Trapezoid drawing working, triangles still broken...

src/pslg.ts

@@ -28,7 +28,12 @@ export class Point {
     constructor(
         public readonly coordinate: Coordinate,
         public readonly name?: string,
-    ) {}
+    ) {
+        this.coordinate = {
+            x: parseFloat(coordinate.x.toFixed(12)),
+            y: parseFloat(coordinate.y.toFixed(12)),
+        }
+    }
 
     get x() {
         return this.coordinate.x
@@ -49,6 +54,14 @@ export class Point {
         )
     }
 
+    isLeftOf(x: Point) {
+        return this.x < x.x
+    }
+
+    isRightOf(x: Point) {
+        return this.x > x.x
+    }
+
     public static midpoint(a: Point, b: Point): Point {
         const x = (a.x + b.x) / 2
         const y = (a.y + b.y) / 2
@@ -68,6 +81,17 @@ export class Point {
 }
 
 export class Segment {
+    static fromCombinedHorizontals(a: Segment, b: Segment) {
+        const leftmostA = a.getLeftmostPoint()
+        const leftmostB = b.getLeftmostPoint()
+        const rightmostA = a.getRightmostPoint()
+        const rightmostB = b.getRightmostPoint()
+
+        const leftmost = leftmostA.x < leftmostB.x ? leftmostA : leftmostB
+        const rightmost = rightmostA.x > rightmostB.x ? rightmostA : rightmostB
+        return new Segment(leftmost, rightmost)
+    }
+
     constructor(
         public readonly from: Point,
         public readonly to: Point,
@@ -112,6 +136,19 @@ export class Segment {
         return new Segment(this.from.clone(), this.to.clone())
     }
 
+    getOtherPoint(x: Point) {
+        if ( this.from.is(x) ) return this.to
+        return this.from
+    }
+
+    getLeftmostPoint() {
+        return this.from.x < this.to.x ? this.from : this.to
+    }
+
+    getRightmostPoint() {
+        return this.getOtherPoint(this.getLeftmostPoint())
+    }
+
     is(x: Segment) {
         return (
             (
@@ -148,65 +185,70 @@ export class Segment {
         )
     }
 
+    yValueIsWithinRange(y: number, inclusive = true) {
+        if ( inclusive ) {
+            return y >= this.ymin && y <= this.ymax
+        }
+
+        return y > this.ymin && y < this.ymax
+    }
+
+    xValueIsWithinRange(x: number, inclusive = true) {
+        if ( inclusive ) {
+            return x >= this.xmin && x <= this.xmax
+        }
+
+        return x > this.xmin && x < this.xmax
+    }
+
     hasPoint(x: Point) {
-        return !(
+        return (
             this.from.is(x)
             || this.to.is(x)
         )
     }
 
-    getIntersectionWith(x: Segment): Point | undefined {
-        const slope = this.slope
-        const xSlope = x.slope
-
-        if ( slope === xSlope ) return
-
-        const b1 = this.yIntercept
-        const b2 = x.yIntercept
-        const m1 = this.slope
-        const m2 = x.slope
-
-        if ( Math.abs(m1) === 0 && Math.abs(m2) === Infinity ) {
-            if ( x.xmin <= this.xmax && x.xmin >= this.xmin ) {
-                if ( this.ymin <= x.ymax && this.ymin >= x.ymin ) {
-                    return Point.from(x.xmin, this.ymin)
-                }
-            }
-        }
-
-        if ( Math.abs(m1) === Infinity && Math.abs(m2) === 0 ) {
-            if ( this.xmin <= x.xmax && this.xmin >= x.xmin ) {
-                if ( x.ymin <= this.ymax && x.ymin >= this.ymin ) {
-                    return Point.from(this.xmin, x.ymin)
-                }
-            }
-        }
-
-        const intersectX = (b1 - b2) / (m2 - m1)
-        const intersectY = this.getYAtX(intersectX)
-        if ( intersectX <= Math.max(this.from.x, this.to.x) && intersectX >= Math.min(this.from.x, this.to.x) ) {
-            return Point.from(intersectX, intersectY)
-        }
-    }
-
     getIntersectionWithin(x: Segment): Point | undefined {
-        const slope = this.slope
+        const intersection = this.getIntersectionWith(x)
-        const xSlope = x.slope
 
