Gens/GS II

Gens/GS II is a partial rewrite of Gens/GS written by GerbilSoft. Gens/GS II improves the basic framework of the emulator, which will allow for the addition of many new features.

New features in Gens/GS II

• The UI now uses the Qt 4 library instead of GTK+ on Linux and Win32 on Windows. This means only one UI needs to be maintained for all platforms, instead of maintaining two separate UIs. It also means that Mac OS X is now supported natively.
• Full Unicode support provided by the Qt 4 library. (The onscreen display is still limited to cp1252; I may extend this later, but it's unlikely.)
  • libgens does not use Qt, though it handles strings using UTF-8 natively. For full compatibility, it has parts of Gens/GS r7+'s Win32 Unicode Translation Layer in order to convert strings to/from ANSI and UTF-16 as necessary.
• The UI and emulation code are split into separate internal projects: libgens (for emulation) and gens-qt4 (for Qt4 UI). Additional UIs can be added later for other platforms, e.g. gens-win32 (for a minimal Win32 UI for Win9x, since Qt4 doesn't work on 9x) and gens-wii.
• ZOMG savestate format. Compared to the previous GSX-extended format, the ZOMG savestate format has much more comprehensive documentation and is extensible in a well-defined manner.
• OpenGL rendering. Gens/GS had OpenGL rendering on Linux, but Gens/GS II uses OpenGL rendering on all supported platforms.
• OpenGL shaders. Shader programs are used to provide certain effects, such as fast blur and the paused tint. Software fallbacks are still provided for systems that don't have the GL_ARB_fragment_program extension.
• 1x and 2x renderers are removed in favor of simply blitting to the OpenGL texture. 2x support is emulated by setting 640x480 output with nearest-neighbor interpolation.
• Support for more types of input devices. 3-button and 6-button gamepads are supported, but in addition, 2-button (SMS) gamepads are now supported. Teamplayer and 4WP support is much improved, and there's initial Sega Mouse support. The controller configuration interface is not complete yet, so it's not possible to configure the controllers at the moment.
• Improved I/O tristate control. If a controller bit is set to input, then that bit shows up as a 1 on the controller side. Gens and Gens/GS do not properly implement this, but Gens/GS II does.
• Screenshots are now always saved in PNG format.
• The VDP emulator has been ported from x86 assembly language to C++. (This was partially done in Gens/GS r7+, but Gens/GS II finishes it.) Among other things, it now passes all tests in Nemesis' Sprite Masking & Overflow Test ROM.
• Interlaced mode is now displayed using "flickering" interlaced (like Regen). That is, even fields are shown on one frame, and odd fields are shown on the next. This is a configurable option, and can be switched to flickering, even only (Gens-style), and odd only. 2x resolution mode (Kega-style) will be added later.
• Initial 64-bit and PowerPC ports. Compiling on these platforms currently results in a "no-emulation" build; that is, the CPU cores are not compiled, since they're still written in x86 assembly language. This does let me test the other components on these platforms, though. (DEBUGGING PURPOSES ONLY!)

Known Issues

• Framedropping doesn't work yet. If the system slows down for any reason, the emulator will stutter instead of dropping frames.

Features not ported from Gens/GS yet

• MDP plugin support.
• Color adjustment.
• Sega CD and 32X emulation.
• Configuration. (Most options are currently hard-coded, including aspect ratio constraints, interlaced display mode, and color scale method.)