Here are the classes, structs, unions and interfaces with brief descriptions:

CAa	Affine interval arithmetics
CAlgebraic	Trivariate polynomials of maximum degree 15
CAnalyticPalette	Procedurally defined palettes
CAnalyticScalarField	A core analytic three-dimensional scalar field
CAnalyticScalarField2	A core analytic two-dimensional scalar field
CAnalyticVectorField	A core analytic three-dimensional vector field
CAnalyticVectorField2	A core analytic two-dimensional vector field
CAnnulus2	An annulus, the region between two concentric circles
CArray	A core three dimensional lattice structure
CArray2	A base two-dimensional array structure
CArray2I	A base two-dimensional array of integers
CArrayIndex	A three dimensional grid structure with an index set for every cell
CArrayIndex2	A two dimensional lattice structure with an index set for every cell
CAxis	A core axis class
CAxis2	A core axis class
CBezierCubicPatch	Cubic Bézier patches
CBezierCurve	Bézier curves
CBezierPatch	Bézier patches of dimension n<16
CBezierQuadricCurve	Piecewise Bézier quadric curves
CBox	An axis aligned box
CBox2	Axis aligned box in the plane
CBoxEmpty	An axis aligned box, same as Box, but hollow
CBoxSet2	A simple set of boxes
CBoxSphere	Axis aligned box sphere
CBubble	Bubbles
CCage	An axis aligned cage
CCamera	A simple camera
CCapsule	A line-swept-sphere
CCapsule2	A line-swept-cricle
CCellularNoise	Procedural noise using Voronoi decomposition of space
CCellularTurbulence2	Fractal Brownian motion from a cellular noise function
CCircle	Circles
CCircle2	Circles in the plane
CCircleArc	Circle arcs in three dimensions
CCircleArc2	Circle arcs in the plane
CClothoid2	Clothoid curves
CColor	Color with alpha channel in RGB space
CColorField	A base two-dimensional field of colors
CComplex	Complex numbers
CCone	Cones defined as truncated cones
CConeSphere	Cone-Spheres, defined as rounded truncated cones
CConvex2	Convex polygons in the plane
CCubic	Cubic polynomials
CCubicCurve	Cubic curves
CCubicCurve2	Cubic curves in the plane
CCubicCurve2Set	Piecewise cubic curves in the plane
CCubicCurveSet	Piecewise cubic curves
CCubicSet	Piecewise cubics
CCuboctahedron	A cuboctahedron is a polyhedron with 8 triangular faces and 6 square faces
CCuboid	Cuboids
CCylinder	A cylinder characterized by its end vertices and radius
CCylinderBox	A box with rounded corners only along the z axis
CDiamond2	A diamond in the plane
CDisc	A disc in three dimensions
CDisc2	A disc in two dimensions
CDiscSet2	A simple set of discs
CDiscSystem	A particle system constrained to an implicit surface
CDiscTile	Poisson tiling
CDla	A base diffusion limited aggregation class
CDla2	A diffusion limited aggregation class
CDodecahedron	A dodecahedron
CDynamicArrayIndex	A three dimensional grid structure with an index set for every cell
CEdenAnisotropicGrowth2	Off-lattice Eden growth with an anisotropic growth probability
CEdenGrowth	Off-lattice Eden growth
CEdenGrowth2	Off-lattice Eden growth
CEllipse2	Axis aligned ellipses
CEllipsoid	Ellipsoids
CExponentialSimplexNoise	Exponential noise functions based on simplex noise
CFrame	Solid transformations
CFrame2	Solid transformations in the plane
CFrameCurve	Piecewize frame curves
CFrameScaled	A transformation defined as the composition of a rotation, a translation and a scale
CFrameScaled2	A transformation defined as the composition of a rotation, a translation and a scale
CGaborNoise	Procedural noise using sparse Gabor convolution
CGenericPalette	Core class for palettes
CGeometricGraph2	A simple geometric graph
CHashing	Hashing functions
CHemiSphere	Hemispheres
CHemiSphereDisc	Hemisphere-disk
CHexagon2	Flat topped hexagon in the plane
CHexagonal	Vertical hexagonal prism
CHexagonAlpha2	Hexagon with arbitrary orientations
CHexagonArray2	A core hexagonal grid
CHsl	Color in HSL space
CIa	Intervals of two reals
CIcosahedron	An icosahedron
CIcosidodecahedron	An icosidodecahedron
CInfiniteArray	Virtual infinite grid
CIRect2	Axis aligned integer rectangle
CIrregularOctogon	Irregular octogon (in the plane)
CKTope	Convex polytopes with fixed normals, also referred to as k-topes
CLab	Color in Lab space
CLens	Lenses with uniform radius
CLens2	Lenses in the plane with uniform radius
CLine	A line defined by two points
CLine2	Lines in the plane
CLinear	Linear polynomials
CMath	Core class implementing some useful functions and constants
CMatrix	This class implements 3² matrix
CMatrix2	This class implements 2² matrix
CMatrix4	This class implements 4² matrix
CMesh	Core triangle mesh class
CMesh2	Planar triangle mesh. ,
CMeshColor	Core triangle mesh class with color support
CMeshStack	A framework for creating an object incrementally
CMeshTopo	Core triangle mesh with indexed neighboring triangles
CNewCone	Cone
CNoise	Perlin noise
