08/06/93: started the project from scratch 
15/06/93: Tcl-language binding
16/06/93: persistence added
17/06/93: added modelling transformations
** V0.1 released
23/06/93: singular intersection point replaced by an intersection queue storing
	  ALL intersections in hierarchical order
25/06/93: two abstarct camera classes: RaytracerCamera and ShaderCamera
25/06/93: hierarchical directory structure of YART installation
25/06/93: all GL stuff put in extra subdirectory
28/06/93: automatic creation of object code dependencies
30/06/93: added TestShaderCamera, not compatible to any raytracer, only for testing the shader
	  primitives
30/06/93: added PolyMarkers, PolyLines, PolyGones for shader but not for raytracer
	  each vertex can edited, inquired; vertex can inserted and deleted 	
30/06/93: inquiry for Tcl-constructors added: "Sphere ?" 
01/07/93: hierarchy implemented: fathers and childrens, access to both
01/07/93: spline implemented - only for shader but not for raytracer
** V0.15 released
02/07/93: autmatic generation of NROFF and WWW(Html) documents implemented
05/07/93: X11 pixmap added
05/07/93: generic event controlled input server added 
05/07/93: generic callbackoriented input device added
05/07/93: uniform callback handling added - both Tcl and C++ callbacks supported
06/07/93: empty bodys added for GL stuff (x11/x11xx.c), thus you can link the
	  program without GL 
06/07/93: if C++ objects have 0 as name, no Tcl and HashEntry command will be created
	  -> thus internal objects in complex objects can be hidden
06/07/93: identifier generator created. can be used for light sources, for instance
	  to get the smallest availbale number 
06/07/93: light on/off method added
06/07/93: source-files changed from .c to .C - some compilers need it so (DEC's cxx) 
06/07/93: event classes defined 
07/07/93: surface changed: emission added, rgb-values for diffuse, specular, emission 
08/07/93: callback oriented pick device added 
08/07/93: callback oriented locator device added 
** V0.2 released
13/07/93: surface: +=shininess
13/07/93: vertex: += normal vector
13/07/93: quadric(*RT*) implemented
13/07/93: sphere reimplemented (multiple inheritance: rendering->quadmesh, raytracing->quadric) 
14/07/93: GL light render methods implemented [Roland Schachtschabel]
14/07/93: GL normal vectors for primitives implemented [Roland Schachtschabel]
14/07/93: ellipsoid, plane implemented (*RT*)
15/07/93: quadmesh added (*SH*)
** V0.25 released
20/07/93: quader added (*SH*)
21/07/93: OFF reading class added
21/07/93: Polyset added
22/07/93: Fillstyle attribute added and to polygon added
22/07/93: DOS compatible file names
23/07/93: perspective camera added (*RT*)
** V0.30 released
26/07/93: RadiusAttribute removed, Sphere now needs Radius in Constructor, but of
	  course it can be changed later
26/07/93: SolutionAttribute added allowing a dynamic degree of conversion of high
	  level primitives (SPhere) when broken into low-levels (Quadmesh)
27/07/93: sphere implementd (*SH*)
28/07/93: in scene now only root objects!!! all functions now working recursively
29/07/93: damned references removed from Vector, Color
29/07/93: matrix acces changed, "changed" flag added
29/07/93: new organization of system dependend stuff - no more defines!!
29/07/93: Pixmap full abstract! new Class for immediate display: PixmapDisplay
29/07/93: Polyset removed, because it will be redundant in future
29/07/93: low-level graphics functions to minimize the system dependend stuff
30/07/93: every primitive now has 2 lists of childs: "parts" and "children"
02/08/93: automatic management of parts and childs
02/08/93: hierarchical rendering and raytracing
02/08/93: a clear set of primitive flags and rebuild functions defined
02/08/93: optimation for large sets of parts without own modelling transformation
	  (ignorePartModelling)
02/08/93: missing initialization for input devices inserted: on()
03/08/93: fix coord rotation/transformation added [Roland Schachtschabel]
03/08/93: + Tcl interface to math lib functions
03/08/93: attribute inheritence
04/08/93: access to attributes: set, get, clear, class
04/08/93: Spaceball support (*SGI GL*) [Roland Schachtschabel]
04/08/93: ColorAttribute removed because only used in Light sources
04/08/93: + TK - SGI GL Mixed Programming Support [Roland Schachtschabel]
05/08/93: + correct matrix down transformation for parts without own modelling transformation
	  when raytracing
05/08/93: type orthogonal access to attributes
05/08/93: + sleep function
05/08/93: + PHIGS PLUS alpha port [me and Rainer Barth]
05/08/93: + user extensible FileHandler device class + related event class
06/08/93: + PHIGS debugging support
06/08/93: + "special" method of Output class, can used for hidden messages for log files etc.
