Sonic Retro, “Sonic Physics Guide: Jumping”

Cite as: Sonic Retro, “Sonic Physics Guide: Jumping”
Original: https://info.sonicretro.org/index.php?title=SPG:Jumping&oldid=359032
Archived: https://web.archive.org/web/20251210184938/https://info.sonicretro.org/SPG:Jumping
Accessed: 2026-10-20
Credit: Sonic Physics Guide, written and maintained by the Sonic Retro community.
Notes: Revision oldid=359032 ("last edited on 27 July 2023"), read from the Wayback copy because the live site serves a bot challenge.

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Sonic's jump speed, `son_jumpspeed`, is `$680` subpixels per frame (6.5 px/frame) out of water.	`Constants`	T3
`Sonic_Jump` adds the jump speed along the ground normal (`CalcSine` of angle − `$40`); on flat ground that is exactly `-$680` to Y speed, nothing to X.	`Jump Velocity`	T3
During a jump, with no jump button held, `Sonic_JumpHeight` clamps any rise faster than 4 px/frame to exactly `-$400`.	`Variable Jump Height`	T3
In the airborne-rolling mode (`Sonic_MdJump2`), the release check runs before `ObjectFall` moves Sonic and adds gravity.	`Variable Jump Height`	T3
Sonic doesn't move on the press frame; `Sonic_Jump` drops its return address, skipping the rest of the grounded routine, `SpeedToPos` included.	`Bugs when Jumping`	T3