POV-Ray object model

/* These fields are common to all objects. */

#define OBJECT_FIELDS        \
  METHODS *Methods;          \
  int Type;                  \
  OBJECT *Sibling;           \
  TEXTURE *Texture;          \
  TEXTURE *Interior_Texture; \
  INTERIOR *Interior;        \
  OBJECT *Bound;             \
  OBJECT *Clip;              \
  LIGHT_SOURCE *LLights;     \
  BBOX BBox;                 \
  TRANSFORM *Trans;          \
  TRANSFORM *UV_Trans;       \
  SNGL Ph_Density;           \
  unsigned int Flags;

/* These fields are common to all compound objects */

#define COMPOUND_FIELDS \
  OBJECT_FIELDS         \
  OBJECT *Children;

// ...

struct Object_Struct
{
  OBJECT_FIELDS
};

struct Compound_Object_Struct
{
  COMPOUND_FIELDS
};