Boulder Dash Preview

[tokra]

Peiselulli of tRSi has converted Boulder Dash for the VIC-20. He is still unsure what to do with it, so there's no download-link, but just this amazing preview on YouTube:

https://www.youtube.com/watch?v=1yhZ8Ty3bLo

[beamrider]

Wow - that looks amazing!

[mingle]

That looks too good to be true - is that really running on a VIC-20?!?

[mrr19121970]

It looks great.... had to check it wasn't 1st April

[AndyH]

Looks superb. The scrolling is so smooth too - i suspect it is the Vic registers to shift the screen? I notice the game goes full screen once past the title screen, the timing is spot on.

[Vic20-Ian]

Fantastic!

I hope this gets released and is entered in the Things We want to see / hear competition on Denial.

viewtopic.php?f=1&t=10130

[Miklós]

Very nice.

Exactly these tracks are my favorites, I played a lot with this part on C64. Watching the youtube video, I was relieved.
Thank you, Wonderful.

[javierglez]

Looks superb. The scrolling is so smooth too - i suspect it is the Vic registers to shift the screen? I notice the game goes full screen once past the title screen, the timing is spot on.

This plus a raster interrupt to separate the scores row from the play area

[hasseapa]

Wonderful. Compared to the C64 version, it shows a little less horizontally and a little more vertically. The playing area (excluding the status bar) must be 232x208. Is this done by the same guy that did the Gianna Sisters scrolling background demo?

[aeb]

Nice work!

[R'zo]

Awesome work! Looks amazing! I'm blown away!

[Victragic]

Looks great, the sort of game that suits the PAL Vic very nicely. Would have loved this on a cartridge back in the early 80s!

I'm guessing the horizontal scrolling is a combination of changing the value in $9000, as well as having characters offset by one mc pixel.. there really aren't that many elements in the game so you could pre-render for all possibilities.

Vertical scrolling - as far as I'm aware you can only set the vertical position of $9001 for an entire screen refresh, meaning to keep the score in the same place and prevent wobbling edges you would have to redefine the characters in the score line, as well as fixing the top and bottom line of the Playfield by nulling $9002 at the right time (no raster interrupts on the Vic).

Is an amazing looking game, really shows how capable the Vic and the coder(s) are.

[AndyH]

I'd love to know the tricks.

For the horizontal, if you slow down the video to 0.25 you can see it is moving two multicolour pixels at a time when it scrolls, so this is the usual 4 hi-res pixel increments from the horizontal register.

For vertical, I wonder if there is some trick that is done with some exact timing on the vertical reg and/or others to achive that split? Or if it is something else.

Either way, to get the scrolling to appear consistently smooth without apparent judders is hugely impressive.

[Mayhem]

Someone from BGG (who currently own the rights to Boulder Dash) is aware of this, and they are looking to licence and maybe put out a release. So we shall see if that transpires...

[beamrider]

@AndyH

I did a similar split on my Super Mario demo. You need to have a raster split as VicTragic says then change the screen to point somewhere else (I used zero page). If you have vertical scrolling then you need to re-render the static text characters to compensate for the vertical-scroll offset otherwise it judders as you scroll up and down (because $9001 is only latched during the VBI).

https://www.youtube.com/watch?v=ANJQ5tZBhAs

If, as you say, he's only scrolling in 1/2 char increments, then that is fairly easy by just manipulating registers. To scroll in single multi-color pixels requires use of pre-rendered shifted pairs (as I did and I think is done in Cheese & Onion) or adjusting the actual character data in real-time like in mountain king below.

https://www.youtube.com/watch?v=tAItz1ig6B0

He doesn't have any sprites as such I see, so the problem becomes a fair bit easier. Still a great achievement though.

+
You can also download ex6.zip from this thread which has smooth 4-way scrolling with a fixed area at the bottom.
viewtopic.php?f=2&t=8620&start=45#p96212
As you can see there were a few differences between VICE and real h/w in that thread that never got resolved.