Orbiting around point

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#1

I have a mesh at the (0, 0, 0) and camera further away looking At that point. I want to rotate camera around the mesh, however it does not always work as expected. When camera is facing mesh from the front moving mouse up/down on X axis rotates around the mesh as expected:

However if i look at mesh from the side then moving mouse up/down on X axis rotates around mesh as if rotation was in mesh local space:

This is how i attempt rotation:

camera_->GetNode()->RotateAround(Vector3::ZERO, Quaternion(
    input->GetMouseMoveY() * 0.1f * lookSensitivity_,
    input->GetMouseMoveX() * 0.1f * lookSensitivity_, 0
), TS_WORLD);

Any idea how i could make it rotate so that moving mouse on X axis would make camera go up/down same way like it works when looking at model from the front?

#2

Hey here is something that I started coding just last night for my own purposes, sorry it’s in C#:

class CameraOrbitComponent : Component
    {
        public float _verticalTheta { get; set; } = 0f;
        public float _horizontalTheta { get; set; } = 0f;

        public Node _targetNode { get; set; }

        public Node _cameraNode { get; set; }

        public CameraOrbitComponent()
        {
            ReceiveSceneUpdates = true;
        }

        protected override void OnUpdate(float timeStep)
        {
            Vector3 targetPos = _targetNode.WorldPosition;
            Vector3 heading = targetPos - _cameraNode.WorldPosition;
            float radius = heading.Length;
            
            float moveSpeed = 10.0f;
            if (this.Application.Input.GetKeyDown(Key.A)) _horizontalTheta -= moveSpeed;
            if (this.Application.Input.GetKeyDown(Key.D)) _horizontalTheta += moveSpeed;

            _cameraNode.LookAt(_targetNode.Position, Vector3.Up);
            _cameraNode.Rotation = new Quaternion(_cameraNode.Rotation.PitchAngle, _cameraNode.Rotation.YawAngle, 0f);

            _cameraNode.Position = new Vector3(radius * (float)Math.Cos(_horizontalTheta), _cameraNode.Position.Y, radius * (float)Math.Sin(_horizontalTheta));
        }
    }
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#3

I use RotateAround for Quatter’s camera with pre-multiplied Quaternions:

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#4

Your solution is so much better :slight_smile: - I will be stea… umm, learn from it thank you very much.

#5

@Modanung that has issue similar to gimbal lock. Besides what exactly is a rotation? A delta rotation? Absolute rotation of some kind?

#6

I suppose, yaw&pitch angles. And nobody usualy cares about gimbal lock for cameras unless you truly need three degrees of freedom.

#7

I am doing model viewer app. It gets really awkward when trying to look at the head of character if there is gimbal lock.

@Modanung thanks for that snipped, it led to a successful solution:

camera_->GetNode()->RotateAround(Vector3::ZERO,
    Quaternion(input->GetMouseMoveX() * lookSensitivity_, camera_->GetNode()->GetUp()) * 
    Quaternion(input->GetMouseMoveY() * lookSensitivity_, camera_->GetNode()->GetRight()),
    TS_WORLD
);
2 Likes