- Will IGL Trace work with a PenTablet monitor, such as the WACOM or
the new Sony LX960?
-
We have used IGL Trace with the WACOM pen and tablet, but not with a
tablet monitor. In principle, IGL Trace should work with any device that
directly substitutes for the mouse.
- Why aren't my traces being saved?
- Check the file system. If the disk is full, or if the files and/or directories
have Read Only status, then IGL Trace will not modify or write contour files.
Unfortunately, IGL Trace issues no error messages when a write fails.
- Is there a maximum number of different contours that I can make and follow
for each study? The name table appears to have a maximum of about 20.
- There is no maximum number of contours within a section, as far as I know.
The contours for each section are stored in a separate file, so total numbers
of contours in the study should not limited either.
The contour name table is just a convenient place to store frequently used
contour name/color combinations and then access them by keystrokes.
It is limited by the number of keys on the keyboard.
There can be as many different contour names as you want in a study, but
only contours which share the same contour name are considered to be the
same object for purposes of 3D reconstruction and measurement.
Also, contour names are limited to 8 characters.
- Contours drawn by hand contain many minute loops that cause the 3D Surface output
to be erroneously covered with large exterior triangles. These loops are very hard to see
and it is very labor intensive to find and correct them. Is there an easier way to get
rid of them?
- Loops generate errors in the surface because the algorithm is no longer able to
correctly distinguish "interior" from "exterior" contours. Recall that clockwise contours
mark the "exterior" or outer boundary of the object while counterclockwise contours mark
"interior" holes. A contour with a loop will not be interpreted correctly.
Loops are generated when the hand jiggles during tracing. This is particularly problematic
when tracing on high resolution images. It can help to adjust mouse sensitivity or to
zoom in when tracing so that jiggles don't result in large loops. Also, try tracing with
high zoom, so that the section pixels are at least as large as the screen pixels. This
minimizes the amount of deviation introduced by inadvertent jiggles.
Small loops can usually be eliminated by setting the "Max Error" to a large value when
generating a 3D Surface. Setting this to 5 pixels, for example, makes it unlikely that
loops smaller than 5 pixels in diameter will be retained in output. You can also try using
"Shrink Each", "Expand Each" and "Force Clockwise" in the 3D Surface dialog. These
parameters were added to provide easier ways for overcoming problems with traces such as
loops and orientations.
- When I zoom in to a region in my image and then use Fit Window to Image, contours
are misplaced. How can I get around this problem?
-
After Fit Window to Image is used on a subimage, contours will be misplaced. Resize
the window slightly by dragging on the lower righthand corner and the contours should
return to their proper positions.
- How are wildfire contours generated?
-
When a section is first opened it is assigned an arbitrary threshold of 160, but the
user can select any value from 0-255 by using the slider in the Contrast Dialog. In
the default mode, wildfires will expand into all four-connected pixels that are
greater than the threshold. By using the Configure-Wildfires submenu the user can
change the mode of expansion. "More" changes the algorithm to expand into
all eight-connected neighbors. "Less" changes the algorithm to expand into only
those four-connected pixels that also have a neighboring above-threshold pixel.
- Will I be able to easily change colors in a 3D rendering environement?
- Yes, you can import your reconstruction into some other rendering program
and apply whatever coloring or texturing you want. Alternatively, colors can be changed in
the VRML file as described in the next answer.
- When I generate output from the 3D Menu, all I get is a text file displayed in
Notepad. How do I see the 3D image?
- You'll need a VRML viewer to see the 3D output. The text displayed in Notepad is
the actual VRML that is generated. A VRML viewer (several are listed on the tools page)
can convert this text file into a 3D image.
You can also configure IGL Trace to output the VRML directly to your VRML viewer
instead of to Notepad. (See the directions in IGL Trace's Help.)
- Displaying the Trace output in CosmoPlayer the image is too small and off screen.
In fact it is even hard to find the contour set. How can I more easily see my output?
- Trace generates 3D coordinates (in microns) based on the image size
and the section thickness and section number. Thus, an object can be
very far away from the origin (to which CosmoPlayer is nominally
oriented) when the section thickness is 100 microns and the object starts
at section 20. Likewise, a distance of 200 microns within a section
would put the object far off to one side. One solution is to enter
units in millimeters even though the program says microns. This would
probably bring everything back into view.
Alternatively, you could use another program to view your reconstructions.
CosmoPlayer is probably not the optimal viewing tool, especially when
viewing 3D lines. Try instead GLView, listed under VRML viewers
on the tools page, or 3Space Assistant which will automatically
center the object in the field of view.
- The *.wrl files created by IGL Trace are quite large. When importing them
into Crossroads and "converting" them again to VRML 1.0 format they tend to become much smaller.
Is this just a format question, or am I loosing needed information in the
conversion?
- Crossroads eliminates the normal vectors (which are used by some 3D viewers to
improve smoothing). If you see no difference in the two cases then you don't
need them. You can prevent them by selecting Normals->None in the Surface dialog.
