SG_NODE(3)

NAME
SG_Node - Agar-SG base node class

SYNOPSIS

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

DESCRIPTION
SG_Node is the base class for any element of a SG(3) scene. This includes geometrical elements (e.g., SG_Object(3)) as well as non-geometrical elements (e.g., SG_Light(3), SG_Camera(3)).

Nodes are organized in a tree structure, and the position of a SG_Node in relation to its parent is determined by a 4x4 transformation matrix (see M_Matrix(3)).

INHERITANCE HIERARCHY
AG_Object(3) -> SG_Node.

INTERFACE
void SG_RegisterClass(SG_NodeOps *ops)

void SG_NodeInit(void *node, const char *name, const SG_NodeOps *ops, Uint flags)

void * SG_NodeAdd(void *pnode, const char *name, const SG_NodeOps *ops, Uint flags)

void SG_NodeAttach(void *pnode, void *node)

void SG_NodeDetach(void *pnode, void *node)

void SG_NodeDraw(SG *sg, SG_Node *node, SG_View *view)

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

The SG_NodeInit() function initializes the given SG_Node structure. It is usually invoked from node constructor functions. The name argument is a string identifier for the node. ops points to the SG_NodeOps structure which contains class information. The flags argument should be 0. The SG_NodeAdd() variant also allocates, initializes and attaches the node to a parent node.

The SG_NodeAttach() and SG_NodeDetach() functions attach/detach a node to/from a given parent.

The SG_NodeDraw() function is used to render a node to the display. It is normally only invoked from the draw operation of SG_View(3) (or another visualization widget derived from SG_View). SG_NodeDraw() assumes that the node's transformation matrix has already been applied to the current viewing matrix.

NODE TRANSFORMATIONS
The following calls multiply a node's transformation matrix T with a translation, scaling or rotation matrix. Note that the T matrix may also be manipulated directly with the M_Matrix(3) interface.

void SG_Identity(SG_Node *node)

void SG_Translate(SG_Node *node, M_Real x, M_Real y, M_Real z)

void SG_Translatev(SG_Node *node, M_Vector3 v)

void SG_TranslateX(SG_Node *node, M_Real x)

void SG_TranslateY(SG_Node *node, M_Real y)

void SG_TranslateZ(SG_Node *node, M_Real z)

void SG_Scale(SG_Node *node, M_Real s)

void SG_Rotatev(SG_Node *node, M_Real theta, M_Vector3 axis)

void SG_RotateI(SG_Node *node, M_Real theta)

void SG_RotateJ(SG_Node *node, M_Real theta)

void SG_RotateK(SG_Node *node, M_Real theta)

void SG_Rotatevd(SG_Node *node, M_Real degrees, M_Vector3 axis)

void SG_RotateId(SG_Node *node, M_Real degrees)

void SG_RotateJd(SG_Node *node, M_Real degrees)

void SG_RotateKd(SG_Node *node, M_Real degrees)

void SG_GetNodeTransform(void *node, M_Matrix44 *T)

void SG_GetNodeTransformInverse(void *node, M_Matrix44 *T)

M_Vector3 SG_NodePos(SG_Node *node)

M_Vector3 SG_NodeDir(SG_Node *node)

M_Real SG_NodeSize(SG_Node *node)

SG_Identity() sets the transformation matrix of the node to the identity matrix.

The SG_Translate*() functions multiply T by a translation matrix.

The SG_Scale() function multiplies T by a uniform scaling matrix.

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

SG_Rotatev() generates a rotation of theta radians around axis.

Note that most of the preceding functions are trivial wrappers around M_Matrix(3) functions (applied to the transformation matrix T of the node).

The SG_GetNodeTransform() function returns a transformation matrix mapping the node back to world coordinates (i.e., by computing the product of the transformation matrices of the node and its parents). SG_GetNodeTransformInverse() returns the inverse of this matrix.

The SG_NodePos() function returns a vector representing the absolute world coordinates of a node. SG_NodeDir() returns a normalized vector representing the direction of a node with respect to the world Z axis (i.e., the Z axis of the origin node). SG_NodeSize() returns the absolute scaling factor of an object.

STRUCTURE DATA
For the SG_Node object:

Uint flags
    Option flags (see “FLAGS” section).
SG *sg
    Back pointer to parent SG(3) object.
M_Matrix44 T
    Transformation matrix (relative to parent node).

FLAGS
For the SG_Node object:

SG_NODE_SELECTED
    Node is selected (e.g., for edition).

EXAMPLES
See sg/sg_dummy.c in the Agar source distribution for an example node class implementation.

SEE ALSO
M_Matrix(3), M_Real(3), M_Vector(3), SG(3), SG_Intro(3)

HISTORY
The SG_Node node class first appeared in Agar 1.6.0.