A fast, easy to use, free, and community supported 2D game engine
DevSdk
Member
Hello,
I have a little question for a problem I'm not able to solve.
I apply some transformation matrixes to my active camera in the updateBeforeTransform. I would like to been able to put an arrow always on the center of the camera view. The arrow should not rotate with the camera (I mean, it should not rotate towards the camera, it's actually pointing on another object), but should always be visible on the center of the screen.
How can I achieve that?
Thank you!
You have a couple of options:
CC3Layer. See the joysticks and buttons in the CC3DemoMashUp demo for how to do this.
cc3v(0.0, 0.0, -10.0). This is because the camera looks down the -Z axis of its local coordinate system.
Your arrow will then move and rotate along with the camera.
The camera is like any other node. You can be add it to another node, if you want it to follow another node around (like a behind-the-player view), and you can add other nodes to it (such as a light that moves with the camera).
...Bill
DevSdk
Member
@Bill Hollings
Hi Bill and thank you for your answer.
Yes, it's the second one what I want. A 3D object.
I tried what you suggested, and indeed I can see the arrow. But when I apply the transformation matrix to the camera the arrow doesn't move with the camera. Don't know why...
I add the camera and the arrow to the scene this way:
CC3Camera *cam = [CC3Camera nodeWithName:@"Camera"];
cam.farClippingPlane = 3000;
cam.location = cc3v(0, 0, 0);
[self addChild:cam];
[self addContentFromPODFile:podPath withName:@"Arrow"];
CC3MeshNode *arrow = (CC3MeshNode*)[self getNodeNamed: @"Arrow"];
[cam addChild:arrow];
[arrow setUniformScale:200];
[arrow setLocation:cc3v(0, 0, -300)];When I change the camera transformation matrix:
CC3GLMatrix *mat = [[CC3GLMatrix alloc] init];
[mat populateFromQuaternion:camQuaternion];
[self.activeCamera setTransformMatrix:mat];The arrow remains on its position on the world and doesn't "follow" the camera...
What could be the problem?
Thanks!
Is there a reason why you are trying to replace the transformation matrix, instead of simply using the quaternion property (or rotateByQuaternion: method for deltas) of the camera?
Setting the transformMatrix directly interferes with the mechanism for propagating changes in the camera to its child nodes. You'd generally have to set the transformMatrix of the child nodes manually as well. And constantly allocating matrices all over the place can't help much with performance. :-)
If there is not a strong reason for using a matrix, try using the transform properties instead. You'll likely get better results.
...Bill
DevSdk
Member
That did the trick!
I know it was not a very performant way to do it, but I would have look into it soon. I didn't know that the transformMatrix interferes with the child nodes.
There is no real reason to allocate a CC3GLMatrix, but I don't know exactly how to do this:
CC3GLMatrix *mat = [[CC3GLMatrix alloc] init];
[mat populateFromQuaternion:newQuaternion];
[mat rotateByX:-90];
CC3Vector4 modQuat = [mat extractQuaternion];
[self.activeCamera setQuaternion:modQuat];How can I do "rotateByX: -90" on the quaternion without using the CC3GLMatrix?
Anyway thank you very much! You saved my day! :)
Apply the Euler X-axis rotation directly to the camera.
[self.activeCamera rotateBy: cc3v(-90, 0, 0)];
will do it.
If you really need to set that initial quaternion, you can apply that directly to the camera too:
self.activeCamera.quaternion = newQuaternion;
[self.activeCamera rotateBy: cc3v(-90, 0, 0)];
will set the rotation of the camera to the initial quaternion that you have, and then rotate it around the X-axis by 90 degrees clockwise.
...Bill
You must log in to post.