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			<title>qdelaunay -- Delaunay triangulation</title>
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			<h1><a
			href="http://www.geom.umn.edu/graphics/pix/Special_Topics/Computational_Geometry/delaunay.html"><img
			src="qh--dt.gif" alt="[delaunay]" align="middle" width="100"
			height="100"></a>qdelaunay -- Delaunay triangulation</h1>

			<p>The Delaunay triangulation is the triangulation with empty
			circumspheres. It has many useful properties and applications.
			See the survey article by Aurenhammer [<a
			href="index.htm#aure91">'91</a>] and the detailed introduction
			by O'Rourke [<a href="index.htm#orou94">'94</a>]. </p>

			<blockquote>
			<dl>
			<dt><b>Example:</b> rbox r y c G0.1 D2 \| qdelaunay <a href="qh-opto.htm#s">s</a>
			<a href="qh-optf.htm#Fv">Fv</a> <a href="qh-optt.htm#TO">TO
			result</a></dt>
			<dd>Compute the 2-d Delaunay triangulation of a triangle and
			a small square.
			Write a summary to the console and unoriented regions to 'result'.
			Merge regions for cocircular input sites (i.e., the
			square).</dd>
			<dt> </dt>
			<dt><b>Example:</b> rbox r y c G0.1 D2 \| qdelaunay <a href="qh-opto.htm#s">s</a>
			<a href="qh-optf.htm#Fv">Fv</a> <a href="qh-optq.htm#Qt">Qt</a></dt>
			<dd>Compute the 2-d Delaunay triangulation of a triangle and
			a small square. Write a summary and unoriented
			regions to the console. Produce triangulated output.</dd>
			<dt> </dt>
			<dt><b>Example:</b> rbox 10 D2 \| qdelaunay <a
			href="qh-optq.htm#QJn">QJ</a> <a href="qh-opto.htm#s">s</a>
			<a href="qh-opto.htm#i">i</a> <a href="qh-optt.htm#TO">TO
			result</a></dt>
			<dd>Compute the 2-d Delaunay triangulation of 10 random
			points. Joggle the input to guarantee triangular output.
			Write a summary to the console and the regions to
			'result'.</dd>
			</dl>
			</blockquote>

			<p>Qhull computes the Delaunay triangulation by computing a
			convex hull. It lifts the input sites to a paraboloid by adding
			the sum of the squares of the coordinates. It computes the convex
			hull of the lifted sites, and projects the lower convex hull to
			the input. Each region of the Delaunay triangulation
			corresponds to a facet of the lower half of the convex hull.
			Facets of the upper half of the convex hull correspond to the <a
			href="qdelau_f.htm">furthest-site Delaunay triangulation</a>.
			See the examples, <a href="qh-eg.htm#delaunay">Delaunay and
			Voronoi diagrams</a>.</p>

			<p>See <a href="qh-faq.htm#TOC">Qhull FAQ</a> - Delaunay and
			Voronoi diagram questions.</p>

			<p>If you use '<a href="qh-optq.htm#Qt">Qt</a>' (triangulated output),
			all Delaunay regions
			will be simplicial (e.g., triangles in 2-d). Some regions may be
			degenerate and have zero area. Qhull can identify coincident
			points. If you do not use 'Qt', cocircular and cospherical data will lead
			to non-simplicial output (e.g., a square).

			<p>If you use '<a href="qh-optq.htm#QJn">QJ</a>' (joggle), all Delaunay regions
			will be simplicial (e.g., triangles in 2-d). Duplicate points will
			create small regions since the points are joggled apart. See <a
			href="qh-impre.htm#joggle">Joggled input or merged facets</a>. </p>

			<p>The output for 3-d Delaunay triangulations may be confusing if the
			input contains cospherical data. See the FAQ item
			<a href=qh-faq.htm#extra>Why
			are there extra points in a 4-d or higher convex hull?</a>
			Avoid these problems with triangulated output ('<a href="qh-optq.htm#Qt">Qt</a>') or
			joggled input ('<a href="qh-optq.htm#QJn">QJ</a>').
			</p>

			<p>The 'qdelaunay' program is equivalent to
			'<a href=qhull.htm#outputs>qhull d</a> <a href=qh-optq.htm#Qbb>Qbb</a>' in 2-d to 3-d, and
			'<a href=qhull.htm#outputs>qhull d</a> <a href=qh-optq.htm#Qbb>Qbb</a> <a href=qh-optq.htm#Qx>Qx</a>'
			in 4-d and higher. It disables the following Qhull
			<a href=qh-quick.htm#options>options</a>: <i>d n v H U Qb QB Qc Qf Qg Qi
			Qm Qr QR Qv Qx TR E V FC Fi Fo Fp Ft FV Q0,etc</i>.


