Commented-out signature page
Venn diagrams for Boolean operations
Improved ray-casting diagrams
Just say depth-masking instead of depth-buffer masking
Fixed a missing 'to' in Depth-Masking approach section
Removed paragraphs about approaches being CPU- or GPU-based
Don't need 'current' when talking about why OpenGL 3
Diagram of clipping process for Boolean XOR
Fixed caption of depth-masking screenshot
Say 'approach' in screenshot captions for approaches
Say 'on some systems' when talking about performance boost of optimized slicing
Removed duplicate 'future' in last paragraph
Put caption of listing below it
Diagram for volume representations