ("Mask" menu, "New", then "From Image..."). Use the "source opacity" option.



You'll now have a mask that is completely opaque (non-transparent) which you can't see but need to edit. "Mask" menu, select "Edit" and "View Mask". Now make the foreground color black (0,0,0) and select a paintbrush that is round, relatively large (30 pixels or so), and has an antialiased edge. Draw on the image in a non-frog area and you'll see that part of the image become transparent (and tinted red since "view mask" is active).



What you need to do now is paint around the entire outline of the frog, using a smaller brush when needed. You can also use the "fill" tool when the outline is complete to remove most of the outer background, but you'll probably need to use the paintbrush again to remove some fringes.



(Might be a good time to save the image. Use a new name or file format so the original image isn't overwritten -- we'll need it for the background image in Illusion.) Now we need to save the mask to an alpha channel. From the "Mask" menu select "Save to Alpha Channel" then just click OK, then OK again when it asks you for a name. As a final step, delete the mask now -- I'm not sure if this step is needed, but it seems to help reduce the white "halo" around the image. "Mask" menu, select "Delete", then when it asks if you want to merge the mask into the current layer click NO. Note that when you delete the mask it will look like the background of the image is visible again -- don't worry about that, since the alpha channel is still present.

Now we just need to get the image resized and saved to TGA. When the image that you want to use as a particle shape image is not square and/or is larger than 128x128, you'll want to make it square and resize it to 128x128 yourself. If you let Illusion resize it (particle shape images are always forced to 128x128 in v1.1) you may not get the best results. First we'll make the image square. Use the rectangular selection tool and select the frog. Try to get the selection as close to the edges of the frog as possible (but leave a small gap). This will ensure that the important part of the image is as large as possible when we resize it. Now use the "crop to selection" ("Image" menu) function.

To get the image square now (so it doesn't distort when Illusion imports it), use the "Canvas Size" function on the "Image" menu.



Set the options as shown here, and set both width and height to the current width or current height, whichever one is larger. You should now have a square image. Now resize it to 128x128: from the "Image" menu select "Resize" then set it to 128x128. The final step is to save the image as a TGA. If you get a warning about "limitiations of the file format..." just click YES.




Step 2: Goodbye Frog

Now that we have the frog isolated from the background, we need to erase the frog from the background (otherwise we won't be able to make it disappear when it explodes). This is actually a pretty simple step in this example, because the background is pretty uniform (wood) and we're going to put a blast mark over it so we don't have to get it perfect. Select the "clone" tool, and set the size of the brush pretty big (about 1/2 the frog size) then SHIFT-click to the right of the frog to set the "anchor point" -- the point of the image the will be cloned. Now draw on the frog, but only in a horizontal line, and at the same height as the anchor point.



Set the anchor point a little higher and erase the top part of the frog, then set it lower and erase the lower part of the frog. You'll see some difference in brightness because of the cloning, but you can fix that a little by resetting the anchor point and touching things up. As I said, it doesn't need to be perfect. Here's mine:



You can see that it's not a perfect blend, but good enough for my purposes!





Step 3: That's going to leave a mark

Now for the blast mark. (This step probably has a hundred different ways it could be done, but this is just the way I did it.) First, take the image without the frog that we just made and create a new layer. "Layers" menu, "New Raster Layer". Make sure the options are checked as shown (the defaults):



We'll make the blast mark by starting with a black filled ellipse, then using the "smudge" tool to make the radiating streaks. Select the "preset shapes" tool, then select "ellipse" in the "shape type" box of the Tool Options window. Make sure "antialias" is checked, and "create as vector" is NOT. Then click where the frog would be sitting and draw the ellipse so it looks like it matches the angle of the "floor" that the frog was on.



Now the hardest part -- at least it was for me. Select the "Retouch" tool, and select the "smudge" tool. What makes this part difficult is that it takes a little experimentation in brush size and speed at which you draw. The idea is to start at the center of the ellipse and smudge straight outward. I used UNDO a lot, since a lot of my lines weren't too straight. I made some shorter, fatter streaks (draw slower) and some long, thin streaks (draw faster). Like I said, you have to experiment a little. When you're satidfied with your results, adjust the opacity of the layer to 50% or something like that so the wood shows through the blast a bit.



Now all that is left to do is get the blast mark isolated from the background image -- that's why we put it on a separate layer. Turn off the background image, so only the blast layer is visible. Now Copy the layer ("Edit" menu, "Copy"), then Paste it as a new Image ("Edit", "Paste", "as new image"). We need to create a mask for this new "blast only" image, so from the "Mask" menu select "New" then "from image". Choose the "Source Opacity" option and click OK. Now save the mask to alpha channel as before, then delete the mask.

Now make the image square (using "canvas size") and resize it to 128x128 as before. If you made some really long thin streaks at the sides of the blast, you might want to crop the image a little before resizing. Those very thin streaks will not really add anything (if they're even visible) to the image after it is resized to 128x128. You also may notice a little bit of a white "halo" around the balst mark edges. Don't worry about it in this case -- we'll take care of that in Illusion. Save the image as TGA, and this step is finished.

Now we've got our frog and blast mark images (for particle shape images) and we've got a frogless image that we can use as a bg image... we just need one more thing: the "ribit" text.




Step 4: Say It!

The "ribit" text was really simple to make. I use a 300x300 black image, then use the "text" tool to create white text, filling as much of the image as possible. To make the little "speech indicator" I just drew a little triangle with the "preset shapes" tool, creating it as a vector object, then rotated the vector object to get it angled the way I wanted it. Then I used the "Copy Merged" command (from the "Edit" menu), then Pasted as a new image. Then I resized the new image to 128x128 and saved the image as PNG. (I will be importing this into Illusion as a "regular grayscale" shape, which means I don't need an alpha channel.)







Now, let's get to Illusion!



part 2...





Alan Lorence    11 Aug 00