Sloped Sprites

Submission Details

Name:	Sloped Sprites
Author:	Djief
Added:	2024-04-03 10:38:13 AM
Tool:	Asar
Requires Free Space:	Yes
Bug Fix:	No
Featured:	No
Description:	Patch to make platform sprites able to be set to act as slopes for Mario. Includes a modified carrot top lift set to act as slope. Had to resubmit because of a dumb mistake I made within the first file.
Tags:	lorom sa-1 sliding slopes sprite
Comments:	2 (jump to comments)

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Comments (2)

Maarfy 2024-04-03 10:43:13 AM Link

It took me a long time to figure out what to do with this one. This was a narrow accept overall, but it would've been a narrow reject as well. The hijack is improperly restored, but it's a one-line fix. The code is inefficient, but it's so small that optimization wouldn't save a whole lot. The readme doesn't provide any clear examples for setting slope behavior in a sprite (and the included sprite's new code is uncommented), but it kind of can't because any sprite you'd want to modify will be different.

In the end, I've decided that it's worthwhile enough to accept with the hijack repaired. I've left a comment on the only other fixed-grade sloped sprite I can think of with instructions on how to make it interact with this patch, should that be of interest to anyone.

Optimization notes: Show/Hide

The hijack at $00EE26 could be optimized quite a bit despite its size. The code uses a JSL to jump into freespace, then returns directly to a JMP $EEE1. Instead, the code could hijack $00EE28 with a JML, and return with another JML directly to $00EEE1.

The code this hijack ultimately returns to, $00EEE1, quickly overwrites X in all cases without using the old value. X is thus free for use as an index in your freespace code, which both eliminates the need to preserve the data bank and allows you to switch from freecode to freedata.

Your code branches to directly set Y with #$20 if !SpriteSlopeType is zero, and sets Y from a table if it's not. There's no reason the zero case can't be merged into the table, saving you a branch (and a DEY). All in all, this hijack can be distilled all the way down into this:

Code

org $00EE28
	autoclean JML SetSlopeY
	NOP

freedata

SlopeY:
db $20
db $01,$08,$0C,$1D
db $06,$0B,$0D,$1F

SetSlopeY:

	LDX !SpriteSlopeType
	LDA.l SlopeY,x
	TAY
	JML $00EEE1|!bank

Tested with Asar 1.81, Lunar Magic 3.40, SA-1 1.40, Snes9x 1.62.3, BSNES Accuracy 0.7.1, PIXI 1.40, Mega Mole, But Sloped.

Klug 2023-11-25 09:44:47 AM Link

What a game-changer. LUL