-        // FIXME account for overlapping parallel lines
+        if ( intersection ) {
-        if ( slope === xSlope ) return
+            if ( !this.hasPoint(intersection) && !x.hasPoint(intersection) ) {
-
+                return intersection
-        const b1 = this.yIntercept
-        const b2 = x.yIntercept
-        const m1 = this.slope
-        const m2 = x.slope
-
-        const intersectX = (b1 - b2) / (m2 - m1)
-        const intersectY = this.getYAtX(intersectX)
-        if ( intersectX < Math.max(this.from.x, this.to.x) && intersectX > Math.min(this.from.x, this.to.x) ) {
-            return Point.from(intersectX, intersectY)
             }
         }
+    }
+
+    getIntersectionWith(seg: Segment): Point | undefined {
+        const [x1, y1] = [this.from.x, this.from.y]
+        const [x2, y2] = [this.to.x, this.to.y]
+        const [x3, y3] = [seg.from.x, seg.from.y]
+        const [x4, y4] = [seg.to.x, seg.to.y]
+
+        const x12 = x1 - x2
+        const x34 = x3 - x4
+        const y12 = y1 - y2
+        const y34 = y3 - y4
+
+        const c = x12 * y34 - y12 * x34
+
+        if ( !Math.abs(c) ) {
+            return
+        }
+
+        const a = x1 * y2 - y1 * x2
+        const b = x3 * y4 - y3 * x4
+
+        const x = (a * x34 - b * x12) / c
+        const y = (a * y34 - b * y12) / c
+
+        const point = Point.from(x, y)
+        if (
+            this.xValueIsWithinRange(point.x)
+            && seg.xValueIsWithinRange(point.x)
+            && this.yValueIsWithinRange(point.y)
+            && seg.yValueIsWithinRange(point.y)
+        ) return point
+    }
 
     getLength(): number {
         return Math.sqrt(
@@ -268,6 +310,10 @@ export class Segment {
     get ymax() {
         return Math.max(this.from.y, this.to.y)
     }
+
+    toQuickDisplay() {
+        return [this.from.coordinate, this.to.coordinate]
+    }
 }
 
 export class Circle {
@@ -706,6 +752,10 @@ export class Graph {
         })
     }
 
+    getSegmentsEndingAt(point: Point): Segment[] {
+        return this.segments.filter(segment => segment.hasPoint(point))
+    }
+
     removeSegment(x: Segment) {
         this.segments = this.segments.filter(segment => !segment.is(x))
     }

src/trapezoidTriangulation.ts

@@ -55,72 +55,72 @@ export function triangulate(originalGraph: Graph): Graph {
     // For each vertex in the original graph, create a horizontal line that
     // extends in both directions until it intersects with either (1) the boundary
     // or (2) a segment in the graph.
-    for ( const point of graph.points ) {
+    const originalPoints = [...graph.points]
+    for ( const point of originalPoints ) {
         if ( boundary.isBoundaryPoint(point) ) continue  // skip boundary points
 
-        // Create the segment extending out to the left boundary
+        // First, check if there is a horizontal segment ending at this point
-        const leftPoint = Point.from(leftBound.from.x, point.y)
+        // extending toward the left
-        let leftSegment = new Segment(point, leftPoint)
+        const hasLeftHorizon = graph.getSegmentsEndingAt(point)
+            .some(segment => segment.isHorizontal() && segment.getOtherPoint(point).isLeftOf(point))
 
