Partially transparent textures, why do some work and some don't

[pmolsen]

Why do some partially transparent textures work and some don't when
uploaded to the 3D buildings layer?

If you look at my Q1 model at
http://sketchup.google.com/3dwarehouse/details?mid=3b86d7995aac79079cf69f6066d75cb8
which is located at 28.006s, 153.43e the top fin of the building
should be partially transparent. It displays in GE fine from SU but it
displays as completely opaque in the 3D buildings layer.

Now look at the tennis court fences at Beaver Creek tennis center at
39.6044N, 106.5116w They are only partially transparent but they look
fine in the 3D buildings layer (apart from the usual problem of only
being textured one side, which mucks up the texture on the reverse
side.)

[SketchUp Guide Allison]

Hi pmolsen,

Transparent .pngs (with the transparency "baked in" to the .png alpha
channel) work. SketchUp material transparency (material details ->
opacity < 100%) does not; if you want a partially opaque material
you'll need to convert the texture to a .png and alter its alpha value
using your favorite image editing software.

-- Allison

On Jul 1, 11:21 pm, pmolsen <pe...@peterolsen.com.au> wrote:
> Why do some partially transparent textures work and some don't when
> uploaded to the 3D buildings layer?
>

> If you look at my Q1 model athttp://sketchup.google.com/3dwarehouse/details?mid=3b86d7995aac79079c...

[GaryM]

Allison,

That doesn't necessarily work either. I make up all my transparencies
with Paint Shop Pro (never SU's transparency option) using the alpha
channel, and be sure to texture both sides. They all look fine when
placed in GE directly from SU. After the 3DW KMZ appears, however, the
transparencies are often messed up.

Not always, however. The problems seem to be when you are looking
through *two* transparencies, such as the two sides of the glass-
walled skywalks in some of my models. The transparencies become
blotchy, partially opaque, or (in one case) the buildings behind them
disappear. Only some of the buildings, however. Some of them remain
visible through the skywalks.

I put up a photo. See the link in the thread (in this subforum) "More
Strange Transparency Behavior."

[SketchUp Guide Allison]

Hi Gary,

That's a Google Earth transparency stack rendering issue. There isn't
a workaround for it at the moment, that I know of, but I've forwarded
the image to the client team for further review.

-- Allison

[pmolsen]

I just created a partially transparent square with Paint.Net and set
the Alpha channel to 190 (out of 255) - higher value = more solid
colour. Saved as 32-bit PNG. Textured the glass fin with it. In SU it
looks good but when I display the model in GE the material is totally
opaque. So that is actually worse than before using the SU
transparency slider, because with it the model would look fine in GE
when displayed from SU but no good in the 3D buildings layer.

Everything I read about Paint.Net suggests that it saves the Alpha
channel correctly. My created material is saved at
http://www.schoolzonelights.com.au/glasstexture.png if anyone can
check it.

Here is another possibility. Does anyone out there have or know of a
model in the 3D buildings layer with some partially transparent
greenish coloured glass on it, that displays correctly in the GE 3D
buildings layer? Then I can just steal the material from that model
and include in mine.

[pmolsen]

I think I figured it out. I was doing two things wrong I think.
Firstly I forgot to turn off the 3D Buildings layer so I had the new
and old models superimposed. But in the meantime I discovered in
Paint.Net that there is a foreground and a background colour. Doh!.
The transparency of the background colour was set to maximum. I turned
it down to zero (fully transparent) and left the primary colour alpha
at 190. Now it displays fine in GE from SU. So I will upload the model
and see how it goes when it is next updated in the 3D buildings layer.

[GaryM]

Here is one I made up with your RBG values in Paint Shop Pro. It's a
24-bit with alpha channel. It also works fine on your model when
placed in GE from SU. If the other doesn't work, you can try it.

http://groups.google.com/group/SketchUp/web/q1glass.png

[pmolsen]

I cannot get 24 bit PNG's from Paint.Net to work at all with SU and
GE. I am talking about images with fully transparent cutouts. The
transparent areas come out solid white or black. They have to be 32-
bit for them to work.

[GaryM]

Did you try that one? It worked for me on your model. It actually is
32-bit ---24 bits RGB + 8-bit alpha channel.

I've even made PNGs with different amounts of transparency in
different portions of the image. They worked correctly when placed in
GE from SU, but not after appearing on the layer.

[Lorenz Eisermann]

Hey, let's challenge Google's GE coders. I'm anxious to see how this
one will render:

http://sketchup.google.com/3dwarehouse/details?mid=bca9575f80ffdc7f9e0320731cb2ea25&ct=lc&prevstart=0&hl=en

Depending on the point of view you may look through six faces with
different levels of transparency stacked in depth. Works great with
the local KMZ file.

Have fun!
Regards,

Lorenz

www.HausFilm3D.de

[GaryM]

Loren,

From here, when you look through the glass on the top tier
(observation deck) the wall and railing on the opposite side
disappears. That does not happen, however, when looking through the
glass on the lower levels. This occurs both with the KMZ DL'd from the
warehouse, and also with the KMZ SU generates when placing the model
(from the downloaded SKP) from SU directly into GE.

