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Commando from C64 with Atari + VBXE sources, is it possible and how fast?


shanti77

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How does the game conversion from C64 to Atari using VBXE look like, the author has little knowledge of the C64 architecture, but is learning;) When I found the described source code for this game on C64, I thought it would be a pity not to use it. By the way, you can learn a bit of C64 architecture and VBXE handling.

 

 

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Possible for sure.  I'd guess he's using the VBXE bitmap to do the sprites though they still look to be in 160 res.

Then you have the attribute map which is way more powerful than the attributes a C64 or stock Atari can do - allowing individual colour and palette selection per cell for each pixel value.

Rendering a standard C64 sized sprite comes to 504 pixels which should translate to about over 1,030 VBXE cycles (more in case of background merge operations)

Running at ~ 14 MHz the VBXE has about 284,000 cycles per frame.  About 68,000 would be lost to a 320x200 overlay + attribute map.

More cycles are lost if the CPU and Antic need to access VBXE memory though worst case there might be around 35,000 per frame.

Assuming you just do an erase/redraw for each object then you should be able to do about 90 sprites which is probably more than the CPU could handle though creative use of blits can help with that also.

 

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47 minutes ago, shanti77 said:

It is now possible to play and loop the game.

c.zip 26.88 kB · 8 downloads

Thank you so much @shanti77, it looks and plays incredible so far!

 

Unfortunately I'm get screen data corruption on Altirra 4.01 with (NTSC or PAL with VBXE enabled) around the time where the two guards are leading the prisoner off the screen, before that everything looks perfect. What settings should this be played with?

 

- James

 

image.thumb.png.b895731f3df010515a1361672714ea5d.png

 

image.thumb.png.da1c0e72096e30bd7aeceee2c528bdac.png

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10 hours ago, shanti77 said:

@ZeroPage Homebrew The game is only played on the NTSC version, probably not made during vertical blanking with more sprites. Set the emulator to PAL and everything should work.

That did it, thank you so much Janusz! Will you also be porting over a POKEY version of Rob Hubbard's incredible C64 music from the game? The Commando music is definitely one of my favourites from the C64 SID chip.

 

- James

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"I found the described source code for this game" - that is the most surprising part for me - I never thing these things when I search for them :-).

Looking forward to see the code how you use the VBXE.

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@Wrathchild I scooped up the file with HexEdit, because the VBXE window is 16KB and the image is a little bigger. It should also be remembered that in .bmp lines are written from bottom to top.

 

Of course you have to remove the $436 bytes header first. In total, $36 bytes is the header, and $400 is the color palette in the notation Blue, Green, Red, 00 (Only if it is a .bmp file saved in 256 colors).

Edited by shanti77
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file sprites256.bmp division:

-----------------------

header $436 bytes (remove)

-------------------------

sprites3.spr $1f80 bytes

-------------------------

sprites2.spr $3f00 bytes

-------------------------

sprites1.spr $3f00 bytes

-------------------------

sprites0.spr $3f00 bytes

 

/////

Each sprite is 2 pages in VBXE memory (512KB), 24x21 = 504bytes

Edited by shanti77
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I notice the sprites are still at 160 res.  Did you use blit with 2x H-zoom or are the objects still at 320 res which could allow an easy improvement if someone redrew them?

 

(OK, I guess 504 bytes would mean stored at 320h res)

Edited by Rybags
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Game plays nicely, very smooth' but at some point if possible fix the music and add fx (if this isn't possible then it's not a problem, but Commando is as popular for its music as it is for the game.)

 

Not trying to be negative, I love the work involved and truly appreciate it..

 

Thanks..

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8 minutes ago, shanti77 said:

@MclaneincIt's very easy to add new music with effects, just need someone to create it.

Excellent...Where's Miker when you need him :)

 

Seriously, any folks out there interested, get in touch with Shanti!

Edited by Mclaneinc
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As for the additional levels (Nostalgia version), you could probably get them from the C64 game. The levels are probably read there, but maybe not all of them. The basic maps are probably the same (possibly some minor corrections), just after firing a given level, track the location of the board appearance data (40x200 = 8000bytes) and a set of characters (2048bytes). All that remains is to track the trigger board (when new enemies are to appear, depending on the map fragment the hero is on), and the terrain mask table (256 bytes describe each character 0 = normal, 1 = no entry, 2 = sprite under the background, 4 = trench or water). Maybe you would need to add some extra actions for your opponents and finish the level. This, however, takes some time.

 

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26 minutes ago, shanti77 said:

This, however, takes some time.

Then it takes time, we all should be just happy it's being worked on, no need to rush or to feel like you are being rushed..

 

Like the old saying, good things come to those that wait..

 

Thank you for the great work..

 

Paul..

 

PS, As a C64 owner I love the work Nostalgia do so would love to see any of their extra work in your port, thanks for thinking about adding it.

Edited by Mclaneinc
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