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M109uk
24-10-2003, 07:12 PM
Hi again,

I have a very tricky question here, i would like to make a holographic effect using 3D Objects..

I Probably will have to do this by rendering to a texture and then doing something to the texture, but does any one know how to do this? I have seen an Hologarphic effect using NV Shaders but sadly my card doesnt support them :(

Thanx for any help :)

Avatar
28-10-2003, 09:24 AM
If I had to make an hologram here is how I'd do it(with D3D ^^ but I guess it can be applied to OGL :)) :

1- Activate backface culling
2- Set alpha-blending to a pretty high level
3- Render you object ...

It would make a transluscent object, wouldn't it ?

M109uk
28-10-2003, 03:34 PM
It would work that way, but i also want it to flicker with the lines going through it.. i cant think of a way to describe it.. it would basicly have transparent vertical lines going through the rendered objects?!

Avatar
28-10-2003, 07:56 PM
Hum, yes, it would be a lot more complicated ...

I don't know if you can apply camera space coordinates instead of world space coordinates but if you can, here is how you should do :

1- Set for the 1st texture level world space coordinates
2- Set your object texture on the 1st level
3- Set for the 2nd texture level camera space coordinates
4- Set your hologram texture (a simple scanline texture would be ok)
5- Multiply the first level with the second, so that every times the scanline is black the texture disappear
6- Set alpha-blending on

It appears to be simple, but I guess you'll have to work on it because it won't do the good result the first time ^^ (I think :P)

But this is the way I would have done it :)

Hope that helped!

Bye
Avatar

M109uk
29-10-2003, 06:17 AM
lol ok, i might just give that kinda effect a miss for now, and just have a simple effect.

Thanks for your help anyway :)

User137
13-01-2005, 11:42 PM
It would work that way, but i also want it to flicker with the lines going through it.. i cant think of a way to describe it.. it would basicly have transparent vertical lines going through the rendered objects?!

Not sure what you are exactly after, but sounds like it could be done this way:
-Draw your transparent line with alpha 0 and depth mask on
-Draw hologram with depthmask off, but still depth test on

That leaves hologram a hole in place the invisible line goes.

Or... you may mean plane instead of line...
Also animated texture is an option :P

{MSX}
14-01-2005, 07:50 AM
you could also have a good effect scaling the model a small quantity randomly.
If you think about Leila ologram in starwars, it was wobbling (hope this verb make sense :P), like a television image badly tuned.

At least, it would be easy to implement :P

User137
15-01-2005, 01:13 PM
:o

Check this out:
http://www.freewebs.com/loknar/holo.zip

I only drew the ship with random alpha value, and that's it really. I'll put there interference lines when i get back home...

tux
15-01-2005, 01:34 PM
looks good with vsync turned on, but turned off its really bad :(

User137
15-01-2005, 11:35 PM
Put new implementation there now:
http://www.freewebs.com/loknar/holo.zip

This time ship alpha is static, but there's interference lines, and also projection lines ^ ^

Ok.. as much for this demo.

Edit: Seems that freewebs doesn't allow to direct downloads from web sites. Works if address is put manually on address bar :P

Traveler
16-01-2005, 11:38 AM
Looks good! How does it look when you randomly move the object a little on the x plane? I think it may give it a bit of a distortion effect.

Btw, how did you do the projection lines? Is it a texture or just a bunch of lines?

User137
16-01-2005, 01:27 PM
It is bunch of lines as you said :)
Drawn to random vertices of model.

That "flicker" effect is 4 invisible planes filling the z-buffer. For that i had to invert modelview matrix for it to look almost same from all angles.

savage
16-01-2005, 09:43 PM
Hey Traveller, excellent Competition logo. Is PGD able to use it? Have you mentioned it to WILL?

Traveler
16-01-2005, 10:30 PM
Hey Traveller, excellent Competition logo. Is PGD able to use it? Have you mentioned it to WILL?

Thanks for the compliment!
The two fighters were made for WILL to use in his demo. The banner was something I thought of later. I think it turned out pretty good, especially with the smoketrail and all.

But sure, you may use it for whatever you like.

savage
16-01-2005, 10:33 PM
Great!! Look for it to appear on bdn.borland.com if they approve my competition announcemnt submission.