Pixel distortion/offset

[Damon Caskey]

One effect I have noticed a lot of games use or have used is to simulate transparency by distorting or offsetting the background layer behind target sprite. For example, in SOR3 Yamoto has a very convincing invisibility effect by making the spirte fully transparent and then shifting the background behind him a single pixel. It's clever workaround for a system that couldn't hope to process a transparency mask. Older PC screen savers often worked by warping random portions of the desktop, and newer 3D games use a similar effect for motion blurs.

How difficult would it be I wonder to add something like this to the drawmethod functionality?

DC

[utunnels]

That sounds good.
I was thinking about a clipping/alpha masking feature lately, but found it would be too complex due to  multitudinous sprite/screen functions.

Pixel Distortion alone should be easy, unless you want to use it with other draw methods.

[Damon Caskey]

That sounds good.
I was thinking about a clipping/alpha masking feature lately, but found it would be too complex due to  multitudinous sprite/screen functions.

Actually Plombo already added alpha masking support in revision 2852. Unfortunately I can't find the post that documents how to use it. Should have been kept even through the wipe, but it might have been deleted by mistake.

Pixel Distortion alone should be easy, unless you want to use it with other draw methods.

Sweet. I can think of several occasions when it would work better then a transparency.

DC

[utunnels]

Actually Plombo already added alpha masking support in revision 2852. Unfortunately I can't find the post that documents how to use it. Should have been kept even through the wipe, but it might have been deleted by mistake.

I knew that. But if I'm not mistaken, the alpha mask is part of the sprite and can't be used separately.

What I mean is a clipping feature (either use alpha masking trick or just a simple rectangle) many game engine might have. For example, you set a clipping area in current screen/viewport, then all shapes and sprites will be restricted in this area, extra parts will be cropped.

This feature is not that important,  I just happened to recall it when I saw this topic.


Another related idea is the ability to set transparency, but that also needs a lot of modification in current sprite code, so I leave it alone.


Despite the easiness of the logic, there are several difficulties.

1. The effect in the video showed some waving effect, which means there should be one or more time based parameters.

2. If the sprite is by any of the edges of the screen, the distorted pixels may fall outside the display area. Though this little glitch can be ignored if the modder always put the sprite at the center of the screen.

3. Duplicate functions for 8bit and 16bit screen, flip and non-flip version of the sprites.

[Plombo]

That sounds good.
I was thinking about a clipping/alpha masking feature lately, but found it would be too complex due to  multitudinous sprite/screen functions.

Actually Plombo already added alpha masking support in revision 2852. Unfortunately I can't find the post that documents how to use it. Should have been kept even through the wipe, but it might have been deleted by mistake.

It should still be on the wiki.

[Damon Caskey]

So it is... 

[utunnels]

Just noticed an interesting thing.
While playing Ninja Warriors, I found a certain boss had a similar effect.
Though the distortion might be a bit more complex, like a standard water transform, but only within limited area.