CNoise2	Perlin noise
CNoiseTurbulence	Turbulence computed from a modified noise function
CNoiseTurbulence2	Turbulence computed from a modified noise function
CNonic	Nonic polynomials
COctahedron	An axis aligned octahedron
COctic	Octic polynomials
COctogon2	Regular Octogons (in the plane)
COrientedBox	An oriented box
COrientedBox2	An oriented box
CPalette	Palette with array of colors
CParametric	Generic parametric curves
CParametricSurface	Parametric surface patches
CParticleSet	Core particle set
CParticleSet2	Core particle set in the plane
CPentagon2	Flat topped pentagon in the plane
CPhasor	Phasor noise
CPlane	A plane defined by its analytic equation
CPointCurve	Piecewise point curve
CPointCurve2	Piecewise point curve in the plane
CPolygon2	Polygons in the plane
CPolygonal	Polygons
CPolygons2	Set of disjoint polygons
CPolynomial	Polynomials of degree lower than or equal to 11
CPyramid	An axis aligned pyramid
CQuadrangle	Quadrangles
CQuadrangle2	Convex quadrangles in the plane
CQuadric	Quadric polynomials
CQuadricCurve	Quadric curves
CQuadricCurve2	Quadric curves in the plane
CQuadricCurve2Set	Piecewise quadric curves
CQuadricCurveSet	Piecewise quadric curves
CQuadricSurface	Quadric surfaces
CQuartic	Quartic polynomials
CQuaternion	Quaternions
CQuintic	Quintic polynomials
CRandom	This class implements several random number generators wrapped in a single class
CRandomFast	A fast linear congruential random number generator
CRay	A ray characterized by its origin an unit direction vector
CRay2	A ray characterized by its origin an unit direction vector
CRayStep	Core class for stepping along a ray
CRectangles	Rectangles
CRectangles2	Rectangles in the plane
CRevolutionQuadricTube	Surface of revolution with a quadric curve
CRevolutionQuadricVolume2	Symmetry axis of revolution with a quadric curve
CRhombicDodecahedron	A rhombic dodecahedron
CScalarAlpha	A pair of two reals, one defining a value, the other an alpha value
CScalarField	A base three-dimensional field of real values
CScalarField2	A base two-dimensional field of real values
CScalarHexagonField2	A base two-dimensional field of real values on a hexagonal grid
CScalarPoint2	Internal class for sorting points
CScalarPointSlope2	Internal class for sorting points
CScales	Scales defined as the difference between two spheres, not a lens
CSector	Intersection between a cone and a sphere
CSector2	Intersection between a cone and a circle in the plane
CSegment	A segment defined by its end vertices
CSegment2	Segments in the plane
CSegmentSet2	Set of line segments in the plane
CSeptic	Septic (heptic) polynomials
CSextic	Sextic polynomials, also known as hextics
CShuffle	Shuffling algorithms for generation permutation tables
CSimplex	Implicit simplex decomposition of space
CSimplex2	Implicit simplex decomposition of the place
CSimplexNoise	Simplex noise
CSimplexNoise2	Simplex noise in the plane
CSimplexNoise4	Simplex noise functions
CSimplexTurbulence	Fractal Brownian motion from a simplex noise function
CSimplexTurbulence2	Fractal Brownian motion from a simplex noise function
CSlab	A simple slab class
CSmoothBox2	A box domain with a cubic falloff
CSmoothDisc2	A disc domain with a cubic falloff
CSmoothEllipse2	An ellipse with a smooth falloff, resembles a compact scaled Gaussian
CSmoothSegment	A segment skeleton with a quadric or cubic falloff
CSmoothSphere	A sphere domain with a cubic falloff decay
CSmoothVertex	A vertex skeleton with a quadric or cubic falloff
CSmoothVertex2	A vertex skeleton with a cubic falloff
CSphere	Spheres
CSphereSet	A simple set of spheres
CSphereTile	Poisson sphere tiling for importance sampling
CSpheroid	Spheroids are symmetric ellipsoids, i.e., with the same radial coefficients a = b ≠ c
CSun	Position of the sun in the sky
CTaper	Barr's tapering deformation
CTaper2	Tapering deformation performed in a disc
CTetrahedra	A simple tetrahedron
CTorus	A simple torus
CTriangle	Base minimum storage triangle class
CTriangle2	Base minimum storage triangle class in the plane
CTubular	A tube, i.e., a pierced cylinder
CTurbulenceWormNoise	Turbulent worm noise
CTwinDisc2	Twin discs in the plane with uniform radius
CTwist	The twist deformation
CTwist2	The twist deformation in the plane
CVec2I	Point in three dimensions with integer coordinates
CVec3I	Point in three dimensions with integer coordinates
CVector	Vectors in three dimensions
CVector2	Vectors in two dimensions
CVectorField	A base three-dimensional field of Vector values
CVectorField2	A base two-dimensional field of Vector2 values
CVectorSet	A simple set of vectors
CVectorSet2	A simple set of vectors in the plane
CVoroNoise	Procedural noise using Voronoi decomposition of space
CVoxel	A base three-dimensional voxel
CWormNoise	Worm noise
CXyz	Color in XYZ space