Difference between revisions of "Fix Scattered Rings Underwater Physics"

Revision as of 21:29, 20 December 2015

(Original guide for all 3 games by redhotsonic)

Quote from redhotsonic, - "Ah, the scattered rings when you get hurt. It can cause slowdown to your game, and even mess up the underwater palette. Now, when Sonic is underwater, his movement and his gravity is changed so he moves slower to act like he's in water. But when he is hurt under water, isn't it funny that the scattered rings still act the same as if you weren't in water?"

This is something that occurs in all 3 Sonic the Hedgehog Mega Drive games (and by 3, that IS counting S3&K as one game, though S&K has no water anyway, so it wouldn't be included regardless... but I digress). But is it really a bug, or is it merely a design choice? In either case, it's something that could stand to be fixed, and this guide tells you how to fix the ring physics in all of the games. First off... let's start with the original:

Sonic 1 HiveBrain fix

(Addition by Luigi Hero)

First, in your disassembly, go to "Obj37_MakeRings:" and find this bit of coding: <asm> bsr.w CalcSine move.w d4,d2 lsr.w #8,d2 </syntaxhighlight>

Just underneath, paste this: <asm> tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skiphalvingvel ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w obY(a0),d6 ; Is the ring object underneath the water level? bgt.s @skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower

@skiphalvingvel: </syntaxhighlight>

You should end up with something looking like this: <asm>Obj37_MakeRings: ; XREF: Obj37_CountRings move.b #$37,0(a1) ; load bouncing ring object addq.b #2,$24(a1) move.b #8,$16(a1) move.b #8,$17(a1) move.w 8(a0),8(a1) move.w $C(a0),$C(a1) move.l #Map_obj25,4(a1) move.w #$27B2,2(a1) move.b #4,1(a1) move.b #3,$18(a1) move.b #$47,$20(a1) move.b #8,$19(a1) move.b #-1,($FFFFFEC6).w tst.w d4 bmi.s loc_9D62 move.w d4,d0 bsr.w CalcSine move.w d4,d2 lsr.w #8,d2 tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skiphalvingvel ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w $C(a0),d6 ; Is the ring object underneath the water level? bgt.s @skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower

@skiphalvingvel: asl.w d2,d0 asl.w d2,d1 move.w d0,d2 move.w d1,d3 addi.b #$10,d4 bcc.s loc_9D62 subi.w #$80,d4 bcc.s loc_9D62 move.w #$288,d4 </syntaxhighlight>

This ensures that, when underwater, the rings' x_vel and y_vel are halved so they appear to be moving slower.

Next, go to label "Obj37_Bounce:" and under this... <asm> move.b ($FFFFFEC7).w,$1A(a0) bsr.w SpeedToPos addi.w #$18,$12(a0) </syntaxhighlight>

...place this: <asm> tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skipbounceslow ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w $C(a0),d6 ; Is the ring object underneath the water level? bgt.s @skipbounceslow ; If not, branch and skip underwater commands subi.w #$E,$12(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect

@skipbounceslow: </syntaxhighlight>

You can change the value of the gravity if you like, but I found $E to suit. Anyway, you should have something looking like this: <asm> Obj37_Bounce: ; XREF: Obj37_Index move.b ($FFFFFEC7).w,$1A(a0) bsr.w SpeedToPos addi.w #$18,$12(a0) tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skipbounceslow ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w $C(a0),d6 ; Is the ring object underneath the water level? bgt.s @skipbounceslow ; If not, branch and skip underwater commands subi.w #$E,$12(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect

@skipbounceslow: bmi.s Obj37_ChkDel move.b ($FFFFFE0F).w,d0 add.b d7,d0 andi.b #3,d0 bne.s Obj37_ChkDel jsr ObjHitFloor tst.w d1 bpl.s Obj37_ChkDel add.w d1,$C(a0) move.w $12(a0),d0 asr.w #2,d0 sub.w d0,$12(a0) neg.w $12(a0) </syntaxhighlight>

This ensures that, when underwater, the gravity is not as great. Otherwise, the rings will gain speed and then it won't give the desired underwater effect.

