\chapter{BUILDING A TIN WOODSMAN}

\begin{figure}
\centering \includegraphics{wm-prims.ps}
\caption{WoodsMan Primitives.}
\label{wm-prims}
\end{figure}

The purpose of this tutorial is to demonstrate how to build a model using
a few basic primitives.  The model to be constructed is a tin woodsman.
The four primitives used in the construction of the tin woodsman
are an ARB8, a cylinder, an ellipsoid, and a torus.
These four primitives will be duplicated several times,
and each copy will be modified using solid editing,
to obtain the required shapes.
The finished version of this database can be found in
the BRL-CAD Package file ``db/woodsman.g''.

\section{Create Primitives}

\noindent{\tt
\$ {\em mged woodsman.g} \\
BRL-CAD Release 3.0 Graphics Editor (MGED) Compilation 82 \\
    Thu Sep 22 08:08:39 EDT 1988 \\
    mikel@video.br:/cad/.mged.4d2 \\
 \\
woodsman.g: No such file or directory \\
Create new database (y|n)[n]? {\em y} \\
attach (nu|tek|tek4109|ps|plot|sgi)[nu]? {\em sgi} \\
ATTACHING sgi (SGI 4d) \\
Untitled MGED Database (units=mm) \\
mged> {\em size 20} \\
mged> {\em title A Tin Woodsman} \\
mged> {\em in solid8 rpp} \\
Enter XMIN, XMAX, YMIN, YMAX, ZMIN, ZMAX: {\em -1 1  -1 1  -1 1} \\
mged> {\em in torus tor} \\
Enter X, Y, Z of vertex: {\em 0 0 0} \\
Enter X, Y, Z of normal vector: {\em 0 1 0} \\
Enter radius 1: {\em 1} \\
Enter radius 2: {\em 0.2} \\
mged> {\em in ellipsoid ellg} \\
Enter X, Y, Z of vertex: {\em 0 0 0} \\
Enter X, Y, Z of vector A: {\em 1 0 0} \\
Enter X, Y, Z of vector B: {\em 0 0.5 0} \\
Enter X, Y, Z of vector C: {\em 0 0 0.5} \\
mged> {\em in cylinder rcc} \\
Enter X, Y, Z of vertex: {\em 0 0 0} \\
Enter X, Y, Z of height (H) vector: {\em 2 0 0} \\
Enter radius: {\em 1} \\
mged>
}

At this point, the screen should look like Figure \ref{wm-prims}.

\section{Copy Primitives and Set Up for Edit}

Although eight copies of the ellipsoid and two copies of the cylinder
shall be used in the final solid, fewer copies are made initially since there
is replication in the editing of these primitives.

\noindent{\tt
mged> {\em cp ellipsoid e.2} \\
mged> {\em cp ellipsoid e.6} \\
mged> {\em cp cylinder c.1} \\
mged> {\em cp solid8 s.1} \\
mged> {\em cp torus t.1} \\
mged> {\em Z} \\
mged> {\em e e.* c.1 t.1 s.1} \\
vectorized in 0 sec \\
mged>  \\
}

\begin{figure}
\centering \includegraphics{wm-hat1.ps}
\caption{Funnel Bowl Cylinder After Rotation.}
\label{wm-hat1}
\end{figure}

\begin{figure}
\centering \includegraphics{wm-hat2.ps}
\caption{Funnel Bowl Cylinder After End Scaling.}
\label{wm-hat2}
\end{figure}

\begin{figure}
\centering \includegraphics{wm-hat3.ps}
\caption{Funnel Bowl Cylinder After Moving.}
\label{wm-hat3}
\end{figure}

\begin{figure}
\centering \includegraphics{wm-tube.ps}
\caption{Funnel Tube Scaled and Positioned.}
\label{wm-tube}
\end{figure}

\section{Create Funnel Hat}

The solid ``cylinder'' has a height vector (``H'') which is 2mm
long.
This will be used to good advantage, to make the Tin Woodsman's
funnel hat, with the bowl of the funnel being 2mm high,
and the tube of the funnel being 2mm long.
The tube of the funnel will point straight up the +Y axis.

\noindent{\tt
mged> {\em sed c.1} \\
mged> {\em Select the ``Rotate'' entry in the solid edit menu} \\
mged> {\em p 0 45 90} \\
mged>
}

This places the cylinder so that the lines BD and AC are at the outer
ends of the cylinder.  See Figure \ref{wm-hat1}.

Next, the cylinder is shaped to look like the top of a funnel.
The vectors c and d are scaled.

