View source for OB3D IFF 3-D Object Format

= OB3D =

</pre>
                    FORM OB3D (revision 1)
                   ------------------------
                              by
                       Roberto Speranza


   This is a modified specification of the OB3D FORM, proposed a few
weeks ago.   Much concern was raised about the earlier FORM's inflexibility.
I have tried to address that here by adding flexibility to the majority of
the chunks by making them tag-based.
	This will define what I consider to be the bare minimum I require of
this FORM for my own program plus anything I can think of to accomodate other
programs I am aware of as well suggestions posed by others.  Additional chunks
or additional tags for chunks currently defined in this proposal will have
to be discussed as soon as possible after this posting.  I want this minimum
definition approved so that I can begin the task of re-writing my reader/writer
software to handle all of this.  To add the flexibility requested, the reader
software has to increase in complexity somewhat.   Here are a few
highlights of the revised FORM:

- almost all chunks are tag-based
- SPLN chunk updated to handle NURBs (non-uniform rational B-Splines)
- SURF and NURB chunk merged with a new chunk, PRIM, which will contain
  ALL primitives; polygons, bicubic surfaces, NURB surfaces, and other
  primitives such as spheres, cones, etc.
- precision concerns have been eliminated by the addition of variables
  to the PREF chunk that are designed to inform the reader software of
  the precision of floats used in the file
- the addition of a MACR chunk for stroing ASCII macros such as AREXX
  macros or scripts


   The following is a list of chunks and their descriptions followed by
a detailed description of all the tags currently defined.

-----------------------------------------------------------------------------
FORM


struct FORMstruct
{
   ULONG ID;
   ULONG Size;
}


OB3D


PREF (optional)

struct PREFstruct
{
   ULONG Id;
   ULONG Size;
   UWORD preflines;
   ULONG prefsize;
   UB�TE Prefs[prefsize];
   UB�TE pad;  /* to make chunk even length, if necessary */
}

The character array Prefs consists of lines of ASCII text terminated by
newlines (\n).   The NumLines field tells you how many lines in case you want
to read it in a line at a time.

Each line takes the following form:

variable=value(s)   (more than one value will be separated by spaces)

This type of preferences layout was selected for generality and easy
expansion.  This will also allow for program preferences to be stored in IFF form.
If this chunk is present, it will contain preferences for the reader code
as well as any program preferences.  Here are some variables to start us off:


   Variable       Suggested Value(s)
   --------       ------------------

   TIMEUNITS      FRAMES or SECONDS depending on application

   FRAMERATE      60

   TIMEFLOAT      IEEESINGLE   (32 bit)
                  CHARSTRING   ( length (UWORD) + length characters )
                               (not null terminated)
                  ULONGINT     (32 bit)

   TIMEBASE       1            (number to divide TIMEFLOAT by to get value in TIMEUNITS)
                               (primarily for specifying how to convert ULONGINTS to
                                a floating point quantity if desired)

   STARTFRAME     1 (or whatever)

   ATTFLOAT       IEEESINGLE   (32 bit)
                  CHARSTRING   ( length (UWORD) + length characters )
                               (not null terminated)
                  UB�TE        ( 8 bit)
                  UWORDINT     (16 bit)
                  ULONGINT     (32 bit)

   ATTBASE        1            (number to divide ATTFLOAT by to get value in TIMEUNITS)
                               (primarily for specifying how to convert non-floating
                                point quantities to a floating point quantity if desired)

   FLOAT          IEEESINGLE   (32 bit)
                  CHARSTRING   ( length (UWORD) + length characters )
                               (not null terminated)

   COORFLOAT      IEEESINGLE   (32 bit)
                  IEEEDOUBLE   (64 bit)
                  IEEEEXTENDED (96 bit)
                     This is supported by the
                     MC6888x FPUs. Manx's m.lib
                     supports this format as a
                     long double.
                  CHARSTRING   ( length (UWORD) + length characters )
                               (not null terminated)

   ANGLEUNITS     DEGREES
                  RADIANS

   DISTANCEUNITS  MILLIMETRES
                  CENTIMETRES
                  METRES
                  KILOMETRES
                  INCHES
                  FEET
                  �ARDS
                  MILES

-----------------------------------------------------------------------------
MACR (optional)

struct MACRstruct
{
   ULONG Id;
   ULONG Size;
   ULONG NumMacros;
   struct
   {
      UWORD namelen;       /* length of name */
      UB�TE name[namelen]; /* name of macro  */
      ULONG macsize;
      UWORD maclines;
      UB�TE Macro[macsize];
   } [NumMacros]
   UB�TE pad;  /* to make chunk even length, if necessary */
}

The character array Macro consists of lines of ASCII text
terminated by newlines (\n).  The field maclines tells you how many lines
of text are in the macro in case you want to read it one line at a time.