09/08/93: + lookat-matrix for raytracer [Ralf Boese]
** V0.35 released
10/08/93: + base classes for scientific visualization
11/08/93: bug in RT_String removed
11/08/93: + RT_Quadmesh-method for automatic computation of normal vectors
11/08/93: + Torus (*SH*)	
11/08/93: + vertex access to scientific objects
11/08/93: + 2DPerimetricLattice
12/08/93: + Cone (*SH*)
13/08/93: + Cylinder (*SH*) 
16/08/93: + visible/invisible method for primitives
16/08/93: + access to objects in scene ( get_objects )
16/08/93: every camera now has it's own scene usable for interaction feedback
17/08/93: + refresh for X11 Pixmap [Kim Q. Liu]
19/08/93: + Tcl class system (single inheritance of members and methods)
19/08/93: + fillstyle for quadmesh
19/08/93: + {RANGE 1 "-r +r"} for method descriptions
19/08/93: + isA method for RT_Object (so you can ask if an object is from class C or
	    from a subclass of C
19/08/93: + boundary box for primitives (MC)
19/08/93: + recursive  boundary box for primitives (MC) including childs
19/08/93: correct aspect ratio for raytracer
20/08/93: + visibility of bounding boxes
20/08/93: - BUG: modelling -> display list refresh!!!
20/08/93: - BUG: parts inserted a wrong matrix - must be modelling matrix!!!
23/08/93: - BUG: console defined twice in rtsh if already defined when loading a file
23/08/93: + access to the default attributes from both Tcl and C++ (try "AttributeObject ?")
23/08/93: + two new draw styles: FilledBoundingBox and HierarchicalFilledBoundingBox	
26/08/93: + manipulator device [Roland Schachtschabel)]	
26/08/93: + bump mapping demo
26/08/93: + destructor for Tcl classes (recursive)
26/08/93: + new global function: RT_primitives (acces to all -fatherless- primitive objects
	    currently existing
26/08/93: + new global function (C++-usage only): init only minimal stuff (interpreter +
            hash table)
01/09/93: + RT_include (Inclusion of - Tcl - father classes)
02/09/93: + virtual method: RT_Primitive::inverse(): map a 3D point in a 2D area needed for textures
02/09/93: + Mapping class; needed for Texture- and Bump mapping
02/09/93: + 2 sample textures taken from VORT's ART
03/09/93: + Facet and Polyhedron classes [Rainer Barth]
03/09/93: + Image base class representing arbitrary pixmap files
06/09/93: + Subclass SGIImage for SGI RGB files
06/09/93: + ImageMapping class
07/09/93: + automatic management of related objects
07/09/93: + dithering for X11 Pixmap (Juergen Nuetzel, Heiko Fischer, Rainer Barth)
08/09/93: RT_save changed so that saved scenes are restartable
08/09/93: + RT_source - cmd: orig. "source" + search paths
08/09/93: Scene, Camera, Pixmap, Mapping changed (using autom. managem. of rel. obj.)
08/09/93: + bounding boxes for primitives (torus, cone, cylinder)
08/09/93: + SVGA support [Christoph Hornung, Juergen Nuetzel, Heiko Fischer]
** V0.40 released
<holidays for 5 weeks>
20/10/93: - BUG: in normal computing of the quadric
21/10/93: - BUG: in intrsect computing of the quadric
22/10/93: - BUG: transmission computing changed
25/10/93: system includes (the "extern C" -problem)
25/10/93: + Class for Complex Numbers
27/10/93: + Torus: intersect computing (*RT*) 
29/10/93: + Torus: normal computing (*RT*)
29/10/93: + Quader: normal and intersect (*RT*)
01/11/93: + MC2WC, WC2MC - macros for normals, rays, intersects
01/11/93: + Tcl/C++-Variable (rt_)Ray/PickDebug for debugging of raytracing/picking
01/11/93: CHANGED: OneRayCamera - new constructor/methods
03/11/93: valid intersections should checked now with "ray->valid( t )" instead of " t > 0"
04/11/93: Raytracer optimization (Hierarchical Bounding Boxes including CHilds)
09/11/93: - BUG: SGIImage::write works correctly now
09/11/93: CHANGED: src/image.h: local struct _Image -> global struct RT_SGIImageStruct
	  'cos some compilers dont like the type-local types (gcc2.3.3)
09/11/93: + dynamic dimensions for Image classes
10/11/93: + Pixmap: Method "getPixel"
11/11/93: + Animation Base Class: Recorder and ImageRecorder
23/11/93: + robot-Demo (to be extended!)
