Draw on a Surface with a line

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 From:  NCEL (NCELIKGIL)
976.1 
Hi Michael,

Fantastic application! I love it....
I am a relic of The silicon Graphics age back in 1991...when Alias Studio cost $50,000. I used Alias Studio on an SGI running Irix. To me, the original Alias Studio was the Holy Grail of design tools, I think my memory glorifies it more than it was, but compared to the DOS applications on my home computer, it simply looked Alien. Its sad, this beautiful approach to building 3D surfaces was available to mankind almost twenty years ago. Anyway, no need to dwell on the past. I recently saw a demo of Alias Studio, it had this great 3D sketching tool that you can use with a tablet. What sucks is that they adopted MAYA's Interface for Studio a while back. Essentially killing the Alias product with its dizzying mosaic of tiny picture buttons & right click pop up menu's that turns the work flow into this oppressive sludge. Its almost Ironic that of all companies AutoDesk acquired Alias, the people who brought the world Autocad, an application who's interface still carries hints of its DOS & vector roots...blahh!

Back to MOI . . .
I'm glad that you focused on simplicity with MOI it looks great and I love its workflow. Here is the first thing on my wish list.

Something that Alias did not have...
In real life you can draw on a vase or on curved surface guided by the tip of your pencil and your eye's ability to perceive spacial differences.
However landing a line on a curved spline surface with a user looking through some obfuscated window at the surface is a dicey situation.
I'm sure the math is inherently more complicated since Sketchup can only do this on Flat Surfaces. It also guides the users pen with dotted line axis indicators which helps so much because you always know where the line is headed. Is it technically possible to draw with any line tool directly on spline surfaces as if the line were restricted to motion only on the surface contour. If a line is not possible, could you land points on a surface, since a point can simply be a line intersecting the surface in space. Maybe each point could reference the surface normals around it to fix an axis point on the surface then chain points together to form an accurate line. I am not sure if I am describing this technically correct but I know from Rhino3d and Alias that you can project lines on to surfaces and then trim and cut those surfaces into new shapes. I would love to just take my tablet and draw on the model with the pen, the surface would automatically split into two distinct surfaces and then I could push and pull the thing into new shapes. I mean Sketchup solved so many of 3D modelings problems, there is no need to look back, if ability & time permits it.

Thanks Love your product.....

EDITED: 3 Oct 2007 by NCELIKGIL

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 From:  Michael Gibson
976.2 In reply to 976.1 
Hi Nuri, I'm glad that you are enjoying MoI!

There have been quite a few requests for direct drawing on surfaces, so it is something that I am looking at doing in the future. But unfortunately it is a quite difficult area of work. The difficulty will make it likely that I will have to push off working on that area for some time yet...


> Is it technically possible to draw with any line tool directly on spline surfaces as
> if the line were restricted to motion only on the surface contour.

There are different methods that make this possible, but each of them tend to have drawbacks.

Each spline surface has a UV "parameter space" in it, kind of like a texture space. One method is to draw the line in this parameter space and then push that parameter space curve up into 3D. But this has some difficulties, like it doesn't behave well when you cross the seam of a closed shape like a cylinder, and it is also limited to only working on a single spline surface at a time, not across edges of an assembly of joined surfaces.

There are other methods that are possible to try, but each method that I know of tends to have some difficult calculation or some other type of drawback to it.


> but I know from Rhino3d and Alias that you can project lines on to surfaces
> and then trim and cut those surfaces into new shapes.

Yup, this also works in a similar way in MoI. Trimming has a projection method built into it when you trim surfaces with curves, and you can also use Construct / Curve / Project to manually project a curve on to a surface to use for some other construction.


> I would love to just take my tablet and draw on the model with the pen, the surface
> would automatically split into two distinct surfaces and then I could push and pull
> the thing into new shapes.

One problem is that this method of splitting into different pieces and then push/pulling them will tend to create blocky, hard-edged type shapes like the way Sketchup works.

To make something that would be able to sketch on a smooth surface, and then also push-pull it with the result being another smoothly connected surface is a really difficult problem to solve...

Really the whole underlying structure of trimmed NURBS technology is just not good at that kind of very "squishy" type of manipulation.

There are a new set of sculpting type applications out there now, like ZBrush, Mudbox, and Modo - these are polygon based and kind of fundamentally more squishable than a CAD NURBS model is. Those programs have a big focus on deforming the shape by drawing on it, so something like that may be more in line with what you are mentioning here...

- Michael
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 From:  NCEL (NCELIKGIL)
976.3 In reply to 976.2 
Thanks for the detailed response.
I tried a few boolean operations & projecting curves between surfaces and like you said the resulting curves from projected and intersecting surfaces are extremely complex they seem to have thousands of points. Alias did the same thing except that it had a nice tool that could rebuild a curve from that complex curve that had resulted from projection or intersecting boolean operations. I would use the rebuild curve tool as often as possible to build what in my mind were cleaner models. I think this was because I thought that trimmed surfaces were actually hidden and still actually physically there. So I would go back in with a network of curves and rebuild the hole into the surface.

I think my question would be is it possible to have a rebuild curve tool for curves resulting from such operations.

EDITED: 3 Oct 2007 by NCELIKGIL

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 From:  Michael Gibson
976.4 In reply to 976.3 
Hi Nuri, yes that is definitely possible. There have been several requests for a command to rebuild curves like you're asking about. I definitely want to include a tool for that in version 2.0 .

- Michael
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