Improve via graph topology: exclusive via regions, T-intersection detection, filler region routing, ripcost to via regions

fixtures/via-graph-solver/via-graph-solver01.fixture.tsx

@@ -1,8 +1,8 @@
 import { GenericSolverDebugger } from "@tscircuit/solver-utils/react"
+import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 import { ViaGraphSolver } from "lib/ViaGraphSolver/ViaGraphSolver"
 import { createViaGraphWithConnections } from "lib/ViaGraphSolver/via-graph-generator/createViaGraphWithConnections"
 import { generateViaTopologyRegions } from "lib/ViaGraphSolver/via-graph-generator/generateViaTopologyRegions"
-import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 
 const baseGraph = generateViaTopologyRegions(viaTile, {
   graphSize: 5,

fixtures/via-graph-solver/via-graph-solver02.fixture.tsx

@@ -1,8 +1,8 @@
 import { GenericSolverDebugger } from "@tscircuit/solver-utils/react"
+import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 import { ViaGraphSolver } from "lib/ViaGraphSolver/ViaGraphSolver"
 import { createViaGraphWithConnections } from "lib/ViaGraphSolver/via-graph-generator/createViaGraphWithConnections"
 import { generateViaTopologyRegions } from "lib/ViaGraphSolver/via-graph-generator/generateViaTopologyRegions"
-import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 
 const baseGraph = generateViaTopologyRegions(viaTile, {
   graphSize: 5,

fixtures/via-graph-solver/via-graph-solver03.fixture.tsx

@@ -1,8 +1,8 @@
 import { GenericSolverDebugger } from "@tscircuit/solver-utils/react"
+import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 import { ViaGraphSolver } from "lib/ViaGraphSolver/ViaGraphSolver"
 import { createViaGraphWithConnections } from "lib/ViaGraphSolver/via-graph-generator/createViaGraphWithConnections"
 import { generateViaTopologyRegions } from "lib/ViaGraphSolver/via-graph-generator/generateViaTopologyRegions"
-import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 
 const baseGraph = generateViaTopologyRegions(viaTile, {
   graphSize: 5,

fixtures/via-graph-solver/via-graph-solver04.fixture.tsx

@@ -1,8 +1,8 @@
 import { GenericSolverDebugger } from "@tscircuit/solver-utils/react"
+import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 import { ViaGraphSolver } from "lib/ViaGraphSolver/ViaGraphSolver"
 import { createViaGraphWithConnections } from "lib/ViaGraphSolver/via-graph-generator/createViaGraphWithConnections"
 import { generateViaTopologyRegions } from "lib/ViaGraphSolver/via-graph-generator/generateViaTopologyRegions"
-import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 
 const baseGraph = generateViaTopologyRegions(viaTile, {
   graphSize: 5,

fixtures/via-graph-solver/via-graph-solver05.fixture.tsx

@@ -1,4 +1,5 @@
 import { GenericSolverDebugger } from "@tscircuit/solver-utils/react"
+import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 import { createConnectionPort } from "lib/JumperGraphSolver/jumper-graph-generator/createConnectionPort"
 import { createConnectionRegion } from "lib/JumperGraphSolver/jumper-graph-generator/createConnectionRegion"
 import type {
@@ -11,7 +12,6 @@ import type { ViaByNet, ViaTile } from "lib/ViaGraphSolver/ViaGraphSolver"
 import { ViaGraphSolver } from "lib/ViaGraphSolver/ViaGraphSolver"
 import { findBoundaryRegionForPolygons } from "lib/ViaGraphSolver/via-graph-generator/findBoundaryRegionForPolygons"
 import { generateViaTopologyRegions } from "lib/ViaGraphSolver/via-graph-generator/generateViaTopologyRegions"
-import viaTile from "assets/ViaGraphSolver/via-tile-4-regions.json"
 
 // ── Configuration ──────────────────────────────────────────────────────
 const TILE_SIZE = 5
@@ -462,11 +462,11 @@ for (const xyConn of connections) {
   allRegions.push(endRegion)
 
