
Version 9.0
-----------

* New IRIT commands
  + CRVKERNEL - Computes the kernel of a close curve.
  + CRC2CRVTAN - find circles of prescribed radii tangent to two curves.
  + CBIARC - Biarc fitting to freeform curves.
  + SRF3TANS - a plane tangent to a surface/surfaces at 3 locations.
  + SRF2TANS - a developable bi tangent to a surface/surfaces.
  + CARCLEN - Curve arc length approximation.  
  + FITPMODEL - fit a primitive shape to a given polygonal model.
  + ANALYFIT - linear/quadratic surface fit to a given polygonal model.
  + PTREGISTER - register two points sets for rigid motion.
  + SFLECNODAL - Flecnodal curves on surfaces.
  + SVOLUME - volume of shape bounded by freeforms.
  + SMOMENTS - moments over freeforms.
  + FIXPLNRML - fix normals of polygonal models.
  + FIXPLGEOM - fix geometry of polygonal models.
  + TNSCRCR - tangents to two circles.
  + DIST2FF - Distance fields between two freeform curves/surfaces.
  + SPLITLST - splits lists of objects to object list.
  + PRINTFILE - redirects the PRINTF command to a file.
  + MPOWER, MBEZIER, MBSPLINE - Multivariate constructors.
  + UVPOLY - sets uv coordinates to polygonal models.
  + TOFFSET - trim global/local intersections in offsets.
  + SASPCTGRPH - derives the topological aspect graph of a freeform srf on S^2.
  + TEXTWARP - text warping along a freeform surface.
  + PRINTER - Polygon Ray Intersection.
  + SRFKERNEL - Kernel of freeform closed surfaces.
  + SASYMPEVAL - Asymptotic directions for parametric surfaces.
  + PPROPFTCH - Fetching of property curves over polygonal objects.
  + PCRVTR - curvature estimation for polygonal meshes.
  + SRAYCLIP - Ray surface intersection using Bezier clipping.
  + BOUNDARY - extracts the boundary of the given geometry.
  + BSCTCYLCYL, BSCTCONCYL, BSCTCONCN2 - New cone/cylinder bisector functions.
  + RFLCTMAT, PROJMAT - constructors for reflection and projection matrices.
  + FNFREE - free user defined function.
  + IDYNMEM = dynamic memory testing routines (debugging purposes).
  + PATTRIB - Set/get attributes to vertices of polygons.
  + PNORMAL - Sets a normal for a vertex in a polygon.
  + SCRVTREVAL - Principal curvatures/directions for parametric surfaces.
  + SRFFFORM - Derives the coefficients of 1st/2nd/3rd fundamental forms.
  + PLANECLIP - Clips a polygonal model against a plane.
  + MAXEDGELEN - subdivides a polygonal models, bounding maximum edge length
  + BLHERMITE - Blending hermite with arbitrary cross section.
  + BLSHERMITE - Blending hermite with arbitrary cross section, over a surface.
  + MVEXPLICIT - Convert multivariate polynomial expressions to bezier.
  + DUALITY - Computes the dual to a curve or a surface.
  + MSCIRC - Computes the minimum spanning circle.
  + CRVDIAMTR - Computes the diameter of a curve.
  + BUMPMAP - add bump geometric details to a given surface.
  + INSERTPOLY - insert a new polygon to existing polygonal object.

* Booleans properly handle disjoint parts.
* Sweep functions also support a list of cross sections.
* Irit file types are "real" finally: "itd", "ibd", "imd" for irit text/binary/
  matrix data.
* New STL2IRIT utility to convert text/binary stl files to irit data.
* Support for the MAGELLAN 6DOF mouse
* Support for PNG images.
* RGB color and UV values in vertices are properly propagated in Booleans.