Sonic 1 Git fix

First, in your disassembly, go to "_incObj\25 & 37 Rings.asm" Go to @makerings: (part of the scattered rings object code) and find this bit of coding: <asm> bsr.w CalcSine move.w d4,d2 lsr.w #8,d2 </syntaxhighlight>

Just underneath, paste this: <asm> tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skiphalvingvel ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w obY(a0),d6 ; Is the ring object underneath the water level? bgt.s @skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower

@skiphalvingvel: </syntaxhighlight>

You should end up with something looking like this: <asm>@makerings: move.b #id_RingLoss,0(a1) ; load bouncing ring object addq.b #2,obRoutine(a1) move.b #8,obHeight(a1) move.b #8,obWidth(a1) move.w obX(a0),obX(a1) move.w obY(a0),obY(a1) move.l #Map_Ring,obMap(a1) move.w #$27B2,obGfx(a1) move.b #4,obRender(a1) move.b #3,obPriority(a1) move.b #$47,obColType(a1) move.b #8,obActWid(a1) move.b #-1,(v_ani3_time).w tst.w d4 bmi.s @loc_9D62 move.w d4,d0 bsr.w CalcSine move.w d4,d2 lsr.w #8,d2 tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skiphalvingvel ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w obY(a0),d6 ; Is the ring object underneath the water level? bgt.s @skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower @skiphalvingvel: asl.w d2,d0 asl.w d2,d1 move.w d0,d2 move.w d1,d3 addi.b #$10,d4 bcc.s @loc_9D62 subi.w #$80,d4 bcc.s @loc_9D62 move.w #$288,d4 </syntaxhighlight>

This ensures that, when underwater, the rings' x_vel and y_vel are halved so they appear to be moving slower.

Next, go to label "RLoss_Bounce:" and under this... <asm> move.b (v_ani3_frame).w,obFrame(a0) bsr.w SpeedToPos addi.w #$18,obVelY(a0) </syntaxhighlight>

...place this: <asm> tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skipbounceslow ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w obY(a0),d6 ; Is the ring object underneath the water level? bgt.s @skipbounceslow ; If not, branch and skip underwater commands subi.w #$E,obVelY(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect

@skipbounceslow: </syntaxhighlight>

You can change the value of the gravity if you like, but I found $E to suit. Anyway, you should have something looking like this: <asm> RLoss_Bounce: ; Routine 2 move.b (v_ani3_frame).w,obFrame(a0) bsr.w SpeedToPos addi.w #$18,obVelY(a0) tst.b ($FFFFF64C).w ; Does the level have water? beq.s @skipbounceslow ; If not, branch and skip underwater checks move.w ($FFFFF646).w,d6 ; Move water level to d6 cmp.w obY(a0),d6 ; Is the ring object underneath the water level? bgt.s @skipbounceslow ; If not, branch and skip underwater commands subi.w #$E,obVelY(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect @skipbounceslow: bmi.s @chkdel move.b (v_vbla_byte).w,d0 add.b d7,d0 andi.b #3,d0 bne.s @chkdel jsr ObjFloorDist tst.w d1 bpl.s @chkdel add.w d1,obY(a0) move.w obVelY(a0),d0 asr.w #2,d0 sub.w d0,obVelY(a0) neg.w obVelY(a0) </syntaxhighlight>

This ensures that, when underwater, the gravity is not as great. Otherwise, the rings will gain speed and then it won't give the desired underwater effect.

Sonic 2 fix

This guide uses the Xenowhirl disassembly, but notes for Git users are available.

