Full Version: Hidden line removal progress

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Hi Martin,

> Actually the way I would do it and also the way that seems to be most logical is the
> attached result by Cinema4Ds Sketch & Toon renderer. This is also similar to mattj example
> from post 6201.28 but without the "overshoot" which again is a personal style.

The style you're showing here is having an accent on the "border against background", having thickness just where the shape touches the background. That's what I'd like to enable by some kind of "outline" option for extracting out those curves.

The other style is not just a difference with "overshoot", it's more about accenting all silhouettes of the object, not just the outermost one. A shape like this should show a bigger difference:



Just the "outline against background" would be like this:



But all silhouettes would be like this:




So I think I want to be able to do both of these kinds of things, like one option to get silhouettes into their own kind of group and another option that will extract out the outer outline only.

Maybe when enabled the outer outline curves would be a duplicated set of curves going over top of the other kinds though.... Not quite sure about that part.

- Michael

Image Attachments:
exterior_edge6.jpg  exterior_edge7.jpg  exterior_edge8.jpg 

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Hi Matt, also I see now that one thing I got confused about comparing your "insect walking" picture against the one Martin posted, was that your one was only a depression and not a full hole all the way through, is that right?

That's why you only had one accented line there, because there was a floor in yours.


Martin, the one that you posted from http://purdy.gatech.edu/wp-content/uploads/2012/07/2_line_wt.pdf - I don't see how I'm going to be able to get that same result with only one of the silhouettes of that through-hole being accented, it's not clear to me which one it would supposed to be so instead I'll probably do both of them.

- Michael

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"""""""""""""I'm not sure about doing a preview, it would be nice to have but I've got to balance that against how much time it would take to implement it"""""""""""""""

I understand, it might be overkill for this feature.

An options button might be interesting instead of adding another dialog.
It would make it a simpler and less intrusive, you change it only if you have to.
Saves could 'stick' between sessions.


Marc

Image Attachments:
Untitled1.png 

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>Martin, the one that you posted from http://purdy.gatech.edu/wp-content/uploads/2012/07/2_line_wt.pdf -
>I don't see how I'm going to be able to get that same result with only one of the silhouettes of that through-hole being accented,
>it's not clear to me which one it would supposed to be so instead I'll probably do both of them.

I regret posting this as it just added confusion. I didn't look carefully. The example shows a subjective way thats difficult or impossible to put into some sort of rule.
I'm fine with your "border against background" method that gives me a rendering like this:

Image Attachments:
border against background.png 

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What will the rule of the internal up arc-circles if this block was on a red table ?
Same rule than an empty backgorund ?
B is satisfying ?





An not only the 2 little arc circles ! As soon as a line has a free touch background all the line must be large!
So a very complex rule!

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It's not complicated: Every edge that "touches" the background must become thick.
It's a way to better visualize the object.
The same way Photoshop would apply an Outer Glow Layer Style to a transparent pixel image.

Image Attachments:
Photoshop Outer Glow.png 

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So your example must look like this

Image Attachments:
Screen Shot 2013-09-30 at 17.20.10.png 

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Yes simple for your example and rule but i have spoken of this one (and it's mixed rule under lined)
http://purdy.gatech.edu/wp-content/uploads/2012/07/2_line_wt.pdf
who seems it-self not well applyed on its example! :)

So be simple is the more easy way! :)

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Martin's rule looks very good, and simple, for having a "heavy" and a "light" line weight.

As in Conrad Taylor's pdf, adding an intermediate line weight, and/or continously tapered line weights,
and/or broken lines, and/or dotted or dashed lines could add additional rules for the computer programmer to figure out :-)

Background tone helps visualization also.

- Brian

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When I was an art director, this was how I taught my artists to weight their line-art drawings.



To emphasize depth. More interior detail would carry thinner associated line weights.

Impossible, I know. The little inside-only buildup doesn't sit well with me.

None the less, I'll be happy to see what comes of all this.

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On this object that seems yet easy
but for a complex one that surely be a nightmare for the coder! :)
Because there is no logic reason that the entiere side circle will be not entierely large, if the straight line "horizontal" is itself large!
They are "touching" both some empty "background"!

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> When I was an art director, this was how I taught my artists to weight their line-art drawings.

