Modifications to prince.exe (hex editing)

[David]

I tried to do this first one, but the Shadow doesn't run to the right of the screen, he stays still after getting out of the mirror

Sorry, I forgot one thing:

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seg002:1000                      autocontrol_shadow_level4 proc far
seg002:1000 80 3E 2B 3D 04                       cmp     char.room, 4
seg002:1005 75 12                                jnz     locret_4699

Search: 80 3E 2B 3D 04 75 12
Change: 04 to room number
Offset: 0x5F34

(at least on DOSBox, on SDLPoP the mirror appears on Room 20 for some reason and on a different column).

Because SDLPoP is not prepared for the hack with allows the room and column numbers to be different.
So it interprets 0x16 (decimal 22) as the room and the column.
Column 22 is column 2 of the second room to the right.
If you numbered the rooms as in the SNES version of Queen Of Light (level 6), then the second room to the right is indeed room 20.

[David]

How can it be made that all guards can fall to other rooms without dying?

Spoiler: show

We can change the code which handles the skeleton falling into the room below.

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in check_guard_fallout():
seg002:0299                      loc_3919:
seg002:0299 80 3E E7 42 04                       cmp     guard.charid, charid_4_skeleton ; skeleton
seg002:029E 75 2F                                jnz     loc_394F
seg002:02A0 A0 E5 42                             mov     al, guard.room
seg002:02A3 98                                   cbw
seg002:02A4 8B D8                                mov     bx, ax
seg002:02A6 D1 E3                                shl     bx, 1
seg002:02A8 D1 E3                                shl     bx, 1
seg002:02AA 8A 87 23 57                          mov     al, link_down_1[bx]
seg002:02AE A2 E5 42                             mov     guard.room, al
seg002:02B1 3C 03                                cmp     al, 3           ; if skeleton falls down into room 3
seg002:02B3 75 1A                                jnz     loc_394F
seg002:02B5 C6 06 DD 42 85                       mov     guard.x, 133
seg002:02BA C6 06 E1 42 01                       mov     guard.curr_row, 1
seg002:02BF C6 06 DF 42 00                       mov     guard.direction, dir_0_right
seg002:02C4 C6 06 E9 42 FF                       mov     guard.alive, 0FFh
seg002:02C9 0E                                   push    cs
seg002:02CA E8 28 00                             call    near ptr leave_guard
seg002:02CD EB 25                                jmp     short locret_3974

At 0x51CE change: 75 2F -> 90 90 -- Don't check guard type.
At 0x51E1 change: 3C 03 -> 3C 00 -- Check for room 0 instead.
At 0x51E3 change: 75 1A -> 74 1A -- If the guard fell into room 0 then he dies.
Adjust the coordinates to the room below:
At 0x51E5 change: C6 06 DD 42 85 -> 80 2E DE 42 BD -- Guard.y -= 189;
At 0x51EA change: C6 06 E1 42 01 -> 80 2E E1 42 03 -- Guard.curr_row -= 3;
Remove the guard from the current room (from the level data):
At 0x51EF change: C6 06 DF 42 00 C6 06 E9 42 FF -> 8B 1E 9E 40 C6 87 CA 57 FF 90 -- level.guards_tile[drawn_room - 1] = -1;
At 0x51F9 change: 0E E8 28 00 -> 90 90 90 90 -- Don't leave the guard, keep track of him.

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in play_guard_frame():
seg000:0F63 A0 2B 3D                             mov     al, char.room
seg000:0F66 98                                   cbw
seg000:0F67 3B 06 9E 40                          cmp     ax, drawn_room
seg000:0F6B 75 4A                                jnz     loc_FB7

At 0x281B change: 75 4A -> 90 90 -- Continue animating the guard even when he is another room.

Known problems:
1. If the guard doesn't die and you follow him down, he will regain his original hit points. Like when you leave a guard and later meet him again.
2. If the guard falls to his death in the room below, the victory music is not played. The splat sound has higher priority than the music.

[Shauing]

[quote=Shauing post_id=34330 time=1642918808
Because SDLPoP is not prepared for the hack with allows the room and column numbers to be different.
So it interprets 0x16 (decimal 22) as the room and the column.
Column 22 is column 2 of the second room to the right.
If you numbered the rooms as in the SNES version of Queen Of Light (level 6), then the second room to the right is indeed room 20.

So for the SDLPoP, what should I do to make this hack work? Will it have to be two different versions? One for DOS and another for SDLPoP?

[David]

So for the SDLPoP, what should I do to make this hack work? Will it have to be two different versions? One for DOS and another for SDLPoP?

I need to add support for this to SDLPoP.

At this part:

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		process(&custom_saved.mirror_level, 1, {0x08dc7, 0x0a477, 0x09274, 0x099b4, 0x08d30, 0x09e60});
		process(&custom_saved.mirror_room, 1, {0x08dcb, 0x0a47b, 0x09278, 0x099b8, 0x08d34, 0x09e64});
		if (read_ok) custom_saved.mirror_column = custom_saved.mirror_room;

[David]

So for the SDLPoP, what should I do to make this hack work? Will it have to be two different versions? One for DOS and another for SDLPoP?

