Edges become visible through components from a distance


#1

When i view an object from closer up, the object appears totally opaque. However, the further away i view the object from, the more edges from other components directly behind the object begin to appear. For example in a model of a shed:

View close up - only the siding is visible - completely opaque
View further away - the edges of the sheathing behind the siding begin to appear
View even further away - the edges of both the sheathing and the framing behind the sheathing are now visible through the siding

Am I doing something wrong? Is this normal? It makes the model look terrible from a distance when you can see all the edges through each other. Any insights would be appreciated, thanks.

Please note that all my materials used are 100% opaque.


#2

This was the first question I posted to a Sketchup forum. It turns out that this is a shortcoming with OpenGL. Maybe the easiest fix is to put the underlying geometry on a layer and hide it when necessary.

Shep


#3

Thanks for the reply. I could try that, but I’d still like these components visible in the places they’re not behind other objects.


#4

No

Yes. It’s a ‘feature’ of SketchUp’s OpenGL rendering engine.

Generally, the best way to prevent edges showing through is to hide the edges.
Use the Eraser + Shift to hide the offending edges.

See…
Are lines showing through faces from a distance? — SketchUp Sage > Problems > Other Annoyances


#5

Generally, the best way to prevent edges showing through is to hide the edges.
Use the Eraser + Shift to hide the offending edges.

Thanks.


#6

Is there any way to do this to an entire component at once, or does each individual edge have to be done separately?


#7

You can use Thomthoms plugin selection toys to reduce a selection to only edges e.g… Ypu can change their properties with the entitiy info window afterwards.


#8

This happens because when things are scaled down as you zoom out, eventually your outer surface object scales down to the point that it has effectively zero thickness and the objects behind it are at the same location - from OpenGL’s viewpoint. So it displays both. Not a good thing, but also not something that SketchUp can override except, as @Shep and @Geo have suggested, by hiding the objects behind.


#9

It would seem that erasing edges isn’t the greatest solution either. It makes viewing components very difficult unless they’re all different materials or already separated from each other. Oh well, i much prefer functionality to aesthetics anyway. Thanks again folks.


#10

Usually the effect is visible only on screen, and doesn’t affect exported images or printouts. AutoCad 2D hidden line drawing exports, on the other hand, tend to miss some of the lines that should be there.

Lines missing or showing through are somewhat a problem of all methods of calculating hidden line images, not only openGL. I first met with it when making my first 3D model attempts in AutoCad in the late 1980s. It was rather a nuisance when the only output method was a pen plotter. An application simply cannot keep on calculating infinitely so there must be a limit to the accuracy.

Anssi