A "mask" means that the background colour (colour zero) around a Bob is made transparent, so t hat the screen graphics show through. The mask is also used by certain collision detection routines. A mask is automatically set up for every Bob, and the NO MASK command takes away this mask, so that the entire Bob image is drawn on the screen, including its original background colour and any other graphics in colour zero. To remove a mask, simply use this command followed by the number of the Bob image you are interested in.
Never remove a mask from a Bob while it is being displayed on screen, or its image will be scrambled! Remember to always use the BOB OFF command first.
Bob Priority
It is important to understand that every Bob automatically possesses a priority of importance,
and that this priority is based on the Bob's number. So a Bob carries a priority value from 0 to 63,
and AMOS Professional uses this value to decide in which order Bobs are displayed and which
Bobs barge their way in front of others when moving around the screen.
The general rule is that a Bob with a higher priority number is displayed in front of one with a lower priority number. For example, Bob 5 would cut in front of Bob 4, but be obscured if Bob 6 crossed its path. So it is clear that this priority system should always be remembered when you number your Bobs.
AMOS Professional allows changes in the priority system to suit your needs, this first system offers an alternative based not on Bob numbers, but on the position of Bobs on the screen.
PRIORITY ON
instruction: set Bob priority to highest y-coordinate
Priority On
PRIORITY OFF
instruction: set Bob priority to default status
Priority Off
When PRIORITY ON is used, Bobs with the highest y-coordinates take priority on the screen. It is usually best to set hot spots at the bottom of Bobs to exploit this priority, and some superb perspective effects can be created. All that is needed to re-set the original Bob number priorities is to use the PRIORITY OFF command.
PRIORITY REVERSE ON
instruction: toggle on Reverse Priority of Bobs
Priority Reverse On
PRIORITY REVERSE OFF
instruction: toggle off Reverse Priority of Bobs
Priority Reverse Off