-----------------------------------------------------------------------------
SBAS (optional)

struct SBASstruct
{
   ULONG ID;
   ULONG Size;
   ULONG NumSBASes;
   struct
   {
      UWORD basisnum; /* basis number */
      UWORD step; /* point step */
      COORFLOAT Basis[4][4]; /* basis matrix */
   } [NumSBASes];
   UB�TE pad;  /* to make chunk even length, if necessary */
}

This chunk is only required if bicubic surfaces or splines are stored in
the file.  This chunk defines the basis matrix to convert the
control points of the spline to coefficients for the cubic equation that
describes the spline.   The step parameter dictates how to apply the
basis matrix to splines which use more than 4 control points but are
still cubic in nature (like more than one linked up together).

I believe three basis numbers should be reserved for these common
splines:

   Number   Spline Type
   ------   -----------

      0     Bezier spline
      1     Uniform non-rational B-spline
      2     Catmull-Rom spline


I selected these spline types because they are the most common
ones used in modellers and CAD packages.  Any other type can be
defined at will, allowing for custom splines.

-----------------------------------------------------------------------------
TRGB (optional)

struct TRGBstruct
{
   ULONG ID;
   ULONG Size;
   ULONG NumTRGBs;
   struct
   {
      UWORD NumColours; /* number of components in colour model */
      FLOAT ToRGB[NumColours][3]; /* transformation matrix */
   } [NumTRGBs];
   UB�TE pad;  /* to make chunk even length, if necessary */
}

This chunk is optional if all colour data is specified using the RGB colour
model. The transformation matrix for RGB colour data is simply a 3X3 identity
matrix.

For any other colour model, this chunk should be present in order to specify
the number of components used for colours as well as the transformation matrix
used to multiply the colours in the file to RGB.  This should suffice for most
colour models.

example:

   [t00 t01 ... t0n][c0] = [R]
   |t10 t11 ... t1n||c1|   |G|
   [t20 t21 ... t2n]|..|   [B]
                    [..]
                    [cn]

-----------------------------------------------------------------------------
VERT  (optional only when HIER chunk is present else not included)

struct VERTstruct
{
   ULONG Id;
   ULONG Size;
   ULONG NumVERTs;
   struct
   {
      ULONG numtags;
      struct
      {
         ULONG tagtype;
         UB�TE data[tagsize];
      } [numtags]
   } [NumVERTs];
   UB�TE pad;  /* to make chunk even length, if necessary */
}

The VERT chunk stores all vertex information.  This structure is
now tag-based to allow for future expansion and flexibility.  The
following tags are applicable to the VERT chunk:

        OB3D_Parent
        OB3D_Clone
        OB3D_RelSurf
        OB3D_TimeStamp
        OB3D_Cycle
        OB3D_Interpolation
        OB3D_Script

        VERT_Position
        VERT_Velocity

-----------------------------------------------------------------------------
EDGE  (optional; if VERT chunk is missing, it is not included)

   struct EDGEstruct
   {
      ULONG ID;
      ULONG Size;
      ULONG NumEDGEs;
      struct
      {
         ULONG points[2];   /* index to two points of edge */
         ULONG numtags;     /* hook for future tags */
         struct
         {
            ULONG tagtype;
            UB�TE data[tagsize];
         } [numtags]
      } [NumEDGEs]
      UB�TE pad;  /* to make chunk even length, if necessary */
   }

The EDGE chunk stores all edges for programs that use a wireframe
representation in their editors or renderers.  Programs that do not
require edges do not need to store this chunk in their files.  This
will force programs who require edges to reconstruct the edges or
represent the objects with a bounding box.  The tags that are
applicable to this chunk are:

     none at this time


-----------------------------------------------------------------------------
SPLN  (optional; if VERT chunk is missing, it is not included)

   struct SPLNstruct
   {
      ULONG ID;
      ULONG Size;
      ULONG NumSPLNs;
      struct
      {
         ULONG numpts; /* number of points */
         ULONG points[numpts]; /* control pts indices */
         ULONG numtags;
         struct
         {
            ULONG tagtype;
            UB�TE data[tagsize];
         } [numtags]
      } [NumSPLNs]
      UB�TE pad;  /* to make chunk even length, if necessary */
   }


