Useless glitches

Discuss PoP1 for DOS here.
User avatar
SuavePrince
The Prince of Persia
The Prince of Persia
Posts: 1081
Joined: January 26th, 2015, 6:21 pm

Re: Useless glitches

Post by SuavePrince »

atrueprincefanfrom18 wrote: February 17th, 2021, 10:49 am
Norbert wrote: February 17th, 2021, 10:28 am Interesting. Can you describe how to do it?
I know the video shows arrow keys, but I'm unable to replicate it.
I think it only works when Prince has 1 HP. Check the hit points in the video. I think it's basically the case where Prince HP becomes 0 (because of lose tile has hit him), and the game doesn't check if it should stop the Prince from going through the wall when he jumps. The jump keys should be pressed perfect enough, otherwise you would die. I think it's the only frame where you can perform this trick. One frame before or one frame later and the trick won't work. I could do it in SDLPoP (needed 20+ Quickloads, but it should be possible with DOSBox too):


the_trick.p1r


Could be useful if merged with trick 88.

Norbert, I think you should add this to PoPOT (something after a long time ;))...
It is not a trick, since according to previous tests on my part, prince can pass through walls when he is dead
User avatar
VelCheran
Vizier
Vizier
Posts: 122
Joined: May 28th, 2020, 7:26 pm

Re: Useless glitches

Post by VelCheran »

David wrote: March 7th, 2021, 11:22 am Falling through the floor on level 7: https://github.com/NagyD/SDLPoP/issues/229
It could be very useful if only a way to fall a few pixels further to the right was found. But so far it looks like it's impossible :(
User avatar
eien86
Sheikh
Sheikh
Posts: 22
Joined: March 25th, 2021, 5:44 pm

Re: Useless glitches

Post by eien86 »

Useless (for now) for the original Pop, but perhaps interesting for modders. There's a way to bring a guard to a lower level even when it seems impossible because there are spikes below:




[Edit: Embedded video -- ATPFF18]
David
The Prince of Persia
The Prince of Persia
Posts: 2760
Joined: December 11th, 2008, 9:48 pm
Location: Hungary

Re: Useless glitches

Post by David »

If you do Trick 1 with a mirror, the prince will briefly appear on the other side of the mirror.

The real prince is on the left side of the mirror, barely visible.
The other prince on the right is his mirror image.
mirror_trick_1.png
mirror_trick_1.png (2.86 KiB) Viewed 444 times
User avatar
VelCheran
Vizier
Vizier
Posts: 122
Joined: May 28th, 2020, 7:26 pm

Re: Useless glitches

Post by VelCheran »

Nice one! The game is really puzzled by the situation, it seems. It detects the prince as being briefly on the right side of the mirror, thus decides to draw his reflection, but since he really is on the left I guess there's some kind of geometric symmetry involved and it puts it on the right. I don't know if my explanation makes sense but it does in my mind at least :lol:
dmitry_s
Developer
Developer
Posts: 148
Joined: July 27th, 2021, 7:22 am

Re: Useless glitches

Post by dmitry_s »

The game checks if prince is standing on the mirror tile and draws a mirrored reflection of the character by using the opposite direction and distance to the tile calculations.

https://github.com/NagyD/SDLPoP/blob/cd ... 003.c#L582

The assumption is you can only stand on the tile at the right side of the mirror. But just like you can step on switches through gates using certain frames, you can stand on the tile on the left side which causes the shadow image to appear. It can most likely be fixed by adding a `Char.direction` check. The SDLPoP fix for gates probably fixes it as well by properly calculating prince's column.

I have not checked why it uses a standard blitter so shadow looks like prince.
David
The Prince of Persia
The Prince of Persia
Posts: 2760
Joined: December 11th, 2008, 9:48 pm
Location: Hungary

Re: Useless glitches

Post by David »

dmitry_s wrote: January 24th, 2022, 5:03 pm The SDLPoP fix for gates probably fixes it as well by properly calculating prince's column.
Yes, "Settings -> Gameplay -> Fix pressing through closed gates" fixes it.
But even with that fix on, sometimes the mirror image appears briefly when I run into the mirror from the left.
dmitry_s wrote: January 24th, 2022, 5:03 pm I have not checked why it uses a standard blitter so shadow looks like prince.
It's a mirror image what appears in the mirror, not the shadow.
The shadow appears only when you jump through the mirror.

Yeah, it's a bit confusing that the mirror shows the prince's mirror image, but when he jumps through it then his shadow is released.
dmitry_s
Developer
Developer
Posts: 148
Joined: July 27th, 2021, 7:22 am

Re: Useless glitches

Post by dmitry_s »

You are right as always. The reversed image in the object table does not get does OR/XOR'd. That only happens when to the shadow in the Guard slot.
David
The Prince of Persia
The Prince of Persia
Posts: 2760
Joined: December 11th, 2008, 9:48 pm
Location: Hungary

Re: Useless glitches

Post by David »

I found out how to pick up the sword on level 12, without using the Overflow Bug.

I attached a replay file showing how to do it.
level_12_sword_pickup_without_overflow.p1r
(4.24 KiB) Downloaded 13 times
User avatar
atrueprincefanfrom18
Site Shah
Site Shah
Posts: 1776
Joined: January 21st, 2020, 2:53 pm
Contact:

Re: Useless glitches

Post by atrueprincefanfrom18 »

Not sure why I can't play it. Any chance someone could upload a video?
Love to create new MODS :)

My complete list of mods until now!

My channel. Do consider subscribing it! :)
David
The Prince of Persia
The Prince of Persia
Posts: 2760
Joined: December 11th, 2008, 9:48 pm
Location: Hungary

Re: Useless glitches

Post by David »

atrueprincefanfrom18 wrote: October 23rd, 2022, 7:05 am Not sure why I can't play it. Any chance someone could upload a video?
Here is a video of it, recorded from DOSBox.
level_12_get_sword_without_overflow.zip
(241.72 KiB) Downloaded 12 times
User avatar
VelCheran
Vizier
Vizier
Posts: 122
Joined: May 28th, 2020, 7:26 pm

Re: Useless glitches

Post by VelCheran »

Interesting, this works with 1.0 but not with 1.4 so I guess it was known and corrected.
David
The Prince of Persia
The Prince of Persia
Posts: 2760
Joined: December 11th, 2008, 9:48 pm
Location: Hungary

Re: Useless glitches

Post by David »

VelCheran wrote: October 31st, 2022, 4:36 pm Interesting, this works with 1.0 but not with 1.4 so I guess it was known and corrected.
I could do this in PoP 1.4 as well:
level_12_get_sword_without_overflow_PoP1.4.zip
(273.58 KiB) Downloaded 7 times
User avatar
VelCheran
Vizier
Vizier
Posts: 122
Joined: May 28th, 2020, 7:26 pm

Re: Useless glitches

Post by VelCheran »

Indeed, my bad, I probably did something wrong.
Post Reply