04 September 2019, 11:39 | #1 |
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Join Date: Aug 2010
Location: Italy
Posts: 787
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Custom Screens System (fiddling with AMOS Professional and AGA)
This project has been gathering dust for 16 years, but I have finally decided to at least let Amigans know about it.
Back in 2002 (or early 2003) I got in touch with a developer who had released a nice AMOS Professional game. While chatting with him, I had the idea of developing a fancy Copper trick that would have allowed the game he was currently working on to flip the screen as seen in the level introduction screens of Project-X. The trick was never used (and the game was never released), but little by little it developed into a full video system for AMOS Professional that, by exploiting the AGA chipset, greatly expanded the platform's capabilities. As an added challenge, I decided to implement the system using AMOS Professional itself (eventually, for performance reasons, I implemented a procedure in assembly, but I did resist the temptation of doing the same for other procedures). Here's how the system documentation introduces the system itself: The Custom Screens System (CSS) is a system which extends the AMOS Professional screen handling capabilities by exploiting the AGA chipset. It allows to define Custom Screens (CSs), by means of custom Copperlists, that are 100% compatible with the graphic operations (bobs, drawing, texts, buffering, etc.) and that open a wide range of possibilities - most notably non-EHB 64 colors screens and an advanced Dual PlayField mode, named Cross PlayField (XPF). Features: * up to 8 CSs at once; * CSs with up to 64 non-EHB colors; * CSs usable as normal screens for graphic operations; * CSs display window size and position restricted only by hardware limits; * scrolling fully supported; * 35 ns horizontal scrolling granularity; * extended palette control: * 24 bit RGB color values (for everything); * fading from any palette to any other palette; * palette allocation, mixing, masking, etc. * XPF: * up to 8 bitplanes; * per-color opacity/transparency of the Front CS freely defineable; * all that can be done with CSs can be done with XPFs, too; * miscellaneous visual effects; * miscellaneous utility procedures; * Copperlist optimization. The CSs comes in the shape of a collection of procedures written in AMOS Professional itself (except for one written in assembly). This video shows a what the system was capable of; more specifically, how the system can overlay two indipendent screens (in the examples, the background has a depth of 5 bits and the foreground has a depth of 3 bits, but the depths can be any from 2 to 6, as long as their sum is at most 8), manipulate their palettes and degree of blending, and execute the flip screen effect that got everything started. [ Show youtube player ] Although CSS was fully functional and complete with tutorials and documentation, I never distributed it because, at some point, I realized I could have obtained more flexible and performing results by implementing the core idea differently. So, I started a new system from the scratch, called Advanced Video System (AVS). When it was about 80% done, a terrible thing happened: I lost the sources! I managed to recover some older sources, but I felt too bad to restart the development (not to mention that I was about to move country, so I did not have much time left). In my dreams, one day I'll use CSS to rework two old games of mine, but honestly I don't know if I'll ever have a chance to. Edit: eventually, I did write a new engine from scratch - check it out here. Last edited by saimo; 06 June 2021 at 12:09. |
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