PerspectiveCamera: New helper methods getFrustumBounds(), getFrustumSize().

docs/api/en/cameras/PerspectiveCamera.html

@@ -118,6 +118,26 @@ <h2>Methods</h2>
 		<h3>[method:undefined clearViewOffset]()</h3>
 		<p>Removes any offset set by the [page:PerspectiveCamera.setViewOffset .setViewOffset] method.</p>
 
+		<h3>[method:Object frustumCorners]( [param:Float distance] )</h3>
+		<p>
+			Provides positions of the camera's frustum corners at a given distance from the camera.
+			Returns an object with topLeft, topRight, bottomRight, and bottomLeft properties where each property is a
+			[page:Vector3].
+		</p>
+
+		<h3>[method:Vector2 frustumDimensions]( [param:Float distance] )</h3>
+		<p>
+			Calculates the height and width of the camera's frustum at a given distance from the camera.
+			Returns a [page:Vector2] where x is width and y is height.
+		</p>
+
+		<h3>[method:undefined getBounds]( [param:Float distance], [param:Vector2 minTarget], [param:Vector2 maxTarget] )
+		</h3>
+		<p>
+			Calculates the XY of the min/max bounds for the camera's viewable rectangle at a given distance.
+			Results are copied into minTarget and maxTarget input vars.
+		</p>
+
 		<h3>[method:Float getEffectiveFOV]()</h3>
 		<p>Returns the current vertical field of view angle in degrees considering .zoom.</p>
 
@@ -214,6 +234,5 @@ <h2>Source</h2>
 		<p>
 			[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]
 		</p>
-
 	</body>
-</html>
+</html>

src/cameras/PerspectiveCamera.js

@@ -1,5 +1,14 @@
 import { Camera } from './Camera.js';
 import * as MathUtils from '../math/MathUtils.js';
+import { Vector2 } from '../math/Vector2.js';
+import { Vector3 } from '../math/Vector3.js';
+
+// Temp constants used by getBounds(), frustumDimensions(), and frustumCorners()
+const _tempV3 = /*@__PURE__*/ new Vector3();
+const _minTarget = /*@__PURE__*/ new Vector2();
+const _maxTarget = /*@__PURE__*/ new Vector2();
+const _dimensions = /*@__PURE__*/ new Vector2();
+
 
 class PerspectiveCamera extends Camera {
 
@@ -99,6 +108,59 @@ class PerspectiveCamera extends Camera {
 
 	}
 
+	/*
+	 * Provides the topRight and bottomLeft corners of the camera's 2D frustum slice at a given distance.
+	 * Results are copied into minTarget and maxTarget input vars.
+	 */
+	getBounds( distance, minTarget, maxTarget ) {
+
+		_tempV3.set( - 1, - 1, 0.5 ).applyMatrix4( this.projectionMatrixInverse );
+		_tempV3.multiplyScalar( distance / Math.abs( _tempV3.z ) );
+		minTarget.x = _tempV3.x;
+		minTarget.y = _tempV3.y;
+
+		_tempV3.set( 1, 1, 0.5 ).applyMatrix4( this.projectionMatrixInverse );
+		_tempV3.multiplyScalar( distance / Math.abs( _tempV3.z ) );
+		maxTarget.x = _tempV3.x;
+		maxTarget.y = _tempV3.y;
+
+	}
+
+	/*
+	 * Calculates the height/width of the camera's frustum at a given distance.
+	 * returns a Vector2 where x is width and y is height.
+	 */
+	frustumDimensions( distance ) {
+
+		this.getBounds( distance, _minTarget, _maxTarget );
+		_dimensions.x = _maxTarget.x - _minTarget.x;
+		_dimensions.y = _maxTarget.y - _minTarget.y;
+
+		return _dimensions.clone();
+
+	}
+
+	/*
+	 * Calculates Vector3s of the frustum's corners at a given distance from the camera.
+	 * Returns an object with topLeft, topRight, bottomRight, and bottomLeft properties. Each property is a Vector3.
+	 */
+	frustumCorners( distance ) {
+
+		this.getBounds( distance, _minTarget, _maxTarget );
+
+		this.updateMatrixWorld( true, false );
+
+		// .set() -> Calculates the corner position
+		// .applyMatrix4() -> Accounts for camera position/rotation/scale
+		return {
+			topLeft: _tempV3.set( _minTarget.x, _maxTarget.y, - distance ).applyMatrix4( this.matrixWorld ).clone(),
+			topRight: _tempV3.set( _maxTarget.x, _maxTarget.y, - distance ).applyMatrix4( this.matrixWorld ).clone(),
+			bottomRight: _tempV3.set( _maxTarget.x, _minTarget.y, - distance ).applyMatrix4( this.matrixWorld ).clone(),
+			bottomLeft: _tempV3.set( _minTarget.x, _minTarget.y, - distance ).applyMatrix4( this.matrixWorld ).clone(),
+		};
+
+	}
+
 	/**
 	 * Sets an offset in a larger frustum. This is useful for multi-window or
 	 * multi-monitor/multi-machine setups.