			<p><b>Copyright © 1995-2002 The Geometry Center, Minneapolis MN</b></p>

			<hr>

			<h3><a href="#TOP">ｻ</a><a name="synopsis">qdelaunay synopsis</a></h3>

			<pre>
			qdelaunay- compute the Delaunay triangulation.
			input (stdin): dimension, number of points, point coordinates
			comments start with a non-numeric character

			options (qdelaun.htm):
			Qt - triangulated output
			QJ - joggle input instead of merging facets
			Qu - furthest-site Delaunay triangulation
			Tv - verify result: structure, convexity, and in-circle test
			. - concise list of all options
			- - one-line description of all options

			output options (subset):
			s - summary of results (default)
			i - vertices incident to each Delaunay region
			Fx - extreme points (vertices of the convex hull)
			o - OFF format (shows the points lifted to a paraboloid)
			G - Geomview output (2-d and 3-d points lifted to a paraboloid)
			m - Mathematica output (2-d inputs lifted to a paraboloid)
			QVn - print Delaunay regions that include point n, -n if not
			TO file- output results to file, may be enclosed in single quotes

			examples:
			rbox c P0 D2 \| qdelaunay s o rbox c P0 D2 \| qdelaunay i
			rbox c P0 D3 \| qdelaunay Fv Qt rbox c P0 D2 \| qdelaunay s Qu Fv
			rbox c G1 d D2 \| qdelaunay s i rbox c G1 d D2 \| qdelaunay s i Qt
			rbox M3,4 z 100 D2 \| qdelaunay s rbox M3,4 z 100 D2 \| qdelaunay s Qt
			</pre>


			<h3><a href="#TOP">ｻ</a><a name="input">qdelaunay
			input</a></h3>

			<blockquote>
			<p>The input data on <tt>stdin</tt> consists of:</p>
			<ul>
			<li>dimension
			<li>number of points</li>
			<li>point coordinates</li>
			</ul>

			<p>Use I/O redirection (e.g., qdelaunay < data.txt), a pipe (e.g., rbox 10 \| qdelaunay),
			or the '<a href=qh-optt.htm#TI>TI</a>' option (e.g., qdelaunay TI data.txt).

			<p>For example, this is four cocircular points inside a square. Its Delaunay
			triangulation contains 8 triangles and one four-sided
			figure.
			<p>
			<blockquote>
			<tt>rbox s 4 W0 c G1 D2 > data</tt>
			<blockquote><pre>
			2 RBOX s 4 W0 c D2
			8
			-0.4941988586954018 -0.07594397977563715
			-0.06448037284989526 0.4958248496365813
			0.4911154367094632 0.09383830681375946
			-0.348353580869097 -0.3586778257652367
			-1 -1
			-1 1
			1 -1
			1 1
			</pre></blockquote>

			<p><tt>qdelaunay s i < data</tt>
			<blockquote><pre>

			Delaunay triangulation by the convex hull of 8 points in 3-d

			Number of input sites: 8
			Number of Delaunay regions: 9
			Number of non-simplicial Delaunay regions: 1

			Statistics for: RBOX s 4 W0 c D2 \| QDELAUNAY s i

			Number of points processed: 8
			Number of hyperplanes created: 18
			Number of facets in hull: 10
			Number of distance tests for qhull: 33
			Number of merged facets: 2
			Number of distance tests for merging: 102
			CPU seconds to compute hull (after input): 0.028

			9
			1 7 5
			6 3 4
			2 3 6
			7 2 6
			2 7 1
			0 5 4
			3 0 4
			0 1 5
			1 0 3 2
			</pre></blockquote>
			</blockquote>

			</blockquote>
			<h3><a href="#TOP">ｻ</a><a name="outputs">qdelaunay
			outputs</a></h3>
			<blockquote>

			<p>These options control the output of Delaunay triangulations:</p>
			<blockquote>