That problem seems to occur when looking through 2 (or more?) PNGs. SU
Guide Allison mentioned a stack problem. To see the opposite rail on
the top deck you look through 2 PNGs, but only 1 on the lower decks.
You do look though 2 PNGs on the lower decks to see the terrain, which
does not disappear. Would be interesting to see if nearby models
disappeared in that view, but there are none nearby.

[Lorenz Eisermann]

Gary,

Thanx for examining. That's really interesting as all partially
transparent PNGs are rendered without a flaw on my graphics card
(NVIDIA GeForce 8400M GS).
So the issue may also depend on drivers and graphics cards.

The observation deck wall and railing geometry has some depth. I
applied the PNG with cutouts as a (procedural) texture, not as an
image to the entire group. So there is the outside face with cutouts
and the face on the inner side of the deck, too. Next to it is the
glass cube with baked-on reflections and transparency set to 35%. Same
procedure on the opposite face. That's six faces with cutouts and semi-
transparencies in a stack. I can see everything displayed properly on
my system regardless if it's the downloaded KMZ or the SU file I am
looking upon.

Of course, I am still worried what will be the result if Google puts
the model on the 3D layer.

Thanks again.
Regards,

Lorenz

[SketchUp Guide Allison]

Hi Lorenz,

I can absolutely guarantee you'll get transparency burn-through. The
Google Earth layer will not correctly stack transparent textures with
alpha between 0 and 1; that is, it'll handle "cutout" .pngs where the
negative space is completely transparent, but partial transparency is
not supported. There is no current plan to alter this behavior due to
performance implications. The recommended approach for glass-like
textures is to instead use a phototexture of a "typical view" through
the transparent surface instead.

-- Allison

[Lorenz Eisermann]

Allison,

Thanx for that precise statement. Sure, Google has to set up
everything for the least common display technology on the customer's
side. I'll go and agonize what a "typical view" would look like from
all altitudes and angles.

Regards,

Lorenz

On 8 Jul., 18:12, SketchUp Guide Allison <allisonfloyd+...@google.com>
wrote:

> > > disappeared in that view, but there are none nearby.- Zitierten Text ausblenden -
>
> - Zitierten Text anzeigen -

[GaryM]

> Thanx for examining. That's really interesting as all partially
> transparent PNGs are rendered without a flaw on my graphics card
> (NVIDIA GeForce 8400M GS).
> So the issue may also depend on drivers and graphics cards.

That is interesting. I'm running an nVidia 8800 GTS. Haven't updated
the drivers in a while tho.

Here's what is looks like on my system:

http://groups.google.com/group/SketchUp/web/muggel.jpg

I notice that the opposite walls and railings have disappeared even on
the lower decks. That is the warehouse KMZ.

[SnowTiger]

Hi GaryM and Lorenz

I just tried to upload a couple screenshots without any luck.
After the "wheel" spun for about 3 minutes (when I selected Upload
File), all I got saw at the end of the list is this message "
Your group is currently using 99% of its quota - 993.8 MB of 1,000.0
MB.
Delete some files to be able to upload more
"

But I noticed pretty much the same as GaryM.
One thing I did see however that is odd, when looking from the side
that GaryM took his image from, you don't see the opposite wall. But
when you look from the opposite direction, you can see both
walls ??? !!!!

I was hoping to upload an image to show an oddball artifact I always
see when I minimize my side bar (in the upper left of the screen in
GE). I guess I'll show it some other time.

Anyway and BTW - I have a nForce 790i Ultra (Core 2 Quad) with Q6600
processor and dual (SLI) 8800 GT 's and the most up-to-date drivers.

[Lorenz Eisermann]

Hi folks,

thanks to everyone for looking into that issue and commenting. Here's
news from the "Transparency Test Tube". Google yesterday put my tower
model on the 3D layer. In Google Earth fly to

52.417276, 13.625090

or look up my model in 3DWH:

http://sketchup.google.com/3dwarehouse/details?mid=bca9575f80ffdc7f9e0320731cb2ea25&ct=lc&prevstart=0&hl=en

To my surprise the observation deck railing is visible through the
semi-transparent glass cube (all textures being displayed in stack
with some mild Z-fighting, though) while when looking through the
window panes at the lower levels of the tower only the face/texture on
top of the stack (next to view pane) is getting displayed. The stairs
inside and the opposite wall are disappearing IF the opposite wall
also has a section which is not 100% opaque.

All transparencies have been baked into the PNG images which means
that transparency was applied BEFORE importing the textures to
SketchUp. In SU all texture opacity is set to 100%.

So my notion this time is not "Boulder... we have a problem" but
"Allison: Why does it work?"
There is mainly two differences in how I applied textures on the
observation deck compared to the lower levels.
1. Opacity of the glass cube is 35%, opacity of the lower level window
panes is 65% (both set in the image processing, not in SU).
2. When looking through the glass cube the wall next to it (with
railing on top) has its own textured face oriented towards the view
pane. When looking through the lower level windows you look at the
rear face of the opposite wall. The rear faces are not textured.

Which one(s) are making it work on the top level?

Regards,

Lorenz

www.HausFilm3D.de