\noindent{\tt
{\em Select the ``edit menu'' entry in the solid edit menu} \\
{\em Select the ``scale c'' entry in the TGC menu} \\
mged> {\em p .1} \\
{\em Select the ``scale d'' entry in the TGC menu} \\
mged> {\em p .1} \\
mged> \\
}

Figure \ref{wm-hat2} is the new shape of the cone.
Note how the on-screen display records the new lengths of the ``c''
and ``d'' vectors.
This cone must be moved to the planned locations for the top of the head.

\noindent{\tt
{\em Select the ``Translate'' entry in the solid edit menu} \\
mged> {\em p 0 2.2 0} \\
{\em Select the ``ACCEPT Edit'' entry in the button menu} \\
mged> \\
}

The bottom of the hat is now properly shaped and positioned.  The
new version of the solid ``c.1'' has been saved in the model database.
The editor returns to the viewing state.  See Figure \ref{wm-hat3}.

A copy of the saved ``c.1'' cone is made.  A byproduct of the {\em cp}
command is to display the new solid, as if the {\em cp c.1 c.2} command
had been immediately followed by an {\em e c.2} command.
This new solid will be edited to make the neck of the funnel,
which is the top of the hat.
The ``c.2'' copy of the cone must be
scaled down to become a tube and the tube must be placed on top of the
cone ``c.1''.

\noindent{\tt
mged> {\em cp c.1 c.2} \\
mged> {\em sed c.2} \\
{\em Select ``scale A,B'' in the TGC menu} \\
mged> {\em p 0.1} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p 0 4.2 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu} \\
mged>
}

Figure \ref{wm-tube} is the new shape of the funnel tube.
The woodsman's hat is comprised of solids c.1 and c.2.

\begin{figure}
\centering \includegraphics{wm-head.ps}
\caption{Head Sphere.}
\label{wm-head}
\end{figure}

\section{Building the Head}

The head of our Tin Woodsman is perfectly spherical, and will be located
at coordinates (0, 2, 0).
While it would be possible to duplicate the ellipsoid solid created above,
and modify it to produce the desired sphere, since all the parameters
of the head sphere are known, it is more economical simply to use
the {\em in} command to construct it directly.
Figure \ref{wm-head} shows the results of this operation.

\noindent{\tt
mged> {\em in e.1} \\
Enter solid type: {\em sph} \\
Enter X, Y, Z of vertex: {\em 0 2 0} \\
Enter radius: {\em 1} \\
mged>
}

\begin{figure}
\centering \includegraphics{wm-collar.ps}
\caption{The Woodsman's Collar.}
\label{wm-collar}
\end{figure}

\section{Building the Collar}

The torus (primitive t.1) is used to build a collar between the head and
the body.
The ring of the collar is scaled to 0.1 of its original size,
and repositioned at the base of the head.
The results of this step are shown in Figure \ref{wm-collar}.

\noindent{\tt
mged> {\em sed t.1} \\
{\em Select ``scale radius 2'' in the TORUS menu} \\
mged> {\em p 0.1} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p 0 1 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu} \\
mged>
}

\begin{figure}
\centering \includegraphics{wm-body.ps}
\caption{The Woodsman's Body.}
\label{wm-body}
\end{figure}

\section{Building the Body}

The ARB8 (primitive s.1) is used to build the body.
The original height of s.1 is only 2mm;  the required
length of the body is 3mm, so the extrusion command is
used to adjust the position of the lower (-Y) face of the solid.
The result is shown in Figure \ref{wm-body}.

\noindent{\tt
mged> {\em sed s.1} \\
mged> {\em extrude 2367 3} \\
{\em Select ``ACCEPT Edit'' in the Button menu} \\
mged>
}

\begin{figure}
\centering \includegraphics{wm-arm1.ps}
\caption{An Upper Arm Prototype.}
\label{wm-arm1}
\end{figure}

\begin{figure}
\centering \includegraphics{wm-arm2.ps}
\caption{The Woodsman's Arms.}
\label{wm-arm2}
\end{figure}

\section{Building the Arms}

The ellipsoid primitive (e.2) is used to build the upper and lower parts
of the left and right arms.
The original solid ``e.2'' is oriented with the major axis of the ellipse
oriented along the X axis.
The arms need to have the major axis oriented along the Y axis,
so first the solid is rotated.
A more graceful arm is obtained by decreasing the length of
the B and C vectors, and the resulting upper arm solid can be
seen in Figure \ref{wm-arm1}.