			<dl compact>
			<dd><b>Delaunay regions</b></dd>
			<dt><a href="qh-opto.htm#i">i</a></dt>
			<dd>list input sites for each Delaunay region. The first line is the number of regions. The
			remaining lines list the input sites for each region. The regions are
			oriented. In 3-d and
			higher, report cospherical sites by adding extra points. Use triangulated
			output ('<a href="qh-optq.htm#Qt">Qt</a>') to avoid non-simpicial regions. For the circle-in-square example,
			eight Delaunay regions are triangular and the ninth has four input sites.</dd>
			<dt><a href="qh-optf.htm#Fv">Fv</a></dt>
			<dd>list input sites for each Delaunay region. The first line is the number of regions.
			Each remaining line starts with the number of input sites. The regions
			are unoriented. For the circle-in-square example,
			eight Delaunay regions are triangular and the ninth has four input sites.</dd>
			<dt><a href="qh-optf.htm#Fn">Fn</a></dt>
			<dd>list neighboring regions for each Delaunay region. The first line is the
			number of regions. Each remaining line starts with the number of
			neighboring regions. Negative indices (e.g., <em>-1</em>) indicate regions
			outside of the Delaunay triangulation.
			For the circle-in-square example, the four regions on the square are neighbors to
			the region-at-infinity.</dd>
			<dt><a href="qh-optf.htm#FN">FN</a></dt>
			<dd>list the Delaunay regions for each input site. The first line is the
			total number of input sites. Each remaining line starts with the number of
			Delaunay regions. Negative indices (e.g., <em>-1</em>) indicate regions
			outside of the Delaunay triangulation.
			For the circle-in-square example, each point on the circle belongs to four
			Delaunay regions. Use '<a href="qh-optq.htm#Qc">Qc</a> FN'
			to include coincident input sites and deleted vertices. </dd>
			<dt><a href="qh-optf.htm#Fa">Fa</a></dt>
			<dd>print area for each Delaunay region. The first line is the number of regions.
			The areas follow, one line per region. For the circle-in-square example, the
			cocircular region has area 0.4. </dd>
			<dt> </dt>
			<dt> </dt>
			<dd><b>Input sites</b></dd>
			<dt><a href="qh-optf.htm#Fc">Fc</a></dt>
			<dd>list coincident input sites for each Delaunay region.
			The first line is the number of regions. The remaining lines start with
			the number of coincident sites and deleted vertices. Deleted vertices
			indicate highly degenerate input (see'<A href="qh-optf.htm#Fs">Fs</a>').
			A coincident site is assigned to one Delaunay
			region. Do not use '<a href="qh-optq.htm#QJn">QJ</a>' with 'Fc'; the joggle will separate
			coincident sites.</dd>
			<dt><a href="qh-optf.htm#FP">FP</a></dt>
			<dd>print coincident input sites with distance to
			nearest site (i.e., vertex). The first line is the
			number of coincident sites. Each remaining line starts with the point ID of
			an input site, followed by the point ID of a coincident point, its region, and distance.
			Includes deleted vertices which
			indicate highly degenerate input (see'<A href="qh-optf.htm#Fs">Fs</a>').
			Do not use '<a href="qh-optq.htm#QJn">QJ</a>' with 'FP'; the joggle will separate
			coincident sites.</dd>
			<dt><a href="qh-optf.htm#Fx">Fx</a></dt>
			<dd>list extreme points of the input sites. These points are on the
			boundary of the convex hull. The first line is the number of
			extreme points. Each point is listed, one per line. The circle-in-square example
			has four extreme points.</dd>
			<dt> </dt>
			<dt> </dt>
			<dd><b>General</b></dd>
			<dt><a href="qh-optf.htm#FA">FA</a></dt>
			<dd>compute total area for '<a href="qh-opto.htm#s">s</a>'
			and '<a href="qh-optf.htm#FS">FS</a>'</dd>
			<dt><a href="qh-opto.htm#o">o</a></dt>
			<dd>print lower facets of the corresponding convex hull (a
			paraboloid)</dd>
			<dt><a href="qh-opto.htm#m">m</a></dt>
			<dd>Mathematica output for the lower facets of the paraboloid (2-d triangulations).</dd>
			<dt><a href="qh-optg.htm#G">G</a></dt>
			<dd>Geomview output for the paraboloid (2-d or 3-d triangulations).</dd>
			<dt><a href="qh-opto.htm#s">s</a></dt>
			<dd>print summary for the Delaunay triangulation. Use '<a
			href="qh-optf.htm#Fs">Fs</a>' and '<a
			href="qh-optf.htm#FS">FS</a>' for numeric data.</dd>
			</dl>
			</blockquote>

			</blockquote>
			<h3><a href="#TOP">ｻ</a><a name="controls">qdelaunay
			controls</a></h3>
			<blockquote>

