# draw a skewed rectange for each data-point

#     ____
#    G p  D \
#   / o / | |
#  B_t_C  | | 
# |       | +-- $val_height
# | face  | |
# |       | /
# |       E \ 
# |      /  +-- $slant_height
# A____F/   /
#
# \-+-/ \+/
#   |    |
# $ppd   - $consts{slant}