24/11/93: + automatical removing of Parts in ~RT_Primitive, now
25/11/93: + Manual Pages (rtsh, tkrt, rttest)
25/11/93: + hierarchical Directory structure according to the GOOD-project
	look in README.GOO
26/11/93: + text (Rainer Barth and me)
29/11/93: package-concept and separation of scientific stuff 
30/11/93: + RT_packages-command (returning all installed C++ packages)
30/11/93: + RT_Primitive:hide-flag (hide recursively childs so that they can't be seen
	from User Interfaces etc.)
30/11/93: + more Manual Pages (YART binaries, built-in variables and functions)
01/12/93: + Tcl Class inheriting from Primitive
01/12/93: + RT_primitiveClasses-command (returning all C++ primitive classes sorted
	to the packages)
01/12/93: + advanced text methods (alginment, size, ...) [Rainer Barth]
02/12/93: + Tcl/Tk/Yart-Mode for GNU Emacs (19.*) [Gregor Schmid]
02/12/93: CHANGED: src/Makefile: creation of rtsh and tkrt without different
	src/system-Makefiles 
06/12/93: + PixmapDisplay::getpixel() (*X11*)
07/12/93: + Object::print(): regular file descriptors now possible
07/12/93: + Scene::update(): update attributes etc of all primitives inside the scene
14/12/93: - BUG: heavy bug in Raytracer removed. Sorry guys, AT&Ts CC hadn't
	problems with the multiple freeing of one block, but GNU
17/12/93: - BUG: G++ made a unsigned long conversion of RT_Color when a 
	RT_Color was specified as return value; needed three days to find
	the damned thing; Now: RT_Color(RT_Color&) constructor to avoid that
18/12/93: - BUG: (*X11*) Pixmap-error if event and no camera was assigned
18/12/93: + Cylinder (*RT*) [Sebastian Vogt and me]	
18/12/93: - BUG: wrong normal vector of cylinder cover (*SH*)
20/12/93: + Radiosity interface (very alpha) (*X11*) [Heiko Fischer]
20/12/93: CHANGED: PixmapDisplay: using an array to store TrueColor values (*X11*) [Jochen Pohl]
20/12/93: + PixmapDisplay-Tk Widget (*X11*) [Jochen Pohl]
20/12/93: + default font for text [Rainer Barth]
21/12/93: + Cone (*RT*) [Jens Werner]	
22/12/93: + analogue Tcl output object [Roland Schachtschabel]	
22/12/93: + stereo demos for stereo view (ONLY for XS/Elan/Indy) [Roland Schachtschabel]	
** V0.50 released
06/01/94: CHANGED: no more unnecessary CC warnings
06/01/94: + TARGA image class [Heiko Fischer]
06/01/94: + Radiosity interface (*GL*) [Heiko Fischer]
06/01/94: + OFFQuadmesh [Heiko Fischer]
10/01/94: + inverse() for Quader
13/01/94: CHANGED: solution renamed globally to resolution
13/01/94: + inverse() for Cone and Cylinder
14/01/94: CHANGED: naming concept for attributes
19/01/94: CHANGED: background method put frpm Camera to Scene
20/01/94: CHANGED: mapping attribute reimplemented (consistency to the other built ins)
28/01/94: CHANGED: attribute referencing and primitive updateing completely
	  reimplemented 
31/01/94: + general access to attributes in Tcl (attribute, get_attribute)  
01/02/94: CHANGED: using a subscene for light emitting objects when raytracing
01/02/94: + several 3D textures adapted from GRIS Uni T"ubingen, used with friendly permission
02/02/94: - parameter.h, spacball.*, noise.*
02/02/94: CHANGED: reimplemenation of the input devices to support hierarchical 
	  input devices [Roland Schachtschabel]
02/02/94: + Tcl input device classes  similar to the Tcl primitiv classes [Roland Schachtschabel]
11/02/94: CHANGED: primChangedFlag splittet to
	dlChangedFlag - used for shader to rebuild the display list AND
        rsyChangedFlag - used for radiosity to rebuild the RSY presentation of the object
	-> all other flags (geometry changedFlag, matrixChangedFlag, ...) are independent
** V0.60 released		
15/02/94: - BUG: print() method of Tcl Mixed Classes (InputDevice, Primitive)
15/02/94: + bounding boxed for Polyvertex subclasses, Ellipsoid, Polyhedron and Quadmesh
16/02/94: + caching bboxes for Text, OFF*, etc.
