> Character movement is limited to tiles, so you can never stand halfway between two tiles.
[…]
> Examples: Prince of Persia
That is absolutely false. You can stand on any pixel in Prince of Persia. It’s when I find stupid errors like these that I start to question the entire article they appear in.
As I remember, when you step slowly from the middle of a tile, you always end up on the edge of that tile. And if there is a chasm and you try to step once again, you almost trip and regain balance. If there is no chasm, you step to the middle of the next tile.
IIRC, you can adjust your position quite precisely by crouching, which has a side effect of making you move forward a tiny little bit. Yes, stepping towards a chasm will make you stop at the edge, but that does not alter the fact that your position is definitely not clipped to fixed steps, as the article erroneously claims.
When moving horizontally there's very small lag at the start and then he accelerates to full speed pretty much instantly.
When moving vertically by jumping, his speed is straight up set to some constant. There is downwards deceleration by gravity though, leading to "fall faster" tricks:
I’ve implemented platformer collision dozens of times now and the only way I’ve found it to be genuinely smooth is to do it one pixel at a time, just like the author suggests.
But something always bugs me about that - we know the closest edge of the closest obstacle, we know the vector of the player’s motion, by all accounts we should be able to calculate the point of contact in one go without doing any substeps.
And yet, doing it in one pass always seems to result in a myriad of edge cases (literal!) that break the whole thing, unless you do heavy preprocessing, converting your tiles to a graph of lined surfaces, etc etc.
I like the idea of a guide like this. Reminds me of “Implementation of Hex Grids,” another high quality game-related guide: https://www.redblobgames.com/grids/hexagons/implementation.h... and before that, “Beej’s Guide to Network Programming”: https://beej.us/guide/bgnet/
Related. Others?
Guide to implementing 2D platformers (2012) - https://news.ycombinator.com/item?id=31450218 - May 2022 (37 comments)
A guide to implementing 2D platformers - https://news.ycombinator.com/item?id=10202275 - Sept 2015 (32 comments)
The guide to implementing 2D platformers - https://news.ycombinator.com/item?id=4065033 - June 2012 (2 comments)
The Guide to Implementing 2D Platformers - https://news.ycombinator.com/item?id=4005883 - May 2012 (2 comments)
For making the game more fun, you can then add features that are now standard/expected like coyote time. https://www.youtube.com/watch?v=97_jvSPoRDo
> Type #1: Tile-based (pure)
> Character movement is limited to tiles, so you can never stand halfway between two tiles.
[…]
> Examples: Prince of Persia
That is absolutely false. You can stand on any pixel in Prince of Persia. It’s when I find stupid errors like these that I start to question the entire article they appear in.
As I remember, when you step slowly from the middle of a tile, you always end up on the edge of that tile. And if there is a chasm and you try to step once again, you almost trip and regain balance. If there is no chasm, you step to the middle of the next tile.
IIRC, you can adjust your position quite precisely by crouching, which has a side effect of making you move forward a tiny little bit. Yes, stepping towards a chasm will make you stop at the edge, but that does not alter the fact that your position is definitely not clipped to fixed steps, as the article erroneously claims.
> I believe that Mega Man actually employs infinite acceleration, that is, you’re either stopped or on full speed
Yeah, acceleration is essentially infinite.
https://tasvideos.org/GameResources/NES/Rockman/Data
When moving horizontally there's very small lag at the start and then he accelerates to full speed pretty much instantly.
When moving vertically by jumping, his speed is straight up set to some constant. There is downwards deceleration by gravity though, leading to "fall faster" tricks:
https://tasvideos.org/GameResources/NES/Rockman#FallingFaste...
I’ve implemented platformer collision dozens of times now and the only way I’ve found it to be genuinely smooth is to do it one pixel at a time, just like the author suggests.
But something always bugs me about that - we know the closest edge of the closest obstacle, we know the vector of the player’s motion, by all accounts we should be able to calculate the point of contact in one go without doing any substeps.
And yet, doing it in one pass always seems to result in a myriad of edge cases (literal!) that break the whole thing, unless you do heavy preprocessing, converting your tiles to a graph of lined surfaces, etc etc.