Name

peval_view_ori_matrix − Provides for 2D translation and rotation in the xy-plane of the world coordinate system. 

Operating States: PHOP, ∗, ∗, ∗
PHIGS standard function

Syntax

void peval_view_ori_matrix (
  const Ppoint  ∗vrp,        /∗ (I) View reference point, in world
                                    coordinates ∗/
  const Pvec    ∗vup,        /∗ (I) View up vector, in world coordinates ∗/
  Pint          ∗error_ind,  /∗ (O) Error indicator ∗/
  Pmatrix        matrix      /∗ (O) View orientation matrix ∗/
)

Data Structures

typedef struct {
    Pfloat     x;    /∗ x coordinate ∗/
    Pfloat     y;    /∗ y coordinate ∗/
} Ppoint;
typedef struct {
    Pfloat     delta_x;    /∗ delta x value ∗/
    Pfloat     delta_y;    /∗ delta y value ∗/
} Pvec;
typedef Pfloat Pmatrix[3][3];

Description

peval_view_ori_matrix provides for two-dimensional translation and rotation in the xy-plane of the world coordinate system. It returns a two-dimensional (3 x 3) view orientation matrix, which can be passed as input to the pset_view_rep function.  The view orientation matrix in the view representation transforms the PHIGS coordinate system from world coordinate points to view reference coordinate points. 

The specified view reference point is a two-dimensional point that defines a point in world coordinate units, where z is 0.  This point becomes the origin of the view reference coordinate system.  (See Getting Started with DEC PHIGS for information about the view reference coordinate system.) 

The specified view up vector is a two-dimensional vector relative to the view reference point.  It indicates a direction in the world coordinate plane, where z is set to 0 by default.  This direction becomes the v-axis of the view reference coordinate system.  (The n-axis of the view reference coordinate system is parallel to the z-axis of the world coordinate system.  The u-axis of the view reference coordinate system is determined such that the uvn-axes form a right-handed coordinate system.) 

The peval_view_ori_matrix function is a shorthand way of calling peval_view_ori_matrix3, where the following rules apply:
 

•The z-coordinate on the view reference point is 0. 

•The view plane normal is set to [0,0,1]. 

•The z-coordinate of the view up vector is 0. 

•The third row and third column of the resulting 4 x 4 matrix is suppressed. 

The view up vector must have a length greater than 0. 

If the view orientation parameters are consistent and well defined (that is, if they conform to the specified rules and restrictions), a call to this function returns the 3 x 3 view orientation matrix.  Otherwise, a nonzero error indicator is returned. 

See Also

peval_view_map_matrix
pinq_view_facs
pe_inq_ext_view_rep3
pset_view_ind
pset_view_rep