23/02/94: - BUG: Texture3D::print, *MarbleTextures::objectCMD
23/02/94: CHANGED: library names and pathes
23/02/94: + Tcl/C++-Variable for YART binary
01/03/94: - support for older Tcl (and Tk) versions 
01/03/94: CHANGED: if there is only one Tcl return value, the value itself wil be returned
           and can directly be accessed
01/03/94: CHANGED: new Tk (and Tcl) version: 3.6
03/03/94: CHANGED: back to version: 3.3
03/03/94: - BUG: no radiosity output on SGI Hardware lightin machines, bug fixed 
04/03/94: + src/extend.C: initialize here the extension packages
<one week in Amsterdam@CWI>
14/03/94: + classCMDs now return the object name in case of success: Axes a -> a
14/03/94: CHANGED: is_a's, every class needs its own is_a to work correctly
14/03/94: + supersampling raytracing camera [Ken Geis]
28/03/94: - BUG: OneRayCamera dumped when rendering
28/03/94: + man page: Parameters
29/03/94: CHANGED: right-hand-rule for cover of cone and cylinder
29/03/94: CHANGED: PolyHedron (German) renamed to PolyHedra
29/03/94: CHANGED: autoconfig
30/03/94: CHANGED: OneRayCamera::point -> viewpoint (equivalent to LookatCamera)
30/03/94: CHANGED: malloc(realloc)/free in RT_String -> new/delete
30/03/94: + AIX GL interface [Frank Wicht]
31/03/94: CHANGED: new Tk (and Tcl) version: 3.6
05/04/94: CHANGED: RT_[pure]init: allowing a preinitialized interpreter
11/04/94: CHANGED: is_a -> isA
11/04/94: CHANGED: uniform macro names (RTM_xxxxxYyyyyyZzzz)
11/04/94: CHANGED: RT_GeneralListEntry::type removed!! Now, all type checkings before
	down casting are basing on isA()
11/04/94: CHANGED: all globals macros now in */src/macros.h
12/04/94: CHANGED: method names ( aaBbbbCccc or get_aaBbbbCccc instead of aaa_bbbCCC or ... )
	in src/polyhdra.*, src/poly.*, src/quadmesh.*, 	
12/04/94: + OpenGL support (incl Tk support) [Frank Wicht]
15/04/94: CHANGED: RTN_ defines -> const char * 
** V0.70 released	
19/04/94: + class for modelling matrices	
19/04/94: CHANGED: dynamic allocation of modelling matrices
19/04/94: Primitive::update with default parameter to force the creation
	of references
20/04/94: + Primitive:get_worldMatrix()
21/04/94: + autoloading of images in constructor
21/04/94: + update-event type
21/04/94: + far-plane for raytracer
22/04/94: CHANGED: correct handling of events in multiwindow mode (*GL*)
30/04/94: + application specific attribute types, demo test/myattr.C 
02/05/94: + retraversing of parts changed
16/05/94: CHANGED: the AttributeObject should be used only initially, from now
	the reset of the changed state of the attributes will be reset now
	correctly and not inside the Scene::update
16/05/94: CHANGED: Polyhedra -> Polyhedron (this is the final version, now!)
16/05/94: CHANGED: colormap and dithering for X11 [Don Libes]
16/05/94: CHANGED: shader interface renamed to render() instead of renderMe()
16/05/94: CHANGED: return values of get_surface/diffuse/point/... now const refs 
16/05/94: CHANGED: prototypes of the ray-tracer/mapping/light source/... interface
20/05/94: CHANGED: namelist from Attribute constructor removed
24/05/94: - BUG: Tcl::update() -> referencing parts and children, too
24/05/94: CHANGED: InputDevice: fatherType replaced
26/05/94: CHANGED: high level prim. files -> src/high directory
26/05/94: CHANGED: primitive::render -> default: rendering the parts
26/05/94: + Pick Mode for primitives
26/05/94: CHANGED: display list also for parts, but only if the part hasn't a father
26/05/94: CHANGED: enum for BoundingBox mode
26/05/94: CHANGED: BBox removed from primitive - not longer a part!
