Glass rendering black - another desperate plea for help

[misimon]

Hi All,

I'm another newbie who can't render glass (in Skindigo) without using the 'Thin Glass' material setting. It just goes black. Having trawled through all the forums the repeated advice is to make glass with a thickness, but my understanding of sketchup is that everything is made up from planes with no depth. Alternatively there is a lot of reference to 'flipping meshes' to face out or 'checking normals', but I've no idea how to do this.

Any help would be greatly appreciated as all the other aspects of the renders seem to be working really well.

Thanks.

[Borgleader]

What they mean by giving it depth, is that you can't have a window that is simply a single plane. It needs to be a cube, or well cuboid. Of course it'll be made up of 6 planes (top, bottom, left, right, front, back) but the important part is it needs volume. This is due to the formula behind refraction/reflection and all that physics mumbo/jumbo.

Your "cube"'s normals point outwards. You could also post a screenshot of skindigo in wireframe mode (with normals visible if possible).

[CTZn]

We are aware about that particular workflow SketchUp users have. It will probably be taken into account in the future, though it doesn't belong to me to tell.

Until then, it is correct not to treat single sheets as volumes, any harsh may it sound for you.

Why is the glass rendering black ? Because the light entered a glass material by passing through the sheet, and will be subject to absorbtion until it passes through the same material again. In that case, the absorbtion depth will be:

from the glass > to the front wall > back to the glass (approximately). In most cases this means travelling through glass for meters, hence the light extinction.

Making glass panes volumes instead allow the light to enter, then exit the glass object after the few millimeters.

[misimon]

Thanks Guys, I appreciate the help. It seems to be that the way I draw in Sketchup may be a little lazy and I've now discovered that in order to implement Borgleader's advice, the 'volumes' need to be constructed separately and inserted into a model without any faces in contact with those of other objects/materials. Having done this for both glass and water, all is working fine.

[galinette]

Hello,

This is because sketchup automatically welds geometries and volumes. So it is hard to make a closed glass cube that contacts the window frame without having sketchup merging the faces, screwing up the materials.

You can have faces in contact, but to avoid problems, the glass cube must be modelled separately in a place clear from other geometries, then grouped, then moved to its desired location. Sketchup will not do automatic welding for primitives that belong to different groups.

Etienne