/* Last edited on 2025-01-01 15:10:17 by stolfi */

/* ---------------------------------------------------------------------- */
/* pst_geom.{h,c} */

typedef struct pst_geom_sphere_t /* Parameters of a sphere's image: */
  { r2_t ctr;    /* Center (pixels). */
    double rad;  /* Radius (length of shortest semidiameter). */
    r2_t str;    /* Stretch vector (longest semidiameter minus {rad}). */
  } pst_geom_sphere_t;
  /* A {pst_geom_sphere_t} describes the perspective projection of a
    spherical object. It is assumed that the sphere radius is small
    compared to the camera-to-object distance, so that the perspective
    projection is well approximated by a parallel oblique projection.
    This assumption should be harmless for a small sphere taken at
    typical camera geometries. */

ellipse_crs_t *pst_geom_sphere_new(void);
  /* Allocates a new {ellipse_crs_t} record. All parameters 
    are set to zero. Fails if no mem available. */

ellipse_crs_t *pst_geom_sphere_new(void)
  { ellipse_crs_t *geo = 
      (ellipse_crs_t *)notnull(malloc(sizeof(ellipse_crs_t)), "no mem");
    geo->ctr = (r2_t){{ 0, 0 }};
    geo->rad = 0;
    geo->str = (r2_t){{ 0, 0 }};
    return geo;
  }