\noindent{\tt
mged> {\em sed e.2} \\
{\em Select ``Rotate'' in the Solid Edit menu} \\
mged> {\em p 0 45 90} \\
{\em Select ``edit menu'' in the Solid Edit menu} \\
{\em Select ``scale B'' in the ELLIPSOID menu} \\
mged> {\em p 0.25} \\
{\em Select ``scale C'' in the ELLIPSOID menu} \\
mged> {\em p 0.25} \\
mged>
}

This e.2 solid will now be moved into final position as the upper left arm.
Then it will be duplicated three times
to make the rest of the arm parts.  Finally, each new arm
part will be translated into the proper position,
as seen in Figure \ref{wm-arm2}.

\noindent{\tt
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p -1.3 0 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the upper left arm} \\
mged> {\em cp e.2 e.3} \\
mged> {\em cp e.2 e.4} \\
mged> {\em cp e.2 e.5} \\
mged> {\em sed e.3} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p -1.3 -2 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the lower left arm} \\
mged> {\em sed e.4} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p 1.3 0 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the upper right arm} \\
mged> {\em sed e.5} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p 1.3 -2 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the lower right arm} \\
mged>
}

\begin{figure}
\centering \includegraphics{wm-leg1.ps}
\caption{The First Leg.}
\label{wm-leg1}
\end{figure}

\begin{figure}
\centering \includegraphics{wm-final1.ps}
\caption{The Tin Woodsman.}
\label{wm-final1}
\end{figure}

\section{Building the Legs}

The ellipsoid primitive (e.6) is used as a prototype
to build the upper and lower parts of both legs from.
The primitive e.6 is scaled, rotated, and translated
into position as the upper left leg, as seen in Figure \ref{wm-leg1}.
Then, copies are made and translated to the remaining positions,
just like the arms were.

\noindent{\tt
mged> {\em sed e.6} \\
{\em Select ``Rotate'' in the Solid Edit menu} \\
mged> {\em p 0 45 90} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p -0.5 -3 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the upper left leg} \\
mged> {\em cp e.6 e.7} \\
mged> {\em cp e.6 e.8} \\
mged> {\em cp e.6 e.9} \\
mged> {\em sed e.7} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p -0.5 -5 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the lower left leg} \\
mged> {\em sed e.8} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p 0.5 -3 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the upper right leg} \\
mged> {\em sed e.9} \\
{\em Select ``Translate'' in the Solid Edit menu} \\
mged> {\em p 0.5 -5 0} \\
{\em Select ``ACCEPT Edit'' in the Button menu -- This is the lower right leg} \\
}

Figure \ref{wm-final1} is the view on the screen, the Tin Woodsman.
Take a moment to use the rotation knobs to view the model from various
angles.

\section{Building Regions}

So far, this example has concentrated on describing the basic shapes
involved in making the Tin Woodsman, without concern for establishing
a proper hierarchical structure.  To illustrate this point,
the various solids will be grouped by purpose and composition.
First, a region will be constructed to contain the torso,
and the color of ``cadet blue'' will be assigned:

\noindent{\tt
mged> {\em r torso.r u s.1} \\
Defaulting item number to 1001 \\
Creating region id=1000, air=0, los=100, GIFTmaterial=1 \\
mged> {\em mater torso.r} \\
Material = \\
Material?  (CR to skip) {\em plastic} \\
Param = \\
Parameter string? (CR to skip) {\em [RETURN]} \\
Color = (No color specified) \\
Color R G B (0..255)? (CR to skip) {\em 95 159 159} \\
Inherit = 0:  lower nodes (towards leaves) override \\
Inheritance (0|1)? (CR to skip) {\em [RETURN]} \\
mged>
}

Second, a region will be constructed to contain the collar,
which will be colored red:

\noindent{\tt
mged> {\em r collar.r u t.1} \\
Defaulting item number to 1003 \\
Creating region id=1002, air=0, los=100, GIFTmaterial=1 \\
mged> {\em mater collar.r} \\
Material = \\
Material?  (CR to skip) {\em plastic} \\
Param = \\
Parameter string? (CR to skip)  {\em [RETURN]} \\
Color = (No color specified) \\
Color R G B (0..255)? (CR to skip) {\em 255 127 0} \\
Inherit = 0:  lower nodes (towards leaves) override \\
Inheritance (0|1)? (CR to skip)  {\em [RETURN]} \\
mged>
}

Third, a region will be constructed to contain all the limbs,
and a flesh color will be assigned.
Even though none of the limbs touch each other, note how they
are combined with the UNION operation, to create a single
object of uniform composition and color.

