Strange render-results

[flipya]

Hi all,

I'm doing some renders on a building and somehow the render for this part doesn't look like it's supposed to.

The frame and glasspanes are nested the same way as on the higher floors, and yet those work out fine. There's another instance of this group in another part of the building and it gives similar results... Show hidden geometry in SU is on, so I can verify that there's nothing blocking the view. Tried rendering just this window-unit (by copying it away from the building and rendering that) and it still gives the same result. Any ideas?

I did a sketchup output and a prelim render to illustrate.




Please help

[WardNL]

Are the faces reversed? Also make sure both the front and the back are painted with the same material.

See my example.

[flipya]

Thanks for the response Ward, but I'm afraid that's not the problem. All surfaces are facing towards camera. Nearly all the surfaces (except for the little panels) are flat btw, no thickness I mean. But that's no issue on the higher elevations so shouldn't be a problem here... I saved the component of the whole windowunit to open in a separate document and give it another shot, just have to wait a little for a render that's cooking right now. If that doesn't work I'll upload it here, maybe someone can give it a go to see whether they get the same result.

[WardNL]

Would you mind sharing the SketchUp model so I can take a look?

[Frederik]

I agree that this could very well be a back-face issue...
However, without the model (or a part of it), it's really difficult to debug from the images you've attached...

[flipya]

OK this is strange... When I export the window-section it renders fine. When I keep it in the document however it screws up no matter where I move it.

I stripped the model down to just two window-sections to meet filesize-requirements. Thanks in advance for giving it a go guys!

[Chris]

Hi flipya, the file you posted renders fine for me... however, I did notice that you have some material issues.

For many faces, you have the front face set to default, a back face material set, and a group / component material face. While this will usually work out, it's a good way to get a confusing render! If you can avoid setting a back color, it's always a good idea, so you don't get confused on what material should show up. If you have to assign a back face, it's a good idea to assign the front face directly as well, not just from the group or component.

[flipya]

Thanks Chris, that helps. Still strange though that it renders ok on your machine

Got the original model from a client who exported it from AutoCAD, and I was wondering why all the backfaces had such an odd color. Now I know. So is there an easy way to fix this for the entire model (it's a pretty big building with many many faces) or should I just run a plugin like this and re-texture the whole d*mn thing?

Also, what do you mean by "a group / component material face" ?

[Chris]

Also, what do you mean by "a group / component material face" ?

I shouldn't have used the word 'face' I just meant material.

In SketchUp, you can apply a material to a front face and / or a back face. You can also apply a material to a group or component, and all the faces (both front and back) in that group or component that have the 'default' material will pretend they have that group / component material. Since Twilight can only render one material per face, it has to choose between 3 materials.

• If a face has the front material applied, Twilight always uses the front material
• If there is no front material, if the face is in a group or component and that group or component has a material, Twilight uses that material
• If neither of the above is true, Twilight will use the back material

Removing the material and starting over may be the best choice, if things have gotten too cluttered. I've never used any of the plugins for it, but I imagine they work well. Alternatively, you can use the SU paint bucket tool to paint the 'default' material onto all the groups, components and faces for the problem area.

[flipya]

So I guess the conclusion (or at least one of them) is to never texture a whole group when there's already other textures used inside it...

BTW, I couldn't for the life of me figure out how to change my default 'non-texture' back to good old white and blue, but found out that copying everything, starting a new file and pasting it in there does the trick. Thanks again for the assistance.