First, go to "loc_120BA:" (part of the scattered rings object code. Git users, Obj37_Init, three '+'s down) and find this bit of coding: <asm> bsr.w JmpTo4_CalcSine move.w d4,d2 lsr.w #8,d2 </syntaxhighlight>

Just underneath, paste this: <asm> tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvingvel ; If not, branch and skip underwater checks move.w (Water_Level_2).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower .skiphalvingvel: </syntaxhighlight>

So, you should end up with something looking like this: <asm> loc_120BA: _move.b #$37,0(a1) ; load obj37 addq.b #2,routine(a1) move.b #8,y_radius(a1) move.b #8,x_radius(a1) move.w x_pos(a0),x_pos(a1) move.w y_pos(a0),y_pos(a1) move.l #Obj25_MapUnc_12382,mappings(a1) move.w #$26BC,art_tile(a1) bsr.w Adjust2PArtPointer2 move.b #$84,render_flags(a1) move.b #3,priority(a1) move.b #$47,collision_flags(a1) move.b #8,width_pixels(a1) move.b #-1,(Ring_spill_anim_counter).w tst.w d4 bmi.s loc_12132 move.w d4,d0 bsr.w JmpTo4_CalcSine move.w d4,d2 lsr.w #8,d2 tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvingvel ; If not, branch and skip underwater checks move.w (Water_Level_2).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower .skiphalvingvel: asl.w d2,d0 asl.w d2,d1 move.w d0,d2 move.w d1,d3 addi.b #$10,d4 bcc.s loc_12132 subi.w #$80,d4 bcc.s loc_12132 move.w #$288,d4 </syntaxhighlight>

This ensures that, when underwater, the rings' x_vel and y_vel are halved so they appear to be moving slower.

Next, go to label "Obj_37_sub_2:" and under this... <asm> move.b (Ring_spill_anim_frame).w,mapping_frame(a0) bsr.w ObjectMove addi.w #$18,y_vel(a0) </syntaxhighlight>

...put this: <asm> tst.b (Water_flag).w ; Does the level have water? beq.s .skipbounceslow ; If not, branch and skip underwater checks move.w (Water_Level_2).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skipbounceslow ; If not, branch and skip underwater commands subi.w #$E,y_vel(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect for the rings .skipbounceslow: </syntaxhighlight>

You can change the value of the gravity if you like, but I found $E to suit. Anyway, you should have something looking like this: <asm> Obj_37_sub_2: move.b (Ring_spill_anim_frame).w,mapping_frame(a0) bsr.w ObjectMove addi.w #$18,y_vel(a0) tst.b (Water_flag).w ; Does the level have water? beq.s .skipbounceslow ; If not, branch and skip underwater checks move.w (Water_Level_2).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skipbounceslow ; If not, branch and skip underwater commands subi.w #$E,y_vel(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect for the rings .skipbounceslow: bmi.s loc_121B8 move.b ($FFFFFE0F).w,d0 add.b d7,d0 andi.b #7,d0 bne.s loc_121B8 tst.b render_flags(a0) bpl.s loc_121D0 jsr (RingCheckFloorDist).l tst.w d1 bpl.s loc_121B8 add.w d1,y_pos(a0) move.w y_vel(a0),d0 asr.w #2,d0 sub.w d0,y_vel(a0) neg.w y_vel(a0) </syntaxhighlight>

This ensures that, when underwater, the gravity is not as great. Otherwise, the rings will gain speed and then it won't give the desired underwater effect.

Sonic 3&K fix

This guide uses the SVN disassembly.

Go to "off_1A658:" (the routines of the scattered rings). You'll see that its first job is to go to "loc_1A67A". That needs changing to "loc_1A68C". So, find this... <asm> off_1A658: dc.w loc_1A67A-off_1A658

dc.w loc_1A75C-off_1A658 dc.w loc_1A7C2-off_1A658 dc.w loc_1A7D6-off_1A658 dc.w loc_1A7E4-off_1A658 </syntaxhighlight>

...and replace it with this: <asm> off_1A658: dc.w loc_1A68C-off_1A658

dc.w loc_1A75C-off_1A658 dc.w loc_1A7C2-off_1A658 dc.w loc_1A7D6-off_1A658 dc.w loc_1A7E4-off_1A658 </syntaxhighlight>

This will skip "loc_1A67A" commands. This is because this location pushes the scattered rings object (or the reverse scattered rings object) to d6. For our water code, we need d6, because all other data registers are being used. It doesn't do this in Sonic 1 or 2 because there's no such thing as "reverse gravity". The scattered rings object needs to be moved to a1, but we can't do it here, because shortly after, a1 is being used for the amount of rings.

