Disabling P/M Graphics on Altirra

[lbaeza]

Hi there

 

Is there a quick and dirty way to make players and missiles invisible on Altirra?

 

Kind regards,

Luis.

[Rybags]

I don't think so - you can do for collisions.

But as your case I've often had the need to disable or change PM attributes to visualize what's going on.

Generally I've done so but using monitor commands to modify registers.

The problem there is that the running program can often undo your handywork within a frame but sometimes that's adequate.

 

You can do such things as set all object positions to zero:  e d000 0 0 0 0 0 0 0 0 (this is an especial case where it'll usually be reset in the next VBlank)

You can disable them in GTIA GRACTL e D01D 00

You can disable the PM DMA in Antic:  e 22F 22 and e D400 22 (or applicable DMA setting that retains width but disables PM fetches)

In some cases you migh also need to zero out the GTIA GRAF registers:  e D00D 0 0 0 0 0 0 0 0

 

To override the program bringing them back you could modify the program code.

Also in theory you could probably define a Cheat that did all of this work for you.

[lbaeza]

Hi Rybags

 

Thanks for your reply. Regarding changing byte values that are overwritten on the next frame...is there a way in Altirra to change a byte in memory and "lock it", that is to say, make it read only?

 

Kind regards,

Luis. 

[Wrathchild]

You can try a different approach.

Most changes to PMs are going to occur during a VBI or DLI.

So you can try the execution of an RTI to clear the PM registers.

e.g.

bx -n db(pc)=$40 "e d000 0 0 0 0 0 0 0 0 0 0 0 0"

 

@phaeron I tried "f d000 L0C 0" but this outputs "Filled D000-D00B." to the console window, any way to disable that?

[phaeron]

5 hours ago, Wrathchild said:

You can try a different approach.

Most changes to PMs are going to occur during a VBI or DLI.

So you can try the execution of an RTI to clear the PM registers.

e.g.

bx -n db(pc)=$40 "e d000 0 0 0 0 0 0 0 0 0 0 0 0"

 

@phaeron I tried "f d000 L0C 0" but this outputs "Filled D000-D00B." to the console window, any way to disable that?

Currently, no, there isn't a way to suppress informative text from debugger commands.