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424 lines
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Graphics Muse
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<!-- =============================================================
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This Page Designed by Michael J. Hammel.
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Permission to use all graphics and other content for private,
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non-commerical use is granted provided you give me (or the
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CD-ROM distributors and commercial ventures interested in
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Michael J. Hammel (mjhammel@csn.net), for permission.
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============================================================= !-->
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<A NAME="musings">
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<table>
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<tr>
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<td>
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<H2>More...</H2>
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<BR clear=both>
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<IMG SRC=../gx/hammel/musings.gif ALT="Musings" ALIGN="left"
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HSPACE="0" VSPACE="0" WIDTH="247" HEIGHT="52">
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</td>
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</table>
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</A>
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<BR clear=both>
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<table>
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<tr><td>
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<UL>
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<LI><A HREF="#ac3d">Review: The AC3D Modeller</A>
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<LI><A HREF="#irtc">more IRTC...</A>
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</UL></td>
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</table>
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<IMG SRC=../gx/hammel/cleardot.gif ALT="indent" ALIGN="left"
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VSPACE="5" WIDTH="1" HEIGHT="1">
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<BR clear=both>
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<table width=100%>
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<tr>
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<td width="100%" align=right>
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<FONT size=1>
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© 1996 <A HREF="mailto:mjhammel@csn.net">Michael J. Hammel</A>
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</FONT></td>
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<tr>
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<td bgcolor="#000000" cellpadding=0 cellspacing=0 valign=top>
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<IMG SRC=../gx/hammel/cleardot.gif ALT="indent" ALIGN="left"
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HSPACE="0" WIDTH="0" HEIGHT="0"></td>
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</table>
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<P>
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<A NAME="ac3d">
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<H4>Review: The AC3D Modeller</H4>
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</A>
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<BR>
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There are only a few 3D modellers available for Linux: AMAPI (which may
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now only be available for the Mac, based on one report I've received),
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Midnight Modeller, SCED/SCEDA, and AC3D. Each of these has its advantages
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and disadvantages. I've tried each of these at least briefly. A couple,
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SCED and AC3D, I've used to actually create scenes. Lets take a quick look
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at one of these - AC3D.
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<table width=100%>
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<tr>
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<td>
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<A HREF="http://www.comp.lancs.ac.uk/computing/users/andy/ac3dlinux.html">AC3D</A>
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comes from <A HREF="mailto:andy@comp.lancs.ac.uk">Andy Colebourne</A>. It
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is a shareware modeller that comes in binary format only. It is available
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for Linux, SGI's and Sun's (both SunOS and Solaris). Once registered you have access to a
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private Web site from which you can download the full version of the software.
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Documentation is a bit sparse (a common problem with much of the software
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available for Linux, in this authors opinion), consisting of about
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12 or 13 pages formatted in either HTML or Postscript. The distribution
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package contains the binary, the HTML manual with a few images and a set
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of object files that are necessary for packages which use the Mesa Graphics
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Library, which AC3D does.
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<td>
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<IMG SRC=../gx/hammel/ac3d.jpg ALT="AC3D" ALIGN="left"
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HSPACE="0" WIDTH="322" HEIGHT="248">
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<BR clear=both>
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<CENTER>
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<B>Figure 1</B>: Example AC3D session (this is taken from the AC3D Web site).
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</CENTER></td>
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</table>
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<BR>
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The interface consists of 4 view windows and a control panel. There are 3
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orthographic views and a 3D view. Changes in one of the orthographic view
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windows are reflected in the other views. Edits are not allowed in the 3D
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view. The 3D view can provide wireframe, filled or textured surfaces.
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My system is not quite fast enough to handle anything but the wireframe
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surface so I won't be able to say much about the texturing features of
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the modeller.
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<BR>
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AC3D supports a number of import file formats, including DXF and Lightwave
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files. It can export POV, RIB, VRML and a couple of other formats. Since
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the modeller is a based on vertices (as opposed to primitives like spheres
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or boxes) it is quite easy to manipulate basic shapes into more complex
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ones. This can be a disadvantage to those used to the CSG aspects of SCED
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or users of POV-Ray, but it really doesn't take that long to get used to.
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Even though the modeller bases its shapes on vertices, there are still a
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collection of basic shapes provided: disk, line, box, sphere, and mesh are
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just some of these. These shapes are displayed with a given number of
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vertices. The number of vertices can be configured and its possible to add
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more vertices where necessary.
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<BR>
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<table width=100%>
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<tr>
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<td>
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One of the nicest features is the ability to extrude a 2D shape into 3
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dimensions. Lets follow an example of this. First, select the "ellipse"
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drawing function from the control panel and create a stretched out ellipse
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in the XY orthographic view.
