Sprite scroll fix - SMW Patches

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Tip: Bad things to do in the title demo: Enter a door or a pipe, activate a P-switch or a star, complete the level, hit a message block, or die. These will either glitch the music, or force the player into an endlessly looping title level until they reset the game.

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SMW Patches - Sprite scroll fix

File Name:

Sprite scroll fix

Added:

2016-05-23 06:31:25 PM

Version History:

View

Authors:

GreenHammerBro

Tool:

Asar

Requires Free Space:

Yes

Bug Fix:

Yes

Featured:

Description:

This patch fixes a bug where if you only clear out $7E1411 and/or $7E1412 and try to manually scroll the screen by incrementing or decrementing $7E1462 and/or $7E1464, sprites may fail to spawn or spawn on the side where the screen moves away from depending on how Mario is positioned to scroll the screen.

Tags:

bugfix, glitch, lorom, needs remoderation, sa-1, scroll

Download:

Download - 3.84 KiB
255 downloads


GreenHammerBro
This is how SMW handles spawning sprites: Code: Show/Hide Code CODE_00F71A: A5 94 LDA RAM_MarioXPos ;\$00 and A = Mario's x position on-screen CODE_00F71C: 38 SEC ;\| CODE_00F71D: E5 1A SBC RAM_ScreenBndryXLo ;\| CODE_00F71F: 85 00 STA $00 ;/ CODE_00F721: CD 2A 14 CMP.W $142A ;\If mario is right side of the static camera region (right side of the area CODE_00F724: 10 02 BPL CODE_00F728 ;/that doesn't scroll the screen horizontally), leave Y = #$02 CODE_00F726: A0 00 LDY.B #$00 ;>Otherwise, rewrite Y = #$00 CODE_00F728: 84 55 STY $55 ;\Set scrolling direction CODE_00F72A: 84 56 STY $56 ;/ CODE_00F72C: 38 SEC ;\Find distance between mario and the center of the static cam region CODE_00F72D: F9 2C 14 SBC.W $142C,Y ;\| CODE_00F730: F0 28 BEQ CODE_00F75A ;/>if zero, skip CODE_00F732: 85 02 STA $02 ;>Store distance into $02 This checks if Mario's X on-screen position is to the right or left of the “center” of the “static camera region” (which is $142A (2 bytes)), to determine the direction to spawn sprites. This patch modifies: Code $00F728 to $00F72B - 4 bytes $00F80C to $00F80F - 4 bytes $00F713 to $00F717 - 5 bytes $00F7F4 to $00F7F8 - 5 bytes To detect a change of X position to determine direction. Thank goodness this works with the extended levels on LM v3+
Posted by: GreenHammerBro - 2019-04-13 01:34:19 AM \| Link

GreenHammerBro
Sprites loading uses $55 to determine which side to spawn.
Posted by: GreenHammerBro - 2018-07-11 02:52:48 AM \| Link

mjbg
i think it really fixed one problem i was having with a level thank you!
Posted by: mjbg - 2017-09-01 12:27:51 PM \| Link

GreenHammerBro
This is a type of bug that can only happen if you are in ASM hacking. That is why it is hard to find that bug. I found this bug during the early development of the Mega Man scroll gates with sprites disappearing.
Posted by: GreenHammerBro - 2016-06-10 01:57:51 AM \| Link

Von Fahrenheit
Moderator's note: A very... conditionally useful patch. It solves a bug I honestly didn't know existed, but if sprites despawning due to camera trickery is a problem in your hack, then this patch is for you! Also big props to GreenHammerBro for taking the time to come up with fixes for all the little bugs in SMW.
Posted by: Von Fahrenheit - 2016-05-23 06:34:22 PM \| Link

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