The SPLN chunk is used to store any spline information.  By using various
tags, any cubic spline or NURB (non-uniform rational B-spline) can
be stored.  The following is a list of tags that can be used for the SPLN
chunk:

        SPLN_Basis
        SPLN_NURB_Order
        SPLN_TrimSurf
        SPLN_NURBKnots
        SPLN_NURBWeights

NOTE: (for cubic splines only)

   numpts=4+n*basisstep

   where         n =  any integer from 0 to infinity
         bassistep =  the step value of the basis matrix
                      used for the spline

-----------------------------------------------------------------------------
PRIM  (optional unless HIER and VERT chunk are missing because it is not included)

   struct PRIMstruct
   {
      ULONG ID;
      ULONG Size;
      ULONG NumPRIMs;
      ULONG numtags;
      struct
      {
         ULONG tagtype;
         UB�TE data[tagsize];
      } [NumPRIMs];
      UB�TE pad;  /* to make chunk even length, if necessary */
   }

   Bicubic surfaces have played a very important role of late in CAD and
commercial graphics.  Applications on the Amiga are now starting to model
objects using bicubic surfaces making this chunk a necessity.
   The importance of the NURB (non-uniform rational B-Spline) has come
about due to the need to represent conics and quadrics accurately
using parametric surfaces.  Bicubic surfaces can only approximate these
surfaces but NURB surfaces can represent them exactly and enjoy the
flexibility of B-splines as well.
   By using various tags, this chunk can store any primitive including
bicubic surfaces, NURB surfaces or polygons.
   This chunk will be used to specify primitive objects.  It is
tag-based, allowing for expansion as different primitives are supported in
the future.   The following tags are applicable to this chunk:

        OB3D_Parent
        OB3D_TimeStamp
        OB3D_Cycle
        OB3D_Interpolation
        OB3D_Script

        PRIM_Points
        PRIM_PolySmoothing
        PRIM_SurfBasis
        PRIM_NURBOrder
        PRIM_Contours
        PRIM_NURBKnots
        PRIM_NURBWeights
        PRIM_TextureSpace
        PRIM_RectangularSolid
        PRIM_Ellipsoid
        PRIM_Prism
        PRIM_SurfaceRevolution
        PRIM_SemiInfiniteSpace
        PRIM_RiSphere
        PRIM_RiCone
        PRIM_RiDisk
        PRIM_RiCylinder
        PRIM_Hyperboloid
        PRIM_RiParaboloid
        PRIM_RiTorus


-----------------------------------------------------------------------------
HIER  (optional; excluded if file is missing both VERT and LAMP chunks)

struct HIERstruct
{
   ULONG ID;
   ULONG Size;
   ULONG NumHiers; /* Number of Hierarchies in chunk */
   struct
   {
      ULONG numtags;
      struct
      {
         ULONG tagtype;
         UB�TE data[tagsize];
      } [numtags]
   } [NumHiers];

   UB�TE pad;  /* to make chunk even length, if necessary */
}

The Hierarchy chunk is used to describe the relationships between objects,
paths and lamps.   The following tags are applicable to this chunk:

        OB3D_Name
        OB3D_Parent
        OB3D_Clone
        OB3D_TimeStamp
        OB3D_Cycle
        OB3D_Interpolation
        OB3D_Texture
        OB3D_Script

        HIER_Type
        HIER_CustomTypeName
        HIER_HierStatus
        HIER_BoundingBox
        HIER_LampType
        HIER_Size
        HIER_Shear
        HIER_LocalOrigin
        HIER_Velocity
        HIER_Axes
        HIER_�PRAngles
        HIER_X�ZAngles
        HIER_Translate
        HIER_Rel�PRAngles
        HIER_RelX�ZAngles

