glass is black if "follow me" option were used

[rifl]

Dear all,

my Name is Florian and i use Indigo Render with Google Sketchup Pro. There is following problem:

There are two possibilitys to draw a Cylinder:
1) Drawing a circle and extrude it to the hight
2) Drawing a vertical rectangle, a horizontal circle (wich starts in the middle of the bottom side of the rectangle) around it and using the "follow me" Feature (like here: http://support.google.com/sketchup/bin/ ... swer=39022, just with a rectangle instead of an treangle)

I assigned a glass material.

If i use Methode 1, the glass is rendered perfect. If i use Methode 2 it's simply black. I attached the File below, so everybody can try it (including igs files)

I need the follow me Feature for a complex form which i can't achive with other Tools. So the question is: Where is my mistake?

Thank you in Advance, Florian

ps: Don't worry about the Camara Settings

[tremo]

Hello Florian, You have to reverse the faces. Front side facing inward, in your example.

1 Select all.
2 Right mouse button.
3 Reverse faces.

[lycium]

I've been investigating with a friend the modelling causes of black glass in scenes from SketchUp, and she made this example of how various ways to model the same object affect the normals and resulting render.

There's a little more information about glass modelling here: http://www.indigorenderer.com/documenta ... ling-glass

[galinette]

Hi,

By doing so, there is a risk that you have a messy geometry, with overlapping & crossing polygons. If you rotate the rectangle by a full 360° circle, you end up with twice the surface everywhere and overlapping polys. If sketchup does not cleanly resolve all the generated problems, you may get strange results with glass.

You could try the following : instead of putting the circle at the middle of the rectangle base, put it on the corner, so that the rectangle base is not a diameter but a radius. This will make a much cleaner geometry.
I'm sure that I generate spheres that way, which work with glass (I draw a half circle, which I "follow me" on a circle, or a circle which I "Follow Me" on a half circle, but using two circles leads to the same issues)

Etienne

Dear all,
2) Drawing a vertical rectangle, a horizontal circle (wich starts in the middle of the bottom side of the rectangle) around it and using the "follow me" Feature (like here: http://support.google.com/sketchup/bin/ ... swer=39022, just with a rectangle instead of an treangle)

[lycium]

Another example of different way of making windows... I had no idea it was so fragile

[CTZn]

It's just an issue with the resulting surface direction, is it ? If not, what's the issue I'm curious !?

With maya depending on the profile direction the i.e. revolved surface will have it's normals pointing in one direction or the other. Either the profile curve or resulting surface directions can be flipped to fix the issue.

[CTZn]

Say for instance, if you tumble the camera around in order to draw the vertical plane, does it fix the resulting pane model ? To project it against the negative axis direction I mean.

[tremo]

It always happens when the front surfaces facing inward. Or if a component has been mirrored.
When groups are mirrored, it does not happen.
Make a test. Delete the glass material. And check what color the faces are pointing outwards.
Gray-blue is the rear, the front side is white. If both surfaces have the glass material, it can not be checked. Or explode the component is rendered black.

Sorry for the poor english.

[CTZn]

Is it how it works: when pulling a pane out of a face, make sure that its forward side remains at the exterior of the pane ?

If so that would seem to be a consistent creation scheme to me. Provided that I'm not missing a point here

[galinette]

Another example of different way of making windows... I had no idea it was so fragile

That's strange, I'm always using the left method but it works...

However, I always apply the glass material after extrusion, and under sketchup every time I apply a material, I apply it on both faces (select all by triple click / apply material / right click - flip faces / apply material / right click flip faces )

Etienne

[tremo]

If we are applying a transparent material. Both faces receive the material. If we apply a non-transparent material. It only gets the clicked face. If we make later in the material is a glass material, the render will not work.
My method is: .
1 Extrude
2 Check that all faces are white.
3 Select All.
4 Apply transparent material.

If we hide in the "styles" the edges. We can easily select all faces. And check both sides in entity info.

[tremo]

If we "follow me" tool-use. Is the result. Often the face reversed. Also in the Sketchup Manual.


http://support.google.com/sketchup/bin/ ... swer=39022

[Pibuz]

I usually do windows in my buildings (...would you bet differently? ), and the tip I can share is ALWAYS CHECK NORMALS. SketchUp is a great tool, but indeed a bit tricky when dealing with normals. I've been using it for years, but still sometimes I can't understand why normals are facing differently from the expected..

Apart from that, applying the glass material to external faces is enough (once you checked the normals pointing outwards), you do not need to apply it to interior faces of the block. I always suggest to my students this workflow:
1. Make the simple geometry
2. check the normals
3. make a group/component
4. triple select the group/component (this will open the block AND select all subfaces)
5. apply the SU glass material
6. exit the block.

This is indeed better than applying the SU glass material to the whole block, which caused some issues in relatively old versions of SkIndigo, and you never know if they could come back again one day or another

[lycium]

Thanks for the great info guys, much appreciated!

Edit: For checking the normals, you can use the "monochrome" display method (the button after "textured") to show front- / back-facing surfaces (front-facing is white, back is blue).

[Pibuz]

Speaking of which, you guys should know that the backface colour is customizable. The blue-ish default tint is sometimes quite hard to distinguish from a surface in the shadow..

So I usually suggest to make it of a more contrasting color, I use red.
Just open the "styles" window, go to the "modify" tab, choose the second cube icon, and change the backface colour (microtutorial end)