[Cyan]<Imaging>Gargoyle>GGLines.mesa!8

GGLines.mesa

Author: Eric Bier on June 4, 1985 4:58:33 pm PDT

Last edited by Bier on October 1, 1985 5:31:09 pm PDT

Contents: Routines for finding the intersections of various types of lines and line segments

DIRECTORY

GGModelTypes;

GGLines: CEDAR DEFINITIONS =

BEGIN

Point: TYPE = GGModelTypes.Point;

Edge: TYPE = GGModelTypes.Edge;

Line: TYPE = GGModelTypes.Line;

Ray: TYPE = GGModelTypes.Ray;

Vector: TYPE = GGModelTypes.Vector;

Lines

CreateEmptyLine: PROC RETURNS [line: Line];

CopyLine: PROC [from: Line, to: Line];

Since lines are fairly large data structures, you may prefer to allocate one with CreateEmptyLine and repeatedly fill it with new data instead of allocating a new one each time.

FillLineFromPoints: PROC [v1, v2: Point, line: Line];

FillLineFromPointAndVector: PROC [pt: Point, vec: Vector, line: Line];

FillLineFromCoefficients: PROC [sineOfTheta, cosineOfTheta, distance: REAL, line: Line];

FillLineFromPointAndAngle: PROC [pt: Point, degrees: REAL, line: Line];

FillLineAsNormal: PROC [line: Line, pt: Point, normalLine: Line];

FillLineLeftOfLine: PROC [line: Line, dist: REAL, parallelLine: Line];

FillLineRightOfLine: PROC [line: Line, dist: REAL, parallelLine: Line];

This procedures allocate a new Line.

LineFromPoints: PROC [v1, v2: Point] RETURNS [line: Line];

LineFromPointAndVector: PROC [pt: Point, vec: Vector] RETURNS [line: Line];

LineFromCoefficients: PROC [sineOfTheta, cosineOfTheta, distance: REAL] RETURNS [line: Line];

LineFromPointAndAngle: PROC [pt: Point, degrees: REAL] RETURNS [line: Line];

LineNormalToLineThruPoint: PROC [line: Line, pt: Point] RETURNS [normalLine: Line];

LineLeftOfLine: PROC [line: Line, dist: REAL] RETURNS [parallelLine: Line];

LineRightOfLine: PROC [line: Line, dist: REAL] RETURNS [parallelLine: Line];

LineMeetsLine: PROC [line1, line2: Line] RETURNS [intersection: Point, parallel: BOOL];

LineMeetsYAxis: PROC [line: Line] RETURNS [yInt: REAL, parallel: BOOL];

LineMeetsEdge: PROC [line: Line, edge: Edge] RETURNS [intersection: Point, noHit: BOOL];

SignedLineDistance: PROC [pt: Point, line: Line] RETURNS [d: REAL];

LineDistance: PROC [pt: Point, line: Line] RETURNS [d: REAL];

PointProjectedOntoLine: PROC [pt: Point, line: Line] RETURNS [projectedPt: Point];

We drop a normal from the point onto the line and find where it hits

the line equation of the normal we drop can be found as in FillLineAsNormal above.

PointOnLine: PROC [line: Line] RETURNS [pt: Point];

Finds any old point on line and returns it.

DirectionOfLine: PROC [line: Line] RETURNS [direction: Vector];

Returns the direction vector of line.

Edges

CreateEdge: PROC [v1, v2: Point] RETURNS [edge: Edge];

CreateEmptyEdge: PROC RETURNS [edge: Edge];

FillEdge: PROC [v1, v2: Point, edge: Edge];

CopyEdge: PROC [from: Edge, to: Edge];

LinePointOnEdge: PROC [pt: Point, edge: Edge] RETURNS [BOOL];

Assumes pt is on edge.line. Is it on edge?

NearestEndpoint: PROC [pt: Point, edge: Edge] RETURNS [endpoint: Point];

DistanceSquaredToNearestEndpoint: PUBLIC PROC [pt: Point, edge: Edge] RETURNS [distanceSquared: REAL];

NearestPointOnEdge: PROC [pt: Point, edge: Edge] RETURNS [onEdge: Point];

Faster than DistancePointToPoint[pt, NearestEndpoint[pt, edge]] (if you don't care what the endpoint is).

DistancePointToEdge: PROC [pt: Point, edge: Edge] RETURNS [distance: REAL];

Perpendicular distance if possible, else distance to nearest endpoint.

DistanceSquaredPointToEdge: PROC [pt: Point, edge: Edge] RETURNS [distanceSquared: REAL];

Points

DistancePointToPoint: PROC [p1, p2: Point] RETURNS [distance: REAL];

DistanceSquaredPointToPoint: PROC [p1, p2: Point] RETURNS [distance: REAL];

PointLeftOfLine: PROC [distance: REAL, pOnLine: Point, line: Line] RETURNS [point: Point];

RAYS -- Used by GGShapes to draw infinite lines (e.g. to do manual clipping)

CreateRay: PROC [basePoint: Point, direction: Vector] RETURNS [ray: Ray];

CreateRayFromPoints: PROC [p1, p2: Point] RETURNS [ray: Ray];

LineRayMeetsBox: PROC [ray: Ray, xmin, ymin, xmax, ymax: REAL] RETURNS [count: NAT, params: ARRAY[1..2] OF REAL];

EvalRay: PROC [ray: Ray, param: REAL] RETURNS [point: Point];

END.