Version 8.0
-----------
* Full line editing capabilities, including history.
* Bug fix in boolean sum/one operations.
* Bug fix in the extrusion operation and added support for caps in curves'
  extrusion.
* Many bug fixes in the booleans of polyhedra.
* Three new line illustration tools - lineshad, aisoshad and izebra.
* New hidden surface removal tools - ihidden.
* Most display devices now support in-view-window rotation and translation
  as well as two levels of fineness with rough levek for active transform
  and fine when in idle.
* Handling COPLANAR polygons is now default to TRUE.
* Equality testing in IRIT now works between almost all objects including
  freeforms.
* New multivariate library.
* COERCE now coerce between surfaces and trimmed surfaces,  between 
  multivariates and curves/surfaces/trivariates, and between Bezier
  and Bspline forms.
* SYMBPROD/DPROD/CPROD/SUM/DIFF now operates on multivariates as well.
* FFMERGE/FFSPLIT now operates on multivariates as well.
* Coplanar polygon handling is much improved.
* New IRIT commands
  + PTS2PLLS - converts points into polylines
  + MATDECOMP - decomposition of homogeneous matrix into rot, scale and trans.
  + TSGREGORY - Creates a triangular gregory patch.
  + SMOOTHNRML - compute smooth vertex normals to polygonal data.
  + VIEWSET - allow switching between several display devices, simultaneously.
  + SETNAME - rename the name of a sub object.
  + GETNAME - gets the name of a sub object.
  + RRINTER - ruled ruled intersection.
  + SPARABOLC - parabolic edges of freeform surfaces
  + CPOWER, SPOWER- definition of power basis curve/surface.
  + SMESH - surface from trivariate mesh.
  + ALGSUM - Algebraic sum surfcae constructor.
  + SWUNGASUM - Algebraic swung sum.
  + ARC360 - upto 360 degrees arc.
  + SREVERSE - reverse a surface.
  + MDERIVE, MDIVIDE, MEVAL, MFROMMESH, MFROMMV, MREFINE, MREGION,
    MREPARAM, MPROMOTE, MMERGE, MREVERSE - operations on multivariates.
  + SURFREVAXS, SURFREV2, SURFREVAX2 - variations on the surface of
    revolution constructor.
  + CONICSEC - conic section's construction.
  + MATPOSDIR - constructs a viewing transformation matrix based on position
    and direction.
  + PMORPH - Morphosis of two polyhedral model.
  + BSCTPLNPT, BSCTCONPT, BSCTCYLPT, BSCTSPRPT, BSCTTRSPT, BSCTPLNLN,
    BSCTCONLN,  BSCTSPRLN, BSCTSPRPL, BSCTCYLPL, BSCTCONPL, BSCTCONSPR,
    BSCTCONCON, BSCTCYLSPR, BSCTSPRSPR, BSCTTRSSPR - bisectors of CSG
    primitives.
  + LINTERP - least squares fitting of a line in R3 to a set of points.
  + CLNTCRSR - process mouse display device mouse events in the server.
  + TRMSRFS - trimmed surfaces constructor from contours in param space.
  + SILHOUETTE - compute silhouette edges of freeform surfaces
  + ISOCLINE - compute isocline edges of freeform surfaces
  + BLOSSOM - blossoming over Bezier and Bspline forms.
  + FFMESH - extraction of control mesh/polygon from a freeform geometry.
  + KNOTCLEAN, KNOTREMOVE - knot removal and cleanup for bspline curves.
  + ISGEOM - query if a given geometry is a line/circle/plane/sphere/
    ruled srf/extrusion etc.
  + SSINTER - general surface surface intersection routine.
  + PPINTER - single polygon polygon intersection computation.
  + MZERO - computes the zero set of multivariates as a point cloud.
  + MBISECTOR - computes the bisector of two surfaces or curve-surface, in R3.
  + RAYTRAPS - computes ray traps between n planar curves
  + SKEL2DINT - computes points of equal distance from three planar entities.
  + EXEC - excute a string command in the IRIT interepreter, indirectly.
  + CAREA - computes the area integral of a curve.
  + SYMBIPROD - inner product of Bspline basis functions.
  + TVZRJACOB - Zero Jacobian of a trivariate.
  + RESET - Reset the environment (clear all variables to initial state)
  + ANIMEVAL - evaluation of animation curves at a certain time.
  + QUADRIC - generates quadric surfaces as rationals.
  + C/SMOEBIUS - Moebius transformation to freeform curves/surfaces.
  + SACCESS - surface/check surface accessibility analysis.
  + NRMLCONE - computes a bound on the normal
  + CINTEG - computation of the integral curve.
  + MRAISE - degree raising for multivariates.
  + CREDUCE - curve degree reduction.
  + RULEDTV - ruled trivariate volume between two surfaces.
  + ATTRPROP - Same as attrib, but propagates the attribute to all sub-parts.
  + ZCOLLIDE - Collision computation between two objects in Z direction.
  + IQUERY - query low level system information.
  + RFLCTLN - compute reflection lines/circles/highlight lines off
	freeform surfaces.

