Fully-automatic. This setting re-activates the normal AUTOBACK system. Under mode 2, whenever graphics are drawn on screen, they will be synchronised with any active Bobs automatically. All worries are taken care of by the system.
Bob drawing modes
Once Bobs have been set up, you are allowed to change the way that they react with other
screen graphics.
SET BOB
instruction: set drawing mode for Bobs
Set Bob number,background,planes,mask
SET BOB is used to change the drawing mode used to display a particular Blitter Object. It is best used before displaying a Bob on the screen. This command has several parameters, of which the first is simply the number of the Bob to be affected.
The second parameter is a number that sets the mode of the background, in other words, the way that graphics underneath the Bob are to be re-drawn. There are three alternative background mode settings. A value of zero automatically replaces the screen background beneath the Bob, after it moves away. This is the standard drawing system, and gives a smooth animation effect when the Bob is moved across the screen.
If the background is a positive number, then the original background graphics are completely forgotten when the Bob moves away, and the area beneath the Bob is replaced by a solid block of colour. The colour is calculated with this formula:
Colour = Background-1
So the following line sets the mode of Bob 1, and draws a block of graphics in colour 9 (calculated as 10-1) whenever the Bob is moved. Notice how commas must be included if other parameter values are omitted.X> Set Bob 1,10,,
Since this operation is much faster than the standard system, it is recommended for bursts of extra speed. It can be used for moving Bobs across areas such as clear blue sky, and is also extremely effective when operated with the various rainbow effects.
The final alternative background setting is to use a negative value. This turns off the re-drawing process, allowing you to fill the old background areas with any colours or patterns you like, using the standard AMOS Professional graphics commands.
After the two parameters that set the Bob number, and the background mode, SET BOB requires a parameter to establish which of the screen planes is to be used for the Bob. The planes setting is a bit-map, consisting of a binary number where each digit represents one plane of the screen, and each plane represents one bit of the final colour to be displayed on screen. The numbering system works like this:
Plane: 543210 Digit: %111111