SeedBorn | Replacing Draw Functions with SRM @SeedBorn | Uploaded 4 years ago | Updated 2 hours ago
Actors that are displayed have a pointer in their instance to a draw function in their overlay, at offset 134 in OoT and 13C in MM. This function runs every frame and handles writing the actor's display lists. The offset it has (in each game) happens to be such that when we do held item SRM, we can write to its two least significant bytes with our angle. This means we can change what code gets run each frame that the actor is meant to be displayed.
I show an example here in which I use SRM to change a bush's draw function to the function that runs when skull kid gives you the Saria's Song heart piece (which will be present wherever a skull kid overlay is loaded). The bush, after causing us to receive a heart piece, breaks (most actors, if we overwrote their draw function instead, would just give us infinite heart pieces...). This isn't a particularly useful example but it should be a good proof of concept.
This can be put into action in Goron City to create a manipulable chest (youtube.com/watch?v=lyfQ8XF_ML0). Another possibility for using this profitably includes skipping the frog HP in MM (twitter.com/TVand/status/1208624737599008773) by changing the frog's draw function to the HP reward one (pastebin.com/BBKi8qB4).
Actors that are displayed have a pointer in their instance to a draw function in their overlay, at offset 134 in OoT and 13C in MM. This function runs every frame and handles writing the actor's display lists. The offset it has (in each game) happens to be such that when we do held item SRM, we can write to its two least significant bytes with our angle. This means we can change what code gets run each frame that the actor is meant to be displayed.
I show an example here in which I use SRM to change a bush's draw function to the function that runs when skull kid gives you the Saria's Song heart piece (which will be present wherever a skull kid overlay is loaded). The bush, after causing us to receive a heart piece, breaks (most actors, if we overwrote their draw function instead, would just give us infinite heart pieces...). This isn't a particularly useful example but it should be a good proof of concept.
This can be put into action in Goron City to create a manipulable chest (youtube.com/watch?v=lyfQ8XF_ML0). Another possibility for using this profitably includes skipping the frog HP in MM (twitter.com/TVand/status/1208624737599008773) by changing the frog's draw function to the HP reward one (pastebin.com/BBKi8qB4).