			<p>These options provide additional control:</p>
			<blockquote>

			<dl compact>
			<dt><a href="qh-optq.htm#Qt">Qt</a></dt>
			<dd>triangulated output. Qhull triangulates non-simplicial facets. It may produce
			degenerate facets of zero area.</dd>
			<dt><a href="qh-optq.htm#QJn">QJ</a></dt>
			<dd>joggle the input to avoid cospherical and coincident
			sites.</dd>
			<dt><a href="qh-optq.htm#Qu">Qu</a></dt>
			<dd>compute the <a href="qdelau_f.htm">furthest-site Delaunay triangulation</a>.</dd>
			<dt><a href="qh-optq.htm#Qz">Qz</a></dt>
			<dd>add a point above the paraboloid to reduce precision
			errors. Use it for nearly cocircular/cospherical input
			(e.g., 'rbox c \| qdelaunay Qz'). The point is printed for
			options '<a href="qh-optf.htm#Ft">Ft</a>' and '<a
			href="qh-opto.htm#o">o</a>'.</dd>
			<dt><a href="qh-optq.htm#QVn">QVn</a></dt>
			<dd>select facets adjacent to input site <em>n</em> (marked
			'good').</dd>
			<dt><a href="qh-optt.htm#Tv">Tv</a></dt>
			<dd>verify result.</dd>
			<dt><a href="qh-optt.htm#TO">TI file</a></dt>
			<dd>input data from file. The filename may not use spaces or quotes.</dd>
			<dt><a href="qh-optt.htm#TO">TO file</a></dt>
			<dd>output results to file. Use single quotes if the filename
			contains spaces (e.g., <tt>TO 'file with spaces.txt'</tt></dd>
			<dt><a href="qh-optt.htm#TFn">TFn</a></dt>
			<dd>report progress after constructing <em>n</em> facets</dd>
			<dt><a href="qh-optp.htm#PDk">PDk:1</a></dt>
			<dd>include upper and lower facets in the output. Set <em>k</em>
			to the last dimension (e.g., 'PD2:1' for 2-d inputs). </dd>
			<dt><a href="qh-opto.htm#f">f</a></dt>
			<dd>facet dump. Print the data structure for each facet (i.e., Delaunay region).</dd>
			</dl>
			</blockquote>

			</blockquote>
			<h3><a href="#TOP">ｻ</a><a name="graphics">qdelaunay
			graphics</a></h3>
			<blockquote>

			<p>For 2-d and 3-d Delaunay triangulations, Geomview ('qdelaunay <a
			href="qh-optg.htm#G">G</a>') displays the corresponding convex
			hull (a paraboloid). </p>

			<p>To view a 2-d Delaunay triangulation, use 'qdelaunay <a
			href="qh-optg.htm#GDn">GrD2</a>' to drop the last dimension. This
			is the same as viewing the hull without perspective (see
			Geomview's 'cameras' menu). </p>

			<p>To view a 3-d Delaunay triangulation, use 'qdelaunay <a
			href="qh-optg.htm#GDn">GrD3</a>' to drop the last dimension. You
			may see extra edges. These are interior edges that Geomview moves
			towards the viewer (see 'lines closer' in Geomview's camera
			options). Use option '<a href="qh-optg.htm#Gt">Gt</a>' to make
			the outer ridges transparent in 3-d. See <a
			href="qh-eg.htm#delaunay">Delaunay and Voronoi examples</a>.</p>

			<p>For 2-d Delaunay triangulations, Mathematica output ('<a
			href="qh-opto.htm#m">m</a>') displays the lower facets of the corresponding convex
			hull (a paraboloid). </p>

			<p>For 2-d, furthest-site Delaunay triangulations, Mathematica output ('<a
			href="qh-optq.htm#Qu">Qu</a> <a
			href="qh-opto.htm#m">m</a>') displays the upper facets of the corresponding convex
			hull (a paraboloid). </p>

			</blockquote>
			<h3><a href="#TOP">ｻ</a><a name="notes">qdelaunay
			notes</a></h3>
			<blockquote>

			<p>You can simplify the Delaunay triangulation by enclosing the input
			sites in a large square or cube. This is particularly recommended
			for cocircular or cospherical input data.

