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Shazz · Posted: Fri Oct 22, 2004 1:08 am Post subject: Stream texture

Hello there !

I'm trying to code it but a question never killed anybody (or I hope so...), is it possible to stream a texture to the GS, I mean let's say that my framebuffer = a texture (not true but basically it is as I 'just' map a texture to the screen, the GS is not involved for any 3D rendering in my case) ?

And a want to update this framebuffer in parts and not globally (in my case, per line), so is it possible to only modify a part of the existing texture present in the GS memory ?

I try to see if I can tweak the TEX0_x Register to only update a part of the GS memory...with a good choice of the base pointer and TEX_DECAL switch...
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blackdroid · Joined: 17 Jan 2004 Posts: 564 Location: Sweden

uhm yes technically you can update parts of a texture.
but sending just on line ? what are you trying to achieve ( in any case im sure you will be wasting cycles )
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Shazz · Posted: Fri Oct 22, 2004 5:47 pm Post subject:

All the details are available on my blog : www.acerockerz.free.fr/blog/

But I can symmarize in a few lines :

The goal is to "externalize" the Planar2Chunky routine from the emulator core (so running within the EE) to the VU1, basically, the core sends the source videobuffer (organized in 4 planes) & the palette to the VU1 to perform the texture generation and then send the texture to the GS to display it on the screen : target framebuffer (a 2D buffer so).

So as the whole texture won't fit into the 16Kb my idea was to stream the source videobuffer line by line to the VU1 which can update the texture (the target videobuffer) and do P2C conversion, 16 colors to 16bbp...

Why line by line is because the Atari ST can handle palette update at each HBL so I wouls send each new line updated with the associated palette.

So, if it is possible I would fit into the 16Kb but maybe problems of sync and "DMA waits" can occur...
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MrHTFord · Joined: 10 Feb 2004 Posts: 35 Location: England

Shazz,

AFAIR the Atari ST can have it's palette changed as and when you want. It's just a set of registers. Yes, lots of demos did change it in the HBL interrupt, but lots of plasma demos changed it constantly.

Anyway, it's been years since I did any ST stuff, so my memory could be corrupted.

Shazz · Posted: Fri Oct 22, 2004 10:13 pm Post subject:

Hello Mr HTFord,

Nice to see an old ST coder here ! :D

Yep you're right, the palette register is usually changed at the HBL for rasters but nothing forbid to change it more frequently, I would think that the minimum should be 16 pixels as the planes are organized to handle 16 pixels so changing the palette in the middle of a plane should provoke I think really strange things....

I'll ask if there is some cases when it occurs... some demos...

By the way, this is more a technical challenge than to improve the emulation at this level, currrently the CaSTaway emulator core manage lines and not pixels so, it would be a good start ;-)
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Shazz · Posted: Fri Oct 22, 2004 11:15 pm Post subject:

Mr HTFord,

Shazz · Posted: Sat Nov 06, 2004 8:37 pm Post subject: