Full Version: Hidden line removal progress

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hi michael

See attached pdf for more explanation of different line styles needed. At the end of the day if you can export everything except the red dotted lines (hidden lines) and then a simple line style to differentiate the others that would be great. I tried recently export a chain done using the brilliant chain script and the silhouette command. I then exported to illustrator but it was just too cumbersome to clean up. This work would go a long way to making this process a lot more painless.

hope my sketch clarifies things

Another thing on this subject, when exporting to eps, is it possible for any circles/ellipses to have just 4 points at the major and minor axes. This would clear up a lot of points and make editing/construction easier. See bottom sketch in pdf. I suspect that this bit maybe why Isodraw can charge such a high price as we are moving from 3D objects to postscript language which is moving out of your field . .

Matt

Attachments:
lineHelp.pdf

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Hi,

This is great news, the samples are looking great!

The rendering and vector curves overlapped is something I have never seen and will be a major timesaver for my work.

When profile lines have less segments (joined curves) it's easier to edit afterward.
I imagine it must be hard to set a mechanism that works great in all situations though.

I use hidden lines from time to time in illustrations or schematics.

As mentioned, a closed shape for the main silouhette would be great.
An option for different colored lines could be enough to edit the thickness of lines in 2d vector editors (for example oulines, details and hidden.)

It might be interesting to have a special export window, like when exporting polygons.
It could have a preview and some options for including the rendering or not, lighting options, hidden lines, resolution, etc.

Or maybe a 'options' button in the export pdf file dialog window could be handy.

Marc

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Michael, thanks a lot for working on the much needed hidden line removal.

I attached a nice pdf about the two lineweight illustration principle from
http://purdy.gatech.edu/wp-content/uploads/2012/07/2_line_wt.pdf

I don't know if you can control line caps on export but this is also covered.

It doesn't hurt if the hidden lines also get exported as long as they can be easily turned on and off like on a seperate layer for example.

Attachments:
2_line_wt.pdf

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"""""""""""""""""""Also I was thinking for the background bitmap image to maybe shrink that down by half in width and height to get a downsampled antialiased result with a bit of blending in the border areas and also cutting down file size by a ways.""""""""""""""""""

I'm not sure I understand what this mean, would it be easy to post examples?

Marc

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"""""""""""I mean like the faint dashed lines that are displayed in MoI's viewport. For modeling purposes it's good to have some access to those to be able to select them, but do you use them in your illustration work as well for some things or not really?""""""""""

For me it would be nice to have access to these (as seperate object/sets as mentiond). It would allow me to easily reconstruct certain parts. Like the "six legged pod" example. If I needed more of parts of the legs that were hidden, I could use those to generate something at the proper perspective. There are some 2d techniques that can require "seperating" the parts of the charactor/object onto layers/assigments.

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Hi Michael ..

I personally like the look of objects in MoI now. I often darken the visible edge lines. On my display the hidden lines are lighter and thinner and that's great though I would like it if they could be dashed.

I would also like an alternative where the surfaces did not have any color at all so that for some illustrations it would appear simply as a line drawing.

cheers,
eric

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Hi Matt, thanks for the additional explanation.

So let me make sure I understand the insect walking rule properly. I think it's about local silhouette areas, with a silhouette spot being defined by 2 conditions (previously I accidentally only wrote about one of these conditions). The 2 conditions are:
- On a smooth surface, where the surface normal is at a 90 degree angle to the viewing direction.
- On a sharp juncture between 2 surfaces, where one surface normal points towards the viewing direction and the other points away from it.

And maybe for open surfaces (instead of solids) a third condition is a "naked" edge, meaning an edge that belongs to only one surface rather than being joined between 2 surfaces.


Would having all spots that fit that criteria sorted as "Outer edges" work properly? Or is there some way for an edge to need to be considered an "Outer edge" that does not fit under this definition?


You wrote:

> For me instead of an image a sihouette shape
> would be more advantageous. This could be done if
> you can get your outer boundary shape going :-)

You mean a closed silhouette vector path? Unfortunately I'm not very confident about getting a totally clean actually closed shape for the outer boundary, I'm just hoping to slice things up so that you would have some curves separated out on that full object outside boundary so you could have another kind of thickened shape there like the one shown in the file here: http://moi3d.com/forum/index.php?webtag=MOI&msg=4277.14


> Another thing on this subject, when exporting to eps, is it possible for any circles/ellipses
> to have just 4 points at the major and minor axes.

