Figure 13-1 shows how the geometry-building classes fit into a class hierarchy.

Figure 13-1. Class Hierarchy of Geometry-Building Tools

The class hierarchy of opGeoBuilder and its children mimics the Cosmo3D hierarchy of csGeoSet and its children, which are the classes for vertex-based geometries. The methods in opGeoBuilder manipulate a vertex array developed from a csGeoSet. The methods in its children manipulate objects in the corresponding descendents of csGeoSet by using common functionality in opGeoBuilder.

You can therefore derive a class from opGeoBuilder to build a subclass of csGeoSet; for models, use the classes opTriSetBuilder, opTriFanSetBuilder, and opTriStripSetBuilder.

This chapter discusses

Also, this chapter discusses in more detail opGeoConverter and opColorGenerator, which were briefly mentioned in Chapter 3.

The classes opTriFanner and opTriStripper, which appear in Figure 13-1, were discussed in “Creating OpenGL Connected Primitives”.

The class has the following main methods:

class opGeoConverter
{
opGeoConverter(csGeoSet::NormalBindEnum   nb = csGeoSet::NO_NORMAL,
               csGeoSet::ColorBindEnum    cb = csGeoSet::NO_COLOR,
               csGeoSet::TexCoordBindEnum tb = csGeoSet::NO_TEX_COORD);
opGeoConverter(csGeoSet *g,
               csGeoSet::NormalBindEnum   nb = csGeoSet::NO_NORMAL,
               csGeoSet::ColorBindEnum    cb = csGeoSet::NO_COLOR,
               csGeoSet::TexCoordBindEnum tb = csGeoSet::NO_TEX_COORD);
~opGeoConverter();

void addGeoSet(csGeoSet *g);

void done();

static bool isConvertable(csGeometry *g);

int getNTriangles() const;
opTriangle *getTriangle(int i) const;

int getNVertices() const;

csGeoSet::NormalBindEnum getNBind() const;
csGeoSet::ColorBindEnum getCBind() const;
csGeoSet::TexCoordBindEnum getTBind() const;

csVec3f *getOverallNormal() const;
csVec4f *getOverallColor() const;
csContext::CullFaceEnum getOverallCullFace() const;
void setNormalTolerance(float norm_tol);
float getNormalTolerance() const);
};

The accessor functions retrieve the numbers of triangles and vertices, and the normal, color, and texture bindings of the first csGeoSet included in the hash tables. You can also test whether a given csGeoSet can be converted; that is whether it is a csTriSet, a csTriFanSet, or a csTriStripSet.

Because instances of opGeoConverter maintain tables of hashed attributes, you can reduce memory consumption by destroying opGeoConverters that you no longer need.

The class has the following main methods:

class opColorGenerator
{
public:
opColorGenerator(const csVec4f *color=NULL);
void genOverallColor(const csVec4f *color=NULL);
void genPrimColor();

csGeoSet::ColorBindEnum getCBind() const;
const csVec4f *getOverallColor();
const csVec4f *getPrimColor();
static opColorGenerator* noColors();
};

The class opGeoBuilder provides the common functionality needed by its children to build csGeoSets. You are unlikely to use opGeoBuilder to build a csGeoSet, but rather one of its children, opTriSetBuilder, opTriFanSetBuilder, or opTriStripSetBuilder.

opGeoBuilder is derived from the base class opGeoTool, which provides basic accessor functions used by all geometry building classes, but which you should not use.

class opGeoBuilder : public opGeoTool
{
public:
opGeoBuilder(const opGeoConverter *gc=NULL);
virtual ~opGeoBuilder();

void setColorBind(csGeoSet::ColorBindEnum cBind);
void setNormalBind(csGeoSet::NormalBindEnum nBind);
void setTexCoordBind(csGeoSet::TexCoordBindEnum tBind);

void addVertex(const opVertex *v);

void finishPrim(const csVec4f *color, 
                const csVec3f *normal);
void finishSet( csGeoSet *geoSet, 
                const csVec4f *color, 
                const csVec3f *normal);
};

The class opTriSetBuilder is an opGeoBuilder that provides the necessary tools to build a csTriSet from a set of triangles along with per-triangle attributes, or from the data in an opGeoConverter.

class opTriSetBuilder : public opGeoBuilder
{
public:
opTriSetBuilder(const opGeoConverter *gc=NULL);
virtual ~opTriSetBuilder();

// Add triangle with optional PER_PRIMITIVE
// attribute values.  
void addTriangle( const opTriangle *t, const csVec3f *normal);
void addTriangle( const opTriangle *t, const csVec4f *color=NULL,
                                       const csVec3f *normal=NULL);



// Finish set with option of passing OVERALL attribute values. 
csTriSet *done( const csVec3f *normal);
csTriSet *done( const csVec4f *color=NULL, const csVec3f *normal=NULL);

static csTriSet *convert( const opGeoConverter *gc, 
                  opColorGenerator *cg = opColorGenerator::noColors());
static csTriSet *convert( csGeometry *geom,
                  opColorGenerator *cg = opColorGenerator::noColors());
};

The class opTriFanSetBuilder is an opGeoBuilder that provides the necessary tools to build a csTriFanSet from a set of triangles along with per-triangle attributes or from the data in an opGeoConverter.

class opTriFanSetBuilder : public opGeoBuilder
{
public:
opTriFanSetBuilder(const opGeoConverter *gc=NULL);
virtual ~opTriFanSetBuilder();

// Add triangle with optional PER_PRIMITIVE attribute values.  
void addTriangle(const opTriangle *t, const csVec3f *normal);
void addTriangle(const opTriangle *t, const csVec4f *color=NULL,
                 const csVec3f *normal=NULL);

// Finish fan with option of passing OVERALL attribute values. 
void finishFan(const csVec3f *normal=NULL);
void finishFan(const csVec4f *color,const csVec3f *normal=NULL);

// Finish set with option of passing OVERALL attribute values. 
csTriFanSet *done( const csVec3f *normal);
csTriFanSet *done( const csVec4f *color=NULL, 
                   const csVec3f *normal=NULL);
};

The class opTriStripSetBuilder is an opGeoBuilder that provides the necessary tools to build a csTriStripSet either from a set of triangles along with per-triangle attributes or from the data in an opGeoConverter.