-        // Get segments that intersect with this
+        let leftmostPoint: Point = point
-        const leftIntersectingSegments = (graph.segments
+        let rightmostPoint: Point = point
-            .map(segment => {
+        let leftIntersectionRay: Segment
-                if ( boundary.isBoundarySegment(segment) ) {
+        let rightIntersectionRay: Segment
-                    // Exclude boundary segments
+
-                    return undefined
+        if ( !hasLeftHorizon ) {
+            const leftRaySegment = new Segment(point, Point.from(boundary.getLeftBoundary().xmin, point.y))
+            const [leftIntersectingSegment, leftIntersectingPoint] = getFirstIntersectingSegmentInDirection(
+                leftRaySegment,
+                boundary,
+                graph,
+                GraphDirection.LEFT
+            )
+
+            leftmostPoint = leftIntersectingPoint
+            leftIntersectionRay = leftIntersectingSegment
         }
 
-                return {
+        // First, check if there is a horizontal segment ending at this point
-                    segment,
+        // extending toward the left
-                    intersect: segment.getIntersectionWithin(leftSegment),
+        const hasRightHorizon = graph.getSegmentsEndingAt(point)
+            .some(segment => segment.isHorizontal() && segment.getOtherPoint(point).isRightOf(point))
+
+        if ( !hasRightHorizon ) {
+            const rightRaySegment = new Segment(point, Point.from(boundary.getRightBoundary().xmin, point.y))
+            const [rightIntersectingSegment, rightIntersectingPoint] = getFirstIntersectingSegmentInDirection(
+                rightRaySegment,
+                boundary,
+                graph,
+                GraphDirection.RIGHT
+            )
+
+            rightmostPoint = rightIntersectingPoint
+            rightIntersectionRay = rightIntersectingSegment
         }
-            })
+
-            .filter(group => group && group.intersect) as Array<{segment: Segment, intersect: Point}>)
+        if ( !leftmostPoint.is(rightmostPoint) ) {
-            .sort((a, b) => {
+            // Check if this point has a line segment extending from both sides.
-                return b.intersect.x - a.intersect.x  // Sort by right-most x-value
+            // If so, then the line segment will bisect a captive area to create 2 trapezoids,
+            // so we need to make 2 line segments.
+
+            let hasSegmentBelow = false
+            let hasSegmentAbove = false
+            graph.getSegmentsEndingAt(point)
+                .forEach(segment => {
+                    const otherPoint = segment.getOtherPoint(point)
+                    if ( otherPoint.y > point.y ) hasSegmentAbove = true
+                    if ( otherPoint.y < point.y ) hasSegmentBelow = true
                 })
 
-        // Check if there was a nearer intersecting segment
+            if ( hasSegmentAbove && hasSegmentBelow ) {
-        const firstLeftIntersectingSegment = leftIntersectingSegments?.[0]?.segment
+                trapezoidSegments.push(graph.findExistingSegmentOrAdd(new Segment(leftmostPoint, point)))
-        if ( firstLeftIntersectingSegment ) {
+                trapezoidSegments.push(graph.findExistingSegmentOrAdd(new Segment(rightmostPoint, point)))
-            // Modify the leftSegment to end at the intersection point
+            } else {
-            const leftIntersect = graph.findExistingPointOrAdd(leftIntersectingSegments[0].intersect)
+                trapezoidSegments.push(graph.findExistingSegmentOrAdd(new Segment(leftmostPoint, rightmostPoint)))
-            leftSegment = new Segment(point, leftIntersect)
             }
-
-        // Create the segment extending out to the right boundary
-        const rightPoint = Point.from(rightBound.from.x, point.y)
-        let rightSegment = new Segment(point, rightPoint)
-
-        // Get segments that intersect with this
-        const rightIntersectingSegments = (graph.segments
-            .map(segment => {
-                if ( boundary.isBoundarySegment(segment) ) {
-                    // Exclude boundary segments
-                    return undefined
         }
-
-                return {
-                    segment,
-                    intersect: segment.getIntersectionWithin(rightSegment),
-                }
-            })
-            .filter(group => group && group.intersect) as Array<{segment: Segment, intersect: Point}>)
-            .sort((a, b) => {
-                return a.intersect.x - b.intersect.x  // Sort by left-most x-value
-            })
-
-        // Check if there was a nearer intersecting segment
-        const firstRightIntersectingSegment = rightIntersectingSegments?.[0]?.segment
-        if ( firstRightIntersectingSegment ) {
-            // Modify the leftSegment to end at the intersection point
-            const rightIntersect = graph.findExistingPointOrAdd(rightIntersectingSegments[0].intersect)
-            rightSegment = new Segment(point, rightIntersect)
-        }
-
-        const graphLeftSegment = graph.findExistingSegmentOrAdd(leftSegment)
-        const graphRightSegment = graph.findExistingSegmentOrAdd(rightSegment)
-        trapezoidSegments.push(graphLeftSegment, graphRightSegment)
     }
 