- I use the Trace Regions command to create many contours on each section. 3D Studio MAX
is slow to load one reconstruction and very slow to merge two.
How can I make reconstructions which are quicker to load and manipulate in 3dsmax?
- You can limit the size of the surface reconstruction (i.e. the number
of planar faces) by increasing the Max. Error in pixels allowed during
surfacing. Using Trace Regions creates very pixelated contours that
probably need to be simplified during surfacing.
Try setting the Max. Error in the Surface dialog to 5 or 10 pixels.
Also, turn off the generation of surface Normals to reduce the size of
the file.
You may also be able to reduce the number of extraneous contours by
adjusting the threshold (in the Contrast dialog) prior to Trace Regions.
- When I export one particular object as a 3D surface, I keep getting
a fatal error: "acos: DOMAIN error", which terminates the program. Is this
something I can fix?
- This error may be coming from the computation of normal vectors, try turning
off normal generation by selecting None of the Normals box in the Surface dialog.
If you can isolate the contours which are causing the problem, you may be able
redraw them to eliminate the problem.
- I have reconstructed two objects and I would like
to display them both but with different colors. How should I
proceed? Is it enough to define a contour using another color for the pencil ?
Or is there any special procedure ?
-
IGL Trace only outputs colored 3D objects when more than one
object is being created, e.g. from the 3D->Lines menu.
When a VRML object is created from the 3D->Surfaces menu it is
a single object and has the default VRML color which is gray.
You can color this object by inserting a material descriptor in
the VRML (.wrl) file. You can also color objects and combine them into a single
VRML scene by using the program
MergeWRL avaliable on the tools page.
- I have a whole bunch of objects all named the same. When I export as
a 3D surface, the surfacing algorithm connects all these objects together. Do I
need to go back and rename all these individually (and then export them
all individually) to get them to split up? Or is there something else I
can do?
- Yes, the program will link together contours with the same name because
it thinks they're the same object. You might be able to avoid renaming
everything by renaming on only those that are close together and performing
surfacing over narrow ranges of sections.
- How can I make my 3D output be an open tube rather than a closed tube?
- To open the tube, simply uncheck the "Show upper horizontal faces" and
the "Show lower horizontal faces" items on the 3D->Surface dialog box.
- When I view my 3D reconstruction the orientation of the reconstruction is
rotated 180 degrees. Why?
- The orientation in the viewer program depends on how it interprets the positive
z-direction. In Trace, section 1 is assumed zero (in z-direction) and each
subsequent section is interpreted as an increment in the positive z-direction.
There is also a discrepancy between the handed-ness of the coordinate systems
that will be corrected in future versions.
- Is there an easy way to print my 3D images?
- To get a high-quality result, you'll want import the VRML file into
a 3D renderer program. If you just want to save what you
see in your browser/VRML, I suggest a screen capture utility such as
obtained by using the Print Screen button on your keyboard. The
Print Screen button copies the screen as a bitmap to the clipboard
which you can then import into another program for editing and printing.
- What program should I use to do 3D rendering?
- We have used 3D Studio MAX for all of our rendering. It runs under Windows NT and
appears to be fully compatible with the output generated by IGL Trace. It imports
VRML 1.0 objects directly.
3D Studio seems to support all the features we need and can certainly handle
large 3D scenes.
More limited rendering is available from a VRML viewer such as Cosmoplayer
or the free GLView on the tools page.
- When a .wrl object created by Slabs is
imported into trueSpace, each slab is treated as
a separate object, which makes it very hard to change the material, color,
etc. Is there some way for me to modify the VRML code to make sure that
all these slabs are grouped together?
- Try passing the slabs .wrl through MergeWRL. This will add an outer
separator that trueSpace should respect. Corssroads will also do a similar
thing.
- The images on your website look smoother than the output I'm getting, were they
postprocessed with another program or is there some other trick to it?
- The 3D images on our website were generated with 3D Studio MAX. Smooth shading
in this program is very good. We also use texturing to help hide the transitions
between surface patches. Take a look at your reconstructions using something
like 3Space Assistant (see VRML Viewers on the tools page) to see if they appear smoother.
If the problem is with IGL Trace 3D->Surface output, try increasing the Max Error
parameter, and/or shrinking and expanding the contours. There may be large effects
based on how the contours are generated or drawn.
- How can I get a three dimensional scale bar for my reconstructions?
- To generate a scale bar, just draw one into two sections and surface
it. This is easy provided images are calibrated.
- I would like to create a movie in an .AVI file from the animations
obtained with CosmoPlayer. How can I do this? What kind of software should I use?
- We use 3D Studio MAX to generate our animations. It designed to produce nice .AVI files.
- I find that the 3D surfaces are too huge for my rendering program. What can I do?
- If the problem with surfacing is the number of surface patches produced,
make sure that you set the Max. Error value high in the Surfacing dialog.
