Direct Camera Control in ProScene

jimthree

Direct Camera Control in ProScene

in Contributed Library Questions • 2 years ago

Hi.

I'm continuing to have a lot of fun working with ProScene, but there is something I can't get my head around. I know ProScene has extensive camera profiles (such as 'wheeled arcball' and 'third person' for example), but I can't find a simple, more basic way of manipulating the camera object. (And I'll admit that this is almost certainly down to my lack of knowledge of 3D programming conventions and maths, not the library!)

I want to be able to apply translations and rotations to a single object (the camera), without having to use a look-at point, or camera target. In 3D modelling tools that I've used in the past (such as 3Ds Max) this was called a 'free' camera, rather than a targeted camera.

My ultimate aim in this is to be able to control the camera in a ProScene using my 3D Connexion Space Navigator, (there is an old discussion on it here: http://processing.org/discourse/yabb2/YaBB.pl?num=1201465182 which works very well for integration with processing). However as this is a fairly rare desktop accessory, for the purposes of this discussion we should just think of the question as one of controlling the camera directly with any source of translation and rotation input.

I suspect the answer to this might lie in ProScene's first or third person camera profiles, but I can't see an interface to the translation and rotation in the reference docs. Has anyone got any direction on this?

cheers

Jim

Replies(15)

nakednous

Re: Direct Camera Control in ProScene

2 years ago

Hi,

Camera profiles can only handle mouse bindings. You need low-level camera control and the re are a couple of methods that provide it: Camera.setPosition and Camera.setOrientation. More manual control can be gained by getting a reference to the camera frame and then manipulating it directly: Camera.frame (check the Camera and Frame api). You can use whatever camera profile you want, but THIRD_PERSON.

It would be great to support other devices in proscene. Maybe that could be achieved through procontroll. Never tried it though.

Hope that helps!

Jean Pierre

jimthree

Re: Direct Camera Control in ProScene

2 years ago

Hi Jean Pierre!

Thanks for the comments above, I've nearly got it working, I have the camera translations working fine, using:

cam_pos.set(cam_pos.x+sliderXpos.getValue(),cam_pos.y+sliderYpos.getValue(),cam_pos.z+sliderZpos.getValue());
scene.camera().setPosition(cam_pos);

however, using set.Orientation only allows me to control rotations around the camera's X and Y axis:

cam_rot.set(cam_rot.x+sliderXrot.getValue(),cam_rot.y+sliderYrot.getValue(),cam_rot.z+sliderZrot.getValue());
scene.camera().setOrientation(radians(cam_rot.y),radians(cam_rot.x));

Is there a way of setting the rotation around the Z axis using setOrientation?

I'm guessing not, and I need to move over to using camera.frame.setOrientation() here as you suggested, however I can't find any examples of it's usage. Can you point me towards any examples of how to implement this?

If I use the frame methods for translating and rotating the camera, will the camera still be keyframe-able?

thanks

Jim

nakednous

Re: Re: Direct Camera Control in ProScene

2 years ago

Hi Jim,

Yes, there's a way. For instance, the following code rotates the camera around the z axis quarter pi radians:

scene.camera().setOrientation(new Quaternion(new PVector(0,0,1), PApplet.QUARTER_PI));

The Quaternion class also has a method Quaternion.fromAxisAngle(axis, angle) that might be handy, please have a look at its api. Have also a look at the CajasOrientadas example.

You may achieve exactly the same result as above using a reference to the camera frame, as:

scene.camera().frame().setOrientation(new Quaternion(new PVector(0,0,1), PApplet.QUARTER_PI));

Cheers,

Jean Pierre

jimthree

Re: Direct Camera Control in ProScene

2 years ago

I've had a bit of time to look at this today, and I'm having some difficulty with the quaternions.