     // Now, go through and identify trapezoids for all the horizontal segments we just added
@@ -154,6 +154,7 @@ export function triangulate(originalGraph: Graph): Graph {
             GraphDirection.LEFT
         )
 
+        console.log('got leftIntersectSegment', leftBoundaryHorizontalSegment.toQuickDisplay(), leftIntersectSegment.toQuickDisplay(), leftIntersectPoint.coordinate)
         leftBoundaryHorizontalSegment = new Segment(verticalMidpoint, leftIntersectPoint)
 
         // Repeat to get the right boundary
@@ -196,21 +197,42 @@ export function triangulate(originalGraph: Graph): Graph {
         // Let's find the segments that make up the trapezoid
         // We will do this by re-creating segments for the four sides of the trapezoid
         // Split the left-side on the intersection point
-        let [leftSegment1, leftSegment2] = leftIntersectSegment.splitAt(leftIntersectPoint)  // This is not right. Needs to be `segment`'s intersect point, not the midpoint intersect point
+        const leftSegmentIntersectPoint = leftIntersectSegment.getIntersectionWith(segment)
+        if ( !leftSegmentIntersectPoint ) {
+            console.log('!leftSegmentIntersectPoint', segment.toQuickDisplay(), leftIntersectSegment.toQuickDisplay())
+            throw new Error('Unable to find trapezoid segment intersection')
+        }
+
+        // TODO Account for the case where we don't need to split the segment.
+        let trapezoidLeftBoundSegment = leftIntersectSegment
+        let leftSegment1: Segment | undefined
+        let leftSegment2: Segment | undefined
+        if ( !leftIntersectSegment.hasPoint(leftSegmentIntersectPoint) ) {
+            let [localLeftSegment1, localLeftSegment2] = leftIntersectSegment.splitAt(leftSegmentIntersectPoint)
             graph.removeSegment(leftIntersectSegment)
-        leftSegment1 = graph.findExistingSegmentOrAdd(leftSegment1)
+            leftSegment1 = graph.findExistingSegmentOrAdd(localLeftSegment1)
-        leftSegment2 = graph.findExistingSegmentOrAdd(leftSegment2)
+            leftSegment2 = graph.findExistingSegmentOrAdd(localLeftSegment2)
 
             // We care about the upper-segment from the split, as that is the bound of our trapezoid
-        const trapezoidLeftBoundSegment = leftSegment1.ymin === leftIntersectPoint.y ? leftSegment1 : leftSegment2
+            trapezoidLeftBoundSegment = leftSegment1.ymin === leftSegmentIntersectPoint.y ? leftSegment1 : leftSegment2
+        }
 
         // Repeat this process for the right-side segment
-        let [rightSegment1, rightSegment2] = rightIntersectSegment.splitAt(rightIntersectPoint)
+        const rightSegmentIntersectPoint = rightIntersectSegment.getIntersectionWith(segment)
-        graph.removeSegment(rightIntersectSegment)
+        if ( !rightSegmentIntersectPoint ) throw new Error('Unable to find trapezoid segment intersection')
-        rightSegment1 = graph.findExistingSegmentOrAdd(rightSegment1)
-        rightSegment2 = graph.findExistingSegmentOrAdd(rightSegment2)
 
