Monday, August 27, 2012

OutRun C++ Engine Tech Demo 2

At last, here's a new demo of the OutRun engine. The entire game is ported, aside from sound and the service mode.

In terms of functionality, this release is bare bones. There is no menu system yet, all options are hardcoded and you have to play the game windowed.

It would be great if you could report bugs (and I'm sure there will be plenty) in the comments below. Please verify any subtleties against MAME for reference.


  • Conversion time from decompiled code: 1 year 10 months.
  • Estimated ratio of time spent coding vs. debugging: 1:5
  • Road rendering code: 1500 lines
  • Ferrari handling & rendering: 1680 lines
  • Code to render level objects: 1050 lines
  • General sprite handling code: 890 lines
  • Traffic handling code: 675 lines
  • Code to handle crash routines: 1450 lines


  • Cursors: Steering
  • Z: Accelerate
  • X: Brake
  • Space: Gear Change
  • 5: Insert Coin
  • 1: Start
  • F1: Pause
  • F2: Advance a frame when paused (useful for observing visual problems)
  • F3: Toggle/Freeze timers. (i.e. infinite time)
In a future revision, there will be options to custom the controls and the analogue sensitivity. I find MAME's default setup too twitchy, so you'll find the steering a little more heavy in comparison. 

Enhancements over original:

In a future revision, enhancements will be optional and there will be a menu toggle to enable/disable them.



Thursday, August 23, 2012

End Sequence Bugs

Here's another bug in the original game; the leftmost two end sequences have a palette issue which causes the male sprite to suddenly change in appearance. In the screenshot below, we're approaching the goal banner.

Then, as if by magic, the colour of the man's top changes to light blue!

But don't worry, on reaching the finish line it's back to dark blue again. 

The game code swaps to an animation playing routine at the point of the colour change. It should be seamless. But it seems as if 2 of the 5 end routines are configured incorrectly. 

Why am I noticing such trivial details? Because the engine is now complete (minus sound and test mode). Expect a test release in the next week! 

In other news, I updated the Philko bootleg page with some new pictures. 

Thursday, August 02, 2012

Light at the end of the tunnel...

It's been nearly two years since I started rewriting OutRun, and three years since I begun decompilation work. This is, and feels like, a long time. According to Yu Suzuki, the original game took four programmers between eight and ten months to complete, so I'll take some reconciliation from the fact this was only a part-time project.

Following the success of the decompilation work, I expected the rewrite to be plain sailing. In fact, the rewrite proved tough - really tough! The size and complexity of the codebase meant I spent an inordinate length of time debugging. Writing your own code from scratch is comparitively easy; your intentions are clear and tracking errors is straight forward. Finding the source of a bug in thousands of lines of ported assembler can be a nightmare.

Debugging ultimately became a case of stepping through the suspected area of code line-by-line and comparing results with the MAME debugger. I invoked crazy tactics along the way; I coded routines to utilise MAME memory dumps for the road layer to quickly determine whether bugs were caused by erroneous code or if data in memory was at fault. This also enabled me to compare the original with my port from an identical starting point.

The other complication was the way in which the original codebase was designed and structured. The style of code varies dependent on who was working on it and by god, they produced a lot of it. The hardware specifications were insane by 1986 standards, and the coding team appear to have approached the project with the view that space and clarity were not a primary concern. There is a huge amount of code duplication and multiple routines that perform similar tasks with minor modifications. Despite evidence of code reuse at Sega, there should be no doubt that this is disposable code, not a reusable game engine. In fairness, the programming team would have been under considerable time pressure.

So what's next? I'm going to port the final chunk of code to handle the game completion sequence. This consists of a big switch table to manually send commands to the sub CPU handling the road layer (similar to the road split, but not quite the same), code to control the Ferrari AI during this period (similar to attract mode, but not quite the same), code to blit the timing information to the screen (similar to other digit blitting routines but not quite the same) and code to handle the animation sequences (similar to the start line intro sequence but not quite the same). Now, you're beginning to understand the OutRun codebase!

Once this is complete, I will release a new build for testing purposes. I was going to release sooner, but I'm so close in terms of porting the entire core engine I'm going to hold back. This build will run at 60fps and feature a selection of other minor improvements not in the original game. From this point onwards, the fun begins and we can start to include extra functionality and enhancements. It will also be a good point to port the code to a variety of platforms. I will be looking for help once I tidy up the codebase a little further.

I hope that explains where the project is, feel free to comment below if you have questions.

UPDATE: Tantalisingly close... bonus points code done, bonus sequence AI done, bonus track control done. Just the animation sequences now.