			<p>A non-simplicial Delaunay region indicates nearly cocircular or
			cospherical input sites. To avoid non-simplicial regions either triangulate
			the output ('<a href="qh-optq.htm#Qt">Qt</a>')or joggle
			the input ('<a href="qh-optq.htm#QJn">QJ</a>'). Alternatively, use an <a
			href="qh-impre.htm#exact">exact arithmetic code</a>.</p>

			<p>Delaunay triangulations do not include facets that are
			coplanar with the convex hull of the input sites. A facet is
			coplanar if the last coefficient of its normal is
			nearly zero (see <a href="../src/user.h#ZEROdelaunay">qh_ZEROdelaunay</a>).

			<p>See <a href=qh-impre.htm#delaunay>Imprecision issues :: Delaunay triangulations</a>
			for a discussion of precision issues. Deleted vertices indicate
			highly degenerate input. They are listed in the summary output and
			option '<a href="qh-optf.htm#Fs">Fs</a>'.</p>

			<p>To compute the Delaunay triangulation of points on a sphere,
			compute their convex hull. If the sphere is the unit sphere at
			the origin, the facet normals are the Voronoi vertices of the
			input. The points may be restricted to a hemisphere. [S. Fortune]
			</p>

			<p>The 3-d Delaunay triangulation of regular points on a half
			spiral (e.g., 'rbox 100 l \| qhull d') has quadratic size, while the Delaunay triangulation
			of random 3-d points is
			approximately linear for reasonably sized point sets.

			<p>With the <a href="qh-in.htm#library">Qhull library</a>, you
			can use <tt>qh_findbestfacet</tt> in <tt>poly2.c</tt> to locate the facet
			that contains a point. You should first lift the point to the
			paraboloid (i.e., the last coordinate is the sum of the squares
			of the point's coordinates -- <tt>qh_setdelaunay</tt>). Do not use options
			'<a href="qh-optq.htm#Qbb">Qbb</a>', '<a href="qh-optq.htm#QbB">QbB</a>',
			'<a href="qh-optq.htm#Qbk">Qbk:n</a>', or '<a
			href="qh-optq.htm#QBk">QBk:n</a>' since these scale the last
			coordinate. </p>

			<p>If a point is interior to the convex hull of the input set, it
			is interior to the adjacent vertices of the Delaunay
			triangulation. This is demonstrated by the following pipe for
			point 0:

			<pre>
			qdelaunay <data s FQ QV0 p \| qconvex s Qb3:0B3:0 p
			</pre>

			<p>The first call to qdelaunay returns the neighboring points of
			point 0 in the Delaunay triangulation. The second call to qconvex
			returns the vertices of the convex hull of these points (after
			dropping the lifted coordinate). If point 0 is interior to the
			original point set, it is interior to the reduced point set. </p>

			</blockquote>
			<h3><a href="#TOP">ｻ</a><a name="conventions">qdelaunay conventions</a></h3>
			<blockquote>

			<p>The following terminology is used for Delaunay triangulations
			in Qhull for dimension <i>d</i>. The underlying structure is the
			lower facets of a convex hull in dimension <i>d+1</i>. For
			further information, see <a href="index.htm#structure">data
			structures</a> and <a href="qconvex.htm#conventions">convex hull
			conventions</a>.</p>
			<blockquote>
			<ul>
			<li><em>input site</em> - a point in the input (one dimension
			lower than a point on the convex hull)</li>
			<li><em>point</em> - a point has <i>d+1</i> coordinates. The
			last coordinate is the sum of the squares of the input
			site's coordinates</li>
			<li><em>coplanar point</em> - a <em>coincident</em>
			input site or a deleted vertex. Deleted vertices
			indicate highly degenerate input.</li>
			<li><em>vertex</em> - a point on the paraboloid. It
			corresponds to a unique input site. </li>
			<li><em>point-at-infinity</em> - a point added above the
			paraboloid by option '<a href="qh-optq.htm#Qz">Qz</a>'</li>
			<li><em>lower facet</em> - a facet corresponding to a
			Delaunay region. The last coefficient of its normal is
			clearly negative.</li>
			<li><em>upper facet</em> - a facet corresponding to a
			furthest-site Delaunay region. The last coefficient of
			its normal is clearly positive. </li>
			<li><em>Delaunay region</em> - a
			lower facet projected to the input sites</li>
			<li><em>upper Delaunay region</em> - an upper facet projected
			to the input sites</li>
			<li><em>non-simplicial facet</em> - more than <em>d</em>
			input sites are cocircular or cospherical</li>
			<li><em>good facet</em> - a Delaunay region with optional
			restrictions by '<a href="qh-optq.htm#QVn">QVn</a>', etc.</li>
			</ul>
			</blockquote>
			</blockquote>
			<h3><a href="#TOP">ｻ</a><a name="options">qdelaunay options</a></h3>

