Author Topic: Terrain and the strange things it does  (Read 2559 times)

Offline Glom

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Terrain and the strange things it does
« on: January 06, 2017, 04:05:19 PM »
I am a wreck. In 24 days I will complete the sale of my flat bringing to an end three and a half months of agonising. I am so jumpy at every little sound.

The latest trigger was a stripe on my ceiling. A stripe that was slightly darker than the surrounding white. Very slightly. Oh no. Is the radiator pipe for the flat above leaking and staining my ceiling? Why would it form a stripe? Maybe water is pooled into a channel by the beams in the ceiling and has been permeating through evenly?

Then a thought occurs. Anisotropy. No plaster in this place is laser straight. The experience getting my wardrobe fitted revealed that. Indeed, I look at where the ceiling joins the coving and I notice a slight angle.

The light source in the room was a lamp at the side shining across the stripe, with the stripe angled slightly away. Just a couple of degrees. I test this by moving the lamp to the other side of the room and sure enough, the very slightly darker stripe becomes a highlight.

It just goes to show what even tiny variations in a surface can do, especially to someone in a neurotic mindset looking for faults. We hear conspiracists complain about light patches suggesting the presence of spot lights, when the simply explanation is the anisotropy of the terrain is causing the highlight to be slightly angled more towards the Sun. But of course, if you want to find fault, you'll invent all sorts of cow and chicken stories to fit irrelevant blemishes.

Of course, if in a few days, the ceiling comes down and water is pissing everywhere, I'll ask this be deleted.

And what's that sound? Oh it's my dishwasher. Never mind.

Offline nomuse

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Re: Terrain and the strange things it does
« Reply #1 on: January 06, 2017, 06:07:22 PM »
And another reason why we in theater instinctively texture all surfaces (that is, give them some color variation). Because solid color isn't. If you try to make it flat and plain what you get instead is every single seam and fleck and shadow. Instead, make it so the texture you are adding will dominate.

I'm about to do the same thing on a set I'm lighting next week; I'm going to put breakups in all the front lighting because there are some visible and ugly seams in the painted scenery. It also really helps to disguise the edges of the light cones and the various crossing shadows.

Offline ka9q

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Re: Terrain and the strange things it does
« Reply #2 on: January 07, 2017, 04:24:05 AM »
Sounds like a "still life" version of the Uncanny Valley.

That is, unless you're sure you can achieve perfection, it's best not to try. :)

Offline nomuse

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Re: Terrain and the strange things it does
« Reply #3 on: January 07, 2017, 11:33:19 AM »
Yah. We're going through hell now on some acoustic panels. Two different clients want them flat off-white. Which means every dust smear, fabric ripple, shadow, even the density of the backing material shows up. Means a lot more work, and at least one of these clients is high-maintenance enough to scream if there is any visible defect.

Thing of it is? These have printed surfaces. So to get that off-white color it is actually being run through a giant fabric printer. With all the potential for ink drips and smears and transfer marks that entails, of course. But...printed. So it could have a subtle texture printed right in. A hint of a weave, a barely-there cross-hatch or pebbling, some gaussian noise; any of these would make them in my opinion look vastly better.

Heck, most walls in your house are textured for exactly that reason. It just plain looks better. Even an actually perfect flat surface won't present that way to your brain, because your eyes aren't set up for that. They're going to throw phosphene-like effects at any void.

Offline Obviousman

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Re: Terrain and the strange things it does
« Reply #4 on: January 07, 2017, 08:20:10 PM »
It's amazing, isn't it? For example, I'm standing on the scales and they say I have put on 2KG over Xmas. That has to be an illusion, right?

Offline dwight

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Re: Terrain and the strange things it does
« Reply #5 on: January 07, 2017, 08:56:40 PM »
Yeah because everyone knows it should add way more than that!😉
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Offline Peter B

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Re: Terrain and the strange things it does
« Reply #6 on: January 08, 2017, 06:11:58 AM »
It's amazing, isn't it? For example, I'm standing on the scales and they say I have put on 2KG over Xmas. That has to be an illusion, right?

Localised gravitational anomaly...

Yep.

Definitely.

Offline raven

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Re: Terrain and the strange things it does
« Reply #7 on: January 08, 2017, 10:40:11 PM »
Speaking of terrain, looking at Apollo anaglyphs is just amazing. The monotone nature of the terrain can make it blend together into a mass in a 2D single image, but it just pops when in 3D. You can see all the hillocks and little dips and climbs. It's really quite spectacular. Really helps you appreciate just how rough it all is.

Offline ka9q

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Re: Terrain and the strange things it does
« Reply #8 on: January 10, 2017, 03:00:44 AM »
Yes, I keep trying to say exactly that to hoaxers who complain about this or that not looking "right".

Offline AstroBrant

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Re: Terrain and the strange things it does
« Reply #9 on: January 12, 2017, 02:56:48 AM »
Very good post, Glom. Thank you. I might share it somewhere, IYDM.
May your skies be clear and your thinking even clearer.
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Offline JayUtah

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Re: Terrain and the strange things it does
« Reply #10 on: January 12, 2017, 10:01:59 AM »
Speaking of terrain, looking at Apollo anaglyphs is just amazing. The monotone nature of the terrain can make it blend together into a mass in a 2D single image, but it just pops when in 3D. You can see all the hillocks and little dips and climbs. It's really quite spectacular. Really helps you appreciate just how rough it all is.

