SK(3)

NAME
SK - Agar dimensioned 2D sketch

SYNOPSIS

    #include <agar/core.h>
    #include <agar/sk.h>

DESCRIPTION
The Agar SK class implements a general-purpose 2D "sketching" engine with dimensioning and geometrical constraint solving. Sketches define a set of elements and a set of relations between those elements.

Elements are organized in a tree (the same structure is used to described group and leaf nodes). Each element in the graph is associated with a transformation matrix. The major sketch elements are points, lines and arcs, but other types can be added through a class registration interface.

Relations represent geometric constraints affecting points, lines, circles, segments and arcs. The following constraints are implemented:

•   Parallelism
•   Incidence
•   Perpendicularity
•   Tangency
•   Concentricity
•   Colinearity
•   Explicit distance
•   Explicit angle

The SK_View(3) widget is commonly used to display and edit SK objects.

INHERITANCE HIERARCHY
AG_Object(3) -> SK.

INITIALIZATION
SK * SK_New(void *parent, const char *name)

The SK_New() function allocates, initializes, and attaches a SK object.

NODE MANIPULATION
void SK_RegisterClass(SK_NodeOps *ops)

void SK_NodeInit(void *node, const SK_NodeOps *ops, Uint flags)

void * SK_NodeAdd(void *pnode, const SK_NodeOps *ops, Uint flags)

void SK_NodeAttach(void *pnode, void *node)

void SK_NodeDetach(void *pnode, void *node)

The SK_RegisterClass() function registers a new node class, described by the given SK_NodeOps structure.

The SK_NodeInit() function initializes the given SK_Node structure. It is usually invoked from node constructor functions. ops points to the SK_NodeOps structure which contains class information. The flags argument should be 0. The SK_NodeAdd() variant also allocates, initializes and attaches the node to a parent node.

The SK_NodeAttach() and SK_NodeDetach() functions attach/detach a node to/from a given parent.

NODE TRANSFORMATIONS
These functions multiply a node's transformation matrix T with a translation, scaling or rotation matrix. They are only aliases for M_Matrix * functions, except that they accept a pointer to a node instead of a matrix.

void SK_Translatev(SK_Node *node, M_Vector3 v)

void SK_Translate2(SK_Node *node, M_Real x, M_Real y)

void SK_Scalev(SK_Node *node, M_Vector3 v)

void SK_Rotatev(SK_Node *node, M_Real theta, M_Vector3 axis)

void SK_Rotatevd(SK_Node *node, M_Real degrees, M_Vector3 axis)

void SK_GetNodeTransform(void *node, M_Matrix44 *T)

The SK_Translate*() functions multiply T by a 2D translation matrix.

The SK_Scalev() function multiplies T by a 2D scaling matrix.

SK_Rotate*() multiply T by a 2D rotation matrix. Angles are given in radians, except for SK_Rotate*d() variants which accept angular arguments in degrees.

SK_Rotatev() generates a rotation of theta radians around axis. The SK_Rotate*() variants with the "d" suffix accept angles in degrees instead of radians.

The SK_GetNodeTransform() function returns a matrix which is the product of the transformation matrices of the given node and all of its parents.

SEE ALSO
M_Matrix(3), M_Vector(3), SG_Intro(3), SK_View(3)

HISTORY
The SK engine first appeared in Agar 1.6.0.