Next, go to "off_1A670:" This is extremely similar to what we just done, but for reverse gravity, so there's no point explaining what it's doing here as I just did that. Anyway, you should see this... <asm> off_1A670: dc.w loc_1A67A-off_1A670

dc.w loc_1A7E8-off_1A670 dc.w loc_1A7C2-off_1A670 dc.w loc_1A7D6-off_1A670 dc.w loc_1A7E4-off_1A670 </syntaxhighlight>

...replace it with: <asm> off_1A670: dc.w loc_1A68C-off_1A670

dc.w loc_1A7E8-off_1A670 dc.w loc_1A7C2-off_1A670 dc.w loc_1A7D6-off_1A670 dc.w loc_1A7E4-off_1A670 </syntaxhighlight>

Again, this will skip "loc_1A67A" commands. Explained why above.

Next, go to "loc_1A67A:" and you should see this: <asm> loc_1A67A:

move.l #Obj_Bouncing_Ring,d6 tst.b (Reverse_gravity_flag).w beq.s loc_1A68C move.l #Obj_Bouncing_Ring_Reverse_Gravity,d6 </syntaxhighlight>

Notice "Bouncing_Ring" (and the reverse one) is being pushed to d6. We need d6, so, delete it. It's no longer needed. Trust me. We have now freed d6, although we've lost pushing the scattered rings into place. Do not worry, that's next.

Next, go to "loc_1A6B6:". The very first command should be "addq.b #2,5(a1)" Just before that, add this: <asm> move.l #Obj_Bouncing_Ring,(a1) tst.b (Reverse_gravity_flag).w beq.s .notreverse move.l #Obj_Bouncing_Ring_Reverse_Gravity,(a1) .notreverse: </syntaxhighlight>

Yes, you might recognize this. It's part of that code you'd just deleted. We're pushing the scattered rings back into place. But instead of putting it to d6, we're putting it to a1. a1 is now available as it's not being used again for a while.

So you have something looking at this: <asm> loc_1A6B6: move.l #Obj_Bouncing_Ring,(a1) tst.b (Reverse_gravity_flag).w beq.s .notreverse move.l #Obj_Bouncing_Ring_Reverse_Gravity,(a1) .notreverse: addq.b #2,5(a1) move.b #8,$1E(a1) move.b #8,$1F(a1) move.w $10(a0),$10(a1) move.w $14(a0),$14(a1) move.l #Map_Ring,$C(a1) move.w #$A6BC,$A(a1) move.b #$84,4(a1) move.w #$180,8(a1) move.b #$47,$28(a1) move.b #8,7(a1) move.b #-1,(Ring_spill_anim_counter).w tst.w d4 bmi.s loc_1A728 move.w d4,d0 jsr (GetSineCosine).l move.w d4,d2 lsr.w #8,d2 asl.w d2,d0 asl.w d2,d1 move.w d0,d2 move.w d1,d3 addi.b #$10,d4 bcc.s loc_1A728 subi.w #$80,d4 bcc.s loc_1A728 move.w #$288,d4 </syntaxhighlight>

Still looking at "loc_1A6B6:", look and find this bit of coding: <asm> jsr (GetSineCosine).l move.w d4,d2 lsr.w #8,d2 </syntaxhighlight>

Just underneath, paste this: <asm> tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvingvel ; If not, branch and skip underwater checks move.w (Water_level).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower .skiphalvingvel: </syntaxhighlight>