Version 7.0
-----------
* Display devices for Windows NT/95 and OS2 are now stable.
* Alpha channel is now properly working in irender.
* IRIT is now fully working on Windows 95 with no network (use to have
  IPC problems).
* Several global name renaming in C space (EPSILON -> IRIT_EPS etc.).
* New irit2pov - IRIT to POVRAY filter.
* Primitive constructors (spheres, cones, etc) can now create freeform
  exact rational surfaces as well as approximated polynomial surfaces.
* Fix two bugs in BBOX of lists and points.
* Support for triangular (Bezier) patches has been added.
* Ability to evaluate a scene at a prescribed animation time in many of the
  tools, such as irender, poly3d-h and the some filters.
* Irender now supports surface function texture useful for curvature display
  as well as contouring texture.
* Instances of geometry are supported (not completely) via a new instance
  type.
* FFCOMPAT also works on trivariates.
* C/SREPARAM works correctly on float/periodic end conditions.
* OFFSET and RULEDSRF now works on polyline/gons.
* SINTERP now allows scattered data (with UV's).
* New IRIT commands
  + TMORPH function - trivariate morphing.
  + TEDITPT function - edit single control point of a trivariate.
  + COVERPT - uniform point distribution on polygonal models
  + COVERISO - uniform curves' based coverage of iso surfaces of trivariates.
  + TVLOAD - load a trivariate out of a data set.
  + MRCHCUBE - marching cubes on volumeric data sets and trivariates.
  + TRIANGL - Converts a polygonal model to hold triangles only.
  + TRAISE - raise the degree of a trivariate (Bezier and linear Bsplines)
  + TREPARAM - reparameterization of trivariates.
  + TCRVTR - Curvature properties of iso surfaces of trivariates
  + PTHMSPR - Point discribution on a hemisphere.
  + SVISIBLE - Cone visibility decomposition of freeform surfaces.
  + ORTHOTOMC - K-Orthotomics of curves and surfaces.
  + SBISECTOR - Bisector surface of a point and a surface.
  + FFORDER - Returns the order(s) of the freeform.
  + FFMSIZE - Returns the size of control mesh/polygon of the freeform.
  + FFKNTVEC - Returns the knot vector(s) of the freeform.
  + FFCTLPTS - Returns the control mesh/polygon of the freeform.
  + CNVXHULL - Computes the convex hull of a poly/curve.
  + CRVPTTAN - All tangents through a point of a curve.
  + CRV2TANS - All bi-tangents to a given curve.
  + PDECIMATE - decimation and reduction of polygonal data.
  + GETATTR - provides a mechanism to fetch attributes.
  + TSEVAL - evaluation of triangular patches.
  + TSNORMAL - normals of triangular patches.
  + TSDERIVE - derivatives of triangular patches.
  + TSBEZIER, TSBSPLINE - triangular bezier/bspline surface constructors.
  + CBISECTOR - bisectors of freeform curves and curve/point.
  + CENVOFF - computes the offset envelope in three space of a planar curve.
  + FFPTDIST - uniform distribution of points on curves or surfaces.
  + FFPOLES - checks if a given freeform has poles.
  + BBOX - returns the Bounding box of the given geometry.