The complication with this is that a non-rational cubic bezier with just 4 points in it cannot make an exact circle or ellipse shape, they can only approximate it. Right now MoI does a general purpose refitting step to convert any kind of rational curve into cubic beziers and general fitting mechanisms like that will end up with more points than things built for certain kinds of shapes. It might be possible in the future to make some special cases for circles and ellipses but that's probably not going to happen during this pass of hidden line removal work.

- Michael

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Hi eric,

> I personally like the look of objects in MoI now. I often darken the visible edge lines. On my display the hidden lines are
> lighter and thinner and that's great though I would like it if they could be dashed.

Are you talking now about MoI's viewport display? Or about PDF/AI export?

For the viewport display, the hidden lines are actually supposed to be dashed currently. Does your display look different than this? :



Those "hidden lines" there are not solid:




> I would also like an alternative where the surfaces did not have any color at all so that for
> some illustrations it would appear simply as a line drawing.

You can get this currently by adjusting some lighting settings so the lighting is so bright it essentially disables shading entirely.

Check out here for a description on how to set that:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3135.3

- Michael

Image Attachments:
hidden_lines1.png  hidden_lines2.png 

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Hi Marc,

> The rendering and vector curves overlapped is something I have never seen and will be a
> major timesaver for my work.

I was hoping it would be useful for your work!


> When profile lines have less segments (joined curves) it's easier to edit afterward.
> I imagine it must be hard to set a mechanism that works great in all situations though.

Also the tricky part is maintaining accuracy, it's fairly natural for fitting mechanisms to use more points in order to make the fitted result reasonably accurate. I may be able to put in some parameters to control the accuracy level at some point but I'm not quite sure about having that done for this round of work.


> As mentioned, a closed shape for the main silouhette would be great.

Unfortunately I think that's going to be really difficult to achieve, I think the best that I'll be able to do is to have an option to just try and separate out portions of curves that are on the full object silhouette so that you will have something to work with, and if you just want to make an accented border it just having a set of curves in that area may hopefully be enough for that kind of use without it being fully closed.


> It might be interesting to have a special export window, like when exporting polygons.
> It could have a preview and some options for including the rendering or not, lighting options,
> hidden lines, resolution, etc.
>
> Or maybe a 'options' button in the export pdf file dialog window could be handy.

Yeah I haven't gotten to this UI part of it yet. I'm fairly certain that PDF export dialog will get bigger with additional options right on that dialog.

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, and I'm not sure if the preview is going to be really particularly useful, like I'm not sure if you'd really be using it as a basis to modify parameters or not as does happen with meshing output.

- Michael

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Hi Marc,

> > """""""""""""""""""Also I was thinking for the background bitmap image to maybe shrink that down by
> > half in width and height to get a downsampled antialiased result with a bit of blending in the border
> > areas and also cutting down file size by a ways.""""""""""""""""""

> I'm not sure I understand what this mean, would it be easy to post examples?

Basically it means whether the background bitmap should be shrunk down by half and kind of blurred somewhat as a side effect of the averaging process during the shrinking.

The sort of good part is that the blurring would give the alpha transparency around the borders of shapes to have some partially translucent spots rather than only having either fully opaque or fully transparent spots with no in between things.

The bad part is that with less resolution the pixels are larger and more noticeable when zoomed in.

Maybe to start with I won't try to do any kind of processing on the background image and just leave it up to you to do any blurring or down sampling if you want that.

- Michael

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Hi Burr,

re: generating hidden lines also in addition to visible lines.

> For me it would be nice to have access to these (as seperate object/sets as mentiond).

I think enough people have mentioned that they will occasionally use these that I'll try to have an option for making them, probably just unchecked by default.

- Michael

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Hi Martin,

> I attached a nice pdf about the two lineweight illustration principle from
> http://purdy.gatech.edu/wp-content/uploads/2012/07/2_line_wt.pdf

Thanks for posting this, this also helps as well. Although in one area it seems to be different than what Matt posted previously, I'll ask some more about that in a separate message in a bit here.


> I don't know if you can control line caps on export but this is also covered.