I need to add support for this to SDLPoP.

Done: https://github.com/NagyD/SDLPoP/commit/ ... b945ffe34a

It turns out that changes to the level 5, 6, 12 shadow are not detected by SDLPoP.
So I need to add them as well, great...

[David]

It turns out that changes to the level 5, 6, 12 shadow are not detected by SDLPoP.
So I need to add them as well, great...

Done, so far only for the level 5 and 6 shadow.
https://github.com/NagyD/SDLPoP/commit/ ... bedc0f016d

[teljesnegyzet]

These are the modifications I've made for my Christmas of Persia mod:

the mouse doesn't appear in the ending sequence

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0E E8 35 FE 9A 64 04 CB 06 B8 09 00 50 0E E8 57 FB

->

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EB 27 35 FE 9A 64 04 CB 06 B8 09 00 50 0E E8 57 FB

drawing flames of torches with alpha and in another position:

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A1 68 59 40 50 2B C0 50 A1 26 43 2D 28 00 50 2B C0 50

->

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A1 68 59 50 2B C0 50 A1 26 43 2D 4A 00 50 B8 10 00 50

drawing flames of torches with alpha in the princess' room:

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FF B4 F4 0D FF B4 F8 0D B8 74 00 50 2B C0

->

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FF B4 F4 0D FF B4 F8 0D B8 74 00 50 B0 10

much shorter intro:

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4C FF 36 8A 58 50 50 50 0E E8 C4 02 B8 03 00

->

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4C FF 36 8A 58 50 50 50 0E E8 C4 02 E9 D5 01

faster paced intro:

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9A 20 72 79 0C C7 06 EC 31 82

->

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9A 20 72 79 0C C7 06 EC 31 10

and

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9A A9 0E 79 0C C7 06 EC 31 CD

->

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9A A9 0E 79 0C C7 06 EC 31 90

and

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9A A9 0E 79 0C C7 06 EC 31 41

->

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9A A9 0E 79 0C C7 06 EC 31 10

and

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9A A9 0E 79 0C C7 06 EC 31 0E 01

->

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9A A9 0E 79 0C C7 06 EC 31 90 00

and

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9A A9 0E 79 0C C7 06 EC 31 EB

->

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9A A9 0E 79 0C C7 06 EC 31 10

the kid already has the sword in level 1:

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83 7E 06 01 74 05 B8 01 00

->

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83 7E 06 22 74 05 B8 01 00

after the intro the first level begins instead of the demo level:

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0E E8 68 00 2B C0 50 9A 00 00 7F 04 8B E5 5D CB

->

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0E E8 68 00 B0 01 50 9A 00 00 7F 04 8B E5 5D CB

and

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83 3E 9A 00 00 74 17 83 7E 06 02 7E 11 C7 06 B8 42 00 00

->

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83 7E 06 01 75 18 C7 06 B8 42 01 00 EB 10 90 90 90 90 90

disabling cutscenes between levels:

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8B 97 A2 0F 89 46 FC 89 56 FE 0B C2 74 1D

->

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8B 97 A2 0F 89 46 FC 89 56 FE 0B C2 EB 1D

shorter outro:

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52 50 B8 01 00 50 0E E8 D1 02 9A 02 1F 00 00 B8 38 00

->

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52 50 B8 01 00 50 0E E8 D1 02 9A 02 1F 00 00 E9 65 02

no stars in the princess' room:

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74 12 B8 05 00 50 9A 0A 04 79 0C

->

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EB 12 B8 05 00 50 9A 0A 04 79 0C

and

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FF 76 FE 2B C0 50 0E E8 54 00 FF 46 FE

->

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FF 76 FE 2B C0 50 0E 90 90 90 FF 46 FE

[AJprince]

It turns out that changes to the level 5, 6, 12 shadow are not detected by SDLPoP.
So I need to add them as well, great...

Done, so far only for the level 5 and 6 shadow.
https://github.com/NagyD/SDLPoP/commit/ ... bedc0f016d

Thanks David, it seems you did somehow make SDLPoP detect level 12 shadow changes. I tested changing the shadow direction in level 12 and it worked.

Would you be able to make SDLPoP detect?:

by teljesnegyzet » December 9th, 2022, 12:46 am
the mouse doesn't appear in the ending sequence

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0E E8 35 FE 9A 64 04 CB 06 B8 09 00 50 0E E8 57 FB

->

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EB 27 35 FE 9A 64 04 CB 06 B8 09 00 50 0E E8 57 FB

[David]

Would you be able to make SDLPoP detect?:

by teljesnegyzet » December 9th, 2022, 12:46 am
the mouse doesn't appear in the ending sequence

Done: https://github.com/NagyD/SDLPoP/commit/ ... 093c8529cf

[AJprince]

Fantastic! Wow! Thanks David. I'll add this "no mouse end sequence" to some of my mods.