So, you should end up with something looking like this: <asm> loc_1A6B6: move.l #Obj_Bouncing_Ring,(a1) tst.b (Reverse_gravity_flag).w beq.s .notreverse move.l #Obj_Bouncing_Ring_Reverse_Gravity,(a1) .notreverse: addq.b #2,5(a1) move.b #8,$1E(a1) move.b #8,$1F(a1) move.w $10(a0),$10(a1) move.w $14(a0),$14(a1) move.l #Map_Ring,$C(a1) move.w #$A6BC,$A(a1) move.b #$84,4(a1) move.w #$180,8(a1) move.b #$47,$28(a1) move.b #8,7(a1) move.b #-1,(Ring_spill_anim_counter).w tst.w d4 bmi.s loc_1A728 move.w d4,d0 jsr (GetSineCosine).l move.w d4,d2 lsr.w #8,d2 tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvingvel ; If not, branch and skip underwater checks move.w (Water_level).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvingvel ; If not, branch and skip underwater commands asr.w d0 ; Half d0. Makes the ring's x_vel bounce to the left/right slower asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower .skiphalvingvel: asl.w d2,d0 asl.w d2,d1 move.w d0,d2 move.w d1,d3 addi.b #$10,d4 bcc.s loc_1A728 subi.w #$80,d4 bcc.s loc_1A728 move.w #$288,d4 </syntaxhighlight>

This ensures that, when underwater, the rings' x_vel and y_vel are halved so they appear to be moving slower.

Next, go to label "loc_1A75C:" and under this... <asm> move.b (Ring_spill_anim_frame).w,$22(a0) bsr.w MoveSprite2 addi.w #$18,$1A(a0) </syntaxhighlight>

...put this: <asm> tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvinggrav ; If not, branch and skip underwater checks move.w (Water_level).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvinggrav ; If not, branch and skip underwater commands subi.w #$E,$1A(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect .skiphalvinggrav: </syntaxhighlight>

You can change the value of the gravity if you like, but I found $E to suit. Anyway, you should have something looking like this: <asm> loc_1A75C: move.b (Ring_spill_anim_frame).w,$22(a0) bsr.w MoveSprite2 addi.w #$18,$1A(a0) tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvinggrav ; If not, branch and skip underwater checks move.w (Water_level).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvinggrav ; If not, branch and skip underwater commands subi.w #$E,$1A(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect .skiphalvinggrav: bmi.s loc_1A7B0 move.b (V_int_run_count+3).w,d0 add.b d7,d0 andi.b #7,d0 bne.s loc_1A7B0 tst.b 4(a0) bpl.s loc_1A79C jsr (sub_F994).l tst.w d1 bpl.s loc_1A79C add.w d1,$14(a0) move.w $1A(a0),d0 asr.w #2,d0 sub.w d0,$1A(a0) neg.w $1A(a0) </syntaxhighlight>

This ensures that, when underwater, the gravity is not as great. Otherwise, the rings will gain speed and then it won't give the desired underwater effect.

This last bit is optional. You only need to do this if you're planning to have reverse gravity underwater. You'd be a bit mental if you do have this, but you never know =P

Go to label "loc_1A7E8:" and under this... <asm> move.b (Ring_spill_anim_frame).w,$22(a0) bsr.w MoveSprite_TestGravity2 addi.w #$18,$1A(a0) </syntaxhighlight>

...put this: <asm> tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvingrevgrav ; If not, branch and skip underwater checks move.w (Water_level).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvingrevgrav ; If not, branch and skip underwater commands subi.w #$E,$1A(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect .skiphalvingrevgrav: </syntaxhighlight>

