SP1 Scrolling: Updated Performance Review
I have reconfigured all tests to use a 16x24-cell scrolling zone, which is a more realistic size for a scrolling game on the ZX. The results are proportionally similar to the previous ones, but with bigger differences between the baseline measurements and the optimized ones in Test 3 and Test 4.
Here is the table with the old and new results in an additional column for comparison:
| Test # | Directory | Description | FPS-16x16 | FPS-16x24 |
|---|---|---|---|---|
| Test 0 | sp1-baseline | PoC to test raw performance of SP1 updating whole scroll area | 22 | 15 |
| Test 1 | sp1-randomtiles | Whole scroll/top-row-update loop, full column scroll and invalidation | 17-18 | 12 |
| Test 2 | sp1-sprites | Test 1, with added moving sprites | 13 | 10 |
| Test 3 | sp1-partial-inv-1 | Test 2, with added partial column invalidation, method #1 | 17-25 | 13-22 |
| Test 4 | sp1-partial-inv-2 | Test 2, with added partial column invalidation, method #2 | 20-25 | 17-23 |
| Test 5 | - | Not implemented | - | - |
| Test 6 | sp1-parallax | Test 3, with 2 added parallax zones scrolling at different speeds | 11-17 | 9-16 |
In this new test it can clearly be seen that the baselines (the ones that manage and invalidate the full area) suffer a big performance penalty when enlarging the scrolling area, while the optimized ones are not quite that affected. Indeed the algorithm in Test 4 seems a real candidate for a good ZX scrolling game, using all SP1 power.
I’d like to thank everyone for the feedback on this series of articles. As I said, I’ll continue on my personal learning path, exploring and documenting some other scrolling techniques, but not SP1 based. I’m really satisfied with all the knowledge gathered here and I hope this can be a reference work for future game developers who want to make a scrolling game.
Have fun
J.