Workprint – March 2018

So let’s get some workprint business out of the way first; since there are now two people showing an interest in converting Vallation to other platforms I might just have to properly shuffle it to the front burner and get on with building the new levels so they actually have a full game to convert. This process will doubtless involve lots of expletives – all aimed at myself for taking shortcuts or bodging – and possibly some rewriting or at least refactoring of the code because it seems to take far more processing time than I remember.

The RLE-based background compression I was mumbling about in the last update is also implemented and works surprisingly well, in fact there’s a simple but functionally complete game wrapped around it now. It has over 56K of background data in there which has been compressed into a mere 23.1K and takes around six minutes to scroll through at one pixel a frame. My intention is to get the entire game done rather than doing a “development diary” so I know it’s finished when writing the C64CD blog posts.

I’ve done a few more tests as regards grabbing video footage, again using VICE and OBS to this time accidentally record a full ten level playthrough of Warhawk. The results look quite solid, but there’s a bit more fiddling with settings I want to do and I have Vegas Pro courtesy of the Humble Bundle to install and get my head around… so who knows, perhaps I’ll become a rich and famous YouTuber? Well okay, probably just a YouTuber but I’m only doing it for the groupies anyway.

In other news, whilst I was away in Kent I met up with fellow Cosine inmates Darren Nevell , Frank Gasking and Sean Connolly for the twice-yearly internal meeting; that makes things sound all official and stuff, but we basically take up a corner of Starbucks and natter for the best part of a day. After nursing a coffee each for a couple of hours we then piled into Level Up and spent a happy hour or so trying to persuade ourselves not to buy everything in sight! Amongst other things I ended up with a PSU for one of my spare Atari 800XLs, a collection of books which are destined for the racking going into my office once it’s decorated including one about BASIC for the Dragon 32, an unboxed freebie of A64 – a C64 emulator for the Amiga which has a dongle for connecting peripherals – and… well, this thing:

Despite looking like an adolescent Enigma machine it’s actually a joystick interface for the Spectrum where each direction and the fire buttons can be connected to keys so pushing left on the stick is, as far as the computer is concerned, someone holding down the O key. I absolutely adore the bizarre but functional nature of this thing; it’s such a perverse work-around for the problem but at the same time will literally work on anything that doesn’t require actual typing to play. Come to think of it, you could also “type” rude words with the joystick…

MD201703 – The Bat-Tro (C64)

Back in the mists of time (or more accurately, last Monday) Cosine released a new demo called MD201703 – The Bat-Tro on the C64 with code and graphics by me and music by aNdy. This came about because a member of Batman Group (the same one behind Batman Forever on the Amstrad CPC – wired some of their Amiga graphics… erm, let’s say “less than wonderfully” before uploading to the C64 Scene Database. Now, I’ve been converting graphics for a very long time so, rather than just saying “those look a bit rough” or something similarly English and reserved, instead it seemed like a fun idea to instead convert one of the Batman logos myself and tart it up a bit.

And once that was done, along came the brilliant idea of turning the picture into an actual demo for release as part of the monthly demo series. That meant poor aNdy was persuaded to produce a soundtrack at the last minute, which was a cover of the first level music from Batman on the Mega Drive – I wanted something less obvious than one of the movie scores or Adam West’s theme and stumbled across Sunsoft’s game whilst looking for a double height character set to convert for the scrolling message. The final SID tune turned up soon after I asked and, despite aNdy’s protestations about minor rough edges, is great stuff.

I mentioned previously about discussing how this works so going from top to bottom… the picture is a high res bitmap but uses eight sprites (two at any point in the picture but recycled four times) in order to circumvent the attribute problems where the light green and yellow blend into other colours on the outer edges. The remaining six sprites are behind the five bats drifting over the picture and the sparkles of light which can be positioned pretty much anywhere over the logo.

The timing sensitive code is in the lower border, powering the sixteen pixel high scroller. The part of the message which is legible uses eight hardware sprites with each supplying three characters to make twenty four in total, but the “smearing” effect is where things get interesting because they’re cycle timed vertical splits of the ghost byte, three on the left side of the screen (the third zeroes the ghost byte for where the scroller starts) and two on the right. It could have been done with colour splits as well (so a raster bar behind the scroller was possible rather than the fixed green background which was quite tempting) but this method doesn’t suffer from the “twinkle” caused by midline colour register changes on a C64C or C128.

Reading that back, I’m wondering again if these descriptions include enough detail? They’re pretty much targeted at other 8-bit programmers, but should I still write in more detail about cycle timing at some point or explain what the ghost byte is… so answers on a postcard to the usual address please, and I’ll see about answering further questions in the comments as usual.

Workprint – March 2017

It’s time for another little update on things that are happening; first off I released a new monthly demo at the start of the week but… umm, sort of forgot to post about it here! That’ll appear in the next day or so – possibly including something of a “how it works” as well to sort of atone for the delay.

I haven’t settled on anything specific for MD201704 just yet – hopefully it’ll be released at a little Cosine get-together near the start of next month if that goes to “plan” – but there are a couple of prototypes which might work for that release. I’ve also had a couple of requests from other groups to code a slideshow and a BBS intro so those should be fun! Both are in the early stages at the moment and the slideshow’s artist is new to the C64 so I’m still walking him through the graphical capabilities right now, but things are going well on that front even if the poor soul is about to be introduced to one of my less than user friendly graphics conversion tools!

Yes, this post is somewhat vague and very light on screenshots but the projects themselves are somewhat nebulous at this point! It’s safe to say that there’ll be raster bars in there somewhere, though…