ALL ORIGINAL ARTWORK ON WHICH SOME OF THESE MODELS ARE BASED ARE COPYRIGHT © THEIR RESPECTIVE OWNERS AND ACKNOWLEDGED.
None of the images below are drawings but the unedited results of rendering true 3D models.
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Note that the image "Opus 2B" can be constructed as a coherent object, as can be seen here. The basis of this and all similar drawings involving cubes is that there are gaps between the cubes of approximately ½ width; however, due to the isometric viewpoint the arrangement is structurally identical to having the cubes physically touching one another with a ½-width offset. The following image, "Opus 1 #293aa", which is the classic triangle of cubes, is in its current form completely impossible as each corner arrangement of three cubes is different to the minimalist "Opus 2B".
"Impossible Penetration"
Coloured copy of a line sketch from The Eye Beguiled & Adventures With Impossible Figures.
The following three images show stills from the animation of an impossible inside corner of a cube morphing to an impossible outside corner of a cube, via a truncated tri-bar, though notice it's only the width of the 'walls' that change: the hole remains the same size.
These shapes are all possible : only the perspective makes them seem odd.