It is possible for me to control line caps in the PDF file, but trying to do this implies both discovering and maintaining some information about how different categories of lines touch one another. There's a good possibility that trying to figure that out and maintain that information throughout the whole process could add quite a bit of complexity to the whole thing so it's not too likely that I'll attempt that part.


> It doesn't hurt if the hidden lines also get exported as long as they can be easily
> turned on and off like on a seperate layer for example.

I'll see about having an option for this.

- Michael

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Hi Matt & Martin - I'm still a bit confused now about what should be considered an "exterior" or "outer" edge.

I think I see that what I was thinking previously about it being silhouettes doesn't seem to be quite right - they seem to be silhouettes but it looks like only some silhouettes are considered exterior and others aren't.

In order for these to be categorized by MoI I need to be able to make some kind of quantifiable way to categorize these things, I can't rely just on human judgement.

So one thing that has me confused right now is in Matt's insect walking PDF above, this is shown as the exterior edge:





In the one Martin posted, this one is shown as the accented edge:





So to me it seems as though those are 2 different choices, the first one is the longer one on the top surface, while the second one is the short one on the bottom side...



As far as silhouettes go, there are these 2 different silhouettes for that hole:






Right now I don't understand how I should distinguish between these to pick just one of them as the exterior edge.

Thanks,
- Michael

Image Attachments:
exterior_edge1.png  exterior_edge2.png  exterior_edge3.png  exterior_edge4.png 

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Hi Michael

Just using the viewport display as an example ... I would like to be able to export to .pdf with this look.

Now when I export to pdf the hidden lines are solid and as strong as the outer edges.

Thanks for the lighting tip ... that works.

However, the hidden lines only show as dashed when I zoom in as far as my display allows but when I save the normal sized screen display to the clip board and then import it in PhotoShop the hidden lines are simply faint light lines ... so if I had a choice I would like the hidden lines to display as somewhat thicker than they are now and a little more broken.

cheers,

eric

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hi micheal

Yup you've you've understood right. Although in later examples which someone posted, the one with a hole in a plate, strictly speaking the thick thin lifework work would be as my image.

As for naked edges, thats down to the illustrators own interpretation so if it could be in its own style for easy selecting it would be a bonus, otherwise for me it would be enough just to be a thin line.

no to worry with the overall shape. I notice even in isodraw that the overall all fill (they call it a contour) is a bit rough but as it is lying under a thick silhouette lie its usually covered.

Matt

Image Attachments:
Screen Shot 2013-09-30 at 8.09.49 AM.png 

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I am a non-expert, but did a google search for lineweight sketching, and line weight hierarchy. Found 3 rules here:

http://www.sketchmyworld.com/line-weight-importance-in-product-sketching/

Basic Line Weight Usage
1.The thinnest line is used to describe the edges of a product that point towards a viewer and also for the inner lines.
2.Second thickness lines are used for outlines (edges that have air behind them). These are not only contour lines, but can also occur within an object.
3.The thickest lines are used for the baselines – lines that show the interface between a product and a ground plane.


(Seems like there are a whole lot of drafting and architectural standards for line weight and line type. A person could
spend a lot of time on this subject, I guess.)

- Brian

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hi micheal

FYI info I have enclosed 2 screenshots of what Isodraw CADprocess churns out from the 3D models. There are two line thicknesses. have colored the thin one blue zoo you can see easily.
It is by no means a perfect process and i usually have to tidy some parts up but it saves me hours.

Matt

Image Attachments:
Screen Shot 2013-09-30 at 8.29.56 AM.png  Screen Shot 2013-09-30 at 8.30.12 AM.png 

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There is a pretty good explanation for the use of different line widths at the beginning of this pdf:

www.conradiator.com/downloads/pdf/Linethicknesses.pdf

Edit: Added link to paper. Deleted pdf as it is copyrighted.

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This paper looked pretty cool. Maybe some good ideas?

www.gvu.gatech.edu/~jarek/graphics/papers/11DrawingSousa.pdf

- Brian

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The example I've posted previously seems to be taken from page 215 of the book "The Complete Technical Illustrator" by Duff/Maxson and I agree there's some personal choice by the illustrator involved about what lines get thick or thin.

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.

Image Attachments:
Sketch-Toon.png 

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