texture transparency 
Author Message
 texture transparency

I have a pice of geometry with a Material transparency (0.5).  When i
apply a texture to this geometry it behaves in one of two ways:

in CP1.2 (on the SGI) the texture also takes the transparency value of
the Material (0.5) and becomes "see-through"

in CP2.2 (the PC) the texture over-rides the transparency values of the
material and is completely opaque.

I want the first effect (see through textures...)but want it to work on
CP2.1 for the PC.  Ideally, i dont want to have to change my image maps
to transparent gifs.

Please help!
--
Gareth Ennis
ABACUS - Strathclyde University

http://www.*-*-*.com/



Fri, 01 Jun 2001 03:00:00 GMT  
 texture transparency
In my experience, the .jpg (which cannot be partly 100% transparent) takes
the transparency of the object.
The .gif (which can be partly 100% transparent) is not affected by the
transparency of the object.


Quote:

> I have a pice of geometry with a Material transparency (0.5).  When i
> apply a texture to this geometry it behaves in one of two ways:

> in CP1.2 (on the SGI) the texture also takes the transparency value of
> the Material (0.5) and becomes "see-through"

> in CP2.2 (the PC) the texture over-rides the transparency values of the
> material and is completely opaque.

> I want the first effect (see through textures...)but want it to work on
> CP2.1 for the PC.  Ideally, i dont want to have to change my image maps
> to transparent gifs.

> Please help!
> --
> Gareth Ennis
> ABACUS - Strathclyde University

> http://iris.abacus.strath.ac.uk/new/



Fri, 01 Jun 2001 03:00:00 GMT  
 texture transparency

Quote:

> In my experience, the .jpg (which cannot be partly 100% transparent) takes
> the transparency of the object.
> The .gif (which can be partly 100% transparent) is not affected by the
> transparency of the object.

GIF is not standard VRML.  Use PNG.  Sorry, somebody had to say it.
OTOH, if PNG had an animation format, then maybe we could put the GIF nonsense
to rest once and for all...
...a little off topic, but does anybody know if an animated PNG is in the
works?

--
To think, that sigs were once a kludge...



Fri, 01 Jun 2001 03:00:00 GMT  
 texture transparency
So is there a transparent PNG and how is its behavior any different?
Quote:


> > In my experience, the .jpg (which cannot be partly 100% transparent) takes
> > the transparency of the object.
> > The .gif (which can be partly 100% transparent) is not affected by the
> > transparency of the object.

> GIF is not standard VRML.  Use PNG.  Sorry, somebody had to say it.
> OTOH, if PNG had an animation format, then maybe we could put the GIF nonsense
> to rest once and for all...
> ...a little off topic, but does anybody know if an animated PNG is in the
> works?

> --
> To think, that sigs were once a kludge...



Sat, 02 Jun 2001 03:00:00 GMT  
 texture transparency

Quote:

> So is there a transparent PNG and how is its behavior any different?

CosmoPlayer 2.1 supports PNGs with full alpha-channel transparency.
Which means you can prepare your texture (in Photoshop, say) with
variable transparency/translucency - some parts totally transparent,
others more dense, etc.

The behavior you're seeing in CosmoPlayer is correct - the transparency
in the texture overrides any transparency in the material - it's in the
VRML97 spec.

If you want to see how I've applied this effect, go to my "Tribute to
Chesley Bonestell" page and look at the rocket exhausts.
http://pluto.njcc.com/~paulsam/moonship/

- Paul

--
***********************************
Paul S. Hoffman
Senior Interface Designer, Cognetics Corporation

Company URL - http://www.cognetics.com
Personal URL - http://pluto.njcc.com/~paulsam
609-799-5005 ext.237 - FAX 609-799-8555



Sat, 02 Jun 2001 03:00:00 GMT  
 texture transparency

Quote:

> I have a pice of geometry with a Material transparency (0.5).  When i
> apply a texture to this geometry it behaves in one of two ways:

> in CP1.2 (on the SGI) the texture also takes the transparency value of
> the Material (0.5) and becomes "see-through"

> in CP2.2 (the PC) the texture over-rides the transparency values of the
> material and is completely opaque.

> I want the first effect (see through textures...)but want it to work on
> CP2.1 for the PC.  Ideally, i dont want to have to change my image maps
> to transparent gifs.

CosmoPlayer 2.1 is behaving according to the spec - transparency (or
lack of it) in the texture overrides the transparency of the material.

Transparent gifs would not do what you want, because their transparency
is either on or off. PNG, however, supports full alpha-channel
transparency, which means you could prepare your texture (in Photoshop,
for instance) with a 50% grey alpha-channel and then it would be
"see-through".  See my examples (rocket exhausts) at
http://pluto.njcc.com/~paulsam/moonship/

- Paul

--
***********************************
Paul S. Hoffman
Senior Interface Designer, Cognetics Corporation

Company URL - http://www.cognetics.com
Personal URL - http://pluto.njcc.com/~paulsam
609-799-5005 ext.237 - FAX 609-799-8555



Sat, 02 Jun 2001 03:00:00 GMT  
 texture transparency
Thanks Paul.
What I have always expected but never seen is a partially transparent cloud.
When I see clouds floating around a globe (http://www.ai.sri.com/geovrml/)
or a cloud billboard, its a transparent GIF.
A cloud with semi-transparent edges would look better.
Quote:

> Transparent gifs would not do what you want, because their transparency
> is either on or off. PNG, however, supports full alpha-channel
> transparency, which means you could prepare your texture (in Photoshop,
> for instance) with a 50% grey alpha-channel and then it would be
> "see-through".  See my examples (rocket exhausts) at
> http://pluto.njcc.com/~paulsam/moonship/

> - Paul

> --
> ***********************************
> Paul S. Hoffman
> Senior Interface Designer, Cognetics Corporation

> Company URL - http://www.cognetics.com
> Personal URL - http://pluto.njcc.com/~paulsam
> 609-799-5005 ext.237 - FAX 609-799-8555



Sat, 02 Jun 2001 03:00:00 GMT  
 
 [ 7 post ] 

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