Add terrain brush core and geometry implementations

src/core/terrain-brush.ts

@@ -0,0 +1,91 @@
+import type { Terrain } from "../document/terrains";
+
+export type TerrainBrushTool = "raise" | "lower" | "smooth" | "flatten";
+
+export interface TerrainBrushSettings {
+  radius: number;
+  strength: number;
+  falloff: number;
+}
+
+export interface ArmedTerrainBrushState extends TerrainBrushSettings {
+  terrainId: string;
+  tool: TerrainBrushTool;
+}
+
+export interface TerrainBrushStrokeCommit {
+  terrain: Terrain;
+  commandLabel: string;
+  tool: TerrainBrushTool;
+}
+
+export const DEFAULT_TERRAIN_BRUSH_RADIUS = 2;
+export const DEFAULT_TERRAIN_BRUSH_STRENGTH = 0.35;
+export const DEFAULT_TERRAIN_BRUSH_FALLOFF = 0.6;
+export const MIN_TERRAIN_BRUSH_RADIUS = 0.25;
+export const MAX_TERRAIN_BRUSH_RADIUS = 12;
+export const MIN_TERRAIN_BRUSH_STRENGTH = 0.05;
+export const MAX_TERRAIN_BRUSH_STRENGTH = 1;
+export const MIN_TERRAIN_BRUSH_FALLOFF = 0;
+export const MAX_TERRAIN_BRUSH_FALLOFF = 1;
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(max, Math.max(min, value));
+}
+
+export function clampTerrainBrushRadius(radius: number): number {
+  if (!Number.isFinite(radius)) {
+    return DEFAULT_TERRAIN_BRUSH_RADIUS;
+  }
+
+  return clamp(radius, MIN_TERRAIN_BRUSH_RADIUS, MAX_TERRAIN_BRUSH_RADIUS);
+}
+
+export function clampTerrainBrushStrength(strength: number): number {
+  if (!Number.isFinite(strength)) {
+    return DEFAULT_TERRAIN_BRUSH_STRENGTH;
+  }
+
+  return clamp(
+    strength,
+    MIN_TERRAIN_BRUSH_STRENGTH,
+    MAX_TERRAIN_BRUSH_STRENGTH
+  );
+}
+
+export function clampTerrainBrushFalloff(falloff: number): number {
+  if (!Number.isFinite(falloff)) {
+    return DEFAULT_TERRAIN_BRUSH_FALLOFF;
+  }
+
+  return clamp(
+    falloff,
+    MIN_TERRAIN_BRUSH_FALLOFF,
+    MAX_TERRAIN_BRUSH_FALLOFF
+  );
+}
+
+export function createDefaultTerrainBrushSettings(): TerrainBrushSettings {
+  return {
+    radius: DEFAULT_TERRAIN_BRUSH_RADIUS,
+    strength: DEFAULT_TERRAIN_BRUSH_STRENGTH,
+    falloff: DEFAULT_TERRAIN_BRUSH_FALLOFF
+  };
+}
+
+export function getTerrainBrushToolLabel(tool: TerrainBrushTool): string {
+  switch (tool) {
+    case "raise":
+      return "Raise";
+    case "lower":
+      return "Lower";
+    case "smooth":
+      return "Smooth";
+    case "flatten":
+      return "Flatten";
+  }
+}
+
+export function getTerrainBrushCommandLabel(tool: TerrainBrushTool): string {
+  return `${getTerrainBrushToolLabel(tool)} terrain`;
+}