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OB3D IFF 3-D Object Format

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OB3D

                   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