08-23-2023, 02:54 PM
Hi!
Basic scaling (Neo-Geo style) is quite cheap, if fact zoomed-in layers have more pixel throughput than regular layers, because as each tile covers more screen space, fewer calls are required to fetch the next tile. Affine transformations (SNES-style) are the opposite: as the source and destination scanning are not parallel, every single pixel must fetch its parent tile, and what position occupies inside the tile. Thus these kind of layers offer the worst performance.
90º rotated tiles and sprites may have more cache misses than regular ones, but the overall performance is somewhat similar and it's a rarely used feature. Horizontal and vertical flips are free. When a tile is fetched, some checks and assignments must be done to determine scanning pointers (accounting for flips and 901 rotations), but once they're setup, all the pixels of the tile are output straight. By this rule, 16x16 tiles offer better performance than 8x8.
However if you check the benchmarks, even a Raspberry Pi 3 has enough power to run a standard game at 60 fps. Let's say you render a 16:9 240p game: 400x240 at 60 fps, that's 5.7 MPixels/s. Pixel throughput on a Pi 3 of regular layers and sprites is between 50 - 60 MPixels/s, that is 10x than needed. That leaves plenty of room to overdraw multiple scroll planes and sprites, blending, scaling, etc. Affine layers on a Pi 3 is about 8 Mpixels/s, enough to be used smoothly but don't overdraw a lot -the SNES had just one layer on Affine mode in mode 7-. And we're talking about a Pi 3, that is the humblest thing i have on my hands. The Pi 4 doubles that performance, and any low-end PC has even more power.
Basic scaling (Neo-Geo style) is quite cheap, if fact zoomed-in layers have more pixel throughput than regular layers, because as each tile covers more screen space, fewer calls are required to fetch the next tile. Affine transformations (SNES-style) are the opposite: as the source and destination scanning are not parallel, every single pixel must fetch its parent tile, and what position occupies inside the tile. Thus these kind of layers offer the worst performance.
90º rotated tiles and sprites may have more cache misses than regular ones, but the overall performance is somewhat similar and it's a rarely used feature. Horizontal and vertical flips are free. When a tile is fetched, some checks and assignments must be done to determine scanning pointers (accounting for flips and 901 rotations), but once they're setup, all the pixels of the tile are output straight. By this rule, 16x16 tiles offer better performance than 8x8.
However if you check the benchmarks, even a Raspberry Pi 3 has enough power to run a standard game at 60 fps. Let's say you render a 16:9 240p game: 400x240 at 60 fps, that's 5.7 MPixels/s. Pixel throughput on a Pi 3 of regular layers and sprites is between 50 - 60 MPixels/s, that is 10x than needed. That leaves plenty of room to overdraw multiple scroll planes and sprites, blending, scaling, etc. Affine layers on a Pi 3 is about 8 Mpixels/s, enough to be used smoothly but don't overdraw a lot -the SNES had just one layer on Affine mode in mode 7-. And we're talking about a Pi 3, that is the humblest thing i have on my hands. The Pi 4 doubles that performance, and any low-end PC has even more power.