Pretty much every NPC in Cavestory will use framerects, or numbers that determine the borders of that NPC's sprites.
Such NPCs will use sprites taken from spritesheets, such as NpcSym.
Now, let's take a look at the Pot entity, which is NPC #78. The offset is 4367E0 if you look it up in the compendium.
Here I've highlighted the rects in green:
Address Command Comments 004367E0 PUSH EBP 004367E1 MOV EBP,ESP 004367E3 SUB ESP,20 004367E6 MOV DWORD PTR SS:[EBP-20],0A0 ;these are the framerects. 004367ED MOV DWORD PTR SS:[EBP-1C],30 004367F4 MOV DWORD PTR SS:[EBP-18],0B0 004367FB MOV DWORD PTR SS:[EBP-14],40 00436802 MOV DWORD PTR SS:[EBP-10],0B0 00436809 MOV DWORD PTR SS:[EBP-0C],30 00436810 MOV DWORD PTR SS:[EBP-8],0C0 00436817 MOV DWORD PTR SS:[EBP-4],40 0043681E MOV EAX,DWORD PTR SS:[EBP+8] 00436821 CMP DWORD PTR DS:[EAX+4C],0 00436825 JNE SHORT 00436846 00436827 MOV ECX,DWORD PTR SS:[EBP+8] 0043682A ADD ECX,54 0043682D MOV EDX,DWORD PTR SS:[EBP-20] 00436830 MOV DWORD PTR DS:[ECX],EDX 00436832 MOV EAX,DWORD PTR SS:[EBP-1C] 00436835 MOV DWORD PTR DS:[ECX+4],EAX 00436838 MOV EDX,DWORD PTR SS:[EBP-18] 0043683B MOV DWORD PTR DS:[ECX+8],EDX 0043683E MOV EAX,DWORD PTR SS:[EBP-14] 00436841 MOV DWORD PTR DS:[ECX+0C],EAX 00436844 JMP SHORT 00436863 00436846 MOV ECX,DWORD PTR SS:[EBP+8] 00436849 ADD ECX,54 0043684C MOV EDX,DWORD PTR SS:[EBP-10] 0043684F MOV DWORD PTR DS:[ECX],EDX 00436851 MOV EAX,DWORD PTR SS:[EBP-0C] 00436854 MOV DWORD PTR DS:[ECX+4],EAX 00436857 MOV EDX,DWORD PTR SS:[EBP-8] 0043685A MOV DWORD PTR DS:[ECX+8],EDX 0043685D MOV EAX,DWORD PTR SS:[EBP-4] 00436860 MOV DWORD PTR DS:[ECX+0C],EAX 00436863 MOV ESP,EBP 00436865 POP EBP 00436866 RETNWell look at that. [EBP-4], [EBP-8], [EBP-C], and so on. The framerect values are being MOVed into local variables!
The rects are nothing but a set of numbers, as follows:
A0,30,B0,40,B0,30,C0,40All of those numbers are in hexadecimal format. Let's convert them to decimal:
160,48,176,64,176,48,192,64Well, that's not helpful. What do these numbers mean?
MS Paint
Open up NpcSym.pbm (or NpcSym.bmp, if you set it up that way) using Microsoft Paint.
First, go to the Magnification Tool and zoom in a few times until the picture is sufficiently big. Then, go to the Paintbrush Tool and select a line thickness of 1-pixel. We're not going to edit anything, but I want you to pay close attention to the little coordinate system on the bottom panel of the program.
You can think of the framerects as the borders of the sprites of any Cavestory NPC:
Notice that this corresponds perfectly with our set of numbers:
160,48,176,64,176,48,192,64We've concluded that the Pot entity contains 2 sprites, a big pot and a small pot.
Address Instruction Comments 004367E6 MOV DWORD PTR SS:[EBP-20],0A0 ;left border of sprite 1 (big pot) 004367ED MOV DWORD PTR SS:[EBP-1C],30 ;upper border of sprite 1 004367F4 MOV DWORD PTR SS:[EBP-18],0B0 ;right border of sprite 1 004367FB MOV DWORD PTR SS:[EBP-14],40 ;bottom border of sprite 1 00436802 MOV DWORD PTR SS:[EBP-10],0B0 ;left border of sprite 2 (small pot) 00436809 MOV DWORD PTR SS:[EBP-0C],30 ;upper border of sprite 2 00436810 MOV DWORD PTR SS:[EBP-8],0C0 ;right border of sprite 2 00436817 MOV DWORD PTR SS:[EBP-4],40 ;bottom border of sprite 2The framerect borders for any entity will be in the order {left, upper, right, lower}, with each framerect listed one after the other. By editing these rects, you can change the sprites of any NPC to your liking. This is especially important when making custom NPCs, when you have to specify your own rects.
Not only NPCs use rects. Weapons, bullets, and basically anything else that has a sprite will also use framerects.
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