#Outline drawings
9 messages in this thread
I am looking for a program to use for patent drawings. I basically need to
create isometric or perspective outline drawings, as opposed to rendered
images. Wireframe views are not acceptable, because they contain extraneous
lines (for example, the lines which divide the segments of an an object that
has been swept). Does Visual Reality have a way of producing 3D outline
drawings without those extraneous lines?
Michael –
I don't know of any 3D software that does not initially subdivide curved
surfaces into facets. However, packages such as DesignCAD 3D v4.xx let you
decide how many facets you want. Depending on the size of the object, using,
say, 360 facets around the perimeter gives a pretty smooth surface – but one
cluttered with lines. If you want smooth curves, you have to model.
What you can do, with a wireframe, is store it as a 2D image after you create
it. Then you can go into the 2D image with a 2D package and edit-out any lines
you think are extraneous. 2D-3D combos can be had for about $500 or less on
the street.
— gtm —
George,
>>>I don't know of any 3D software that does not initially subdivide curved
surfaces into facets. <….>
If you don't mind me jumping in, but this is exactly how Animation:Master and
Playmation from Hash, Inc work — with splines and patches. Their curves aren't
maybe as easy to control as Bezier but there are no facets or flat surfaces in
there at all (unles you want them flat and straight, of course) or the curve
resolution issues — all are perfectly smooth, regardless of how close you get
with the camera. Because of that, you don't ever have to worry about facet
angles and smoothing setting — if there is any edge (even 175 deg. angle) it
will render as such… (This sometimes drives me nuts in the traditional
polygon based 3D rendering programs.)
A:M & Playmation are the only programs that works that way that I know of, but
there might be others…
Hash, has a section on this forum, so you can find more from them on the
subject if you are interested…
Pawel
Pawel –
Thanks for the come-back and for the info. The way Hash works is news to
me. Not sure I understand how it works – how, for example, you can tell a
sphere from a flat circle until it's rendered. What IS Hash, anyway, a
modeling program or a rendering program (or both)? Also, did you by any chance
send a copy of your message to Michael Katz? He raised the initial question
about polygons in 3D.
— gtm —
George,
I did't see Michael's message (I am using WinCis and sometimes I miss things
and later it is too late <g>) I hope what I said about hash is somehow relevant
to his concernes…
As for Hash, it is a very powerful suite of programs that are especially well
designed for "character" modeling, animating and rendering. It is available
across platforms for Windows (with 2 rendering engines, one running in pure DOS
for extra speed), Mac, PowerMac and SGI. (They started on Aminga but about a
year ago stopt supporting it). Its renderer is based ray tracing technology
only. There is so much to this program that I don't really know where to start
— you would have to ask me some specific questions if you are interested.
>>>how, for example, you can tell a sphere from a flat circle until it's
rendered.
You can't miss it, you see it as a wireframe in any of the set views (top,
bottom left, right ect.) or any perspective you want… The surfaces can only
"hang" on patches that have 3 or 4 points attached, so your sphere might look
similar to other 3d wireframe models out there. (With much fewer control points
— 8 "slices" horizontally and 8 sections verticaly will do). If you simply had
a circle with 8 even sections, nothing would render (too many points), you
would have to make 2 connections with extra splines going across (they would be
straight since they would have only 2 control points). There is a bit more
planing when working with splines. It is more similar to building real world
wireframes for paper sculptures and takes some readjustmen if you are coming
from the more traditional modeling background…
Pawel
Pawel –
The subject of extraneous lines in wireframe models was raised by Michael
Katz in his message #3301 in the VISOFT Forum (check it out). He needs to make
patent drawings in isometric or perspective, and he objects, for example, to
lines in wireframes to which he refers as "extraneous," giving the example of
lines generated when surfaces are "swept."
The first response I thought of was, "get a package which erases hidden
lines," but then realized that the surface polygons in swept shapes would still
be there until the shape was rendered (or modeled).
If I get your despcription of Hash correctly, the same goes for it.
Suggested to Michael that he get a 2D-3D combo package, create the model in 3D,
save it in 2D, and then, in 2D, edit-out the lines he doesn't want. He does
not want to model or render his image.
Hash sounds very powerful. Dunno if it is for me, though. Need to render
entire buildings. Most useful tools for me are the ability to make glass (for
windows), cast shadows, and introduce atmospheric effects, which Renderize Live
seems to offer – although I am far from fluent in its use and really don't know
how well it will do those things. Main problem right now is with DXF
translations.
My application-models are created in a separate package (DesignCAD 3D) and
imported into RL as DXF files, which RL reads. That is why I got RL Since DXF
translating is not an exact science (or so it seems, although it should be),
99% of the translation succeeds, leaving about 1% of oddball conditions in the
imported image. Not too bad, really, except that the oddities sneak up on you,
revealing themselves sometimes only after you've done a rendering (aarrrgh
time).
Ah, the joys of rendering . . .
— gtm —
George,
Thanks for your suggestions. I am already using DesignCad and have considered
doing just what you suggested — transfer the 3D model to the 2D program and
then delete the extra lines. I was hoping there was a more "automatic" way of
doing this, but maybe that was wishful thinking.
Correct me if I am wrong, but I believe there may be another drawback to that
solution: When a wireframe of a curved object is transferred to 2D, I don't
know if there is necessarily a line generated which corresponds to the visible
edge of the object. There may be lines very close to either the front of back
of the "edge" but I don't think any of these represents the true edge. (Unless
the "hide hidden lines" command generates an "edge" line — do you know if it
does?)
I think an alternative solution may be to export a rendered image to a drawing
program such as Corel and to trace over to visible edges. May be very tedious,
though. If I get around to trying it (I haven't learned Corel yet), I will let
you know how it turns out.
Thanks again for your help,
Michael Katz
Michael –
Good point about the "true edge." Not only may that happen in 2d, it does
happen in 3D. However, the more segments you call for, the closer to a "true
edge" you are going to get. Also, if you pick the correct number of segments,
and the correct viewing angle, you should be able to get a true-edge line. The
"correct number of segments" is either an odd number or an even number (don't
ask me which) – but it is the number which puts the joint between adjacent
facets at the perimeter of the shape. Say you were looking at a sphere
head-on. An even number of facets (say 32) puts 16 on one hemisphere and 16 on
the other. Looking at that head-on, you see the true edge (polluted somewhat
by the facets going the other way). It depends how accurate you need the image
to be.
Removing hidden lines does not solve the problem. A true edge is not
substituted for the faceted one. Your idea of tracing the edge may be the
ticket. After creating the image in 3D and importing it into 2D, you can use
the "C" command in DCAD to create a curve around the perimeter by selecting the
apex of each visible facet. Then erase the facets. You have revealed a very
interesting problem for all drawing programs. The escape hatch for all is the
rendering, which smooths the whole shape, but which now, on thinking about your
point, may not reveal the true edge either.
I guess it depends on how accurate your image has to be. Is the problem
associated with the dimensioning of your shapes or the appearance of the
shapes? Let me know how it goes.
— gtm —
George,
Thanks for your comments.
To answer you question, I am mainly concerned about the appearance of the
objects, as I want the outline drawings for illustration purposes. I suppose
that, in most cases, the "true edge" issue is not critical. I will let you
know if and when I resolve the problem of producing 3D outline drawings.
Michael Katz