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-1b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 2</B>: An ellipse
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</CENTER>
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<tr>
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<td>
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Next, change the <I>Edit</I> type to "vertex" in the control panel and select all
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the vertices on the lower half of the ellipse (but not the ones on the end
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of the ellipse). Delete these with the "delete" function in the control
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panel. Then select the two lowest vertices and insert some new vertices (as
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shown in Figure 3).
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-2b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 3</B>: The ellipse has been halved and some new vertices added.
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</CENTER>
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</td>
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<tr>
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<td>
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This next part is a little tricky. What you want to do is select the
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vertices on each end of the object and move them, one at a time, until you
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get a slightly rounded effect. Then select 4 or 5 of the vertices on the
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back end (the left side in Figure 4) and strecth them out a little, to
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flatten the wings trailing edge. Then get rid of the extra vertices along
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the bottom of the wings edge by selecting them and using the "delete"
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function in the control panel. The result should look something like
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Figure 4.
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-3b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 4</B>: The wing edge takes shape
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</CENTER>
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</td>
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<tr>
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<td>
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This isn't bad, but a wing should be smoother around the top and edges,
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so change the <I>Edit</I> type to "Object" and select the wing. Then
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use the "Spline Surfaces" option from the <I>Object</I> pull-down menu.
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This adds a bunch of new vertices to the object and creates a smoother
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line around the wing.
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-4b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 5</B>: Smoothing the wing edge.
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</CENTER>
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</td>
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<tr>
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<td>
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Now lets take this simple shape and extrude it. Make sure the
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<I>Edit</I> type is still "Object" and select the wing edge. We need
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to change to the XZ orthographic view window. Up to this point we've
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been using the XY viewport. Click on "Extrude" under the <I>Mouse</I>
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options in the control panel. Grab the object in the XZ viewport and
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drag up. The original points stay put and a new set of points is moved
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to where ever you drag to. Once you let go of the mouse button you'll
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see the new points get connected to their corresponding points on the
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original object. Notice how the connecting lines aren't quite straight.
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This would be bad for a real wing, so we'll straighten them out.
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-5b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 6</B>: The wing edge gets extruded.
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</CENTER>
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</td>
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<tr>
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<td>
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In this next figure, the control panel was used to change the
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<I>Edit</I> mode to "vertices" and the vertices on the
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new side of the extruded object
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have been selected. Once selected, the "move" option under the
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<I>Mouse</I> features allows the selected vertices to be moved as a
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group. When these vertices are moved the lines connecting them to the
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opposite end are redrawn. You can play with this a bit in order to get the
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connecting lines to become straight. Note that its not absolutely
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necessary to correctly align the two ends of the extruded object, but this
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is one way to do so if you feel it necessary.
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-6b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 7</B>: The ends of the extruded object are aligned.
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</CENTER>
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</td>
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<tr>
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<td>
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Now switch back to the "object" <I>Edit</I> mode and select the object.
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The bounding box (in green) has handles that can be grabbed to drag
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the bounding box to resize the object. Use the middle top and bottom
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handles to make the object wider in the XZ view.
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-7b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 8</B>: Stretch the object a bit.
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</CENTER>
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</td>
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<tr>
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<td>
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Next, switch back to "vertices" <I>Edit</I> mode and select the vertices
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on one end of the object. Click on "Create Surface" under
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<I>Functions</I> in the control panel. If the surface (as viewed in the 3D
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view) does not appear solid you can select "Poly" under <I>Surface</I> to
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create a solid surface to close the end of the object. Repeat this process
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for the other end.
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<P>
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Viola! You've got a solid surfaced wing, just like the one in Figure 9.
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(The grid is an option for the 3D view window and not part of the image.)
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Of course, this is a pretty simplistic example, but you should get the
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idea of how easy it is to create shapes using AC3D. You'll need to export
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the file to POV or RIB format and add some real textures to finish up the
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project, of course.
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<td>
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<CENTER>
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<IMG SRC=./gx/hammel/wing-9b.jpg ALT="AC3D" ALIGN="middle"
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HSPACE="5" WIDTH="341" HEIGHT="279">
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<BR clear=both>
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<B>Figure 9</B>: The solid surfaced wing.
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</CENTER>
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</td>
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</table>
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<BR>
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When I first started examining modellers I got my hands on SCED, a nifty
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modeller from Stephen Chenney. One of the nice features of SCED is that it
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is constraint based - you can join objects using CSG and then constrain
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them to certain points. This allows you to create an arm, for example,
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that can bend only at the elbow. AC3D works similarly in that you can
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rotate any set of points around a single point within one of the
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orthographic views. For example, if I created an arm I could select
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"Rotate" from the control panel and then use the mouse to rotate the arm
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around a single point, such as the elbow, in one of the 2D view windows.
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If I need it to move in 3D I need to do this type of rotation in 2 or more
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of the 2D view windows. This process is a little different than SCED,
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which can move objects in 3 dimensions, but the result is the same. In
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fact, at times it can be a little easier to keep your bearings using
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multiple rotations in 2D.
