Difference between revisions of "Fix Accidental Deletion of Scattered Rings"
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Scarred Sun (talk | contribs) m (Text replacement - "</asm>" to "</syntaxhighlight>") |
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bcs.s BranchTo5_DeleteObject ; HERE | bcs.s BranchTo5_DeleteObject ; HERE | ||
bra.w DisplaySprite | bra.w DisplaySprite | ||
− | </ | + | </syntaxhighlight> |
It has this code because when rings reach to the bottom of the level, they delete themselves, so they do not spawn at the top of the level (they won't loop). This is a good thing, as we don't want rings looping, right? But there is an issue with levels that are y-wrapped enabled. | It has this code because when rings reach to the bottom of the level, they delete themselves, so they do not spawn at the top of the level (they won't loop). This is a good thing, as we don't want rings looping, right? But there is an issue with levels that are y-wrapped enabled. | ||
Line 56: | Line 56: | ||
bcs.s RLoss_Delete ; if yes, branch | bcs.s RLoss_Delete ; if yes, branch | ||
bra.w DisplaySprite | bra.w DisplaySprite | ||
− | </ | + | </syntaxhighlight> |
Right after the first branch to "RLoss_Delete", insert this: | Right after the first branch to "RLoss_Delete", insert this: | ||
Line 62: | Line 62: | ||
cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? | cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? | ||
beq.w DisplaySprite ; if so, branch | beq.w DisplaySprite ; if so, branch | ||
− | </ | + | </syntaxhighlight> |
So, you have something like this: | So, you have something like this: | ||
Line 76: | Line 76: | ||
bcs.s RLoss_Delete ; if yes, branch | bcs.s RLoss_Delete ; if yes, branch | ||
bra.w DisplaySprite | bra.w DisplaySprite | ||
− | </ | + | </syntaxhighlight> |
==Sonic 1 fix- Hivebrain's 2005 Disassembly== | ==Sonic 1 fix- Hivebrain's 2005 Disassembly== | ||
Line 90: | Line 90: | ||
bcs.s Obj37_Delete ; if yes, branch | bcs.s Obj37_Delete ; if yes, branch | ||
bra.w DisplaySprite | bra.w DisplaySprite | ||
− | </ | + | </syntaxhighlight> |
Right after the first branch to "Obj37_Delete", insert this: | Right after the first branch to "Obj37_Delete", insert this: | ||
Line 96: | Line 96: | ||
cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? | cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? | ||
beq.w DisplaySprite ; if so, branch | beq.w DisplaySprite ; if so, branch | ||
− | </ | + | </syntaxhighlight> |
So, you have something like this: | So, you have something like this: | ||
Line 110: | Line 110: | ||
bcs.s Obj37_Delete ; if yes, branch | bcs.s Obj37_Delete ; if yes, branch | ||
bra.w DisplaySprite | bra.w DisplaySprite | ||
− | </ | + | </syntaxhighlight> |
==Sonic 2 fix== | ==Sonic 2 fix== | ||
Line 125: | Line 125: | ||
bcs.s BranchTo5_DeleteObject | bcs.s BranchTo5_DeleteObject | ||
bra.w DisplaySprite | bra.w DisplaySprite | ||
− | </ | + | </syntaxhighlight> |
Right after the first branch to "BranchTo5_DeleteObject", insert this: | Right after the first branch to "BranchTo5_DeleteObject", insert this: | ||
Line 131: | Line 131: | ||
cmpi.w #$FF00,($FFFFEECC).w ; is vertical wrapping enabled? | cmpi.w #$FF00,($FFFFEECC).w ; is vertical wrapping enabled? | ||
beq.w DisplaySprite ; if so, branch | beq.w DisplaySprite ; if so, branch | ||
− | </ | + | </syntaxhighlight> |
