GXR questions

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dominicbeesley
Posts: 464
Joined: Tue Apr 30, 2013 11:16 am

GXR questions

Postby dominicbeesley » Wed Nov 29, 2017 7:33 pm

This split from a hardware thread about a hardware blitter: viewtopic.php?f=3&t=14125

I'm thinking of (not promising anything) an attempt to accelerate the graphics extension rom. I have little experience of it (beyond trying it out at school decades ago).

I have some questions:
- was it possible to have masks for sprites
- are the sprite files that are saved in any way similar to the later Arthur/Risc OS sprite files?

I'm sure there will be more questions to come!

D

jregel
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Location: Gloucestershire

Re: GXR questions

Postby jregel » Wed Nov 29, 2017 9:52 pm

I don't know the answers to your questions, but the BBC Master Welcome disc has the SPRITER ROM image in the $.LIBRARY directory. This adds the sprite handling part of the GXR that wasn't included in the Master MOS.

It was discovered (in this thread that the SPRITER code is only 9K (the remaining 7K of the sideways RAM is used for storing the sprite data). This 9K includes the sprite editor as well as the VDU extensions, so that might be easier to disassemble?
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RobC
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Re: GXR questions

Postby RobC » Wed Nov 29, 2017 10:24 pm

I don't remember the Sprite ROM handling masks and I can't find any mention of them in the manual:
http://mdfs.net/Docs/Books/Manuals/AcornGXR.txt

Not sure about the format but as RISC OS sprites can have masks, I'd suspect they are different (although possibly the same as RO sprites that don't have masks?).

dominicbeesley
Posts: 464
Joined: Tue Apr 30, 2013 11:16 am

Re: GXR questions

Postby dominicbeesley » Thu Nov 30, 2017 10:42 am

Thanks lads, I'll have to have a look at the various ROMs when I get a chance and see what the files look like in a hex editor.

If I do anything I'll try and do masks as well without upsetting the API too much.

Some example of actual software that used the GXR would be in order. If there's not software that uses it being actively used I would maybe not worry myself too much about sticking to the original API?

D

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jgharston
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Re: GXR questions

Postby jgharston » Thu Nov 30, 2017 11:28 am

dominicbeesley wrote:Some example of actual software that used the GXR would be in order. If there's not software that uses it being actively used I would maybe not worry myself too much about sticking to the original API?

Graphics tests much of the GXR functionality comparing it with doing the same operations manually.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

dominicbeesley
Posts: 464
Joined: Tue Apr 30, 2013 11:16 am

Re: GXR questions

Postby dominicbeesley » Fri Dec 01, 2017 12:02 pm

Thanks I'll give that a whirl later, I need to get the sideways RAM thing working on the blitter card or blow a GXR rom...


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