Auto alpha-channel billboards tutorial

I actually started reading the iClone manual. And I immediately found a fab shortcut for automatically making 2D cut-out billboards. Press Crtl on your keyboard, as you drag a PNG image to the stage from Windows Explorer, and iClone automatically makes it into a cut-out billboard prop. You just have to have the right sort of PNG image.

Here’s how to do it…

1. Open up Photoshop — I’m using Photoshop CS3. Open File | New. Make sure the setting for the new file says “Transparent” like this…

You should have a chequerboard on your new image — that means your background layer is set to transparent…

2. Now open a second file — this is the file that contains the object you want to lay over the top of your transparent background.

3. Use Photoshop’s Magic Wand tool to select the object. Assuming you have a plain or fairly neutral background, you can probably use a Magic Wand Tolerance setting of about “30” and it should give you a good fit. Now look to see if there are any areas that the Magic Wand tool didn’t reach into. Such as these…

If there are such areas, put the cursor in them and then right-click and “Add” them to the selection.

4. When you’re happy you’ve got a complete selection, right-click on the middle of the object and choose “Select Inverse”. Now Crtl + C will copy it to the Clipboard.

5. Now switch back to your first transparent-background image, and Ctrl + V to paste the object in from the Clipboard. If the cut-out is too big, either enlarge the canvas (Image | Canvas Size) or scale the object (Edit | Transform | Scale). It should now look like this…

Do NOT flatten layers before saving.

6. Now go to File | Save for Web… Ensure you save the image as a PNG-24 with Transparency ticked…

Only PNG will work with iClone for this trick.

7. Now load up iClone and then open Windows Explorer to find your saved picture. Hold down Crtl while dragging the picture in from Windows Explorer…

8. iClone will work for a moment (you may see a progress bar), then will automatically turn the picture into a properly cut-out prop on the stage…

And you never once saw, or even had to think about, Photoshop alpha-channels or the opacity materials box in iClone!

Once you have such a cut-out 2D prop, iClone can set it to always face the camera.

Depending on the quality of your cut-out, it might have some unwanted fringing on the edges. This can be a particular problem on images that start off in low-grade form, such as the silhouette below which was a horrible sub-greyscale bitmap .tif file. In some situations the fringing can be disguised somewhat by using camera depth-of-field…

… but you may need to go back to Photoshop and start again by making a cleaner cut-out. Consider using the Extract filter tool or the Refine Edges selection options.

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3 thoughts on “Auto alpha-channel billboards tutorial

  1. Oh man, if I’d only read that myself ages back… Great find! Thanks for sharing. (Must remember: PNG with Transparency… must remember… must…)

  2. Pingback: Making props for CrazyTalk Animator « :: m y C L O N E ::

  3. Got a slight fringing ‘line’ problem around the top/sides of your cut-out panel? Thanks to Mark for showing how to cure it. Change the Planar tiling settings for the cut-out prop from 1.00 to 0.99 on both settings, and click apply.

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