-----------------------------------------------------------------------------
ATTR  (optional if TXTR is not present)

   struct ATTRstruct
   {
      ULONG ID;
      ULONG size;
      ULONG NumATTRs;
      struct
      {
         ULONG numtags;
         struct
         {
            ULONG tagtype;
            UB�TE data[tagsize]
         } [numtags]
      } [NumATTRs]

      UB�TE pad;  /* to make chunk even length, if necessary  */
   }

The ATTR chunk stores all information about attributes.  The following tags
are used for this chunk:

        OB3D_Name
        OB3D_TimeStamp
        OB3D_Cycle
        OB3D_Interpolation

        ATTR_ColourSize
        ATTR_Diffuse
        ATTR_Reflect
        ATTR_Transmit
        ATTR_Ambient
        ATTR_Illumin
        ATTR_Opacity
        ATTR_IndexRefract
        ATTR_SpecHighLight
        ATTR_PhongHighLight
        ATTR_HighlightColour
        ATTR_LightIntensity
        ATTR_LightDirection
        ATTR_ConeLight
        ATTR_AreaLight
        ATTR_Fog
        ATTR_DepthCue
        ATTR_EnvironIllumin
        ATTR_EnvIndexRefract

I am sure there are attributes that have been missed.  Further
discussion and debate over this specification should result in the
missing attributes being defined.

-----------------------------------------------------------------------------
TXTR  (optional)

   struct TXTRstruct
   {
      ULONG ID;
      ULONG Size;
      ULONG NumTXTRs;
      struct
      {
         UWORD namelen;
         UB�TE name[namelen]; /* name of texture */
         ULONG numtags; /* number of tags for texture */
         struct
         {
            ULONG tagtype;
            UB�TE data[tagsize];
         } [numtags]
      } [NumTXTRs];

      UB�TE pad;  /* to make chunk even length, if necessary  */
   }

The TXTR chunk stores all information about textures.  The following tags
are used for this chunk:

        OB3D_Name
        OB3D_TimeStamp
        OB3D_Cycle
        OB3D_Interpolation
        OB3D_Texture
        OB3D_Script

        TXTR_RenderType
        TXTR_Space
        TXTR_BoundingBox
        TXTR_Center
        TXTR_BitMap
        TXTR_Checker
        TXTR_Gradient
        TXTR_Brick
        TXTR_Wood
        TXTR_Wave
        TXTR_BumpMap


I have just defined some textures to start us off.  I attempted to define
some common textures used by most amiga rendering programs.  Further
discussion and debate over this specification should result in the
missing attributes being defined.

-----------------------------------------------------------------------------
BACK  (optional)

   struct BACKstruct
   {
      ULONG ID;
      ULONG Size;
      ULONG numtags;
      struct
      {
         ULONG tagtype;
         UB�TE data[tagsize];
      } [numtags]
   }


   The BACK chunk is used to store all information required to describe
the background of a rendered scene.  As needs expand, tags can be added
to accomodate additional information.

        BACK_GroundTexture
        BACK_SkyTexture
        BACK_EnviroTexture

-----------------------------------------------------------------------------
OBSV  (optional)

   struct OBSVstruct
   {
      ULONG ID;
      ULONG Size;
      ULONG NumOBSVs;
      struct
      {
         ULONG numtags;
         struct
         {
            ULONG tagtype;
            UB�TE data[tagsize];
         } [numtags]
      } [NumOBSVs]
   }

   The OBSV chunk stores all parameters necessary to describe the view.
The following tags are applicable to this chunk:

        OB3D_TimeStamp
        OB3D_Cycle
        OB3D_Interpolation

        OBSV_ObserverHierarchy
        OBSV_TargetHierarchy
        OBSV_Observer
        OBSV_Target
        OBSV_Distance
        OBSV_Orientation
        OBSV_Tilt
        OBSV_FieldofView
        OBSV_RecordingMedium
        OBSV_FocalLength
        OBSV_Aperture
        OBSV_StopNumber
        OBSV_ShutterSpeed
        OBSV_Separation

-----------------------------------------------------------------------------
DISP  (optional)

   struct DISPstruct
   {
      ULONG ID;
      ULONG Size;
      ULONG NumDisps;
      struct
      {
         ULONG numtags;
         struct
         {
            ULONG tagtype;
            UB�TE data[tagsize];
         } [numtags]
      } [NumDisps]
   }

The DISP chunk is to be used to save the various displays programs use.
The tags used for this chunk are:

        OBSV_Observer
        OBSV_Target
        OBSV_Distance
        OBSV_Orientation
        OBSV_Tilt
        OBSV_FieldofView
        OBSV_RecordingMedium
        OBSV_FocalLength
        OBSV_Aperture
        OBSV_StopNumber
        OBSV_ShutterSpeed
        OBSV_Separation

        DISP_WindowParms
        DISP_ViewStatus
        DISP_FrameRate

-----------------------------------------------------------------------------

Tags for the OB3D FORM
----------------------

Label                  Offset
Data                   Description
----                   -----------

                       OB3D_TagBase+ (0x00000000)
OB3D_Name                   0
UWORD namelen;
UB�TE name[namelen];   name of entity (not null terminated)

OB3D_Parent                 1
ULONG parent;          index to parent entity

OB3D_Clone                  2
ULONG clone;           index to clone entity

OB3D_RelSurf                3
ULONG relsurf;         index to clone entity

OB3D_TimeStamp              4
TIMEFLOAT timestamp;   timestamp for tags that follow

OB3D_Cycle                  5
TIMEFLOAT start,
TIMEFLOAT length;      start ad length of cycle

OB3D_Interpolation          6
ULONG status;          interpolate parameters to next key-frame
                       possible status flags are:

                           Label       Value  Description
                           -----       -----  -----------

                                  0x00000800  reserved for interpolation
                                      to      flags not yet contemplated
                                  0x00000010

                        PVSPLINE  0x00000008  spline parameters to next
                                              key-frame using positions
                                              and velocities

                         PSPLINE  0x00000004  spline parameters to
                                              next key-frame using
                                              positions only

                          LINEAR  0x00000002  linearly interpolate
                                              parameters to next key-frame

                             OFF  0x00000001  turn off


OB3D_Texture                7
ULONG texture;         index to entity's texture

OB3D_Script                 8
UWORD namelen;
UB�TE name[namelen];   name of script

-----------------------------------------------------------------------------
                       VERT_TagBase+ (0x00010000)
VERT_Position               0
COORFLOAT position[3];   position of vertex at the indicated key-frame

VERT_Velocity               1
COORFLOAT velocity[3];   velocity of vertex at the indicated key-frame

-----------------------------------------------------------------------------

                       SPLN_TagBase+ (0x00020000)
SPLN_Basis                  0
UWORD basisnum;          index to basis matrix for cubic spline

SPLN_NURB_Order             1
UWORD order;             order of NURB

SPLN_TrimSurf               2
ULONG trimsurf;          index to surface that this spline trims

SPLN_NURBKnots              3
UWORD num;
FLOAT knots[num];        array of knot values for NURB

SPLN_NURBWeights            4
COORFLOAT
weights[numpts];         array of weights for control points

-----------------------------------------------------------------------------

                       PRIM_PolyTagBase+ (0x00030000)
PRIM_Points                 0
ULONG numpts;
ULONG points[numpts];    array of control point indices
                         (for NURB and bicubic surfaces,

                           numpts = upts*vpts
                           where there are vpts rows of upts indices)


PRIM_PolySmoothing          1
UWORD smoothing;         The smoothing variable describes the type
                         of normal smoothing to use when rendering
                         polygons.
                         The following values are valid:

                         0 - no smoothing
                         1 - Phong normal smoothing

                       PRIM_SurfTagBase+ (0x00031000)
PRIM_SurfBasis              5
UWORD ubasis, vbasis;    basis index for u and v direction

PRIM_NURBOrder              1
UWORD uorder, vorder;    order of NURB for both u and v directions

PRIM_Contours               2
UWORD ucon, vcon;        contours for both u and v direction

PRIM_NURBKnots              3
UWORD unum, vnum;
FLOAT uknots[unum];
FLOAT vknots[vnum];      NURB knots for both u and v direction

PRIM_NURBWeights            4
COORFLOAT weights
[numupts*numvpts];       array of weights for control points

PRIM_TextureSpace           5
FLOAT umin, vmin,
      umax, vmax;        Mapping limits in texture space


                       PRIM_PrimTagBase+ (0x00032000)
PRIM_RectangularSolid       0
                         orientation/size/position determined by parent
                         hierarchy

PRIM_Ellipsoid              1
                         orientation/size/position determined by parent
                         hierarchy