So, you have something like this: | So, you have something like this: | ||
Line 145: | Line 145: | ||
bcs.s BranchTo5_DeleteObject | bcs.s BranchTo5_DeleteObject | ||
bra.w DisplaySprite | bra.w DisplaySprite | ||
− | </ | + | </syntaxhighlight> |
==Sonic 3K fix== | ==Sonic 3K fix== | ||
Line 159: | Line 159: | ||
cmp.w $14(a0),d0 | cmp.w $14(a0),d0 | ||
bcs.s loc_1A7E4 | bcs.s loc_1A7E4 | ||
− | </ | + | </syntaxhighlight> |
Right after the first branch to "loc_1A7E4", insert this: | Right after the first branch to "loc_1A7E4", insert this: | ||
Line 165: | Line 165: | ||
cmpi.w #$FF00,($FFFFEE18).w ; is vertical wrapping enabled? | cmpi.w #$FF00,($FFFFEE18).w ; is vertical wrapping enabled? | ||
beq.w loc_1A7B0 ; if so, branch | beq.w loc_1A7B0 ; if so, branch | ||
− | </ | + | </syntaxhighlight> |
So, you have something like this: | So, you have something like this: | ||
Line 178: | Line 178: | ||
cmp.w $14(a0),d0 | cmp.w $14(a0),d0 | ||
bcs.s loc_1A7E4 | bcs.s loc_1A7E4 | ||
− | </ | + | </syntaxhighlight> |
=The bug explained= | =The bug explained= |
Revision as of 21:29, 20 December 2015
(Original guide by redhotsonic)
Contents
The Problem
There is a glitch within the scattered rings. Let me explain. In the scattered rings code, there is a check to see if rings have reached the bottom of the level and if so, to delete themselves. Here is some code from Sonic 2's scattered rings object.
<asm>loc_121B8:
tst.b (Ring_spill_anim_counter).w beq.s BranchTo5_DeleteObject move.w (Camera_Max_Y_pos_now).w,d0 ; HERE addi.w #$E0,d0 ; HERE cmp.w y_pos(a0),d0 ; HERE bcs.s BranchTo5_DeleteObject ; HERE bra.w DisplaySprite
</syntaxhighlight>
It has this code because when rings reach to the bottom of the level, they delete themselves, so they do not spawn at the top of the level (they won't loop). This is a good thing, as we don't want rings looping, right? But there is an issue with levels that are y-wrapped enabled. Easy example: Sonic 2's Metropolis Zone, Act 2.
If you go to these co-ordinates in MTZ2, you will see Asteron (starfish badnik) to the right. Go to him and let him hurt you.
I've just got hurt, look at all the rings that are about to scatter. But, the bottom line of the level is right above me.
Look at that! Most of my rings have suddenly vanished! To help, I've drawn a red line. That's the line where if the rings reach, to delete themselves. The rings think that that line is the bottom of the level, but because this level is y-wrapped, technically, there is no "bottom of level". So we still want the rings to be there so we can collect them.
NOTE: This bug is also present in Sonic 1 & 3K, but it is quite hard to pull the glitch off. Generally because the only time you're passing the y-wrap in S1 and S3K, is when you're in the water slide in LZ Act 3, or in the ice tunnel in ICZ Act 1.
But if you're editing these level layouts to cross the y-wrap quite often, the glitch may become more apparent. And you might want to fix it. Therefore, we will cover fixing this for ALL 3 games! Lets start with Sonic 1, and work our way forward...
The Fix
NOTE: The fix I have added, I've not equated. That way, the fix is compatible with any disassembly you are using. I've told what disassembly for which game I'm going by, but if you're using any other disassembly, you can still use my fix. Credit to Berserker6 for adding the Hivebrain 2005 instructions.