   // Find the nearest boundary region for each endpoint
-  const startBoundary = findBoundaryRegionForPolygons(
-    start.x,
-    start.y,
-    allRegions,
-  )
+  const startBoundary = findBoundaryRegionForPolygons({
+    x: start.x,
+    y: start.y,
+    regions: allRegions,
+  })
   if (startBoundary) {
     const startPort = createConnectionPort(
       `conn:${connectionId}:start-port`,
@@ -477,7 +477,11 @@ for (const xyConn of connections) {
     allPorts.push(startPort)
   }
 
-  const endBoundary = findBoundaryRegionForPolygons(end.x, end.y, allRegions)
+  const endBoundary = findBoundaryRegionForPolygons({
+    x: end.x,
+    y: end.y,
+    regions: allRegions,
+  })
   if (endBoundary) {
     const endPort = createConnectionPort(
       `conn:${connectionId}:end-port`,

lib/ViaGraphSolver/ViaGraphSolver.ts

@@ -184,6 +184,25 @@ export class ViaGraphSolver extends HyperGraphSolver<JRegion, JPort> {
     return crossings * this.crossingPenalty + crossings * this.crossingPenaltySq
   }
 
+  override isRipRequiredForPortUsage(
+    region: JRegion,
+    _port1: JPort,
+    _port2: JPort,
+  ): boolean {
+    // Via regions are exclusive - if the region has any assignment from a
+    // different connection, using it requires ripping. This ensures the solver
+    // properly considers via region exclusivity during pathfinding.
+    if (region.d.isViaRegion) {
+      const assignments = region.assignments ?? []
+      return assignments.some(
+        (a) =>
+          a.connection.mutuallyConnectedNetworkId !==
+          this.currentConnection!.mutuallyConnectedNetworkId,
+      )
+    }
+    return false
+  }
+
   override getRipsRequiredForPortUsage(
     region: JRegion,
     port1: JPort,

lib/ViaGraphSolver/polygonPerimeterUtils.ts

@@ -12,6 +12,7 @@ type Point = { x: number; y: number }
 /**
  * Check if two 2D line segments intersect (excluding shared endpoints).
  * Uses the cross product method for robust intersection detection.
+ * Also detects T-intersections where one segment's endpoint lies on the other segment.
  */
 function lineSegmentsIntersect(
   p1: Point,
@@ -42,11 +43,55 @@ function lineSegmentsIntersect(
   const d3 = cross(p1, p2, p3)
   const d4 = cross(p1, p2, p4)
 
-  // Check if segments straddle each other
+  // Check if segments straddle each other (proper crossing)
   if (d1 * d2 < 0 && d3 * d4 < 0) {
     return true
   }
 
+  // Check for T-intersections: one segment's endpoint lies ON the other segment
+  // This happens when one cross product is ~0 and the point is within segment bounds
+  const pointOnSegment = (
+    point: Point,
+    segStart: Point,
+    segEnd: Point,
+    crossProduct: number,
+  ) => {
+    if (Math.abs(crossProduct) > eps) return false
+    // Point is on the line, check if it's within segment bounds
+    const minX = Math.min(segStart.x, segEnd.x) - eps
+    const maxX = Math.max(segStart.x, segEnd.x) + eps
+    const minY = Math.min(segStart.y, segEnd.y) - eps
+    const maxY = Math.max(segStart.y, segEnd.y) + eps
+    return (
+      point.x >= minX && point.x <= maxX && point.y >= minY && point.y <= maxY
+    )
+  }
+
+  // Check if p1 or p2 lies on segment p3-p4 (but not at endpoints, already checked)
+  if (pointOnSegment(p1, p3, p4, d1)) {
+    // p1 is on segment p3-p4, check it's not at the endpoints
+    if (!pointsCoincident(p1, p3) && !pointsCoincident(p1, p4)) {
+      return true
+    }
+  }
+  if (pointOnSegment(p2, p3, p4, d2)) {
+    if (!pointsCoincident(p2, p3) && !pointsCoincident(p2, p4)) {
+      return true
+    }
+  }
+
+  // Check if p3 or p4 lies on segment p1-p2 (but not at endpoints)
+  if (pointOnSegment(p3, p1, p2, d3)) {
+    if (!pointsCoincident(p3, p1) && !pointsCoincident(p3, p2)) {
+      return true
+    }
+  }
+  if (pointOnSegment(p4, p1, p2, d4)) {
+    if (!pointsCoincident(p4, p1) && !pointsCoincident(p4, p2)) {
+      return true
+    }
+  }
+
   return false
 }
 

