I found a rendering error - extruded object sometimes invisible or partly invisible

[Erik the Anarchitect]

I was writing a program where a wall drawn by extruding a zigzagging path with a rectangular cross section.

Looking at it from certain angles the wall fades out of view. As you move close to it it becomes invisible or partly invisible.

I am using Firefox on a Mac.
There are other objects in the scene. The wall rests on a large disk. There are rectangular posts that the viewer is looking past.


The name of the program is wallzig, and it is on my user page, in case you want to try to replicate the result.
http://www.glowscript.org/#/user/Erik_the_Anarchitect/folder/Public/program/wallzig

If you move the POV between the posts, the wall vanishes as you move toward it.

Is there a way to make the extruded object less likely to do this?

[Bruce Sherwood]

This is not an extrusion issue but problems of "z-depth". You would see this problem with any object you place in that position. Note that if you rotate the camera to put the extrusion near the "camera" there is no problem with the extrusion, but when you move close to the other objects they disappear.

If you are going to explore a very large space and depth I think you can't rely on the basic zoom capabilities but must do something like what is done in the Stonehenge example program, in which the camera itself is moved.