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.Dd December 21, 2022
.Dt SG 3
.Os Agar 1.7
.Sh NAME
.Nm SG
.Nd Agar-SG 3D scene graph
.Sh SYNOPSIS
.Bd -literal
#include <agar/core.h>
#include <agar/sg.h>
.Ed
.Sh DESCRIPTION
The
.Nm
object is a general-purpose scene-graph, or a collection of nodes (i.e.,
.Xr SG_Node 3
objects) organized in a tree structure.
The
.Ft SG_Node
object is used to describe both "group" nodes and "leaf" nodes.
.Pp
Scene-graphs are usually rendered using the
.Xr SG_View 3
widget (or a subclass of it).
.Sh INHERITANCE HIERARCHY
.Xr AG_Object 3 ->
.Nm .
.Sh INITIALIZATION
.nr nS 1
.Ft "SG *"
.Fn SG_New "void *parent" "const char *name" "Uint flags"
.Pp
.Ft "void"
.Fn SG_Clear "SG *sg"
.Pp
.nr nS 0
The
.Fn SG_New
function allocates, initializes, and attaches a
.Nm
object.
Acceptable
.Fa flags
options include:
.Bl -tag -width "SG_SKIP_UNKNOWN_NODES "
.It SG_OVERLAY_WIREFRAME
Overlay wireframe onto geometric objects when rendering scene.
.It SG_OVERLAY_VERTICES
Overlay vertices onto geometric objects when rendering scene.
.It SG_OVERLAY_VNORMALS
Overlay vertex normals when rendering scene.
.It SG_OVERLAY_FNORMALS
Overlay facet normals when rendering scene.
.It SG_SKIP_UNKNOWN_NODES
When loading the contents of a scene, ignore unknown/unimplemented
elements (otherwise, encountering an unknown node will make the load
operation fail).
.It SG_NO_DEFAULT_NODES
Don't create the default nodes (e.g.,
.Sq Camera0 ,
.Sq Light0 ) .
.El
.Pp
The
.Fn SG_Clear
routine reinitializes
.Fa sg
to an empty scene.
If default nodes (e.g.,
.Sq Camera0 )
are used, they are preserved but their state is reinitialized.
.Sh NODE QUERIES
.nr nS 1
.Ft "SG_Node *"
.Fn SG_SearchNodes "SG_Node *parent" "const char *name"
.Pp
.Ft "void *"
.Fn SG_FindNode "SG *sg" "const char *name"
.Pp
.Ft "int"
.Fn SG_Intersect "SG_Node *node" "M_Geom3 g" "M_GeomSet3 *S"
.Pp
.nr nS 0
The
.Fn SG_SearchNodes
function scans all descendants of
.Fa parent
for a node of the specified name.
The
.Fn SG_FindNode
function searches the entire scene graph
.Fa sg
for a node of the specified name.
On success,
.Fn SG_SearchNodes
and
.Fn SG_FindNode
return a pointer to the matching node.
.Pp
The
.Fn SG_Intersect
function performs an intersection test between the given node and an
arbitrary geometrical object
.Fa g
(see
.Xr M_Geom3 3 ) .
The function returns 1 if the objects intersect, 0 if they don't
intersect, or -1 if the test is not implemented.
If the
.Fa S
argument is non-NULL, the intersections are computed and returned as one
or more geometrical objects, into
.Fa S .
The structure pointed to by
.Fa S
should have been previously initialized with
.Xr M_GEOM_SET_EMPTY 3 .
.Sh SEE ALSO
.Xr sgedit 1 ,
.Xr M_Matrix 3 ,
.Xr M_Plane 3 ,
.Xr M_Real 3 ,
.Xr M_Vector 3 ,
.Xr SG_Intro 3
.Sh HISTORY
The
.Nm
library first appeared in Agar 1.6.0.