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A first-person engine in 265 lines of JS

playfuljs.com

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Re: A first-person engine in 265 lines of JS

#41

Post by bitL »

roryokane wrote: post #28

It is very interesting to me that you need to multiply the distance-to-wall by the cosine of the angle to transform the image from fisheye to normal. It makes me wonder, why is it that our eye in real life sees straight lines as straight, the way this demo renders the image? To illustrate the question, see https://en.wikipedia.org/wiki/File:Panotools5618.jpg – why do we see the world as in the bottom image instead of…

I was trying to crack exactly the same problem a decade ago - I was very frustrated by "classical" perspective distortions (such as looking up and down at a very tall pole, you notice in 3D projection the projected width at a given height changes depending on the pitch angle, which is counter-intuitive as your eye doesn't do that). I searched for answers, read Denis Zorin's disertation from Caltech, various different camera models etc. After one talk with a neurosurgeon he mentioned that those "perspective distortions" are perceived often by patients after a brain surgery and as the brain heals the normal undistorted picture begins to emerge. I am still curious if there is a more realistic mathematic formula that would allow us to have exactly the same perspective projection in 3D graphics as we have with our eyes. Anyone knows any recent research on this subject?

Re: A first-person engine in 265 lines of JS

#42

Post by lfuller »

roryokane wrote: post #28

It is very interesting to me that you need to multiply the distance-to-wall by the cosine of the angle to transform the image from fisheye to normal. It makes me wonder, why is it that our eye in real life sees straight lines as straight, the way this demo renders the image? To illustrate the question, see https://en.wikipedia.org/wiki/File:Panotools5618.jpg – why do we see the world as in the bottom image instead of…

Would it not be because the retina is curved?

Re: A first-person engine in 265 lines of JS

#43

Post by munificent »

roryokane wrote: post #28

It is very interesting to me that you need to multiply the distance-to-wall by the cosine of the angle to transform the image from fisheye to normal. It makes me wonder, why is it that our eye in real life sees straight lines as straight, the way this demo renders the image? To illustrate the question, see https://en.wikipedia.org/wiki/File:Panotools5618.jpg – why do we see the world as in the bottom image instead of…

> It makes me wonder, why is it that our eye in real life sees straight lines as straight, the way this demo renders the image?

Your eye doesn't see it as straight, your brain does. Your eye doesn't actually gather a single coherent image, in fact. It's constantly moving[1], bringing the higher-precision fovea at the center of your retina to bear on interesting parts of the scene.

Your brain then accumulates all of that data into a single coherent "image" which is what you consciously perceive. This is why, for example, you are unaware of the blind spot caused by your optic nerve obstructing your retina[2].

A straight line in the world isn't projected onto a straight line on your eye: after all, the back of your eye is curved. (Even if it was, so what, it's not like your rods and cones are aligned in a nice neat grid.) It's just that you've learned that a line of stimulus curved just so across your visual field corresponds to a straight line in 3D space.

[1]: http://en.wikipedia.org/wiki/Saccade [2]: http://en.wikipedia.org/wiki/Blind_spot_(vision)

Re: A first-person engine in 265 lines of JS

#45

Post by devindotcom »

timpark wrote: post #25
devindotcom wrote: post #18

Heh, reminds me of kkrieger - a first person shooter in 100KB for a scene demo. https://www.scene.org/file.php?file=%2Fparties%2F2004%2Fbrea...

If you missed it a couple of weeks ago, this article about its creation was really interesting: http://fgiesen.wordpress.com/2012/04/08/metaprogramming-for-... ( Thread: https://news.ycombinator.com/item?id=7739599 )

That's great! I did miss it.

Re: A first-person engine in 265 lines of JS

#48

Post by arnorhs »

roryokane wrote: post #28

It is very interesting to me that you need to multiply the distance-to-wall by the cosine of the angle to transform the image from fisheye to normal. It makes me wonder, why is it that our eye in real life sees straight lines as straight, the way this demo renders the image? To illustrate the question, see https://en.wikipedia.org/wiki/File:Panotools5618.jpg – why do we see the world as in the bottom image instead of…

A dumb question/explanation, but wouldn't that be because the screen/viewing pane is flat, while your eye is a ball?

Another way to visualize that calculation, is to see it as if it's adding a curved lens on top of the viewing pane.

I have no idea what I'm talking about, though.

Re: A first-person engine in 265 lines of JS

#49

Post by yellowapple »

roryokane wrote: post #28

It is very interesting to me that you need to multiply the distance-to-wall by the cosine of the angle to transform the image from fisheye to normal. It makes me wonder, why is it that our eye in real life sees straight lines as straight, the way this demo renders the image? To illustrate the question, see https://en.wikipedia.org/wiki/File:Panotools5618.jpg – why do we see the world as in the bottom image instead of…

I've always figured the latter explanation - that the picture from our eyes is distorted like that, but the brain corrects the image (it also doesn't hurt that we have two eyes, where as cameras typically don't; I wonder if multi-lens cameras are also subject to that fisheye effect?).
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