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Submitted by Andrew Perrine, posted on March 08, 2001

Image Description, by Andrew Perrine

Here's a departure from your normal 3d screenshots. Here's an effect I thought up the other night and hadn't recalled seeing before. It allows for a smooth melting/dissolving (kind of hard to describe) of an image.

It's really pretty simple. First you draw the background image (or clear the buffer if you're fading to black). Then you need an alpha texture with a nice gradient (middle picture) which describes the effect you want. You render this solely to the depth buffer with alpha testing on and some number for the vertex alpha (the number will increase or decrease each frame). Then you slap the texture being melted on top of that with a depth test on. If you want to get fancy, you can do what I've done here and do a slightly different alpha test on top of that to get nice little borders around the holes you've made.

Also, though I don't have shots of it here, you could use different alpha textures to get some different effects. Screen wipes or dissolves (see your favorite Star Wars movie for examples) are easy, though you really want the highest possible alpha depth for your texture on something like that. The background also doesn't have to be a single texture, it could be an entire scene. The engine I'm working on currently has a console that "melts in" when you open it, though I'll probably be tired of that soon enough. :)

If you've got any questions/thoughts/whatever feel free to post a comment.

Thanks for looking,
Andrew Perrine

PS - Thanks to id for the excellent door texture. :)

Image of the Day Gallery


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Archive Notice: This thread is old and no longer active. It is here for reference purposes. This thread was created on an older version of the flipcode forums, before the site closed in 2005. Please keep that in mind as you view this thread, as many of the topics and opinions may be outdated.

March 08, 2001, 05:18 AM

Nice ;-)

Yes, today's game really lack some creativity when it comes to scene / level / screen changes ;-) Never noticed that before, but whe I think about it....


Tobias Franke

March 08, 2001, 05:23 AM

Heh, these are the posts were you wish it was a votd (video-of-the-day)... I can well imagine that the effect looks nice!


March 08, 2001, 05:23 AM

Lovely, thats really imaginative. Great work!


March 08, 2001, 05:40 AM

very cool, but i have to say that its been done before.
Ever seen the end scene in Zelda:Ocarina of time, where Ganondorf dissolves just like that?

Its a cool effect.
Would like to see a mpeg of it running in real-time. :)


March 08, 2001, 06:27 AM

Or check out the demoscene, I remember seeing screen-melts in 1000 different styles since 1990 or so.. :)


March 08, 2001, 06:32 AM

I remember Scala coming with billions (approx.) of these wipe .BMPs. They were really quite amusing.


March 08, 2001, 07:15 AM

cool demo effect, and indeed, video of the day would show of the effect better ...


zed zeek

March 08, 2001, 07:25 AM

yeah im a bit tired of the 3d engine thing.
theres a few shots i wouldnt mind posting for IOTD of a few effects (also 3d:) stuff ive made but not really warrenting of a IOTD tag(WTF) perhaps a most recent list of images would be better instead of how it sits at the mo, the one image + bang gone the next day. eg the last 5 images so each image is shown for a few days (working its way down the list)

Warren Marshall

March 08, 2001, 10:13 AM

There's an IOTD gallery you know. :)


March 08, 2001, 11:03 AM

Zed really shows he has been paying attention to the FlipCode site ;)


March 08, 2001, 11:25 AM

You know, it's not dark.
But anyway, it remembers me good old movie, which was almost as horible as this IOTD image. The similar level of horror, I should say.


March 08, 2001, 11:40 AM

Oh great, it looks like MC BAXTON is back to posting his useless comments again.

Scrambled Monkey

March 08, 2001, 12:07 PM

At first glance, I was like, what the hell is that? A building in an RTS getting hit with goofy white bombs? hahaha. Then I read the description... Funny how your eyes can play tricks on you. It looks really cool, I bet it looks great animated! Do you have a link to a demo? I'd try it myself, but my 3d engine that I (mis)use to try out new ideas is falling apart as it is, and it would be hell trying to hack a screen transition in :)


March 08, 2001, 01:13 PM

I haven't played Zelda in a while, so I don't remember that particular scene. Is it anything like one of the very first bosses you kill (one eyed thing that crawls around on the ceiling)? That broke apart in a somewhat similar way. Not quite the same, but I think that may be due to a lower precision in the N64 (if it does in fact have a lower pecision).


March 08, 2001, 01:26 PM

I've actually been working on a little demo of this with a laser beam type thing that you can melt apart an object with (nothing too fancy). Unfortunately, I discovered the other night that it looked absolutely horrible with 16-bit textures. I was almost positive I had tested that before, but I guess not. Anyway, I've got a few ideas on how to fix it, and I'll post a link to the demo here whenever I get it done (for those few who like to browse the iotd archives).


March 08, 2001, 02:59 PM

Effect of "image worms" can be interesting, however, it could be even better if used together with some precisious original data alteration.

Jukka Liimatta

March 08, 2001, 03:44 PM

I have this "dissolve" effect sourcecode for the OpenGL using stencil buffer-- I didn't write it, and I cannot remember where I really got it from.

However, I put it temporarily onto this URL:

I just thought it was in the spirit of the thread and all that.. the code is as-is I found it from my GL code snippets folder, could been one of the links somewhere in I found it, apologies that my memory fails to remember the "correct" URL.


March 08, 2001, 06:33 PM

This fx is nice. It's nice to see when a "hey, that would be cool..." thing becomes an actual reality.

The engine I'm working on currently has a console that "melts in" when you open it, though I'll probably be tired of that soon enough. :)

nice, maybe if you had your own object oriented GUI, you could implement this feature way up in the abstract "interface element" class. That way, whenever you opened a window, or clicked on a button or check box, they all performed a "meltToScreenView()" method. Of course, you would get sick of it eventually. Still, no harm in trying though.

keep up the cool work!

Mathieu 'POĻ' HENRI

March 08, 2001, 08:04 PM

well, like L.E.Deninger said, that kind of transition effects have been used for decade(s)!

excuse me, but do you all live in caves??

anyway, my goal is not to offend anyone, but I'm puzzled to see the bad "code" culture some people have

whatever, that kind of transition is cool in 32bits (more than in 4-5bits :) when it was first used)


March 08, 2001, 09:19 PM

I think the effect is a bit better than old effects. This type of thing could also be used to cross-dissolve two 3d scenes, and some sort of constructive solid geometry could be done with this effect.


March 08, 2001, 10:42 PM

You know, I just realized it's not all that apparent from the shot I gave or my description that I mainly like this effect on polygonal meshes. I just wanted to give a full on shot for best detail, and putting it on meshes was so obvious to me (since it's mainly what I've been doing) that I didn't even think to mention it.

PS - You know, I used to be a good writer, but it seems like coding has really corrupted my style. I seem to be using parentheses every other sentence (or somewhere thereabouts). I guess it shows that I like to comment, at least. :)


March 08, 2001, 10:47 PM

You know, speaking of writing style, I also seem to say "you know" a lot. Guess I should read my messages over before I post. :)

Fabian Giesen

March 09, 2001, 04:51 AM

Looks nice, although it isn't that impressive when it's not animated :)

Anyway, keep up the nice work!

Mathieu 'POĻ' HENRI

March 09, 2001, 07:02 PM

for sure this effect is a bit better than old effects and can create great transitions

but, it amazed me that some people found that (decade old) thing imaginative

I mean, when you start coding, I guess you start with 2D stuffs, and then learn that sort of effects...

I may be wrong

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