Klye @khird@qoto.org
Mod
Joined Sep 2018
> - thanks for not addressing the no updates,
> - and the no freemo
So to make this abundantly clear:
- I **am** a QOTO mod
- I **am not** the QOTO sysadmin
- Removing spammers **is** a thing I do
- Upgrading QOTO's software **is not** a thing I do
- Adding things to our rules page **is not** a thing I do
- Conjuring up freemo **is not** a thing I do
Nothing you say will change any of the above, so there's no point in complaining further.
@freeschool I'm a mod. My primary contribution here is to keep our timeline free of spammers, and I've issued over three thousand bans to accounts on our server, so you don't have to see people hawking all sorts of rubbish every time you check the timeline. You're welcome. I don't have the authority to modify the QOTO terms - so I offered the help I could, which was advice on how to prevent your data from being scraped, if you want it that way.
> Did you know Google don't have to respect that option ?
Google doesn't have people going and reading the footers of websites to know whether they can scrape them. If you don't want your profile indexed, the way you communicate that to their bot is by setting the `noindex` tag, which is what the opt-out mechanism does. If you're interested in an actual effective solution, that's the way to go; if you're just interested in me making the "token gesture" on your behalf then the answer is no. Even if I had the authority, the text of your demand reads much like those email disclaimers (you know the ones: "This email is intended only for the person or entity to whom it is addressed...") which are generally regarded as ["legally useless"](https://www.economist.com/business/2011/04/07/spare-us-the-e-mail-yada-yada). So it strikes me as pointless visual clutter and I'm not in favour of including it.
> "Well-behaved" Google spider -
are you fucking having a laugh ????
Empirically, [it appears to respect your wishes](https://www.google.com/search?q=site%253Aqoto.org%252F%2540freeschool) if you communicate them in a way it can understand. And there's no need to curse at me.
> "we need to trust them"
I didn't say that, and don't put words in my mouth. Feel free to not trust them, and use the privacy settings (which should work against even ill-behaved bots). But why would you trust them to obey your demand just because it's in the footer rather than the page metadata?
> oh look "Canada's four university football conference championships"
We don't have any rule prohibiting casual discussion among members. In fact, if anything, the fact that you had to go back eight and a half months to find a non-STEM post on my profile should be taken as evidence *against* your argument. But our status as a STEM server is somewhat beside the point - which is, there are valid reasons why someone might want their profile indexed, just as there are valid reasons why you might not. The decision to check the box or not is up to you.
@freeschool Under Settings > Preferences, you'll see an option to opt-out of indexing. That adds an attribute to your profile which well-behaved crawler bots (Google search spider etc) will respect. As a STEM instance, we have plenty of researchers who use their QOTO accounts for professional purposes and *want* their work disseminated as widely as possible.
There are also privacy settings on a per-toot basis, which can prevent even badly-behaved scrapers from seeing your content. This is much more effective than expecting them to abide by the sort of demand you're advocating we post (in all likelihood, a human with control over the bot would never even read it).
@sabbatical Understandable! I suppose it would be possible to make something that *was* both - glass fibres embedded in acrylic. But that's not common to my knowledge - plexiglass doesn't usually have embedded glass fibres, and fibreglass usually uses a different plastic in which to embed them.
@Lana Kentucky tried something similar a while back, I think? They introduced a senior elective called "Biblical literacy" which sounded really objectionable from a separation-of-church-and-state standpoint, but about which I ended up feeling fairly ambivalent.
It was neither religious instruction nor a critical literature class - the idea behind it was that our culture is chock-full of references to the Bible, so educated adults ought to be able to recognize them, even if they don't believe the Bible is the word of God. For example, one should understand that "pieces of silver" carries connotations of betrayal, the same way they know that "Et tu, <name>?" does after they study Shakespeare.
@DaveyDov I think the digital overlay thing they do to put ads on the field dynamically was causing problems.
@peterdrake I think it'd look less weird - to me, the angle between the two rightmost "verticals" is too large for my brain to accept that they're parallel in 3D-space.
I don't know what an artist's advice would be, but from a geometry point of view:
- Fix a string at the vanishing point, and use it as a compass to make an arc near the centre of the page.
- Taking a compass, draw two overlapping circles, each with its centre on the arc.
- Lay your straightedge across the two points where these circles intersect, and draw a line along it.
The advantage to doing it this way is that once you've constructed the first arc, you can move the paper around as much as you'd like without worrying about keeping track of the vanishing point, because all the future work is relative to marks already on the page.
Of course you could come up with another way of constructing that first arc. If you have an angle θ cut out of something rigid or marked on something you can trace, then:
- place its vertex at the centre of the page with arms facing downward
- mark the points where its arms cross the edges of the page
- align the cardboard in any other orientation such that its arms still pass over the edge-marks
- mark the new position of its vertex.
The angle you'd need is related to the page width 𝓦 by θ = π - sin⁻¹[𝓦/(2ℓ₃)].
@peterdrake Nice! I extended the lines out further to see how you did. The blue lines, of course, are very good, the red ones have some variation, and the green ones are similar to the red but have worse outliers. If the extremes were improved a little bit I think it'd be quite good. The lower right corner is the only one I could tell looked wonky without the help of the extended lines.