Version 6.0
-----------
* Periodic Bspline interpolation is now supported.
* Documentation can now be shown as man/html www pages.
* u/v_resolution for polygonization of freeform surfaces.
* dat2irit now supports attributes.
* A new irit2hgl tool - irit 2 hpgl plotter language filter.
* A new irender tool - a quite powerful scan conversion based rendering
  tool.
* Some display devices allows rotation and translation by click and drag in
  the view window.
* Fix a significant memory leak in the parser that was also manifested
  as a bug in functions.
* Have a while clause as well as for loop clause
* Adding a missing "hither" keyword to irit2nff.
* More overloaded operators:
  Vector * Curve -> inner product projection (result is a scalar curve)
  Vector * Surface -> inner product projection (result is a scalar surface)
* Support for polygonization of trimmed surfaces. Not the best, but useful.
* New -B flag for irit2ps - clipping for the drawing window.
* SDIVIDE, SEVAL, STANGENT, SNORMAL has been modified to support
  trimmed surfaces as well.
* Proper initial auto scale to all display devices and proper top/side/up
  views.
* Improved animation interface in the motif based display devices.
* Fix a bug in the curve curve composition code.
* EVOLUTE now compute evolute for curves and mean curvature based evolute
  for surfaces.
* New IRIT commands
  + FFSPLIT, FFMERGE - splits and merges arbitrary curves and surfaces into
	   a list of scalar curves/surfaces.
  + FFPTTYPE - an accessor that returns the type of a freeform.
  + CNORMAL, CNRMLCRV - normal and normal curve for freeform curves.
  + DSTPTLN, DSTPTPLN, DSTLNLN - distance between point, lines, planes.
  + PLN3PTS - plane definition using three points.
  + PTPTLN, PTLNPLN, PTSLNLN - point of intersection or closest point(s)
           of points, lines, and planes.
  + PT3BARY - barycentric coordinates in a triangle.
  + TEXTGEOM - converts text into displayable geometry.
  + AWIDTH, ADWIDTH - width and display width attributes.
  + FFMATCH - computes matching between freeform curves.
  + SGAUSS - computes a scalar field with the gaussian curvature.
  + SFOCAL - computes focal surface using normal curvature in isoparametric
	   directions.
  + SMEANSQR - symbolic computation of mean curvature square field.
  + HERMITE supports cubic hermite construction for curves and surfaces.
  + ROTVEC - rotate around a given vector transformation.
  + ROTZ2V2, ROTZ2V2 - rotate vector to the Z axis transformation.
  + TFROMSRFS to construct a trivariate from a list of surfaces.
  + FLOOR, FMOD, POWER math functions.
  + MOFFSET - yet another offset of crvs using curve's matching (see FFMATCH).
  + SRINTER - surface ray intersector.
  + CONTOUR - slice scalar fields as well as regular surfaces.

* Fix the way illustrt (miss) treated control points.

