Is it possible to make a 3D wall visible only from one side in three.js?

Questions
7

The walls are oriented in such a way, that their local Z axis points outwards. Then I measure the angle between the Z axis of a wall and the Z axis of the camera – if the angle is less than 90 ° then the wall is visible. Of course, instead of calculating the angle, it is faster to calculate the dot product and check the sign.

The hard version is implemented as:

wall.getWorldDirection( v );
camera.getWorldDirection( u );
wall.visible = v.dot(u) > 0;

while the soft version is:

wall.getWorldDirection( v );
camera.getWorldDirection( u );
wall.material.opacity = 2*v.dot(u);

Here is the code: https://codepen.io/boytchev/pen/xxMZzJx

Toggle lines 131/132 to switch between hard and soft versions.

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