-        const trapezoidRightBoundSegment = rightSegment1.ymin === rightBoundaryPoint.y ? leftSegment1 : leftSegment2
+        let trapezoidRightBoundSegment = rightIntersectSegment
+        let rightSegment1: Segment | undefined
+        let rightSegment2: Segment | undefined
+        if ( !rightIntersectSegment.hasPoint(rightSegmentIntersectPoint) ) {
+            let [localRightSegment1, localRightSegment2] = rightIntersectSegment.splitAt(rightSegmentIntersectPoint)
+            graph.removeSegment(rightIntersectSegment)
+            rightSegment1 = graph.findExistingSegmentOrAdd(localRightSegment1)
+            rightSegment2 = graph.findExistingSegmentOrAdd(localRightSegment2)
+
+            // We care about the upper-segment from the split, as that is the bound of our trapezoid
+            trapezoidRightBoundSegment = rightSegment1.ymin === rightSegmentIntersectPoint.y ? rightSegment1 : rightSegment2
+        }
 
         // Now we have all 4 bounding segments. We find the bisector that creates
         // triangles with the largest minimum angle.
@@ -220,25 +242,25 @@ export function triangulate(originalGraph: Graph): Graph {
         const upperRightPoint = graph.findExistingPointOrAdd(Point.from(upperIntersectSegment.xmax, upperIntersectSegment.ymax))
 
         const bottomLeftBisectorSegment = new Segment(lowerLeftPoint, upperRightPoint)
-        // const bottomLeftBisectorUpperTriangle = new Triangle([bottomLeftBisectorSegment, upperIntersectSegment, trapezoidLeftBoundSegment])
+        const bottomLeftBisectorUpperTriangle = new Triangle([bottomLeftBisectorSegment, upperIntersectSegment, trapezoidLeftBoundSegment])
         // const bottomLeftBisectorLowerTriangle = new Triangle([bottomLeftBisectorSegment, segment, trapezoidRightBoundSegment])
         // const bottomLeftBisectorMinAngle = Math.min(bottomLeftBisectorUpperTriangle.getMinimumAngle(), bottomLeftBisectorLowerTriangle.getMinimumAngle())
 
-        const upperLeftPoint = graph.findExistingPointOrAdd(Point.from(upperIntersectSegment.xmin, upperIntersectSegment.ymax))
+        // const upperLeftPoint = graph.findExistingPointOrAdd(Point.from(upperIntersectSegment.xmin, upperIntersectSegment.ymax))
-        const lowerRightPoint = graph.findExistingPointOrAdd(Point.from(segment.xmax, segment.ymin))
+        // const lowerRightPoint = graph.findExistingPointOrAdd(Point.from(segment.xmax, segment.ymin))
-
+        //
         // const topRightBisectorSegment = new Segment(upperLeftPoint, lowerRightPoint)
         // const upperRightBisectorUpperTriangle = new Triangle([topRightBisectorSegment, upperIntersectSegment, trapezoidRightBoundSegment])
         // const upperRightBisectorLowerTriangle = new Triangle([topRightBisectorSegment, trapezoidLeftBoundSegment, segment])
         // const upperRightBisectorMinAngle = Math.min(upperRightBisectorUpperTriangle.getMinimumAngle(), upperRightBisectorLowerTriangle.getMinimumAngle())
-
+        //
         // const optimalBisectorUpperTriangle = upperRightBisectorMinAngle > bottomLeftBisectorMinAngle ? upperRightBisectorUpperTriangle : bottomLeftBisectorUpperTriangle
         // const optimalBisectorLowerTriangle = upperRightBisectorMinAngle > bottomLeftBisectorMinAngle ? upperRightBisectorLowerTriangle : bottomLeftBisectorLowerTriangle
-
+        //
-        // Add the triangles to the graph
+        // // Add the triangles to the graph
         // const upperTriangleSegments = optimalBisectorUpperTriangle.sides.map(side => graph.findExistingSegmentOrAdd(side))
         // graph.findExistingTriangleOrAdd(new Triangle(upperTriangleSegments as [Segment, Segment, Segment]))
-
+        //
         // const lowerTriangleSegments = optimalBisectorLowerTriangle.sides.map(side => graph.findExistingSegmentOrAdd(side))
         // graph.findExistingTriangleOrAdd(new Triangle(lowerTriangleSegments as [Segment, Segment, Segment]))
     }