			<pre>
			qdelaunay- compute the Delaunay triangulation
			http://www.geom.umn.edu/software/qhull

			input (stdin):
			first lines: dimension and number of points (or vice-versa).
			other lines: point coordinates, best if one point per line
			comments: start with a non-numeric character

			options:
			Qt - triangulated output
			QJ - joggle input instead of merging facets
			Qu - compute furthest-site Delaunay triangulation

			Qhull control options:
			QJn - randomly joggle input in range [-n,n]
			Qs - search all points for the initial simplex
			Qz - add point-at-infinity to Delaunay triangulation
			QGn - print Delaunay region if visible from point n, -n if not
			QVn - print Delaunay regions that include point n, -n if not

			Trace options:
			T4 - trace at level n, 4=all, 5=mem/gauss, -1= events
			Tc - check frequently during execution
			Ts - print statistics
			Tv - verify result: structure, convexity, and in-circle test
			Tz - send all output to stdout
			TFn - report summary when n or more facets created
			TI file - input data from file, no spaces or single quotes
			TO file - output results to file, may be enclosed in single quotes
			TPn - turn on tracing when point n added to hull
			TMn - turn on tracing at merge n
			TWn - trace merge facets when width > n
			TVn - stop qhull after adding point n, -n for before (see TCn)
			TCn - stop qhull after building cone for point n (see TVn)

			Precision options:
			Cn - radius of centrum (roundoff added). Merge facets if non-convex
			An - cosine of maximum angle. Merge facets if cosine > n or non-convex
			C-0 roundoff, A-0.99/C-0.01 pre-merge, A0.99/C0.01 post-merge
			Rn - randomly perturb computations by a factor of [1-n,1+n]
			Wn - min facet width for outside point (before roundoff)

			Output formats (may be combined; if none, produces a summary to stdout):
			f - facet dump
			G - Geomview output (see below)
			i - vertices incident to each Delaunay region
			m - Mathematica output (2-d only, lifted to a paraboloid)
			o - OFF format (dim, points, and facets as a paraboloid)
			p - point coordinates (lifted to a paraboloid)
			s - summary (stderr)

			More formats:
			Fa - area for each Delaunay region
			FA - compute total area for option 's'
			Fc - count plus coincident points for each Delaunay region
			Fd - use cdd format for input (homogeneous with offset first)
			FD - use cdd format for numeric output (offset first)
			FF - facet dump without ridges
			FI - ID of each Delaunay region
			Fm - merge count for each Delaunay region (511 max)
			Fn - count plus neighboring region for each Delaunay region
			FN - count plus neighboring region for each point
			FO - options and precision constants
			FP - nearest point and distance for each coincident point
			FQ - command used for qdelaunay
			Fs - summary: #int (8), dimension, #points, tot vertices, tot facets,
			for output: #vertices, #Delaunay regions,
			#coincident points, #non-simplicial regions
			#real (2), max outer plane, min vertex
			FS - sizes: #int (0)
			#real(2) tot area, 0
			Fv - count plus vertices for each Delaunay region
			Fx - extreme points of Delaunay triangulation (on convex hull)

			Geomview options (2-d and 3-d)
			Ga - all points as dots
			Gp - coplanar points and vertices as radii
			Gv - vertices as spheres
			Gi - inner planes only
			Gn - no planes
			Go - outer planes only
			Gc - centrums
			Gh - hyperplane intersections
			Gr - ridges
			GDn - drop dimension n in 3-d and 4-d output
			Gt - transparent outer ridges to view 3-d Delaunay

			Print options:
			PAn - keep n largest Delaunay regions by area
			Pdk:n - drop facet if normal[k] <= n (default 0.0)
			PDk:n - drop facet if normal[k] >= n
			Pg - print good Delaunay regions (needs 'QGn' or 'QVn')
			PFn - keep Delaunay regions whose area is at least n
			PG - print neighbors of good regions (needs 'QGn' or 'QVn')
			PMn - keep n Delaunay regions with most merges
			Po - force output. If error, output neighborhood of facet
			Pp - do not report precision problems

			. - list of all options
			- - one line descriptions of all options
			</pre>

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			<p>Comments to: <a href=mailto:qhull@geom.umn.edu>qhull@geom.umn.edu</a>
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