Unigine.SplineGraph Class
This class is used to manage vertices and segments of spline graphs. UNIGINE's 3D spline system has a wide range of applications, particularly procedural content generation (rivers, roads, pipelines etc.).
A spline graph is determined by a set of points p0, p 1, ... p n and a set of segments (cubic Bezier splines), that connect some or all of these points.
Each segment is determined by the indices of the starting (pSTART ) and ending (pEND ) points and tangent vector coordinates at these points, which determine the form of the segment (tSTART and tEND respectively).
Coordinates of the "up" vector are additionally stored for each point of the segment. You can specify this vector to define orientation of geometry or objects, that can be stretched or tiled along the segments of the spline graph. By default this vector is parallel to the Z axis. The "up" vector does not affect the form of the spline segment.
It is possible to obtain an interpolated value for any point belonging to a segment, this can be used for various purposes (e.g. to change road profile). Interpolated "up" vector can be calculated as follows (pseudocode):
Source code (C++)
vec3 lerpUpVector(vec3 start_up, vec3 end_up, float t) const
{
float angle = acos(dot(start_up, end_up)) * RAD2DEG;
vec3 rotation_axis = cross(start_up, end_up);
return rotateAxisAngle(rotation_axis, angle * t) * start_up;
}See Also#
-
The UnigineScript API sample <UnigineSDK>/data/samples/worlds/spline_graph_00. It illustrates:
- Creation of a SplineGraph from scratch
- Movement of a node along the segments of the SplineGraph
- The C++ API sample <UnigineSDK>/source/samples/Api/Nodes/SplineGraph
- The WorldSplineGraph class article to learn how to generate geometry along a spline graph
- The Spline File Format article to learn how the spline graph data is stored
SplineGraph Class
Properties
int NumSegments#
The total number of segments in the spline graph.
int NumPoints#
The total number of points in the spline graph.
Members
SplineGraph ( ) #
Default constructor. Creates an empty spline graph.SplineGraph ( string name ) #
Constructor. Creates an empty spline graph with a given name.Arguments
- string name - Spline graph name.
SplineGraph ( SplineGraph graph ) #
Constructor. Creates a spline graph by copying a given source spline graph.Arguments
- SplineGraph graph - Source spline graph.
float GetLength ( int index ) #
Returns the length of the segment with a given index.Arguments
- int index - Segment index.
Return value
Segment length.void SetPoint ( int index, vec3 point ) #
Sets new coordinates for the point with a given index.Arguments
- int index - Point index.
- vec3 point - New point coordinates.
vec3 GetPoint ( int index ) #
Returns the coordinates of the point with a given index.Arguments
- int index - Point index.
Return value
Point coordinates.void SetSegmentEndPoint ( int index, vec3 point ) #
Sets the coordinates of the end point for the segment with a given index.Arguments
- int index - Segment index.
- vec3 point - Segment end point coordinates to be set.
vec3 GetSegmentEndPoint ( int index ) #
Returns the coordinates of the end point for the segment with a given index.Arguments
- int index - Segment index.
Return value
Segment end point coordinates.int GetSegmentEndPointIndex ( int index ) #
Returns the index of the end point for the segment with a given index.Arguments
- int index - Segment index.
Return value
Segment end point index.void SetSegmentEndTangent ( int index, vec3 tangent ) #
Sets the tangent coordinates for the end point of the segment with a given index.Arguments
- int index - Segment index.
- vec3 tangent - End point tangent coordinates.
vec3 GetSegmentEndTangent ( int index ) #
Returns the tangent coordinates for the end point of the segment with a given index.Arguments
- int index - Segment index.
Return value
End point tangent coordinates.void SetSegmentEndUpVector ( int index, vec3 up ) #
Sets the "up" vector coordinates for the end point of the segment with a given index.Arguments
- int index - Segment index.
- vec3 up - End point "up" vector coordinates.
vec3 GetSegmentEndUpVector ( int index ) #
Returns the "up" vector coordinates for the end point of the segment with a given index.Arguments
- int index - Segment index.
Return value
End point "up" vector coordinates.void SetSegmentStartPoint ( int index, vec3 point ) #
Sets the coordinates of the start point for the segment with a given index.Arguments
- int index - Segment index.
- vec3 point - Segment start point coordinates to be set.
vec3 GetSegmentStartPoint ( int index ) #
Returns the coordinates of the start point for the segment with a given index.Arguments
- int index - Segment index.
Return value
Segment start point coordinates.int GetSegmentStartPointIndex ( int index ) #
Returns the index of the end point for the segment with a given index.Arguments
- int index - Segment index.
Return value
Segment start point index.void SetSegmentStartTangent ( int index, vec3 tangent ) #
Sets the tangent coordinates for the start point of the segment with a given index.Arguments
- int index - Segment index.