I have tried two different approaches,

scene.camera().setOrientation(new Quaternion(new PVector(0,0,1), radians(cam_rot.z)));

(as you suggested)

and

scene.camera().setOrientation(new Quaternion(0,0,radians(cam_rot.z),1));

(which I will end up using as I need to rotate in all three axis simultaneously, although in this example I'm testing only with Z)

I'm not sure if I actually need to convert cam_rot.z to radians, but it doesn't seem to matter in this case.

The response of cam_rot.Z is a linear increment as I turn the space Navigator in the Z axis. At the current multiplier settings I'm using, the value increases by about 10 degrees per second. However the rotation of the camera is non-linear, starting of with a fast rotation and falling off quickly so that it hardly moves by the time it's rotated beyond 160 degrees and never reaching 180.

I'm sure this is a maths problem, and maths is not one of my strong points. I nearly passed out when I read about Quaternions on wikipedia!

Jim

nakednous

Re: Re: Direct Camera Control in ProScene

2 years ago

Quaternions are a bit tricky to understand (as you guessed, for theoretical details you may refer to this great wikipedia article: quaterions and spatial rotation), but are great to perform rotations. Other nice thing about them (among others) is that they're actually quite simple to use.

It is worth noting that proscene makes extensive use of frames (coordinate systems). Every scene has at least two frames: the world coordinate system (also referred to as the reference frame) where one usually defines the scene objects, and the camera coordinate system that is used to manipulate the camera around the scene. Rotating an object implies defining two things: a rotation axis and an angle (which matches exactly the definition of a quaternion). We just need to be sure respect to what frame the axis is defined.

Enough talk! Now it comes the funny part. A simple yet powerful way to rotate your camera is to use the method Frame.rotate(). For example, the following line rotates the camera around its z-axis an angle of QUARTER_PI radians:

scene.camera().frame().rotate(new Quaternion(new PVector(0,0,1), PApplet.QUARTER_PI));

Observe how the Quaternion defines both, the rotation axis (the PVector) and the angle. Now suppose you want to specify your rotation axis in the world coordinate system. The following line rotates the camera around the world z-axis an angle of QUARTER_PI radians:

scene.camera().frame().rotate(new Quaternion(scene.camera().frame().transformOf(new PVector(0,0,1)), PApplet.QUARTER_PI));

where the method Frame.transformOf() converts vectors from world to frame. This mechanism allows you to achieve whatever transformation you can think of

Observations:

1. A proscene.Frame comprises three attributes: a quaternion (which specifies its orientation) a position and a reference frame (which allows you to create a hierarchy of frames, i.e., a scene graph). The method scene.camera().setOrientation is useful to define the orientation of the Frame. I think that maybe this method is not very handy in your case.

2. A quaternion comprises two attributes: an axis and an and angle which internally are represented as the quadraple: (x,y,z,w). The relation between axis/angle and this quadruple is not that intuitive though. The following code snippet (taken from the Quaternion class) should make it clear:

public void fromAxisAngle(PVector axis, float angle) {
float norm = axis.mag();
if (norm < 1E-8f) {
// Null rotation
this.x = 0.0f;
this.y = 0.0f;
this.z = 0.0f;
this.w = 1.0f;
} else {
float sin_half_angle = PApplet.sin(angle / 2.0f);
this.x = sin_half_angle * axis.x / norm;
this.y = sin_half_angle * axis.y / norm;
this.z = sin_half_angle * axis.z / norm;
this.w = PApplet.cos(angle / 2.0f);
}
}

Thus one should avoid using the constructor: Quaternion(float x, float y, float z, float w) whenever possible and use Quaternion(PVector axis, float angle) or Quaternion(PVector from, PVector to) instead.

Best regards,

Jean Pierre

guess

Re: Direct Camera Control in ProScene

2 years ago

Hello,

I'm trying to figure out the excellent Proscene library and I hope to be able to describe with accuracy what I'm looking for.

I would like to use a camera that is not predetermined by keyframes but rather free floating in 3D space around two or more models.

I'm trying to do three things :

1) To have my program choose more or less random vantage points and to smoothly interpolate to them, while being able to orient the camera to a lookAt point (a part of the current model).