Sonic 1 fix- SVN
Go to "@chkdel:" and you'll see this: <asm> @chkdel: tst.b (v_ani3_time).w beq.s RLoss_Delete move.w (v_limitbtm2).w,d0 addi.w #$E0,d0 cmp.w obY(a0),d0 ; has object moved below level boundary? bcs.s RLoss_Delete ; if yes, branch bra.w DisplaySprite </syntaxhighlight>
Right after the first branch to "RLoss_Delete", insert this: <asm> cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? beq.w DisplaySprite ; if so, branch </syntaxhighlight>
So, you have something like this: <asm> @chkdel: tst.b (v_ani3_time).w beq.s RLoss_Delete cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? beq.w DisplaySprite ; if so, branch move.w (v_limitbtm2).w,d0 addi.w #$E0,d0 cmp.w obY(a0),d0 ; has object moved below level boundary? bcs.s RLoss_Delete ; if yes, branch bra.w DisplaySprite </syntaxhighlight>
Sonic 1 fix- Hivebrain's 2005 Disassembly
Go to "Obj37_ChkDel:" and you'll see this: <asm> Obj37_ChkDel: ; XREF: Obj37_Bounce tst.b ($FFFFFEC6).w beq.s Obj37_Delete move.w ($FFFFF72E).w,d0 addi.w #$E0,d0 cmp.w $C(a0),d0 ; has object moved below level boundary? bcs.s Obj37_Delete ; if yes, branch bra.w DisplaySprite </syntaxhighlight>
Right after the first branch to "Obj37_Delete", insert this: <asm> cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? beq.w DisplaySprite ; if so, branch </syntaxhighlight>
So, you have something like this: <asm> Obj37_ChkDel: ; XREF: Obj37_Bounce tst.b ($FFFFFEC6).w beq.s Obj37_Delete cmpi.w #$FF00,($FFFFF72C).w ; is vertical wrapping enabled? beq.w DisplaySprite ; if so, branch move.w ($FFFFF72E).w,d0 addi.w #$E0,d0 cmp.w $C(a0),d0 ; has object moved below level boundary? bcs.s Obj37_Delete ; if yes, branch bra.w DisplaySprite </syntaxhighlight>
Sonic 2 fix
This guide uses Xenowhirl's 2007 disassembly.
Go to "loc_121B8:" and you'll see this: <asm> loc_121B8: tst.b (Ring_spill_anim_counter).w beq.s BranchTo5_DeleteObject move.w (Camera_Max_Y_pos_now).w,d0 addi.w #$E0,d0 cmp.w y_pos(a0),d0 bcs.s BranchTo5_DeleteObject bra.w DisplaySprite </syntaxhighlight>
Right after the first branch to "BranchTo5_DeleteObject", insert this: <asm> cmpi.w #$FF00,($FFFFEECC).w ; is vertical wrapping enabled? beq.w DisplaySprite ; if so, branch </syntaxhighlight>
So, you have something like this: <asm> loc_121B8: tst.b (Ring_spill_anim_counter).w beq.s BranchTo5_DeleteObject cmpi.w #$FF00,($FFFFEECC).w ; is vertical wrapping enabled? beq.w DisplaySprite ; if so, branch move.w (Camera_Max_Y_pos_now).w,d0 addi.w #$E0,d0 cmp.w y_pos(a0),d0 bcs.s BranchTo5_DeleteObject bra.w DisplaySprite </syntaxhighlight>
Sonic 3K fix
This guide uses the SVN disassembly.
Go to "loc_1A79C" and you'll see this: <asm> loc_1A79C: tst.b (Ring_spill_anim_counter).w beq.s loc_1A7E4 move.w (Camera_max_Y_pos).w,d0 addi.w #$E0,d0 cmp.w $14(a0),d0 bcs.s loc_1A7E4 </syntaxhighlight>
Right after the first branch to "loc_1A7E4", insert this: <asm> cmpi.w #$FF00,($FFFFEE18).w ; is vertical wrapping enabled? beq.w loc_1A7B0 ; if so, branch </syntaxhighlight>
So, you have something like this: <asm> loc_1A79C: tst.b (Ring_spill_anim_counter).w beq.s loc_1A7E4 cmpi.w #$FF00,($FFFFEE18).w ; is vertical wrapping enabled? beq.w loc_1A7B0 ; if so, branch move.w (Camera_max_Y_pos).w,d0 addi.w #$E0,d0 cmp.w $14(a0),d0 bcs.s loc_1A7E4 </syntaxhighlight>
The bug explained
Basically, whenever rings fall to the bottom of the level, they delete themselves to stop from looping and coming from the top of the screen (like Sonic does on y-wrapped levels). But with levels with y-wrap enabled, the rings would still delete themselves when they reached those same co-ordinates. In the pictures provided as examples (In the OP), those rings reached the co-ordinates and deleted themselves, which we don't want theoretically, there is no bottom of level and you want your rings back!
So, all we've done here to all 3 games, is if y-wrap is enabled, do not delete the rings if they've reached the co-ordinates. Only if y-wrap is disabled, will the game delete the rings once they've reached the bottom of the level.
The rings itself will still delete themselves after a certain amount of time, so, you do not need to worry about them being around forever if y-wrap is enabled.