Model Breakup and Z Ordering Problems
This experiment demonstrates how parts of a model break up with
distance from the origin and also how parts of a model are rendered in
the wrong Z or depth order. Before trying this example, if you have not
installed a VRML viewer then please go to these instructions.
Click on this VRML file: ztear/zTear7mil.wrl.
You will see what appears to be a white rectangle with rows of pink
boxes behind.
Actually, it is a series of numbered white squares with red squares
sitting behind. The separation of red and white squares increases from
left to right/top to bottom.
Change viewpoints successively further from the origin by using the
Page Down key or right clicking and selecting them.
As you change to viewpoints increasingly furhter from the origin, you
will first notice gaps forming between tiles. Later on the model will
start to break up noticeably and some red tiles will begin to show in
front of white ones, demonstrating incorrect z buffer ordering. At
large distances from the origin the model break so much that it bears
no resemblance to how it should be rendered (as it appears at the
origin).