Again, you can change the value of the reverse gravity if you like. So, you should have something looking like this: <asm> loc_1A7E8:

move.b (Ring_spill_anim_frame).w,$22(a0) bsr.w MoveSprite_TestGravity2 addi.w #$18,$1A(a0) tst.b (Water_flag).w ; Does the level have water? beq.s .skiphalvingrevgrav ; If not, branch and skip underwater checks move.w (Water_level).w,d6 ; Move water level to d6 cmp.w y_pos(a0),d6 ; Is the ring object underneath the water level? bgt.s .skiphalvingrevgrav ; If not, branch and skip underwater commands subi.w #$E,$1A(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect .skiphalvingrevgrav: bmi.s loc_1A83C move.b (V_int_run_count+3).w,d0 add.b d7,d0 andi.b #7,d0 bne.s loc_1A83C tst.b 4(a0) bpl.s loc_1A828 jsr (sub_FCA0).l tst.w d1 bpl.s loc_1A828 sub.w d1,$14(a0) move.w $1A(a0),d0 asr.w #2,d0 sub.w d0,$1A(a0) neg.w $1A(a0) </syntaxhighlight>

This ensures that, when underwater, the gravity is not as great when it's in reverse gravity mode.

SCHG How-To Guide: Sonic the Hedgehog (16-bit)
Fixing Bugs
Fix Demo Playback \| Fix a Race Condition with Pattern Load Cues \| Fix the SEGA Sound \| Display the Press Start Button Text \| Fix the Level Select Menu \| Fix the Hidden Points Bug \| Fix Accidental Deletion of Scattered Rings \| Fix Ring Timers \| Fix the Walk-Jump Bug \| Correct Drowning Bugs \| Fix the Death Boundary Bug \| Fix the Camera Follow Bug \| Fix Song Restoration Bugs \| Fix the HUD Blinking \| Fix the Level Select Graphics Bug \| Fix a remember sprite related bug
Changing Design Choices
Change Spike Behavior \| Collide with Water After Being Hurt \| Fix Special Stage Jumping Physics \| Improve the Fade In\Fade Out Progression Routines \| Fix Scattered Rings' Underwater Physics \| Remove the Speed Cap \| Port the REV01 Background Effects \| Port Sonic 2's Level Art Loader \| Retain Rings Between Acts \| Add Sonic 2 (Simon Wai Prototype) Level Select \| Improve ObjectMove Subroutines \| Port Sonic 2 Level Select
Adding Features
Add Spin Dash ( Part 1 / Part 2 / Part 3 / Part 4 ) \| Add Eggman Monitor \| Add Super Sonic \| Add the Air Roll
Sound Features
Expand the Sound Index \| Play Different Songs Per Act \| Port Sonic 2 Final Sound Driver \| Port Sonic 3's Sound Driver \| Port Flamewing's Sonic 3 & Knuckles Sound Driver \| Change The SEGA Sound
Extending the Game
Load Chunks From ROM \| Add Extra Characters \| Make an Alternative Title Screen \| Use Dynamic Tilesets \| Make GHZ Load Alternate Art \| Make Ending Load Alternate Art \| Add a New Zone \| Set Up the Goggle Monitor \| Add New Moves \| Add a Dynamic Collision System \| Dynamic Special Stage Walls System \| Extend Sprite Mappings and Art Limit \| Enigma Credits \| Use Dynamic Palettes
Miscellaneous
Convert the Hivebrain 2005 Disassembly to ASM68K
Split Disassembly Guides
Set Up a Split Disassembly \| Basic Level Editing \| Basic Art Editing \| Basic ASM Editing (Spin Dash)

