Help with Camera Constraint Not Updating in Blender

Coding Python Support
1

Hi everyone,

I’m facing an issue with a camera constraint in Blender. When I edit a property in a constraint that I added to a camera, the camera’s position doesn’t change immediately.

I’ve tried the following methods to force an update:

bpy.context.view_layer.update()
bpy.ops.wm.redraw_timer(type='DRAW_WIN_SWAP', iterations=100)

However, it seems that the camera position only updates after the script finishes executing, and I need to get the new position before that.

Has anyone encountered this issue or have suggestions on how to force an immediate update of the camera’s position after changing a constraint property?

Here the code:

def setup_camera(camera, spline, n_points):
    # Store the original location and rotation of the camera
    original_location = camera.location.copy()
    original_rotation_euler = camera.rotation_euler.copy()

    # Create a Follow Path constraint if it doesn't exist
    follow_path = camera.constraints.new(type="FOLLOW_PATH")
    follow_path.target = spline
    # follow_path.use_fixed_location = True

    camera.location = [0,0,0]

    frame_duration = n_points

    points = []
    for frame in range(0, n_points):
        # Set the evaluation time for the path
        t = frame / frame_duration  # Normalized time
        follow_path.offset_factor = t * 100
        points.append(camera.location)
        print(f"Frame {frame}: Camera Position: {camera.location}")

    # Restore the original camera configuration
    camera.location = original_location
    camera.rotation_euler = original_rotation_euler

    # Clean up: Remove the Follow Path constraint
    # camera.constraints.remove(follow_path)
    return points

Thanks in advance for your help!

2

  1. If you try to replicate this constraint manually and check camera.location, it never really changes - you need to take value from the object’s matrix, not from object’s location.

  2. You’re using wrong property for the camera factor:
    image

Has anyone encountered this issue or have suggestions on how to force an immediate update of the camera’s position after changing a constraint property?

Matrices doesn’t update automatically after constraint property is changed, you’ll need to update view layer.

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