Holograms

[M109uk]

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]

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]

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]

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 )

But this is the way I would have done it

Hope that helped!

Bye
Avatar

[M109uk]

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]

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

[{MSX}]

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 ), like a television image badly tuned.

At least, it would be easy to implement

[User137]

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]

looks good with vsync turned on, but turned off its really bad

[User137]

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