Start moving CameraNode and ArCameraNode to Kotlin-math

Author: ThomasGorisse

arsceneview/src/main/java/io/github/sceneview/ar/node/ArCameraNode2.kt

@@ -0,0 +1,65 @@
+package io.github.sceneview.ar.node
+
+import com.google.android.filament.Engine
+import com.google.ar.core.Camera
+import dev.romainguy.kotlin.math.degrees
+import io.github.sceneview.ar.arcore.transform
+import io.github.sceneview.math.toTransform
+import io.github.sceneview.node.CameraNode2
+import kotlin.math.atan
+
+/**
+ * Represents a virtual camera, which determines the perspective through which the scene is viewed.
+ *
+ *
+ * If the camera is part of an [ArSceneView], then the camera automatically tracks the
+ * camera pose from ARCore. Additionally, the following methods will throw [ ] when called:
+ *
+ *
+ *  * [.setParent] - CameraNode's parent cannot be changed, it is always the scene.
+ *  * [.setPosition] - CameraNode's position cannot be changed, it is controlled
+ * by the ARCore camera pose.
+ *  * [.setRotation] - CameraNode's rotation cannot be changed, it is
+ * controlled by the ARCore camera pose.
+ *
+ *
+ *
+ * All other functionality in Node is supported. You can access the position and rotation of the
+ * camera, assign a collision shape to the camera, or add children to the camera. Disabling the
+ * camera turns off rendering.
+ */
+class ArCameraNode2(engine: Engine) : CameraNode2(engine, false) {
+
+    override var verticalFovDegrees: Float
+        get() {
+            val fovRadians = 2.0f * atan(1.0f / projectionTransform.y.x)
+            return degrees(fovRadians)
+        }
+        set(_) {}
+
+    /**
+     * Updates the pose and projection of the camera to match the tracked pose from ARCore.
+     *
+     * Called internally as part of the integration with ARCore, should not be called directly.
+     */
+    fun updateTrackedPose(camera: Camera) {
+        // Update the projection matrix.
+        projectionTransform = FloatArray(16).apply {
+            camera.getProjectionMatrix(
+                this, 0,
+                nearClipPlane, farClipPlane
+            )
+        }.toTransform()
+
+        // Update the view matrix.
+        camera.getViewMatrix(viewMatrix.data, 0)
+
+        // Update the node's transformation properties to match the tracked pose.
+//        if (camera.trackingState == TrackingState.TRACKING) {
+        val cameraTransform = camera.displayOrientedPose.transform
+        if (transform != cameraTransform) {
+            transform = cameraTransform
+        }
+//        }
+    }
+}