Previously the bounding boxes and triangles were maintained in two separate
arrays (Vectors). As the triangle vector was sorted and the bounding-box array
was not , the order of both arrays differed. This meant that the index in one
was different than the other, which caused lookup issues.
To prevent this, the bounding-box is now part of the triangle structure so that
there is a single structure that cannot become out-of-sync anymore.
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