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<BR>
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Since I've never used any of the modellers available for other systems
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(such as high end modellers on SGI's or any of the modellers available for
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Microsoft or Mac systems)
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I can't say how well AC3D compares to them. I do know that I found the
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modeller fairly easy to learn, but I tend to be more motivated than some
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folks. AC3D could use some online help (whats the difference between a
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"Poly" and a "Polyline", for example) and more detailed documentation in
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general. It would also be nice to be able to unhide selected objects
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instead of all hidden objects. Andy has told me that a new version coming
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soon will include the ability to specify the exact dimensions of a selected
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object or set of vertices. This is a very important feature in my eyes. I
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tend to like to use modellers to create individual objets and then use the
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conditional constructs of POV-Ray to position multiple copies of them, such
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as trees or rocks or houses. By constraining an object to a unit size it
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makes it easier to position and resize objects using POV-Ray.
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<BR>
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Of all the modellers I've tried AC3D is probably the easiest to use. Its
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ability to import formats like DXF gives it a step up on SCED, although I
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really like the latter too. I don't particularly mind that you don't get
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the source to AC3D since I'm mostly interested in just using the modeller
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and not in developing new features for it. It would be nice if there were a
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plug-in interface, but I'm not such a power user yet that I need that
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feature. Aside from a lack of detailed documentation, and a few keystrokes
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that are already used by fvwm, I find the AC3D modeller worth the
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registration price.
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<P>
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<table width=100%>
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<tr>
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<td colspan=4 bgcolor="#000000" cellpadding=0 cellspacing=0 valign=top>
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<IMG SRC=../gx/hammel/cleardot.gif ALT="indent" ALIGN="left"
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HSPACE="0" WIDTH="0" HEIGHT="0"></td>
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</table>
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<P>
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<A NAME="irtc">
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<H4>more IRTC...</H4>
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</A>
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<BR>
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The contest started in earnest in May/June of 1996. The topic then was
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Time and there were some stunning entries. In July/August we had fewer
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entries, but the topic - Summer - was a little tougher to nail down.
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In September/October we hit the jackpot with Science Fiction. Well over
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200 entries were submitted for this round. Thats quite a difference from
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the 20-30 submitted during Matt's original contests. Fortunately much of
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the work for viewing, voting, and tabulating information has been
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automated. The contest has been great fun and has been accompanied with
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lively discussions on the associated irtc-l mailing list.
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<BR>
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Unfortunately, there are always those that have to try to ruin things
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for everyone else. We had some people submit images that were fair but not
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likely winners. They then submitted multiple votes. A vote consists of
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ratings of all the images with values between 1-20 for each in 3
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categories - needless to say
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this takes awhile to accomplish. Any vote that does not include ratings
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for all images is not counted in the final tally. The multiple votes were
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done offline (which is permissable) and submitted from different email
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accounts. The artists images received very high marks while all the rest
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received very low (within a very small range) ratings. Then they got some
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of their friends to do the same thing. Beyond this, others have
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submitted numerous entries that they had made in the past (prior to
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the contest) that just happen to fit the category (how many 3D artists, for
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fun or profit, have *never* made a space scene?) in order to turn the
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contest into their own private gallery. The spirit of the competition is
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lost on some people, I'm afraid.
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<BR>
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I haven't done any of the automation nor have I worked on the very
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nice web site for the contest. But I've watched Chip and Bill do so.
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Its very frustrating knowing how much effort they put into this,
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trying very hard not to give themselves or anyone else unfair advantages
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and still make the contest fun for everyone only to see someone still try
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to cheat the system. Why? For a couple of CDs? Remember when the
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Internet was a friendly, honest place?
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<BR>
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Still, the contest continues and the Admin Team is working on ways
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of keeping the contest fun, open to participation, and fair. The
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guys could use a new host for their contest. Walnut Creek, the current
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host, appears to be limiting ftp connections and the amount of disk space
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required for 200+ images can get rather large.
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<BR>
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If you are into 3D rendering for the fun of it you owe it to yourself
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to take a shot at the IRTC. Its fun to see how your images stack
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up against others. Many of the voters offer comments on the images which
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can very useful in any future images you render. Check our the
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<A HREF="http://www.povray.org/irtc/">IRTC Web Site</A>
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to get more details and join in!
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<P>
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<table width=100%>
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<tr>
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<td colspan=4 bgcolor="#000000" cellpadding=0 cellspacing=0 valign=top>
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<IMG SRC=../gx/hammel/cleardot.gif ALT="indent" ALIGN="left"
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HSPACE="0" WIDTH="0" HEIGHT="0"></td>
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</table>
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<table width=100%>
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<tr>
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<td align=right>
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<FONT size=1>
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© 1996 by <A HREF="mailto:mjhammel@csn.net">Michael J. Hammel</A>
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</FONT>
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</table>
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</BODY>
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</HTML>
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