- vec3 tangent - Start point tangent coordinates.
vec3 GetSegmentStartTangent ( int index ) #
Returns the tangent coordinates for the start point of the segment with a given index.Arguments
- int index - Segment index.
Return value
Start point tangent coordinates.void SetSegmentStartUpVector ( int index, vec3 up ) #
Sets the "up" vector coordinates for the start point of the segment with a given index.Arguments
- int index - Segment index.
- vec3 up - Start point "up" vector coordinates.
vec3 GetSegmentStartUpVector ( int index ) #
Returns the "up" vector coordinates for the start point of the segment with a given index.Arguments
- int index - Segment index.
Return value
Start point "up" vector coordinates.int AddPoint ( vec3 point ) #
Adds a point with specified coordinates to the spline graph.Arguments
- vec3 point - Point coordinates.
Return value
Current number of points in the spline graph.int AddSegment ( int start_index, vec3 start_tangent, vec3 start_up, int end_index, vec3 end_tangent, vec3 end_up ) #
Adds a segment to the spline graph.Arguments
- int start_index - Start point index.
- vec3 start_tangent - Start point tangent coordinates.
- vec3 start_up - Start point "up" vector coordinates.
- int end_index - End point index.
- vec3 end_tangent - End point tangent coordinates.
- vec3 end_up - End point "up" vector coordinates.
Return value
Number of segments in the spline graph if a segment was adds successfully; otherwise, -1vec3 CalcSegmentPoint ( int index, float t ) #
Returns the coordinates of the point at the parametrically specified position on the segment (along the T axis).
Arguments
- int index - Segment index.
- float t - Position of the point on the segment, specified parametrically along the T (times axis) in the [0.0f, 1.0f] range.
Return value
Coordinates of the point on the given segment.vec3 CalcSegmentTangent ( int index, float t ) #
Returns the tangent coordinates for the point at the parametrically specified position on the segment (along the T axis).
Arguments
- int index - Segment index.
- float t - Position of the point on the segment, specified parametrically along the T (times axis) in the [0.0f, 1.0f] range.
Return value
Tangent coordinates for the point on the given segment.vec3 CalcSegmentUpVector ( int index, float t ) #
Returns the "up" vector coordinates for the point at the parametrically specified position on the segment (along the T axis).
Arguments
- int index - Segment index.
- float t - Position of the point on the segment, specified parametrically along the T (times axis) in the [0.0f, 1.0f] range.
Return value
"Up" vector coordinates for the point on the given segment.void Clear ( ) #
Clears the spline graph.bool Load ( string name ) #
Loads the spline graph from the specified XML-file.Arguments
- string name - Name of the XML-file to load the spline graph from.
Return value
true if the spline graph was successfully loaded; otherwise, false.void RemovePoint ( int index, bool merge = 0 ) #
Removes a point with a given index from the spline graph.Arguments
- int index - Point index.
- bool merge - Merge flag. When there are two segments attached to the point, use true to merge these segments into one; false removes all segments attached to the point (by default).
void SplitPoint ( int index ) #
Splits the point with the specified index into N points, where N is the number of segments attached to the point. The number of points in the graph shall increase by N-1. All new points will be attached to the corresponding segments.Arguments
- int index - Point index.
void WeldPoints ( int[] indices ) #
Merges all points with given indices into one.Notice
All common segments between these points shall be removed. All points with given indices are removed from the graph, except for the one having the minimum index value, all segments shall be attached to this point. Resulting point shall be moved to the position of the first point in the given array.
Arguments
- int[] indices - Array containing indices of points to be merged into one.
void RemoveSegment ( int index, bool with_points = 0 ) #
Removes the segment with a given index.Arguments
- int index - Segment index.
- bool with_points - Use true to remove segment with its starting and ending points, or false to remove the segment only.
NoticePoints will be removed only in case if they do not belong to other segments. After removal, the last element of the vector of spline graph segments shall be moved to the position of the one removed.
bool Save ( string name ) #
Saves the spline graph to the specified XML-file.Arguments
- string name - Name of the XML-file to save the spline graph to.
Return value
true if the spline graph was successfully saved; otherwise, false.void InsertPointToSegment ( int segment_index, float new_point_t ) #
Inserts a new point into the given segment. The point is parametrically specified on the T (times axis) in the [0.0f, 1.0f] range from the segment's start point.
Arguments
- int segment_index - Segment index.
- float new_point_t - Coordinate of the new point to be added along the horizontal T (times) axis in the range [0.0f, 1.0f].
void GetPointSegmentsIndices ( int index, int[] indices ) #
Retrieves indices of all segments attached to the specified point and puts them to the given index buffer.Arguments
- int index - Point index.
- int[] indices - Index buffer to which segment indices will be added.
Last update:
2022-12-14
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