Version 5.0
-----------
* Animation curves and support of animation in all display devices.
* Many new flags to the display device (as well as new display devices).
* New constants for DEPTH (for trivariates), TRIMSRF_TYPE, TRIVAR_TYPE.
* Format of OFFSET and AOFFSET is slightly modified.
* LOGFILE can change files during IRIT session allowing for writing data
  files on the fly.
* ECHOSRC/DUMPLVL variables were replaced with EchoSource and DumpLevel
  IRITSTATE options.
* PAUSE was renamed into a macro.
* Figures in user manual!
* Programmer's manual (actually more like a reference programmer's manual).
* Periodic curves/surfaces are supported.
* any object with prefix of VIEW_MAT/PRSP_MAT is recognized as these
  important matrices. A complete match used to be required in the past.
* COPLANAR, INTERCRV, and POLYSORT are retired as variables and are now
  set via IRITSTATE.
* New filter dat2bin to convert between text and binary data files.
* New filter irit2iv - irit to SGI's Inventor ascii format.
* The config package prints the command line flags on all tools. New
  config file to illustrt.
* Created a symbolic lib out of cagd lib to hold all symbolic computation.
* Add adaptive routines to subdivide a surface into polygons. The whole
  scheme of srf->polygons was changed accordingly.
* Fix a bug in printing of data in +/-xxx+/-Eyyy format.
* Add "IllustrtNoProcess", "SpeedWave, and "HeatWave" attributes to
  objects in input stream of illustrt.
* Fix a minor bug in irit help document generator in math formulas.
* Fix a minor bug that introduces a return variable from user defined
  functions. Also add debug of user defined functions via IRITSTATE.
* Fix a loop in the list structure when one does "obj = list(obj, obj2);"
* New IRIT commands
  + C/SREPARAM - affine reparametrization of curves and surfaces.
  + PCIRCLE - A polynomial curve approximation of circle.
  + SCRVTR - curvature bounds for surfaces.
  + COERCE - has added semantics for E1/P1 coercetion to E2/P2 for curves and
    to E3/P3 for surfaces.
  + SURFPREV - a polynomial approximation of surface of revolution.
  + IRITSTATE - a unified state modification routine.
  + GPOLYLINE/GPOLYGON are slightly modified with more options.
  + CEVOLUTE - exact computation and rep. of an evolute of a curve.
  + GETLINE - read stdin and construct proper objects from it.
  + LOFFSET - another offset variation.
  + FFEXTREME - Comutes extreme values of curves and surfaces.
  + ERROR function - Error abort functions to be used from user defined funcs.
  + MSLEEP function - millisconed sleep function.
  + CMULTIRES function - Least squares multiresolution decomposition of curves.
  + CMORPH function - curve morphing.
  + RANDOM function - random values function.
  + New format to OFFSET and AOFFSET.
  + PDOMAIN supports trimmed surfaces and trivariates.
  + TRIMSRF constructs a trimmed surface.
  + CTRIMSRF extracts trimming curves from trimmed surfaces.
  + STRIMSRF extracts the surface of a trimmed surface.
  + STRIVAR extracts a surface from a trivariate function.
  + TBEZIER constructs a trivariate Bezier function.
  + TBSPLINE constructs a trivariate Bspline function.
  + TDERIVE differentiates a trivariate function.
  + TEVAL evaluates a trivariate function.
  + TREFINE refines a trivariate function.
  + TREGION extracts a region out of a trivariate function.
  + TDIVIDE subdivides a trivariate function.
  + C/S/TINTERP - a new Bspline interpolation/least squares approximation for
    curves, surfaces, and trivariates.
  + CLNTEXEC/CLNTREAD/CLNTWRITE/CLNTCLOSE - set of routines to communicate
    with several clients. See clients.irt.
  + MOMENT - compute moments of curves.
* Fix a minor bug of profiling an E2 curve with E3 point.
* LISTSIZE was renamed into SIZEOF and supports lists/polys/curves ctlpolys.
  Surface ctl mesh is supported via MESHSIZE.
* SWEEPSRF is split into SWEEPSRF and SWPSCLSRF with more functionality
  and the elimination of the torus bug.
* More overloaded operators:
  CtlPt * Matrix -> CtlPt
  Overloaded unary '-' on a list object reverses the list object.
* Transformations of CtlPt works as it should.
* Surfaces/Curves/Profiling can have different ctl points or even regular
  points.
* rmattr can now remove attributes created by attrib. Objects can be
  attributes as well.
* Objects are read in the proper order - same order as input stream.

Version 4.0
-----------

* New -H flag to poly3d-h to allow dumping the HIDDEN data (with different
  color/attributes...), -q to run quietly, -o for output file.

* If clause was made much more reasonable by defining comparison and
  Logical operators (<, >=, &&, ||, etc.).