You get the same from Mars stereo photography.  It also explains why so much of my early photography of the Utah landscape didn't seem as exciting as when I was standing there.
"Facts are stubborn things." --John Adams

Offline nomuse

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Re: Terrain and the strange things it does
« Reply #11 on: January 12, 2017, 10:43:10 AM »
Well, the eye is a stereoscopic motion camera that does HDR. But that still doesn't quite explain the discrepancy between what it looks like and what it shoots like. I think a lot of that lies in the fact that the foveal view is relatively small in relation to the whole, and our brains largely ignore the background when looking at a really cool bird or something. So what stood out in the mind ends up captured on the frame as a whole bunch of cluttered background detail and a little spec in the middle that looked so much more interesting when you were there.

(I had the same problem grabbing sound effects on location. Most people, even trained sound designers, don't notice all the background noise. Tape, unfortunately, captures it all).

Offline Kiwi

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Re: Terrain and the strange things it does
« Reply #12 on: January 15, 2017, 03:05:09 AM »
Speaking of terrain, looking at Apollo anaglyphs is just amazing. The monotone nature of the terrain can make it blend together into a mass in a 2D single image, but it just pops when in 3D. You can see all the hillocks and little dips and climbs. It's really quite spectacular. Really helps you appreciate just how rough it all is.

Sorry if I sound like a lousy Googler, but can you give specific examples, particularly of any that show both close and distant lunar features?

I've had trouble seeing some 3D images since having cataract surgery, but I'm certainly not complaining because without it I probably would have been totally blind by 2000. The ones that require red and blue goggles are now the hardest to view -- unless, of course,  I have the wrong colours, but I don't know whether I have right or wrong colours.

I have all the Apollo lunar surface photos on my HD from the ALSJ's DVDs, so it's not too hard to put stereo pairs and panorama shots side-by-side, but they have to be placed so I can view them by crossing my eyes, not looking straight, which is also difficult.

The problems the astronauts had with perspective on the moon have always intrigued me, and it took a long time to notice one thing that might cause problems, other than the lack of known objects that give scale.

They were looking at a landscape full of craters, from just millimetres to kilometres in diameter.
At a certain distance the tiniest craters would become too small to see and bigger ones would take over. This would repeat with bigger and bigger craters as far out as craters can be seen, and with no atmosphere to provide haze, the clarity of the view might make it very hard to accurately estimate the size and distance of any particular crater.

It's a sort of visual compression and there's probably a name for it. If so I'd like to know.
« Last Edit: January 15, 2017, 03:11:03 AM by Kiwi »
Don't criticize what you can't understand. — Bob Dylan, “The Times They Are A-Changin'” (1963)
Some people think they are thinking when they are really rearranging their prejudices and superstitions. — Edward R. Murrow (1908–65)

Offline Kiwi

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Re: Terrain and the strange things it does
« Reply #13 on: January 15, 2017, 08:54:23 AM »
...The ones that require red and blue goggles are now the hardest to view -- unless, of course,  I have the wrong colours, but I don't know whether I have right or wrong colours.

Okay, I tried my cardboard red/cyan goggles on some Apollo Anaglyphs and am getting weird results.

Phil Plait recommended this one:
https://www.flickr.com/photos/29774727@N04/4519119504/sizes/o/in/photostream/
which he says is the Apollo 14 landing site. After a lot of study of the maps at the ALSJ I sort of agreed, if the two biggest craters at bottom left are indeed North Triplet and Center Triplet.

But with the goggles on, those two craters look very steep-sided and roughly about 80 to 100 metres deep, yet the Post-Flight Apollo 14 Traverse Map (4.1 MB)
https://www.hq.nasa.gov/office/pao/History/alsj/a14/a14-usgs.jpg
with contour lines, indicates that they are much shallower. I scoured the Apollo 14 ALSJ and found no mention of the depths of the Triplet craters. This PDF without electronic text
https://www.hq.nasa.gov/alsj/a14/a14pp-021-030.PDF
says on page 23, "North Triplet crater had an original depth of about 30 m".

Looking at some Apollo and some non-Apollo anaglyphs I saw three weird effects in many of the photos -- excellent 3D, vastly over-exaggerated 3D, and no 3D at all where it should be. And sometimes a fourth effect -- a strange banding that shouldn't be there.

Now, that could be the result of my goggles (cardboard giveaways from HBO) or my eyes, my age, or poor processing, or any and all of those. In fact some of the anaglyph images looked much better in their original single-image form without the goggles, but without 3D.

Maybe I'm just being fussy. Perhaps spoilt back in the 1950s by those old hand-held 3D viewers with a gazillion two-image black-and-white or hand-coloured cards that used to be in every second-hand store and thrilled me at the age or four, or later spoilt even more at the grand old ages of 6 to 8 by the brilliant Viewmaster system with its fantastic, vibrant colour images. I got one Viewmaster reel for my seventh birthday and bought one or two more with a gift of a few shillings. They seem to have been many times better than these new-fangled anaglyphs, but maybe it was my young eyes that made them so vibrant.

H-E-L-P !!! What's going wrong? I want to see good 3D.
« Last Edit: January 15, 2017, 09:41:58 AM by Kiwi »
Don't criticize what you can't understand. — Bob Dylan, “The Times They Are A-Changin'” (1963)
Some people think they are thinking when they are really rearranging their prejudices and superstitions. — Edward R. Murrow (1908–65)

Offline Rob48

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Re: Terrain and the strange things it does
« Reply #14 on: January 17, 2017, 01:30:46 PM »
Speaking of terrain, looking at Apollo anaglyphs is just amazing. The monotone nature of the terrain can make it blend together into a mass in a 2D single image, but it just pops when in 3D. You can see all the hillocks and little dips and climbs. It's really quite spectacular. Really helps you appreciate just how rough it all is.
I really wish I could see anaglyphs. My eyes don't do that at all (I have one strongly dominant eye and my brain refuses to make 3D pictures work... although strangely some 3D films work OK).