[orx-shapes] Add Box.intersection() and Box.grid()

orx-shapes/src/commonMain/kotlin/primitives/BoxIntersection.kt

@@ -0,0 +1,26 @@
+package org.openrndr.extra.shapes.primitives
+
+import org.openrndr.shape.Box
+import org.openrndr.shape.Rectangle
+import kotlin.math.max
+import kotlin.math.min
+
+/**
+ * Find intersection of [this] and [other]
+ * @return a rectangle shaped intersection or [Rectangle.EMPTY] when the intersection is empty.
+ */
+fun Box.intersection(other: Box) : Box = if (this.intersects(other)) {
+    val tn = this.normalized
+    val on = other.normalized
+
+    val left = max(tn.corner.x, on.corner.x)
+    val right = min(tn.corner.x + tn.width, on.corner.x + on.width)
+    val top = max(tn.corner.y, on.corner.y)
+    val bottom = min(tn.corner.y + tn.height, on.corner.y + on.height)
+    val near = max(tn.corner.z, on.corner.z)
+    val far = min(tn.corner.z + tn.depth, on.corner.z + on.depth)
+
+    Box(left, top, near, right - left, bottom - top, far - near)
+} else {
+    Box.EMPTY
+}