[LesliePere]

Howdy,

I usually render my models from Rhino or Max, but I thought I'm going to render from SketchUp 6 since I've never actually tried it from there. Anyhow, before I start, here's my setup:

SketchUp 6
Maxwell 1.5.1 with SkethUp 1.8b plug
Windows XP Pro SP2

So, let me illustrate with a few images of what is happening. This first image shows only the models, a screenshot from SU. The house is simmetrical, single wall geometry. And I have 2 windows, that are components.




Next, I just want to show the backside of a window. Its faces are removed at the back so it will cut a hole in the wall when placed. I'm only showing the rounded window, but the backside of the other window is constructed the same way. A transparent glass material is assigned to the ... well, glass part of the window(s).




Now, here's a section view of the house. You can see that it's nothing complicated. A simple single wall geometry. The faces and lines are cleaned up so the model is clean. So far so good.




Now, I'm going to place one set of windows (4 of them) on one side of the house and render. As you can see on the image, looks ok. The windows are reflecting the sky.




Here's where the fun starts. I'm going to place the 2 of the other windows (doesn't really matter which ones, but I'm gonna place the curved ones) at the exact opposite side of the house. The location and height of the windows will correspond to the location and height of the square windows - just symmetrically placed at the other side. Now, look what happens. The windows that are on the other side, will somehow show up and reflect in the newly placed windows. Also, it looks as if the walls became double walls - which they aren't, as you can see in the previous screen shots.




Sure enough, if I render the other side now, where the 4 square windows are, here again, the rounded windows that are just placed, reflecting again. As you can see, their location is symmetrical, since the rounded windows are reflecting only in the top-right, and bottom-left square windows, since that is the location where the rounded windows are - just at the other side.




First I thought I have some bad geometry, so I completely reconstructed the models - the house and both windows from scratch, and double checked if the geometries are clean. Well, sure enough, they showed up again.

What the heck is this all about!? Any clues?

Thanks!

PS: Sorry for the long post, hope you didn't fall asleep...

[muttlieb]

That's really bizarre. Is there any way you can post your SketchUp model so we can have a look?

[LesliePere]

Ok, so apparently it was a material issue. I had a siding texture and I created my own material from it. For whatever reason that screwed things up with the window reflections. Don't ask. I don't have an answer. So when I removed the siding material and assigned a material that comes with SU, things were back to normal. Then, I reapplied my own siding material again, and things are fine.

Beats me. I guess it was one of those hickups. Sure messed up my evening a bit... but at least I learned something. (...not sure what exactly though...

[Mattia Sullini]

just a thought, but do those objects have real thickness for the glass pane?
If not it could be a refraction issue...

[LesliePere]

Now I feel stupid. I spoke without looking.

First, Mattia, tx for the input. No, the glass (and everything else) is just a single pane. No thickness.

However, the REAL (and I mean the REAL) reason this happens - and it still does - if during exporting, you click the Options button, and under the Layers group if the "Indirect" checkbox is checked, this weird thing happens. When it's unchecked, then it doesn't happen.

I'm going to try to adjust the thickness of the glass per Mattia's input, and see what happens.

[LesliePere]

Well, that didn't take long. Thanks Mattia! That's what it was. The glass have to have thickness!!!

[Mattia Sullini]

[muttlieb]

By 'adjust thickness of glass', do you mean you've added another face in SketchUp a short distance from the glass to represent the thickness of glass? So you have two faces in SketchUp both assigned your glass material for each pane of glass?

[LesliePere]

yes, muttlieb, that is correct.

[muttlieb]

Interesting. I've always used a single face to represent glass and I've never encountered this issue.

[JDHill]

H Muttleib,

It can only mean that you're using AGS. With a single-surface pane and a true glass material, the light will be refracted only once, and you won't see 'straight' through it. Since AGS has no refraction (i.e. Nd = 1.0), this does not apply.

Cheers,

JD

[muttlieb]

Hi JD,

Yep, I'm using AGS. Thanks for the explanation. So would it give ok results to use AGS with double-surface glass panes? My main modeling app is Revit and my Revit windows have two surfaces that represent the window glass. So for I've been deleting one surface and applying AGS to the other surface. Would I get the same results if I applied AGS to both surfaces?

I suppose I should just go test this myself

Thanks,
muttlieb

[JDHill]

Hi Muttlieb,

It will work fine. However, I would prefer to use single-surface panes, since AGS still blocks some light, extending the time it will take to render.

Cheers,

JD

[thinkbuild]

Greetings All...

Does this mean that if one chooses:

SINGLE SURFACE GLASS
one should NOT assign AGS
PRO - it renders faster
CON - it is less "correct" in terms of rendering

DOUBLE SURFACE GLASS
one SHOULD asssign AGS
PRO - it renders more completely, correctly showing the working of the reflections, etc.
CON - it is harder to model (well, only a little bit), longer rendering.


Am I correct? Please, somebody, advise...

[Bubbaloo]

I wouldn't exactly agree with your statements.
AGS can be used in large architectural renders where refraction and caustics calculations aren't necessary. Can be applied to single or double plane glass.
Real glass should be used on product renders and close-ups that require correct caustics and refractions. Of course you can choose to use real glass on architectural renderings, but it will take longer to clear the noise and you MUST have 2 faces for the glass.