PRIM_Prism                  2
ULONG hierindex;         extrusion of any contour by a specified length
                         index to hierarchy containing the contour and
                         parent hierarchy determines the size

PRIM_SurfaceRevolution      3
UWORD axis;              0 - X,   1 - �,   2 - Z
FLOAT anglerev;          a contour spun around a specific axis

PRIM_SemiInfiniteSpace      4
COORFLOAT
vec1[3], vec2[3];        a plane whose normal (right hand rule)
                         defines the direction in which the
                         space extends

PRIM_RiSphere               5
COORFLOAT radius;
COORFLOAT zmin, zmax;
FLOAT thetamax;          sphere primitive ala RenderMan

PRIM_RiCone                 6
COORFLOAT radius;
COORFLOAT height;
FLOAT thetamax;          cone primitive ala RenderMan

PRIM_RiDisk                 7
COORFLOAT radius;
COORFLOAT height;
FLOAT thetamax;          disk primitive ala RenderMan

PRIM_RiCylinder             8
COORFLOAT radius;
COORFLOAT zmin, zmax;
FLOAT thetamax;          cylinder primitive ala RenderMan

PRIM_Hyperboloid            9
COORFLOAT point1[3],
          point2[3];
FLOAT thetamax;          hyperboloid primitive ala RenderMan

PRIM_RiParaboloid          10
COORFLOAT radiusmax;
COORFLOAT zmin, zmax;
FLOAT thetamax;          cylinder primitive ala RenderMan

PRIM_RiTorus               11
COORFLOAT majorrad, minorrad;
COORFLOAT phimin, phimax;
FLOAT thetamax;          cylinder primitive ala RenderMan


			for details of the RenderMan primitives above,
                        consult pp. 62-63 of the RenderMan Companion by
                        Steve Upstill (Publisher: Addison Wesley)

-----------------------------------------------------------------------------

                       HIER_TagBase+ (0x00040000)
HIER_Type                   0
ULONG type;             type of hierarchy
                        Currently, the following types are supported:

                           Type  Label          Description
                           ----  -----          -----------

                            0    HT_EMPT�       empty

                            1    HT_PATH        path

                            2    HT_OBJECT      object defined using vertices

                            4    HT_CSGOBJECT   object defined using PRIMitives

                            5    HT_LAMP        lamp and possibly objects
                                                (for compatibility with existing software)

                            6    HT_CUSTOM      custom object (type name supplied with tag)

                           10    HT_S�SOBJECTS  objects for internal use only

HIER_CustomTypeName         1
UWORD namelen;
UB�TE name[namelen];   name of custom hierarchy type (not null terminated)



HIER_HierStatus             2
ULONG status;           status of hierarchy

                        Label       Value       Description
                        -----       -----       -----------

                                    0x00800000  reserved for future use
                                        to
                                    0x00010000

                        HEEDGES     0x00008000  draw object during operation

                        HEEXTENT    0x00004000  draw extent during operation

                        HNEDGES     0x00002000  draw object when refreshing

                        HNEXTENT    0x00001000  draw extent when refreshing

                                    0x00000800  reserved for future use
                                        to
                                    0x00000080

                        HUNION      0x00000040  object Boolean OR

                        HINTERSECT  0x00000020  object Boolean AND

                        HSUB        0x00000010  object subtract

                        HOFF        0x00000008  object/hierarchy is off
                                                in editor
                        HTPEDIT     0x00000004  object surface trim curve
                                                points are editable
                        HEDIT       0x00000002  object surface control
                                                points are editable
                        HSELECT     0x00000001  object is selected



HIER_BoundingBox            3
FLOAT low[3], high[3];  bounding box of hierarchy

HIER_LampType               4
UWORD lamptype;         lamp type/behaviour
                           0 - directional light source
                           1 - point source (inverse square law)
                           2 - conical light source
                           3 - cylindrical light source
                           4 - area light source


HIER_Size                   5
COORFLOAT size[3];      size of axes

HIER_Shear                  6
COORFLOAT shear[6];     size of shear components
                           0 - X-axis �-component
                           1 - X-axis Z-component
                           2 - �-axis X-component
                           3 - �-axis Z-component
                           4 - Z-axis X-component
                           5 - Z-axis �-component

HIER_LocalOrigin            7
COORFLOAT locorig[3];   position wrt. parent's space

