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MALON

Y-Shearing, looking all the way up/down

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In software rendering mode for most ports, I know that looking up/down is emulated is not really occurring. It's Y-shearing. So my question is, what would it look like if you could look 90 degrees up or down?

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Think about it this way. The floors would look stretched beyond recognition, and the walls would look as though they are rendered though a kaleidoscope (only not as bad).
It would be nice if the limit could be decreased just a bit though. At the moment, zdooms free look feels just a tad restrictive.

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esselfortium said:

Here's an artist's interpretation of what it would approximately look like if you could look straight up or down with Y-shearing:


Oh god you just made my day!

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That clarinet, or whatever it is, in the pic looks like a cross between something very rude and an extra from "Day of the Tentacle".

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I heard a myth that if you look straight up or down in software mode, your computer will turn into a doom-spectrum hole (which is like a black hole, only with doom-palette colors) that will teleport you and the rest of reality into a new dimension where everything is 2.5d, living things are flat like paper, walls and floors look blocky and pixelated, and the colors will look like Doom's. I also heard that the myth will happen likewise with Duke 3D.

But it's just a myth, right?

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Sorry, but it's a meaningless question. You see how with Y-shearing the walls always appear vertical, no matter how far up or down you look? You could never look straight up or down because it would be impossible.

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I always thought you get a division by zero.

And you know what would happen if you could divide by zero!! But I think someone already mentioned the black hole.

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fraggle said:

the walls always appear vertical, no matter how far up or down you look.


Of course. I learned in art class that the way Doom renders in software mode is akin to 2-point perspective, where objects are rendered due to two seperate points across the horizon. Walls are always vertical because the two points don't have any height difference, and they always stay on the horizon. Looking up or down requires 3-point perspective, where every single line and wall follows 3 points, 2 on the horizon, and 1 below.

But this is Doom, not art class. Who cares about perspective when you shoot rockets at the head of John Romero?

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Y-shearing is a weasely method to make it sorta look like you're looking down when in fact you're still looking straight ahead.

Even at its "lowest", the angle of vision compared to the horizontal is 0°. You're asking how it would look like if 0° went all the way to 90°. It's not even a case of division by zero, it's simply a meaningless question. Like "how old is the tenth of my two sons?" If you've got two sons, you don't have ten of them. If you're looking at an angle of 0°, you're not looking at an angle of 90°.

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Gez said:

It's not even a case of division by zero, it's simply a meaningless question.



Let's just say, it's an undefined situation. Mathematically it's a division by zero, which is a meaningless expression. :D

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Of course what he wants to know is what it would look like if you could keep "looking up" farther than what, say Zdoom allows via y-shearing, even though it obviously wouldn't be 90 degrees. I think I can imagine it, but I'd also be interested in seeing it for myself.

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Maybe an illustration will help (or not :p)



(yes, ZDoom lets you look further down than up. Why? Hell if I know, ask Randy.)

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That's very interesting. I always thought that looking up and down in the software renderer skewed the image somehow in addition to scrolling it, but now I see that looking up and down really does just scroll a tall image.

It all looks so flat now! My suspension of disbelief is destroyed!

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Nuxius said:

(yes, ZDoom lets you look further down than up. Why? Hell if I know, ask Randy.)

From rh-log.txt:

May 1, 1998
[...]
- Played Blood for a little bit. That, and a prior suggestion concerning
  rocket jumping made me decide to make a slight tweak to the freelook
  code: You can now look down twice as far as before.

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Creaphis said:

That's very interesting. I always thought that looking up and down in the software renderer skewed the image somehow in addition to scrolling it, but now I see that looking up and down really does just scroll a tall image.

It all looks so flat now! My suspension of disbelief is destroyed!


Heretic E1M1, with all its support beams in the starting room, is a perfect place to see just how wrong shearing can look.

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