PEXOCCTMCoordFillAreaSet - Computes a Projection of Texture Coordinates for Fill Area Set Primitives

Synopsis

     int PEXOCCTMCoordFillAreaSet(
            PEXOCC context,
            PEXTMCoordData *tm_coord_data,
            PEXPointer facet_data,
            unsigned int count,
            PEXListOfVertexData *vertex_lists
       )

Arguments

context: An OC context returned by a successful PEXCreateOCC call.
tm_coord_data: A pointer to parameterization data for this primitive. (See Description below)
facet_attributes (OCC): A mask indicating the facet attributes provided (PEXGANone, PEXGAColor, PEXGANormal or PEXGAFloatData).
surface_vertex_attributes (OCC): A mask indicating the vertex attributes provided (PEXGANone, PEXGAColor, PEXGANormal, PEXGAEdges, PEXGA2D or PEXGAFloatData).
color_type (OCC): The type of color data provided (PEXColorTypeIndexed, PEXColorTypeRGB, PEXColorTypeCIE, PEXColorTypeHSV, PEXColorTypeHLS, PEXColorTypeRGB8, PEXColorTypeRGB16, PEXColorTypeRGBA, PEXColorTypeRGBA8 or PEXColorTypeRGBA16).
facet_fp_data_count (OCC): The number of optional floating-point numbers for each facet.
surface_vertex_fp_data_count (OCC): The number of floating-point data values defined with each vertex.
facet_data: A pointer to the facet data. See Data Formats.
count: The number of fill areas in the set.
vertex_lists: A pointer to the list of vertex arrays defining each contour of the fill area set. See Data Formats.
data_model (OCC): Specifies the data model used to represent the geometric data.
data_model_specs (OCC): Offset and size data for the PEXDataStride or PEXDataUnpacked data models.

Returns

Zero if successful; otherwise, one of the following:

PEXBadTMPrimitive: Normals are not valid.
PEXBadValue: Projection type is not valid.
PEXBadValue: Texture coordinate location not valid.
PEXBadAlloc: Internal allocation error has occurred.

Description

Invoke PEXOCCTMCoordFillAreaSet to compute a projection of texture coordinates onto a fill area set and store them in the floating-point data areas of each vertex.

To compute texture coordinates, the following values in the tm_coord_data structure must be supplied by the client:

projection: Texture coordinate projection to perform (PEXTMProjectionSphereWC, PEXTMProjectionCylinderWC, or PEXTMProjectionLinearWC).
matrix: If projection is either PEXTMProjectionSphereWC or PEXTMProjectionCylinderWC, this transform is applied to vertices and vertex normals after the mc_transform has been applied. It is used to orient the data relative to the projection object (sphere or cylinder) as described.
p0, p1: If projection is PEXTMProjectionLinearWC, then these elements contain linear projection equations. (See description below.)
coord_source: Source coordinate to compute projections specified with projection type above (PEXTMCoordSourceVertexCoord or PEXTMCoordSourceVertexNormal).
fp_data_index: Index within the vertex floating-point data list in which to store the calculated texture coordinates. Space must already exist in the vertex floating-point data list and the index must point to a valid location. The projection generates a data list of two consecutive floating-point numbers.
mc_transform: This transform is applied to vertices and vertex normals in model coordinates prior to computing the specified projection.

Additionally, for the given projections, the following information must be provided. For projections listed below, those which require a unit direction vector (s0,s1,s2) shall have one determined by the coordinate source selection previously mentioned. If you select PEXTMCoordSourceVertexCoord, then a ray is computed from the WC origin through the vertex to the interior of the projection object. If you select PEXTMCoordSourceVertexNormal, then the primitive's vertex normals (given or implicit) are used to determine the direction. The resulting values (t0,t1) are the texture coordinates stored at the requested index.

PEXTMProjectionSphereWC

The infinite sphere has (0,0,0) as its origin and the +y axis as its axis of revolution. The texture seam sweeps from the +x axis in a counter-clockwise direction [0..2PI]. Given the specified coordinate source, a direction vector (s0,s1,s2) is computed to determine a point on the interior of the sphere. The resulting texture coordinates (t0,t1) are stored in the vertex's floating-point data list.

   t0 = (s0 == 0.0) ? ((s2 > 0) ? 0.75 : 0.25) :
             (-arctan(s2/s0) / (2 * PI) +
             ((s0 < 0) ? 0.5 : (s0 > 0 && s2 > 0) ? 1 : 0)
         )
 
   t1 = arcsin(s1) / PI + 0.5
 
   -PI/2 <= arctan(r) <= PI/2
 
   -PI/2 <= arcsin(r) <= PI/2
 
  Where (s0*s0 + s1*s1 + s2*s2) = 1

PEXTMProjectionCylinderWC

The infinite cylinder has (0,0,0) as its origin and the +y axis as its axis of revolution. The texture seam sweeps from the +x axis in a counter-clockwise direction [0..2PI]. Given coordinate sources which are directional (normal or -reflection), a direction vector (s0,s1,s2) is computed to determine a point on the interior of the cylinder. If the coordinate source is vertex coord, a ray perpendicular to the +y axis through the vertex is computed to determine a point and its height on the interior of the cylinder. The resulting texture coordinates (t0,t1) are stored in the vertex's floating-point data list.

   t0 = (s0 == 0.0) ? ((s2 > 0) ? 0.75 : 0.25) :
        (-arctan(s2/s0) / (2 * PI) +
        ((s0 < 0) ? 0.5 : (s0 > 0 && s2 > 0) ? 1 : 0)
        )
 
    if (coord_source == normal)
      t1 = arcsin(s1) / PI + 0.5
    else
      t1 = y_coord
 
    -PI/2 <= arctan(r) <= PI/2
 
    -PI/2 <= arcsin(r) <= PI/2
 
    Where (s0*s0 + s1*s1 + s2*s2) = 1

PEXExtTMProjectionLinearWC

Arguments for two linear equations are defined as p0 and p1. Given the specified coordinate source, the values are used directly as (s0,s1,s2) to linearly project the values by the equations listed below. The resulting texture coordinates (t0,t1) are stored in the vertex's floating-point data list. (where s3 is assumed to be one as shown in the equations below.)

 
     t0 = s0 * p0[0] + s1 * p0[1] + s2 * p0[2] + 1 * p0[3]
 
     t1 = s0 * p1[0] + s1 * p1[1] + s2 * p1[2] + 1 * p1[3]
 
  The projection of anything other than vertices for this option produces unpredictable visual results.

It is assumed that the vertex list of the specified primitive has sufficient space to insert the needed texture coordinates. If space (indicated by PEXGAFloatData) or valid indices for texture coordinates do not exist, then the implementation issues an error and the data remains unchanged.

Errors