2) To smoothly transition to a routine where I could rotate around this or another model (at a random distance (radius)) with a lookAt point.

3) To be able to go smoothly transition back into routine 1

I hope this is clear...

Any help would be great!

Thanks, Jeff

guess

Re: Direct Camera Control in ProScene

2 years ago

anyone?

nakednous

Re: Re: Direct Camera Control in ProScene

2 years ago

Hi,

I don't know if I understand exactly what you want to achieve. However, you can easily interpolate any camera path provided that you have some keyframes to start with. You can define your keyframes in two different ways: 1. Programmatically: the camera class provide several methods to position and orientate your camera and to add those positions (and orientations) to a path; or, 2. By UI: position your camera with the mouse then press CTRL+n (1<=n>=5). In both cases you can then play your camera path by pressing n or programmatically, e.g., scene.camera().playPath().

Please refer to the CameraInterpolation example if you haven't do it yet.

Hope that helps,

Jean Pierre

_TM_

Re: Direct Camera Control in ProScene

2 years ago

Bonjour Jean Pierre,

First of all, thank you for this library and contribution. I am trying to use your library to attach the camera to a object so when that object rotates, the camera will feel like been attached. I've looked at your examples and posts on the forum but can't find the solution. Proscene seems so rich that I am sure that the solution is there somewhere but I've reached the limit of my understanding.

Thank you for help

))

nakednous

Re: Direct Camera Control in ProScene

2 years ago

Hi TM,

Actually, I'm implementing a demo based on the Luxo that may be handy. The idea (which has been suggested several times) is to attach a second Camera and show the scene from that second point of view.

I hope to include the demo for the upcoming 1.1 release, but if you're in a hurry you may have a look here. Please bear in mind that the demo is a pure java work in progress (that hasn't been ported to Processing, e.g., you need eclipse to run it) and that there's a bug in the InteractiveCameraFrame that prevents correct mouse interaction when manipulating the frame, unless a constraint is attached to it (as it's currently done in the code). It may be handy though ;)

Cheers

_TM_

Re: Re: Direct Camera Control in ProScene

2 years ago

Thank you for your answer JP,

I have a look today at the link, I am not sure that's what I am looking for even tho it sounds like a very useful feature.

Can't find a example online, but it's a simple effect, basically the camera and the object have the same rotation and position but the camera's translate on a axis. Don't know if Im clear...

Anyways, thanks again for the reply (and the lib), I have a look at the code :)
Cheers

UPDATE:

I guess it's like in the FrameInteraction example where one of the box as a transformation applied to, but I need that applied to the camera.

))

nakednous

Re: Direct Camera Control in ProScene

2 years ago

Proscene has a built-in camera profile that attaches the camera to a given interactive frame which is called THIRD_PERSON and has two examples illustrating it: Flock and ThirdPersonCamera. Just don't forget to press the space bar to change the camera profile. In the case of the Flock example for the THIRD_PERSON camera profile to be activated you need first to select a boid (which is done by a mouse click).

Hope that gives you a clue.

_TM_

Re: Direct Camera Control in ProScene

2 years ago

It was all there in the Flock example, I didn't select a boid before change cam, I'm such a idiot! Sorry for all that, and thank you for the heads up.

))

addisandr..

Re: Direct Camera Control in ProScene

2 years ago

Jean Pierre,

What about rotating the camera around the axis through the PVector the camera is looking at? I have a theory of how it would be done, but I can't seem to find the functions I think I would need in your library.

Thanks,

Andrew

nakednous

Re: Direct Camera Control in ProScene

2 years ago

I think the action you're looking for is: Scene.MouseAction.ROLL (btw, you may be also interested in the DRIVE and the LOOK_AROUND actions). You can set it as:

setCameraMouseBinding(Scene.Button.LEFT.ID, Scene.MouseAction.ROLL);

Please refer to the CameraCustomization example.

Otherwise please fill a new ticket asking for the required functionality.

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