\noindent{\tt
mged> {\em r limbs.r u e.2 u e.3 u e.4 u e.5 u e.6 u e.7 u e.8 u e.9} \\
Defaulting item number to 1001 \\
Creating region id=1000, air=0, los=100, GIFTmaterial=1 \\
mged> {\em mater limbs.r} \\
Material = \\
Material?  (CR to skip) {\em plastic} \\
Param = \\
Parameter string? (CR to skip)  {\em [RETURN]} \\
Color = 0 0 0 \\
Color R G B (0..255)? (CR to skip) {\em 255 200 160} \\
Inherit = 0:  lower nodes (towards leaves) override \\
Inheritance (0|1)? (CR to skip)  {\em [RETURN]} \\
mged>
}

Next, the funnel needs to be placed in a region.
For the sake of simplicity, the funnel will be solid, rather
than having a hollow center.
Note that the interior of the funnel overlaps with the top
of the Woodsman's head.
The funnel can be made ``form fitting'' by subtracting out
the overlap zone:

\noindent{\tt
mged> {\em r funnel.r u c.1 - e.1 u c.2 - e.1} \\
Defaulting item number to 1004 \\
Creating region id=1003, air=0, los=100, GIFTmaterial=1 \\
mged> {\em mater funnel.r} \\
Material = \\
Material?  (CR to skip) {\em plastic} \\
Param = \\
Parameter string? (CR to skip) {\em sh=100} \\
Color = (No color specified) \\
Color R G B (0..255)? (CR to skip) {\em 35 107 142} \\
Inherit = 0:  lower nodes (towards leaves) override \\
Inheritance (0|1)? (CR to skip)
mged> {\em l funnel.r} \\
funnel.r (len 4) REGION id=1003  (air=0, los=100, GIFTmater=1) -- \\
Material 'plastic' 'sh=100' \\
Color 35 107 142 \\
\ \ u c.1 \\
\ \ - e.1 \\
\ \ u c.2 \\
\ \ - e.1 \\
mged>
}

\begin{figure}
\centering \includegraphics{wm-hat-E.ps}
\caption{Evaluation of Funnel Hat Region.}
\label{wm-hat-E}
\end{figure}

Note how the boolean expression was written.
The concept that we need to express here is
the combination of all the funnel parts, minus the
portion of the head that overlaps with the inside of the funnel.
The natural way to write this is
\begin{center}
(c.1 union c.2) - e.1
\end{center}
but note that there are no grouping operations permitted in the {\em r}
command.
Furthermore, for historic reasons, union operations bind more loosely than
intersection and subtraction, i.e., there are implied groups
between union operations.  Thus, the expression above needs to be
rewritten as the formula:
\begin{center}
(c.1 - e.1) union (c.2 - e.1)
\end{center}
which with the binding precedence can be expressed as:
\begin{center}
c.1 - e.1 union c.2 - e.1
\end{center}
which is what was entered in the sequence above.
To see the effect that this command had on the shape of ``funnel.r'',
run these commands, the effect of which is shown in Figure \ref{wm-hat-E}:

\noindent{\tt
mged> {\em Z } \\
mged> {\em E funnel.r } \\
vectorized in 1 sec \\
mged>
}

These regions should be grouped together into a group,
for convenience in referencing.  This can be done with these commands:

\noindent{\tt
mged> {\em g man.g collar.r funnel.r limbs.r torso.r} \\
mged> {\em Z} \\
mged> {\em e man.g} \\
vectorized in 1 sec \\
mged>
}

The grouping {\em g} command combined the regions, the Zap command {\em Z}
cleared the screen, and the edit {\em e man.g} command drew the whole
object.
As an exercise, run
the database structure printing command {\em tree man.g}
to obtain a simple depiction of the tree structure that has been created.
For the final step of this example, the model will be ray-traced.
Run the command:

\noindent{\tt
mged> {\em rt -s128} \\
rt -s50 -M -s128 woodsman.g man.g  \\
db title:  A Tin Woodsman \\
Buffering single scanlines \\
initial dynamic memory use=35152.\\
Interpreting command stream in old format\\
GETTREE: 0.01 CPU secs in 1 elapsed secs (1\%)\\
                                              \\
...................Frame     0...................\\
PREP: 0.01 CPU secs in 0.01 elapsed secs (100\%)\\
shooting at 13 solids in 4 regions              \\
model X(-2,2), Y(-6,7), Z(-2,2)\\
Beam radius=0.078125 mm, divergence=0 mm/1mm\\
                                             \\
SHOT: 3.73 CPU secs in 6 elapsed secs (62.1667\%)\\
Additional dynamic memory used=29728. bytes\\
3515 solid/ray intersections: 1005 hits + 2510 miss\\
pruned 28.6\%:  13647 model RPP, 8197 dups, 10740 RPP\\
Frame     0:    16384 pixels in       3.73 sec =    4392.49 pixels/sec\\
Frame     0:    16384 rays   in       3.73 sec =    4392.49 rays/sec (RTFM)\\
\\
Press RETURN to reattach\\
{\em [RETURN]} \\
mged>
}