* Function definition is available (ALIAS is retired). See function/procedure
  in docs and function.irt. See plotter.irt for a nontrivial example.

* Assignments need not be within parenthesis any more. Preceding is
  properly set now.

* New variables are allowed in loops now.

* MSDOS is not really supported (I left DJGCC ifdefs intact although it is
  not tested any more.). EDIT command retired, SYSTEM command modified.
  The main reason is that IRIT can no longer be built in the BC Large model
  and the Huge model will consume pretty much the entire 640k...
  If you have the ability (I do not) to build MSDOS applications with dos
  extenders, and willing to dive in, please let me know.

* The good news is that both OS2 2.x and Window NT 3.1 are fully supported.

* A whole new scheme of display drivers was developed. The display driver is
  a different process. As a result NORMAL, VIEW & INTERACT, BEEP, CLOSED
  functions are retired, and VIEWOBJ controls the display via VIEWxxxx user
  defined functions (in iritinit.irt).
	BEEP, VIEW and INTERACT functions are emulated in iritinit using a
  user defined function. NORMALs as well as other view states can be set via
  user defined function VIEWSTATE.
	poly3d was retired and is replaced by the display drivers which 
  accepts command lines. In other words, the graphics device driver serves as
  display program as well.

* Sweep has a new fourth parameter to allow setting normal of orientation
  (pseudo frenet) frame.

* New line illustration tool - illustrt.

* Lists can now be in any length and are updated dynamically.

* Attributes now can handle spaces by quoting the data:
  attrib( obj, "rgbcolor", "255 0 255" );
  see attrib command for more.

* New filter irit2xfg - IRIT to xfig.
* New filter irit2plg - IRIT to REND386 polygonal format
* New filter irit2scn - IRIT to scn (close to nff format).
* New filter irit2dxf - filters to/from DXF. Not fully functional.
* New filter dxf2irit
* New filter irit2ps  - more versatile filter to PostScript.
* New IRIT commands
  + THISOBJ - returns the type of the object.
  + PRINTF - a formatted printing routine, C printf style.
  + BOOLONE - using a single closed curve subdivided into four segments
							as bool sum input.
  + BSP2BZR - convertion from Bspline to Bezier curves/surfaces.
  + BZR2BSP - convertion from Bezier to Bspline curves/surfaces.
  + FFCOMPAT - making two curves/surfaces compatible (required for
							SMORPH morphing code)
  + HOMOMAT - low level homogeneous matrix constructor.
  + SDERIVE/CDERIVE - compute derivatives.
  + SMERGE - merge two surfaces into one.
  + SMORPH - A convex blend between two compatible surfaces (3d morphing).
  + SNRMLSRF - surface normal.
  + SYMBPROD/SYMBDPROD/SYMBCPROD/SYMBSUM/SYMBDIFF - a whole set of
					         symbolic computation tools.
  + CZEROS - find the zero set of a curve.
  + CEXTREMES - find the extreme set of a curve.
  + NIL - returns an empty list.
  + LISTSIZE - returns the size of a list/poly list/vertex list.
  + COORD - extract a single coordinate from an object.
  + AOFFSET - adaptive, error bounded, offset (slow!).
  + COERCE - coercion of objects.
  + COMPOSE - curve curve and surface curve symbolic composition.
  + PRISA - planar layout of surfaces.
  + CINFLECT - find the inflection points of a curve.
  + CCRVTR - curvature properties of curves.
  + CCINTER - curve curve intersection function.
  + POLY - can accept point and ctlpt types. Has a new second polyline/gon
							       parameter.
  + ADAPISO - adaptive isocurve extraction.
  + CRVPTDST - nearest point on a curve to a point solution (min dist param).
  + CRVLNDST - nearest point on a curve to a line solution (min dist param).
  + PDOMAIN - returns the parametric domain of a curve or a surface.

* Ability to dump UV values of vertices of polygons created from freeform
  surfaces (mainly for 2D texture mapping). See CagdSrf2Polygons and skeleton
  example in iritfltr directory.