lib/ViaGraphSolver/via-graph-generator/createConvexViaGraphFromXYConnections.ts

@@ -95,6 +95,8 @@ export function createConvexViaGraphFromXYConnections(
   const baseGraph: JumperGraph = { regions, ports }
 
   // Add connections to the graph
+  // Note: findBoundaryRegionForPolygons auto-detects convex topology by checking
+  // for filler regions and only connects to them (avoiding tiny isolated convex regions)
   const graphWithConnections = createViaGraphWithConnections(
     baseGraph,
     xyConnections,

lib/ViaGraphSolver/via-graph-generator/createViaGraphWithConnections.ts

@@ -46,11 +46,11 @@ export const createViaGraphWithConnections = (
     )
     regions.push(endRegion)
 
-    const startBoundary = findBoundaryRegionForPolygons(
-      start.x,
-      start.y,
-      baseGraph.regions,
-    )
+    const startBoundary = findBoundaryRegionForPolygons({
+      x: start.x,
+      y: start.y,
+      regions: baseGraph.regions,
+    })
     if (startBoundary) {
       const startPort = createConnectionPort(
         `conn:${connectionId}:start-port`,
@@ -61,11 +61,11 @@ export const createViaGraphWithConnections = (
       ports.push(startPort)
     }
 
-    const endBoundary = findBoundaryRegionForPolygons(
-      end.x,
-      end.y,
-      baseGraph.regions,
-    )
+    const endBoundary = findBoundaryRegionForPolygons({
+      x: end.x,
+      y: end.y,
+      regions: baseGraph.regions,
+    })
     if (endBoundary) {
       const endPort = createConnectionPort(
         `conn:${connectionId}:end-port`,

lib/ViaGraphSolver/via-graph-generator/findBoundaryRegionForPolygons.ts

@@ -49,12 +49,20 @@ function closestPointOnPolygonEdge(
  *
  * Only considers non-pad, non-throughJumper, non-connectionRegion regions
  * that have polygon data.
+ *
+ * For convex topologies (detected by presence of filler regions), only
+ * connects to filler regions to avoid isolated tiny convex regions inside
+ * the tile grid.
  */
-export const findBoundaryRegionForPolygons = (
-  x: number,
-  y: number,
-  regions: JRegion[],
-): BoundaryRegionResult | null => {
+export const findBoundaryRegionForPolygons = (params: {
+  x: number
+  y: number
+  regions: JRegion[]
+}): BoundaryRegionResult | null => {
+  const { x, y, regions } = params
+  // Check if this is a convex topology by looking for filler regions
+  const hasFillerRegions = regions.some((r) => r.regionId.startsWith("filler:"))
+
   let closestRegion: JRegion | null = null
   let closestDistance = Infinity
   let closestPortPosition = { x, y }
@@ -67,6 +75,10 @@ export const findBoundaryRegionForPolygons = (
     )
       continue
 
+    // For convex topologies, only connect to filler regions to avoid
+    // isolated tiny convex regions inside the tile grid.
+    if (hasFillerRegions && !region.regionId.startsWith("filler:")) continue
+
     const polygon = region.d.polygon
     if (!polygon || polygon.length < 3) continue