Added an example to dynamically alter the scene in each frame

brainrender/video.py

@@ -106,22 +106,41 @@
 
     @not_on_jupyter
     def make_video(
-        self, *args, duration=10, fps=30, render_kwargs={}, **kwargs
+        self,
+        *args,
+        duration=10,
+        fps=30,
+        fix_camera=False,
+        render_kwargs={},
+        **kwargs,
     ):
         """
         Creates a video using user defined parameters
 
-        :param *args: any extra argument to be bassed to `make_frame_func`
-        :param duration: float, duratino of the video in seconds
+        :param *args: any extra argument to be passed to `make_frame_func`
+        :param duration: float, duration of the video in seconds
         :param fps: int, frame rate
-        :param **kwargs: any extra keyword argument to be bassed to `make_frame_func`
+        :param fix_camera: bool, if True the focal point of the camera is set based on the first frame
+        :param **kwargs: any extra keyword argument to be passed to `make_frame_func`
         """
         logger.debug(f"Saving a video {duration}s long ({fps} fps)")
         _off = br.settings.OFFSCREEN
         br.settings.OFFSCREEN = True  # render offscreen
 
         self.scene.render(interactive=False, **render_kwargs)
 
+        if fix_camera:
+            first_frame = self.keyframes.get(0)
+            if not first_frame:
+                logger.error("No keyframes found, can't fix camera")
+
+            # Sets the focal point of the first frame to the centre of mass of the
+            # full root mesh, since this focal point is set subsequent frames will
+            # have the same focal point unless a new camera is defined
+            self.keyframes[0]["camera"][
+                "focal_point"
+            ] = self.scene.root._mesh.center_of_mass()
+
         # cd to folder where the video will be saved
         curdir = os.getcwd()
         os.chdir(self.save_fld)
@@ -317,7 +336,6 @@
         elif frame_number > self.last_keyframe:
             # check if current frame is past the last keyframe
             params = self.keyframes[self.last_keyframe]
-            params["callback"] = None
 
         else:
             # interpolate between two key frames

examples/animation_callback.py

@@ -0,0 +1,39 @@
+from brainrender import Animation, Scene, settings
+from pathlib import Path
+
+settings.SHOW_AXES = False
+
+scene = Scene(atlas_name="allen_mouse_25um")
+
+regions = (
+    "CTX",
+    "HPF",
+    "STR",
+    "CB",
+    "MB",
+    "TH",
+    "HY",
+)
+scene.add_brain_region(*regions, silhouette=True)
+
+
+def slc(scene, framen, totframes):
+    # Get new slicing plane
+    fact = framen / totframes
+    shape_um = scene.atlas.shape_um
+    # Multiply by fact to move the plane, add buffer to go past the brain
+    point = [(shape_um[0] + 500) * fact, shape_um[1] // 2, shape_um[2] // 2]
+    plane = scene.atlas.get_plane(pos=point, norm=(1, 0, 0))
+
+    scene.slice(plane)
+
+
+anim = Animation(
+    scene, Path.cwd(), "brainrender_animation_callback", size=None
+)
+
+# Specify camera pos and zoom at some key frames`
+anim.add_keyframe(0, camera="frontal", zoom=1, callback=slc)
+
+# Make videos
+anim.make_video(duration=5, fps=10, fix_camera=True)