HIER_Velocity               8
COORFLOAT velocity[3];  velocity wrt. parent's space

HIER_Axes                   9
COORFLOAT axes[3][3];   normalized axes
                           row 0 - X axis
                           row 1 - � axis
                           row 2 - Z axis

HIER_�PRAngles             10
FLOAT yprang[3];        angles for yaw, pitch and roll

HIER_X�ZAngles             11
FLOAT xyzang[3];        angles for X, � and Z-axis rotations
                        in this order

HIER_Translate             12
COORFLOAT trans[3];     translate last local origin using this vector

HIER_Rel�PRAngles          13
FLOAT yprang[3];        relative angles for yaw, pitch and roll
                        from last key-frame

HIER_RelX�ZAngles          14
FLOAT xyzang[3];        relative angles for X, � and Z-axis rotations
                        in this order from last key-frame

-----------------------------------------------------------------------------

                       OBSV_TagBase+ (0x00050000)
OBSV_ObserverHierarchy      0
ULONG  index;           index to observer hierarchy

OBSV_TargetHierarchy        1
ULONG  index;           index to target hierarchy

OBSV_Observer               2
COORFLOAT Observer[3];  location of observer/camera

OBSV_Target                 3
COORFLOAT Target[3];    location of target

OBSV_Distance               4
COORFLOAT Distance[3];  distance to focal plane

OBSV_Orientation            5
FLOAT yprang[3];        angles for yaw, pitch and roll of camera

OBSV_Tilt                   6
FLOAT tilt;             tilt angle of camera

OBSV_FieldofView            7
FLOAT separation;       separation (for stereo)

OBSV_RecordingMedium        8
FLOAT recwidth,
      recheight;        width/height of recording medium ie.
                        35mm film, CCD, etc.

OBSV_FocalLength            9
FLOAT FocalLength;      focal length of lens : mm

OBSV_Aperture              10
FLOAT aperture;         size of aperture in mm

OBSV_StopNumber            11
FLOAT stopnum;          stop number

OBSV_ShutterSpeed          12
FLOAT shutspeed;        shutter speed

OBSV_Separation            13
FLOAT separation;       view separation (for stereoscopic views)

-----------------------------------------------------------------------------

                       DISP_TagBase+ (0x00060000)
DISP_WindowParms            0
WORD left, top,
      width, height;    parameters of windows in virtual screen coordinates

DISP_ViewStatus             1
ULONG viewstatus;       status of display
                           Label          Value
                           -----          -----
                           VOLUMERENDER   0x00000800  volume rendering
                           RADIOSIT�      0x00000400  radiosity
                           RA�TRACE       0x00000200  raytracing
                           PHONGSHADE     0x00000100  Phong shading
                           GORAUDSHADE    0x00000080  Goraud shading
                           SOLIDMODEL     0x00000040  solid shading
                           HIDDENLINE     0x00000020  hidden line removal
                           WIREFRAME      0x00000010  wireframe
                           ZBUFFER        0x00000008  z-buffer
                           SCANLINE       0x00000004  scanline
                           XSPECS         0x00000002  stereo with XSPECS
                                                      (interlaced)
                           PERSPECT       0x00000001  perspective on


DISP_FrameRate              2
FLOAT framerate;        framerate in display


-----------------------------------------------------------------------------

                       BACK_TagBase+ (0x00070000)
BACK_GroundTexture          0
ULONG texindex;         index to ground texture

BACK_SkyTexture             1
ULONG texindex;         index to sky texture

BACK_EnviroTexture          2
ULONG texindex;         index to environment texture

-----------------------------------------------------------------------------

->Light Characteristics<-
                       ATTR_LightTagBase+ (0x00080000)

ATTR_ColourSize             0
UWORD cols;             number of colour components for attribute

ATTR_Diffuse                1
ATTFLOAT
diffuse[cols];          diffuse colour components

ATTR_Reflect                2
ATTFLOAT
reflect[cols];          reflected colour components

ATTR_Transmit               3
ATTFLOAT
transmit[cols];         transmitted colour components

ATTR_Ambient                4
ATTFLOAT
ambient [cols];         ambient colour components

ATTR_Illumin                5
ATTFLOAT
illumin [cols];         illuminated colour components

ATTR_Opacity                6
ATTFLOAT opacity;       illuminated colour components

