Animated Optical Illusions

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Erockbrox
Posts: 384
Joined: Sun Nov 23, 2014 12:16 pm

Animated Optical Illusions

Post by Erockbrox » Sat Jan 16, 2021 5:17 pm

I stumbled upon this awesome youtube video where they made animated optical illusions by dragging a black bar transparency over a specially created image. Here is the video.

https://www.youtube.com/watch?v=vJpMZ0R89kU

I wondered to myself............... this is animation without being real animation. It is simply an image with another layer sliding across it.

I would think that dragging one layer over an image isn't too computationally taxing, so this could be a really cool visual trick to pull off with older consoles.

Here is a spinning cube running on the SNES.

Image

layer 1
Image

layer 2
Image


The only thing is, on the NES you don't have any layers other than the sprite layer. So the animation could only be as big as a square grouping of all of the sprites. The sprites themselves are the black bars and are 7 pixels thick with 1 pixel being transparent.

So I'm proposing this to the NES community. Can anyone make a small image that animates in this fashion on the NES? How big could you make the image? Essentially its just an image with black sprites scrolling across it.

Making the animation is a little tricky, but basically take photoshop (or any other program). Find or create your own animation. This typically works best for 8 frames of animation. The sprite tile is 8 pixels wide with 1 being transparent so to get the number of frames its 8/1 = 8 frames. So once you have your image, you get the black bars and the image in photoshop. You look at the 1st frame of animation and delete the black bars portion of the image, then slide the black bars over 1 pixel. Then you take the 2nd frame of animation and delete the black bar sections on that image and so on. So you are taking a slice out of each animation frame there is and putting it all into one single image.

lidnariq
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Location: Seattle

Re: Animated Optical Illusions

Post by lidnariq » Sat Jan 16, 2021 5:34 pm

Erockbrox wrote:
Sat Jan 16, 2021 5:17 pm
The only thing is, on the NES you don't have any layers other than the sprite layer. So the animation could only be as big as a square grouping of all of the sprites. The sprites themselves are the black bars and are 7 pixels thick with 1 pixel being transparent.
Have the zoetrope mask move vertically instead of horizontally. Use raster effects to only enable background rendering every Nth scanline.

Alternatively, once you're using raster effects, you could instead set the scroll position every scanline to repeat scanlines and get something more like lenticular print animation

nocash
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Re: Animated Optical Illusions

Post by nocash » Sun Jan 17, 2021 1:16 am

Erockbrox wrote:
Sat Jan 16, 2021 5:17 pm
Here is a spinning cube running on the SNES.
That is pretty cool. There should be better ways to get better animations even on the oldest consoles... but it's really cool as a hidden joke aimed at people whom happen to have a closer look at the program-code, or at the laundry drum shaped BG-layer.
For older consoles with single-BG-layer I would also recommended using horizontal lines. In some cases, a fixed image with palette animation might work, too. But your idea is much funnier : )
Did you try switching to patterns with 2-of-8 lines, or 1-of-4 lines, or up to showing all lines after a while? Might look interesting... and it could be fun to reveal how the effect works.
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calima
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Joined: Tue Oct 06, 2015 10:16 am

Re: Animated Optical Illusions

Post by calima » Sun Jan 17, 2021 1:26 am

That is much the same idea as packing 1-bit graphics into 16-color tiles ala the Sonic 3d intro etc.

Bavi_H
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Location: Texas, USA
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Re: Animated Optical Illusions

Post by Bavi_H » Sun Jan 17, 2021 1:49 pm

Previously, in August 2014: Vertical Line Animation Illusion

Internet Archive Wayback Machine versions of items no longer available:
IllusionTest.nes
NESIllusionTest.png

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