SCHG How-To Guide: Sonic the Hedgehog 2 (16-bit)
Fixing Bugs
Fix Demo Playback \| Fix a Race Condition with Pattern Load Cues \| Fix Super Sonic Bugs \| Use Correct Height When Roll Jumping \| Fix Jump Height Bug When Exiting Water \| Fix Screen Boundary Spin Dash Bug \| Correct Drowning Bugs \| Fix Camera Y Position for Tails \| Fix Tails Subanimation Error \| Fix Tails' Respawn Speeds \| Fix Accidental Deletion of Scattered Rings \| Fix Ring Timers \| Fix Rexon Crash \| Fix Monitor Collision Bug \| Fix EHZ Deformation Bug \| Correct CPZ Boss Attack Behavior \| Fix Bug in ARZ Boss Arrow's Platform Behavior \| Fix ARZ Boss Walking on Air Glitch \| Fix ARZ Boss Sprite Behavior \| Fix Multiple CNZ Boss Bugs \| Fix HTZ Background Scrolling Mountains \| Fix OOZ Launcher Speed Up Glitch \| Fix DEZ Giant Mech Collision Glitch \| Fix Boss Deconstruction Behavior \| Fix Speed Bugs \| Fix 14 Continues Cheat \| Fix Debug Mode Crash \| Fix 99+ Lives \| Fix Sonic 2's Sega Screen
Design Choices
Remove the Air Speed Cap \| Disable Floor Collision While Dying \| Modify Super Sonic Transformation Methods & Behavior \| Enable/Disable Tails in Certain Levels \| Collide with Water After Being Hurt \| Retain Rings When Returning at a Star Post \| Improve the Fade In\Fade Out Progression Routines \| Fix Scattered Rings' Underwater Physics \| Insert LZ Water Ripple Effect \| Restore Lost CPZ Boss Feature \| Prevent SCZ Tornado Spin Dash Death \| Improve ObjectMove Subroutines \| Port S3K Rings Manager \| Port S3K Object Manager \| Port S3K Priority Manager \| Edit Level Order with ASM‎ \| Alter Ring Requirements in Special Stages \| Make Special Stage Characters Use Normal DPLCs \| Speed Up Ring Loss Process \| Change spike behaviour in Sonic 2
Adding Features
Create Insta-kill and High Jump Monitors \| Create Clone and Special Stage Monitors \| Port Knuckles
Sound Features
Expand Music Index to Start at $00 \| Port Sonic 1 Sound Driver \| Port Sonic 2 Clone Driver \| Port Sonic 3 Sound Driver \| Port Flamewing's Sonic 3 & Knuckles Sound Driver \| Expand the Music Index to Start at $00 (Sonic 2 Clone Driver Version) \| Play Different Songs Per Act
Extending the Game
Extend the Level Index Past $10 \| Extend the Level Select \| Extend Water Tables \| Add Extra Characters \| Free Up 2 Universal SSTs

SCHG How-to

Difference between revisions of "Fix Scattered Rings Underwater Physics"

