Fixing graphical glitches

[dmitrys]

Maybe it happened with this slightly different fix I tried, I'm not sure.

Code: Select all

	if (Char.room != curr_room) {
		Char.room = curr_room;
		leave_guard();
	}

Anyway, I added your fix: https://github.com/NagyD/SDLPoP/commit/ ... 8121bf8491

I have tried doing the fix with the code from your post first. But if the kid were return to the room on the left (the original guard room) in the spike row, it would resurrect the guard behind him.

The last screenshot for me is the room with spikes which is the room on the right.

And thanks for including the fix.

[dmitrys]

Also, in the original DOS POP the guard just disappears. Maybe if the fix for disappearing guards is not enabled, it should clear the character and return from the function after the first statement in that "if" clause.

[dmitrys]

My original fix was a bit simplistic. First of all, we need to check if a guard was actually spiked before removing him from the original room. Also, kid on the same row of spikes can make the guard disappear if the drawn room switches automatically, like David mentioned. It happens when kid jumps up or crouches off the ledge.

I also found a related bug as well that my new fix seems to cover.


Post-fix videos (based on modified code below).





The new fix:

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// seg005:01B7
void __pascal far spiked() {
	// If someone falls into spikes, those spikes become harmless (to others).
	curr_room_modif[curr_tilepos] = 0xFF;
	// If someone falls into spikes in a different room
	if (Char.room != curr_room) {
		if (Char.charid == charid_0_kid) {
			// fixes an issue where kid falling into spikes
			// causes guard to disappear
			if (Char.curr_col == -1 && Char.direction == dir_0_right) {
				drawn_room = room_R;
			}
		} else {
			// remove guard from the original room
			level.guards_tile[Char.room - 1] = -1;
		}
		// draw character in the correct room
		Char.room = curr_room;
	}
	Char.y = y_land[Char.curr_row + 1];
	Char.x = x_bump[tile_col + 5] + 10;
	Char.x = char_dx_forward(8);
	Char.fall_y = 0;
	set_sound_pos(Char.room, Char.curr_col, Char.curr_row);
	play_sound(sound_48_spiked); // something spiked
	take_hp(100);
	seqtbl_offset_char(seq_51_spiked); // spiked
	play_seq();
}

[Norbert]

I haven't fully followed the thread. Just chiming in that hopefully SDLPoP will continue to be fully compatible with the original game. That fixes that impact gameplay are not enabled by default, I mean. Where guards land, for example, may impact where the prince can go (e.g. tricks 4 and 151).

[dmitrys]

The first part of the bug where spiked guard gets rendered in the wrong room does not happen in the original game. But the guard does not appear in the next room either. So David might need to add some conditional logic based on the assembly code to make it behave exactly the same; currently it does not.

The second part of the bug (top video in the previous post) where the wrong room is being drawn actually does happen in the original game. It took me 2 attempts to reproduce it. The same code (kid if clause) also fixes the problem where guard disappears when kid falls onto spikes into last tile of one room next to a spiked guard in the next room on the same row. That fix probably should not enabled by default because it is not needed unless you fix the first bug in a way where guard does not disappear in the next room.

[atrueprincefanfrom18]

That fixes that impact gameplay are not enabled by default, I mean.

I think if changing some code is affecting the gameplay such that it's not the same as the default, it's always best to add a toggle screen and have enable and disable options instead of having static code.
Although it improves the behaviour of the game, making it more pleasant to play, it should be same as DOSBox.

[dmitrys]

I think if changing some code is affecting the gameplay such that it's not the same as the default, it's always best to add a toggle screen and have enable and disable options instead of having static code.
Although it improves the behaviour of the game, making it more pleasant to play, it should be same as DOSBox.

I absolutely agree. This is why I described the issue as 2 separate bugs. Spiked guard appearing in the same room is not something that happens in DOS PoP. But he would need to disappear instead of appearing in the next room to be consistent.

The second part of the bug where the wrong room is being displayed after a jump, if fixed, would need to be driven by an option parameter. And the same parameter can make the spiked guard appear in next room (at the correct tile) instead of disappearing.

[David]

Post-fix videos (based on modified code below).

I tried the new code, and if I do what's on the first video, the spiked guard will disappear for two frames when the prince lands in the spikes.

Also, in the original DOS POP the guard just disappears.

The first part of the bug where spiked guard gets rendered in the wrong room does not happen in the original game.

No, the guard will appear in the wrong room.
Open level 11 in a level editor, go to room 22, and in the bottom left corner replace the wall with a floor.
Move the prince's start position where the guard is.
Push the guard into the spikes, and the guard will appear in the bottom left corner.

See also the spike_2 video here: viewtopic.php?p=12715#p12715

[dmitrys]

I tried the new code, and if I do what's on the first video, the spiked guard will disappear for two frames when the prince lands in the spikes.

That does not happen all the time in my mod but I did see it happen. You have to get aligned at a very specific place and then jump and slip at the edge. I am not sure how to fix that issue.

No, the guard will appear in the wrong room.
Open level 11 in a level editor, go to room 22, and in the bottom left corner replace the wall with a floor.
Move the prince's start position where the guard is.
Push the guard into the spikes, and the guard will appear in the bottom left corner.

Maybe DOS POP renders things slightly different as you cannot see the guard at the wall edge, at least in my experience.

I guess that confirms that my fix should not be enabled by default.

[dmitrys]

I played with this glitch a little more. Those missing frames were caused by the drawn room switching back and forth.

Instead of setting the drawn room, redrawing kid and bumping him back to the previous room stops guard from disappearing briefly.

Code: Select all

void __pascal far spiked() {
	int forward_bump = 8;
	// If someone falls into spikes, those spikes become harmless (to others).
	curr_room_modif[curr_tilepos] = 0xFF;
	// If someone falls into spikes in a different room
	if (Char.room != curr_room /* && fixes->??? */) {
		if (Char.charid == charid_0_kid) {
			// fixes an issue where kid falling into spikes disappears
			if (Char.curr_col == -1) {
				draw_kid();
				forward_bump = Char.direction == dir_0_right ? -6 : 16;
			}
		} else {
			// remove guard from the original room
			level.guards_tile[Char.room - 1] = -1;
		}
		// draw character in the correct room
		Char.room = curr_room;
	}
	Char.y = y_land[Char.curr_row + 1];
	Char.x = x_bump[tile_col + 5] + 10;
	Char.x = char_dx_forward(forward_bump);
	Char.fall_y = 0;
	play_sound(sound_48_spiked); // something spiked
	take_hp(100);
	seqtbl_offset_char(seq_51_spiked); // spiked
	play_seq();
}

[David]

I added this last fix to SDLPoP.

[atrueprincefanfrom18]

This could be merged here.

[dmitrys]

I found another glitch with a tall pillar. It happens in the DOS version and in SDLPoP. Notice the black rectangle on top the pillar near kid.

[dmitrys]

The bug also happens if you simply jump near the pillar.

[dmitrys]

@David, thanks for fixing the bug in the Git repository.

There is also a related bug which is caused by a different function. The top of the pillar base becomes pixelated after the jump where kid's hands were. I commented on how I fixed it in the commit for the first fix.