Camera: Add scene.newCamera. Change Camera.fov_4 to match OpenXR's XrFovf

src/objects/camera.nim

@@ -76,7 +76,7 @@ proc newCamera*(engine: MyouEngine, name: string="camera", scene: Scene = nil,
     ## Create a new Camera object. If you supply `scene` it will be added to that
     ## scene.
     var self = new Camera
-    discard procCall(self.GameObject.initGameObject(engine, name))
+    discard procCall(self.GameObject.initGameObject(engine, name, scene))
     self.otype = TCamera
     self.near_plane = near_plane
     self.far_plane = far_plane
@@ -201,11 +201,12 @@ proc calculate_projection*(self: Camera) =
         left = -right
     else:
         # Custom FoV in each direction, for VR
-        let (t,r,b,l) = self.fov_4.get
+        # (left and bottom are usually negative already)
+        let (l,r,t,b) = self.fov_4.get
         top = near_plane * tan(t)
         right = near_plane * tan(r)
-        bottom = near_plane * tan(-b)
-        left = near_plane * tan(-l)
+        bottom = near_plane * tan(b)
+        left = near_plane * tan(l)
     let np_width = right - left
     let np_height = top - bottom
     left += self.shift.x * np_width

src/scene.nim

@@ -441,6 +441,23 @@ proc new_mesh*(self: Scene, name: string,
     self.engine.new_mesh(name, self, draw_method, common_attributes, layout, 
         skip_upload, vertex_count, vertex_array, index_array, pass)
 
+proc newCamera*(self: Scene, name: string="camera",
+        near_plane: float32 = 0.1,
+        far_plane: float32 = 10000,
+        field_of_view: float32 = toRadians(30),
+        ortho_scale: float32 = 8,
+        aspect_ratio: float32 = 1,
+        cam_type: CameraType = Perspective,
+        sensor_fit: SensorFit = Auto,
+        shift: Vec2 = vec2(),
+    ): Camera =
+    ## Create a new Camera object and add it to the scene.
+    ## If the scene doesn't have an active camera, it will be set as active.
+    result = self.engine.newCamera(name, self, near_plane, far_plane, field_of_view,
+        ortho_scale, aspectRatio, cam_type, sensor_fit, shift)
+    if self.active_camera.isNil:
+        self.set_active_camera result
+
 proc set_active_camera*(self: Scene, camera: Camera) =
     ## Change the active camera of the scene, and if there are no viewports in
     ## the main screen, create one.

src/screen.nim

@@ -106,6 +106,7 @@ proc resize*(self: Screen, width, height: int32, orientation = self.orientation)
 proc add_viewport*(self: Screen, camera: Camera) =
     ## Add a viewport to the screen with a given camera.
     
+    assert camera.scene != nil, "Camera needs to added to a scene first."
     let vp = new Viewport
     vp.camera = camera
     vp.clear_color = true

src/types.nim

@@ -247,6 +247,8 @@ type
     SensorFit* = enum
         Auto, Horizontal, Vertical, Cover, Contain
 
+    CameraFov4* = tuple[left,right,top,bottom: float32]
+
     Camera* = ref object of GameObject
         near_plane*: float32
         far_plane*: float32
@@ -257,7 +259,7 @@ type
         cam_type*: CameraType
         sensor_fit*: SensorFit
         shift*: Vec2
-        fov_4*: Option[tuple[top,right,bottom,left: float32]]
+        fov_4*: Option[CameraFov4]
 
         projection_matrix*: Mat4
         projection_matrix_inverse*: Mat4