How to change Sonic's Jumpheight, Top Speed, Acceleration and Deceleration

This guide is for the newcomer learning ASM. This was one of the first things I taught my friend when I first taught him.


HOW TO CHANGE SONIC'S JUMPHEIGHT:


SONIC 1:


Go to Sonic_Jump (Surprisingly enough not Sonic_Jumpheight.) And take a look at this:




Sonic_Jump: ; XREF: Obj01_MdNormal; Obj01_MdRoll


move.b ($FFFFF603).w,d0


andi.b #$70,d0 ; is A, B or C pressed?


beq.w locret_1348E ; if not, branch


moveq #0,d0


move.b $26(a0),d0


addi.b #$80,d0


bsr.w sub_14D48


cmpi.w #6,d1


blt.w locret_1348E


move.w #$680,d2 < Change 680 to any value. Changing it to a higher number makes Sonic jump higher.


btst #6,$22(a0)


beq.s loc_1341C


move.w #$380,d2 < Controls the height of the jump for underwater



SONIC 2:




Sonic_Jump:


move.b (Ctrl_1_Press_Logical).w,d0


andi.b #$70,d0 ; is A, B or C pressed?


beq.w return_1AAE6 ; if not, return


moveq #0,d0


move.b angle(a0),d0


addi.b #$80,d0


bsr.w CalcRoomOverHead


cmpi.w #6,d1 ; does Sonic have enough room to jump?


blt.w return_1AAE6 ; if not, branch


move.w #$680,d2 < Same as in the Sonic 1 section


tst.b (Super_Sonic_flag).w


beq.s +


move.w #$800,d2 ; set higher jump speed if super


+


btst #6,status(a0) ; Test if underwater


beq.s +


move.w #$380,d2 ; set lower jump speed if under









TOP SPEED, ACCELERATION AND DECELERATION:


Go to Obj01_Main:




Obj01_Main: ; XREF: Obj01_Index


addq.b #2,$24(a0)


move.b #$13,$16(a0)


move.b #9,$17(a0)


move.l #Map_Sonic,4(a0)


move.w #$780,2(a0)


move.b #2,$18(a0)


move.b #$18,$19(a0)


move.b #4,1(a0)


move.w #$600,($FFFFF760).w ; Sonic's top speed < change this


move.w #$C,($FFFFF762).w ; Sonic's acceleration < change this


move.w #$80,($FFFFF764).w ; Sonic's deceleration < change this



FOR UNDERWATER:




Obj01_InWater:


move.w ($FFFFF646).w,d0


cmp.w $C(a0),d0 ; is Sonic above the water?


bge.s Obj01_OutWater ; if yes, branch


bset #6,$22(a0)


bne.s locret_12D80


bsr.w ResumeMusic


move.b #$A,($FFFFD340).w ; load bubbles object from Sonic's mouth


move.b #$81,($FFFFD368).w


move.w #$300,($FFFFF760).w ; change Sonic's top speed < change this


move.w #6,($FFFFF762).w ; change Sonic's acceleration < change this


move.w #$40,($FFFFF764).w ; change Sonic's deceleration < change this



SONIC 2:


Go to Obj01_init:




Obj01_Init:


addq.b #2,routine(a0) ; => Obj01_Control


move.b #$13,y_radius(a0) ; this sets Sonic's collision height (2*pixels)


move.b #9,x_radius(a0)


move.l #Mapunc_Sonic,mappings(a0)


move.b #2,priority(a0)


move.b #$18,width_pixels(a0)


move.b #4,render_flags(a0)


move.w #$600,(Sonic_top_speed).w ; set Sonic's top speed < change this


move.w #$C,(Sonic_acceleration).w ; set Sonic's acceleration < change this


move.w #$80,(Sonic_deceleration).w ; set Sonic's deceleration < change this



For Underwater:




Obj01_InWater:


move.w (Water_Level_1).w,d0


cmp.w y_pos(a0),d0 ; is Sonic above the water?


bge.s Obj01_OutWater ; if yes, branch


bset #6,status(a0) ; set underwater flag


bne.s return_1A18C ; if already underwater, branch


movea.l a0,a1


bsr.w ResumeMusic


move.b #$A,(Object_RAM+$2080).w ; load Obj0A (sonic's breathing bubbles) at $FFFFD080


move.b #$81,(Object_RAM+$2080+subtype).w


move.l a0,(Object_RAM+$2080+$3C).w


move.w #$300,(Sonic_top_speed).w < change this


move.w #6,(Sonic_acceleration).w < change this


move.w #$40,(Sonic_deceleration).w < change this

 

Is there a way to make sonic use his walking animation at his normal top speed and use his final running animation at a faster speed? I didn't want to do this, I just want to know if it's possible.

 

Yeah, but i think that needs a few checks using code.

 

Please can you put the asm in a code box

Code:

like this

 

Nice to see you're getting good at ASM and write your own tutorials. A good idea would be to create an equate at the top of the code and all references to the jump height could be changed by changing one line of code. As mentioned before, please surround your code with asm tags.

 

A nice beginners tutorial, I'm glad to see basic stuff like this here, it'll open the eyes to many new-comers I'm sure.

Yes sir, right away sir... oh wait, who are you again? have a nice day sir.

 

Thank you, you want some credit in my hack?

 

I said please

 

I was about to flame liamsonichacker for bumping a one year old topic, but this really gave me the rest. I couldn't resist but laugh, hard.