Why the Intel® RealSense™ Depth Camera D435 is not able to recognize acrylic and poly carbonate (and mostly transparent materials in general) to calculate depth.
In trying to calculate depth of acrylic and polycarbonate walls, the D435 camera sees right through those materials like it isn't there.
The Intel® RealSense™ Depth Camera D435 uses stereo vision to calculate depth, and works by projecting infrared light onto the object.
With transparent surfaces (like acrylic or poly carbonate), the infrared light is not able to project onto the surface, so depth cannot be calculated. Instead it will project the light onto the first opaque object behind the transparent surface.