ATTR_IndexRefract           7
FLOAT indexref[cols];   indices or refraction for each colour components


 7-14    reserved for future light characteristics


->Highlight Parameters<-

                       ATTR_HighlightTagBase+ (0x00081000)

ATTR_SpecHighLight          0
ATTFLOAT
specularpercent,
roughness;              parameters for specular highlights

ATTR_PhongHighLight         1
ATTFLOAT
phongpercent,
phongsize;              parameters for Phong highlights

ATTR_HighlightColour        2
ATTFLOAT
highlight[cols];        highlight colour components


18-19    reserved for future highlight types


->Lamp Attributes<-

                       ATTR_LampTagBase+ (0x00082000)

ATTR_LightIntensity         0
ATTFLOAT intensity;     intensity of light source

ATTR_LightDirection         1
COORFLOAT dir[3];       direction of light source

ATTR_ConeLight              2
FLOAT coneangle,
      conedeltaangle,
      beamdistrib;      parameters for conic light source

ATTR_AreaLight              3
UWORD width, height;    sample grid size for area light source


24-30   reserved for future lamp characteristics


->Environmental Attributes<-

                       ATTR_EnviroTagBase+ (0x00083000)

ATTR_Fog                   31
ATTFLOAT col[cols];     fog parameters
FLOAT mindist;          distance to start fog and fog colours

ATTR_DepthCue              32
ATTFLOAT col[cols];     depth cue parameters
FLOAT mindist;
FLOAT maxdist;          min. and max. distance over which depth cueing
                        will occur

ATTR_EnvironIllumin        33
ATTFLOAT illum[cols];   ambient illumination color components

ATTR_EnvIndexRefract       34
FLOAT index;            index of refraction of the environment


35-50  reserved for future environment attributes


-----------------------------------------------------------------------------

                       TXTR_TagBase+ (0x00090000)


TXTR_Default                0
ULONG attindex;         index to default attribute serve as a base attribute
                        to provide defaults to values not modified by
                        additional texture tags

TXTR_RenderType             1
ULONG rendertype;       tags following this one will define textures for
                        the specified type of rendering

                        The following are valid rendertypes:

                           TXTR_SOLIDSHADING    0x00000001
                           TXTR_GORAUDSHADING   0x00000002
                           TXTR_PHONGSHADING    0x00000004
                           TXTR_ZBUFFER         0x00000008
                           TXTR_RA�TRACING      0x00000010
                           TXTR_RADIOSIT�       0x00000020
                           TXTR_VOLUMESHADING   0x00000040

TXTR_Space                  2
UWORD size;            the size of texture space

TXTR_BoundingBox            3
COORFLOAT low[size],
         high[size];   bounding box of n-dimensional texture space

TXTR_Center                 4
COORFLOAT cen[size];   limits of n-dimensional texture space

TXTR_BitMap                 5
UWORD namelen;
UB�TE name[namelen];   (not null terminated)
UWORD channel;         bitmap texture


                       TXTR_AttribTagBase+ (0x00091000)


TXTR_Checker                0
COORFLOAT scale[size];
ULONG att[2];          checker texture

TXTR_Gradient               1
ULONG att[size*2];     gradient texture

TXTR_Brick                  2
COORFLOAT mortscale;   thickness of mortar
COORFLOAT scale[size]; size of brick
ULONG attindex[2];     brick texture

TXTR_Wood                   3
float ringscale;
ULONG lightcolour,     indices to attributes for light-coloured wood,
      darkcolour;      dark-coloured wood and base attributes

                       TXTR_NormalTagBase+ (0x00092000)


TXTR_Wave                   0
BOOL displacement;
FLOAT phase,amplitude,
   wavelength,damping; wave normal mapping

TXTR_BumpMap                1
FLOAT minheight,
      maxheight;       bump map texture
                       (requires TXTR_BitMap tag to precede it)

--------------------------------------------------------------------------

                       SURF-X_TagBase+ (0x000A0000)
reserved for SurF-X program-specific tags

                       xxxxxx_TagBase+ (0x000B0000)-(0xFFFF0000)
reserved for other program-specific tags or tags for new chunks added to
this spec in the future

these sections can include private tags designed for internal use such
as cutting and pasting.  tags that are general enough for all programs
should go in one of the chunk sections if appropriate
</pre>