* ATTRIButes can be set to any object, not just geometry. attributes names
  are case insensetive. 

* POINTs and PLANEs are now supported objects as well. VECTORs, POINTs,
  CTLPTs are also displayable objects.

* color() and attrib() now can work on lists, in which all elements
  in list will be appropriately updated.

* More overloaded operators:
  String + String -> String
  String ^ Real -> String
  String + Real -> String
  Point  + Vector -> Vector
  Point  * Real -> Point (Scale)
  Point  * Mat -> Point (Transform)
  -Point -> Point (scale by -1)
  -Plane -> Plane (scale by -1)

* New irit configuration variable - FloatFrmt.

* New prsp_mat variable.

* Coplanar polygons are now handled. See coplanar variable and solid2.irt
  for example.

* Boolean opeartions are almost three times faster using bbox and sorting
  optimizations! See polysort variable.

* All utilities now support '-' for stdin read. Under unix, compressed data
  is properly handled (via fork of compress and zcat). For example
  poly3d-h example.dat.Z | irit2ps - > example.ps

* Spline degree raising is implemented using the new symbolic tools.

Here is what is new in version 3.0:
-----------------------------------
1. Normals are fully supported now. Although this increases memory requirements
   (mainly a problem on IBM PC) all files dumped from IRIT now support normals
   as well.
2. A new cut Boolean operation (overloading '/', i.e. C = A / B assigns to C
   the regions in A out B).
   A new merge Boolean operation (overloading '^', i.e. C = A ^ B assigns to
   C all polygons of A and B merged (with no intersection tests.).
3. Support for freeform curves and surfaces (Bezier/NURBS).
   All Boolean are still done using polygonal data the surfaces are converted
   into (No intention to change that in the near future - direct Booleans on
   surfaces requires support of trimmed surfaces and believe me - it is HARD).
   However, quite a few tools to manipulate and maintain the curves and surfaces
   are provided and include:
   a. direct creation of curves and surfaces by specifying control mesh/poly.
   b. evaluation of surface/curve, tangents, normals.
   c. subdivision/refinement.
   d. degree raising (only Bezier).
   e. high level surface creation: ruled srf/extrude/srf of revolution/sweep.
   f. curve constructor out of curve/point pieces.
   g. conversion to polygons of surfaces including normals.
4. Support for SGI 4D systems using gl has been added.
5. lists are much more enhanced now and more functions can now get a list
   of objects where before they could get a single object only (for example
   ability to dump to file/read from file list of objects instead of one).
   This enable merging the *.ply and *.mat into single data files *.dat which
   also include the freeform data (curves and surfaces).
6. Ability to handle closed and open loops within the same polygon (see
   cubes.irt).
7. Much improved documentation.
8. Significant improvement in time of polygonal Boolean operations.
9. Two new variables COPLANAR and POLYSORT.
10. B&W X11 support added ( petern@bion.kth.se  (Peter Nordlund) ).

Version 2.1
-----------
1. Fix problem with Extrude (used to update wrong plane normal), which
   cuased problems in boolean operations.
2. Fix boolean operations causing INTERNAL edges been visible.
3. Fix major memory leak problem (upto %50 less memory usage).

Version 2.0
-----------
1. Program has been ported to unix environment using X11 window system.
   Has been compiled using:
   a. BSD 4.3 using gcc (gnu cc) compiler.
   b. SGI 4d, Irix3.2, using cc.
2. Minor fix in VGA mode.
3. Ability to dump intersection curves instead of the model in geometry
   boolean operation, has been added and is controled via a new variable
   named INTERCRV.
4. Fix severe bug in the convex decomposition (wheel.irt used to be severely
   wrong, o.k. now).

Version 1.1
-----------
1. Full line editing for input line (see irit.doc), including last command
   retrieve.
2. EGA/VGA display device is finally supported.
3. Faster and smaller allocator makes more space and run faster.
