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Cool demo effect


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#1 Pseudo   Members   -  Reputation: 100

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Posted 04 September 1999 - 09:24 AM

I would like to make a feedback effect, where the previous frame, is roto-zommed, and then the new frame is drawn on top of that. I don't know the best way to do this however. Is it a good idea to blt the front buffer (the previous frame) into a texture, and then texturemap a polygon on the backbuffer? This seems like it would work, but I don't texture have to be in powers of 2? so my texture wouldn't be the same size as the frame buffer, and it would look crazy. I have seen the effect I'm going for on many Winamp plugins, so it must not be very hard. Does my method sound like a good way of doing it, or is there a better way? What do you think?

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#2 jens   Members   -  Reputation: 122

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Posted 02 September 1999 - 11:15 AM

hi,
why do you want to use textures and 3d? I'd prefere going with DDraw.
All you need is a backbuffer, a frontbuffer, and a blur-function. Then just do it like that:
1)roto-zoom backbuffer
2)blur backbuffer
3)draw to backbuffer
4)flip
5)jump back to 1)

should be working...the problem will be the blur which is very slow on high resolutions!

ciao...
...jens


#3 Anonymous Poster_Anonymous Poster_*   Guests   -  Reputation:

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Posted 03 September 1999 - 06:02 AM

Ok, now I can explain more specificaly what I mean. I have an idea that goes like this:
1)Blt part of the front buffer to a texture surface.

2)texturemap a polygon on the backbuffer, useing the previously mentioned texture.

3)draw to the back buffer

4)flip, and return to 1)


This will create a feedback effect, and it would be cool, but BltFasting to the texture always fails...and ideas on why?


#4 Khawk   Senior Staff   -  Reputation: 1362

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Posted 03 September 1999 - 10:09 AM

I really don't know why, but I'll take a stab. Since the front buffer is what's being displayed, maybe it's not possible to take data from it and slap it on something else. Again, I'm not real positive, but it's an idea. (in other words, i've never tried it myself :-) ).

Oh, what you could probably do is..
0) Draw your goods on the backbuffer
1)Blt part of the back buffer to a texture surface, instead of the front buffer...since the backbuffer gets all the goods first anyways.

2)texturemap a polygon to an offscreenplain surface, using the previously mentioned texture.

3)draw the goods to the back buffer

4)flip, and return to 1)

I don't how/if it would work, but it's a thought. :-)

Kevin



#5 Anonymous Poster_Anonymous Poster_*   Guests   -  Reputation:

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Posted 04 September 1999 - 09:24 AM

I is fine to blt from the front buffer...I've done it before...I once made a program that did a zoom from the previos frame, and that didn't have any problems...It must be something with how I create the Texture, so someone please help me out.




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