@peterdrake I tried working through the trig to figure out where to place the third point. I assumed you could measure the distances ℓ₁ and ℓ₂ from the image centre to the existing vanishing points, and the perpendicular distance 𝓱 from the image centre to the horizon passing through both points.
The method I came up with requires you to first calculate 𝓭², which is the square of the distance from the observer to the image plane:
𝓭² = √[(ℓ₁² - 𝓱²)(ℓ₂² - 𝓱²)] - 𝓱²
Then you simply divide by the distance to the horizon to calculate the distance from the image centre to the third vanishing point:
ℓ₃ = 𝓭²/𝓱
I don't know how I could test this rigourously, but it gives sensible results at a couple key cases:
- In the correct two-point perspective case, the horizon passes through the image centre, so 𝓱 = 0. The first formula gives the formula 𝓭 = √[ℓ₁ℓ₂] for altitude of a triangle, and the second one blows up as the third vanishing point goes to infinity.
- In the correct one-point perspective case, the line connecting the vanishing point to the centre of the image is perpendicular to the horizon, so ℓ₁ = 𝓱 and ℓ₂ = ∞; consequently, the distance is indeterminate. This corresponds to an extra degree of freedom, as the observer can move directly toward or away from the vanishing point without changing its position on the image plane.
- If ℓ₁ = ℓ₂ = 2𝓱, then ℓ₁ = ℓ₂ = ℓ₃. This corresponds to a pseudo-isometric orientation; all the vanishing points lie at 120° intervals on a circle surrounding the image centre.
@peterdrake Yes, that's correct. It looks like uploading the image broke the animation, but imagine that it overlays another set of lines highlighting the dark square building along the right-hand edge, near the bottom (which is past the right-hand vanishing point, similar to the box in your drawing). The green lines corresponding to the 3D-vertical edges are nowhere near 2D-vertical, which is why the building doesn't look too distorted.
More broadly, imagine you're in the centre of an octahedron with its vertices at the cardinal directions (or whatever alignment corresponds to your drawing, if the boxes aren't oriented with their faces normal to NESW/UD). If the ray from your viewpoint through the centre of your image plane would intersect the octahedron at:
- a face, it's three-point perspective with the vanishing points at the three corners of the triangular face.
- an edge, it's two-point perspective with the vanishing points at the endpoints of the line segment defining the edge.
- a vertex, it's one-point perspective with the vanishing point at the vertex.
@peterdrake Here's an animation I just put together in GIMP from a decent quality photo, not a fisheye lens or anything. Note that each line in 3D space is parallel to the others of the same colour, but orthogonal to those of different colours. But in 2D space, all the lines of a particular colour converge to a single point - even the vertical ones.
@peterdrake I expect it'd look better - at that point everything ought to be lined up. Maybe try tracing that drawing onto another sheet, but offset vertically so it's like you describe? I'm trying to imagine it, and I think my brain is happier with the shape of the box when I picture it down near the bottom edge.
@sabbatical Plexiglass is a trademark for acrylic - it's the same thing!
Polycarbonate's a different thing, but I think the forum post that made that claim is wrong.
@mitch one syllable, but the vowel's a diphthong. Same as my name!
@ShadSterling Oh yeah! definitely a cognitive speed bump when I come across that usage. At one point BLM was the same thing - historically for Bureau of Land Management; for a time in the mid-2010s it was more common to abbreviate the Black Lives Matter slogan to the same acronym.
This is on the right track.
The problem is that your vertical lines (that is, representing vertical edges in 3D space) are all parallel on your 2D image plane.
This means that your image plane is itself vertical. But your viewpoint is above the horizon, and the horizon is above the midpoint of the page. This implies that your image plane is oblique relative to the direction of observation (red line on my diagram) instead of normal to it (green line). That's the difference between a two- and three-point perspective, and the cause of the distortion you see.
The solution is to also draw the vertical dimension with perspective. Because your direction of observation is slightly downward, the third vanishing point should be directly below the midpoint of the image, and probably at quite a distance (it would be infinitely far away only if you were looking perfectly horizontally, which is when your verticals should come out parallel).
I think that with some trig you could work out the proper distance as a function of the coordinates, relative to the centre of the page, of the two existing vanishing points.
@ShadSterling Point of Contact is how I would normally expand it. Proof of Concept is new to me though. What would you use that acronym to represent?
@sabbatical That sounds like an epoxy - they want you to mix two components and apply with a syringe. The point of a solvent weld is that it just dissolves a bit of plastic from each face, creating a thin layer of liquid plastic-in-solvent solution between the two pieces, and then as the solvent evaporates, the plastic remains, leaving it as one continuous piece. Were I in your shoes, I'd just get a can of acetone from the local Rona/Lowes/Home Depot and give that a shot - but your dollar, your decision.
No matter what you use, you'll have to get the two faces lined up as exactly as you can to maximize the surface area in contact (viscous products are more forgiving in this regard, but you have two perfectly mated halves of the fracture, so that's probably more hassle than it's worth). Then you'll need to clamp them together without flexing the join. I think the clamping will be the hard part, because it's a curved surface without anything to easily line them up against.
@sabbatical Hm yeah that looks to be in shear if I understand the orientation correctly. You can still try solvent welding it but you might benefit from coming up with a way to clamp things firmly in place while the weld sets.
🇳🇱