From Sonic Retro

Revision as of 21:29, 20 December 2015

Contents

Sonic 1 HiveBrain fix

Sonic 1 Git fix

Sonic 2 fix

Sonic 3&K fix

@@ Line 13: / Line 13: @@
  move.w d4,d2
  lsr.w #8,d2
-</asm>
+</syntaxhighlight>
@@ Line 27: / Line 27: @@
 @skiphalvingvel:
-</asm>
+</syntaxhighlight>
@@ Line 69: / Line 69: @@
  bcc.s loc_9D62
  move.w #$288,d4
-</asm>
+</syntaxhighlight>
@@ Line 79: / Line 79: @@
  bsr.w SpeedToPos
  addi.w #$18,$12(a0)
-</asm>
+</syntaxhighlight>
@@ Line 92: / Line 92: @@
 @skipbounceslow:
-</asm>
+</syntaxhighlight>
@@ Line 123: / Line 123: @@
  sub.w d0,$12(a0)
  neg.w $12(a0)
-</asm>
+</syntaxhighlight>
@@ Line 136: / Line 136: @@
  move.w d4,d2
  lsr.w #8,d2
-</asm>
+</syntaxhighlight>
@@ Line 150: / Line 150: @@
 @skiphalvingvel:
-</asm>
+</syntaxhighlight>
@@ Line 191: / Line 191: @@
  bcc.s @loc_9D62
  move.w #$288,d4
-</asm>
+</syntaxhighlight>
@@ Line 201: / Line 201: @@
  bsr.w SpeedToPos
  addi.w #$18,obVelY(a0)
-</asm>
+</syntaxhighlight>
@@ Line 214: / Line 214: @@
 @skipbounceslow:
-</asm>
+</syntaxhighlight>
@@ Line 244: / Line 244: @@
  sub.w d0,obVelY(a0)
  neg.w obVelY(a0)
-</asm>
+</syntaxhighlight>
@@ Line 257: / Line 257: @@
  move.w d4,d2
  lsr.w #8,d2
-</asm>
+</syntaxhighlight>
@@ Line 270: / Line 270: @@
  asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower
 .skiphalvingvel:
-</asm>
+</syntaxhighlight>
@@ Line 313: / Line 313: @@
  bcc.s loc_12132
  move.w #$288,d4
-</asm>
+</syntaxhighlight>
@@ Line 324: / Line 324: @@
  bsr.w ObjectMove
  addi.w #$18,y_vel(a0)
-</asm>
+</syntaxhighlight>
@@ Line 336: / Line 336: @@
  subi.w #$E,y_vel(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect for the rings
 .skipbounceslow:
-</asm>
+</syntaxhighlight>
@@ Line 368: / Line 368: @@
  sub.w d0,y_vel(a0)
  neg.w y_vel(a0)
-</asm>
+</syntaxhighlight>
@@ Line 385: / Line 385: @@
  dc.w loc_1A7D6-off_1A658
  dc.w loc_1A7E4-off_1A658
-</asm>
+</syntaxhighlight>
@@ Line 396: / Line 396: @@
  dc.w loc_1A7D6-off_1A658
  dc.w loc_1A7E4-off_1A658
-</asm>
+</syntaxhighlight>
@@ Line 409: / Line 409: @@
  dc.w loc_1A7D6-off_1A670
  dc.w loc_1A7E4-off_1A670
-</asm>
+</syntaxhighlight>
@@ Line 420: / Line 420: @@
  dc.w loc_1A7D6-off_1A670
  dc.w loc_1A7E4-off_1A670
-</asm>
+</syntaxhighlight>
@@ Line 433: / Line 433: @@
  beq.s loc_1A68C
  move.l #Obj_Bouncing_Ring_Reverse_Gravity,d6
-</asm>
+</syntaxhighlight>
@@ Line 446: / Line 446: @@
  move.l #Obj_Bouncing_Ring_Reverse_Gravity,(a1)
 .notreverse:
-</asm>
+</syntaxhighlight>
@@ Line 486: / Line 486: @@
  bcc.s loc_1A728
  move.w #$288,d4
-</asm>
+</syntaxhighlight>
@@ Line 494: / Line 494: @@
  move.w d4,d2
  lsr.w #8,d2
-</asm>
+</syntaxhighlight>
@@ Line 507: / Line 507: @@
  asr.w d1 ; Half d1. Makes the ring's y_vel bounce up/down slower
 .skiphalvingvel:
-</asm>
+</syntaxhighlight>
@@ Line 553: / Line 553: @@
  bcc.s loc_1A728
  move.w #$288,d4
-</asm>
+</syntaxhighlight>
@@ Line 564: / Line 564: @@
  bsr.w MoveSprite2
  addi.w #$18,$1A(a0)
-</asm>
+</syntaxhighlight>
@@ Line 576: / Line 576: @@
  subi.w #$E,$1A(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect
 .skiphalvinggrav:
-</asm>
+</syntaxhighlight>
@@ Line 608: / Line 608: @@
  sub.w d0,$1A(a0)
  neg.w $1A(a0)
-</asm>
+</syntaxhighlight>
@@ Line 621: / Line 621: @@
  bsr.w MoveSprite_TestGravity2
  addi.w #$18,$1A(a0)
-</asm>
+</syntaxhighlight>
@@ Line 633: / Line 633: @@
  subi.w #$E,$1A(a0) ; Reduce gravity by $E ($18-$E=$A), giving the underwater effect
 .skiphalvingrevgrav:
-</asm>
+</syntaxhighlight>
@@ Line 666: / Line 666: @@
  sub.w d0,$1A(a0)
  neg.w $1A(a0)
-</asm>
+</syntaxhighlight>