26/05/94: CHANGED: not longer access to manipulator cursor
26/05/94: CHANGED: manipulator enumerations
26/05/94: CHANGED: manipulator uses feedback scene of camera instead
	of appending a temporary primitive
27/05/94: + Manipulator::print
27/05/94: + Manipulator: different colors for mode()
27/05/94: + Manipulator: objectKilled for current object
27/05/94: CHANGED: Primitive::[get]attribute uses const refs, now
27/05/94: CHANGED: attribute get_ functions ALL () const
29/05/94: CHANGED: put high level stuff that does not belong to the
	minimal kernel into directory "src/high", in future: extra library
29/05/94: CHANGED: Tcl destructor now "~IOM_ErrorBox" instead of "~"
01/06/94: CHANGED: Locator reimplemented now: real 3D
03/06/94: CHANGED: reimplementation of input stuff
06/06/94: + two input demos
07/06/94: + implementation of the ellipsoid
08/06/94: CHANGED: inheritance of Cone, Cylinder
13/06/94: + radiosity rendering (*OpenGL*)
14/06/94: CHANGED: Polyhedron access methods with one index removed
15/06/94: + ambient coefficient to Surface; Surface attribute now: Phong + Emission + BRDF
16/06/96: + image class RGBAImage [Frank Wicht]
16/06/94: + ray-tracing interface for Polygon [J"org Leinhoss] 
16/06/94: + ray-tracing interface for Polyhedron [J"org Leinhoss] 
16/06/94: - global normal removed from Polyhedron [J"org Leinhoss] 
16/06/94: + CompositeTextureMapping for composite objects
21/06/94: CHANGED: orientation of rotations; now maintenance of right-hand-rule
** V0.95 released	
23/06/94: CHANGED: autoupdate of concat matrix when modeling a primitive
06/07/94: + refracted shadows
06/07/94: CHANGED: PointLight ray-tracer implementation
13/07/94: + WorldTextureMapping
28/07/94: + HeightField (based on Quadmesh)
28/07/94: + Quadmesh interface (*RT*)  [J"org Leinhoss] 
28/07/94: + surface interpolations for polygon/-hedron, quadmesh (*RT*) [J"org Leinhoss] 
01/08/94: CHANGED: AmbientLight now uses ambient coefficients of the surface attribute
02/08/94: + Pick: objectKilled for picked object
02/08/94: - RT_new, RT_load
02/08/94: CHANGED: father class for RT_Axes, now polyline as instance object
03/08/94: CHANGED: virtual inheritance removed from Quadric and Qmesh
03/08/94: CHANGED: reimplementation of Quadric
08/08/94: + interface to VOGL - but this is limited to the limitations of VOGL of course
** V1.00 released
16/08/94: CHANGED: reorganisation of textures and mappings to allow bump mapping
16/08/94: + demo bump mapping
18/08/94: + matrix access for Manipulator's cursor object
01/09/94: CHANGED: Heigtfield: z = f(x,y), not y = f(x,z)
01/09/94: CHANGED: Heigtfield: indices used as x,y-coordinates
01/09/94: + Heigtfield:interface (*RT*) [J"org Leinhoss] 
01/10/94: + RT_ConsoleInputCB 
01/10/94: + computeNormals exported for Polyhedron and Quadmesh
05/10/94: CHANGED: RT_CLASS -> Tcl_Object
05/10/94: CHANGED: RT_PRIMITIVE_CLASS -> Tcl_Primitive
05/10/94: CHANGED: RT_INPUT_DEVICE_CLASS -> Tcl_InputDevice
05/10/94: CHANGED: RT_METHOD -> Tcl_Method
25/10/94: + OFF Polyhedron [Bryan Heidorn]
** V1.10 released	
10/11/94: + Hershey fonts [J"org Leinhoss]
15/11/94: CHANGED: Ray-tracing interface for polyline [J"org Leinhoss]
18/11/94: - Spline class (will be replaced by a library in future)
08/02/95: - BUG: delete of Tk-YART-PixmapDisplays didn't work til now 
09/02/95: + VertexManipulation [J"org Leinhoss]
09/02/95: + parametric stuff [Paul Michalik]
07/03/95: + copy method for primitives
08/03/95: CHANGED: much rework on parametric stuff