This certainly looks very good but I have a hard time understanding the rule that requires to continue the thick horizontal line into the object. It's an aesthetical choice isn't it? It looks good and helps even more to understand the shape but it seems to be impossible to put into an algorithm.

Image Attachments:
Extented line.png 

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> seems to be impossible to put into an algorithm.

I do understand the conundrum. This is a tricky thing to negotiate with solid/flat objects. If I was drawing this with pen and paper where the line quality had a bit of natural "grunge" in it, the thick line may have tapered to match the thinner line, or the thinner vertical line would have shared the transition. This is easier to envision when drawing more organic character.

Not possible it seems to do with splines and outlines.

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Hi Michael ..

Yes I do use a script that you did some months ago. I changed the line width to 6 (from 4) and it does now show the hidden lines as small but distinct dashes. I may increase that number to 8.

thanks,
eric

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Hi Michael,

Is it possible to isolate the red lines into a separate layer when exported?

Image Attachments:
Isolate.png 

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Hi Marc,

> An options button might be interesting instead of adding another dialog.
> It would make it a simpler and less intrusive, you change it only if you have to.
> Saves could 'stick' between sessions.

That's definitely less intrusive, but sometimes less intrusive also means the settings are just not found by many users...

I also sort of like to avoid messing around with the system standard dialogs very much. The regular Windows system dialog does not have a button like that. It's possible to customize the dialogs in different ways but it's not all that unusual for that to have maintenence problems down the road.

- Michael

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Hi Martin,

> I'm fine with your "border against background" method that gives me a rendering like this:

A couple of questions about the "border against background" option. I'm thinking of calling it something like "Generate outlines", and when enabled it would make an extra set of curves on separate kind of grouping (grouped either as an actual group or layer or separate color or lineweight or maybe any of these) that would be coincident with the regular edges. So that would mean that the outline curves would stack up on the "regular edges". The reason for this is that otherwise to not have separate stacked up curves would mean having the regular edges broken up into smaller pieces which seems kind of weird. Like on your example this area here:



And also another reason to make the outline a separate set of curves is that I think you'll want the outline to go underneath all the other regular edges and I guess underneath the shaded image as well so that when it's thickened it only adds thickness to only one side of the shape rather than having thickness on both sides. I don't believe that there is any way in PostScript to add thickness to just one side of a path rather than having the thickness be symmetrical around the path center line, I think it has to have some kind of masking for an effect like that.

Then the other thing is that if you have separate multiple objects, I would think that the outline would treat spots where it borders on either the background or the other object as an outline area, so for example with 3 objects like this (that don't touch each other, they just block one another in visibility):



Then I'd think that the outlines would go like this:




Does that seem right? The other possibility would be for outlines to only go against strictly the background and not other objects at all which would be like this:



- Michael

Image Attachments:
martin_edge.jpg  martin_outline1.jpg  martin_outline2.jpg  martin_outline3.jpg 

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Hi Mike,

> When I was an art director, this was how I taught my artists to weight their line-art drawings.

It looks awesome! But unfortunately I think massively difficult to implement.

Not only difficult just to figure out an automated rule for how the thickening should be applied, but also difficult to edit in Illustrator afterwards as well I think, because I don't think there's any way to make a tapering line thickness like that directly on one long center-line curve, I think it has to be done as a closed and filled shape instead.

- Michael

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Hi Martin,

> This certainly looks very good but I have a hard time understanding the rule that
> requires to continue the thick horizontal line into the object. It's an aesthetical choice isn't it?
> It looks good and helps even more to understand the shape but it seems to be impossible
> to put into an algorithm.




If I understand correctly, it's a rule about all sihouettes being accented, regardless of whether they are inside the "outer outline" of the object or not.

It should not be hard to put this one into an algorithm, because the same geometric silhouette condition does hold through that entire edge - it's a silhouette edge because of the 2 surfaces that the edge belongs to, one surface normal points towards the viewer, while the other surface normal points away from the viewer.

It has to do with looking at surface normals, not at what's going on in the 2D screen space image...

- Michael

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Hi danperk,

> Is it possible to isolate the red lines into a separate layer when exported?

Those are the "seam edges" on closed smooth surfaces - I think that these particular kinds of edges just won't be exported at all, unless they are also a silhouette edge.

I haven't got any of the edge filtering out stuff in place yet.

Do you ever see a need where you would actually want those particular edges in the drawing?

- Michael

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