Vector3 gunDirection = new Vector3(mousePosition, 0.0f) - tank.position;
float rotation = atan(gunDirection.Y/gunDirection.X);
Matrix gunTransform = tank.model.Bones["Gun"].Transform;
[XNA] Matrix Transformations: Pointing a gun at a crosshair
Author
Hi there!
I'm trying to make a game using XNA where a tank-like vehicle can be moved left and right, and automatically aims at the mouse cursor.
I know I can calculate a direction vector like this:
A rotation around the Z-axis in radians could then be acquired like this:
I run into problems when I want to apply a rotation to the "Gun" mesh in the tank's model. The transformation matrix of the mesh can be retrieved this way:
How do I alter the gun's transformation matrix to keep it's translation and scale, but have the new rotation?
Thank you in advance,
Arjan B
Unless I'm missing something, you can just multiply the matrix by Matrix.CreateRotationZ(rotation).
Author
I have already tried saving the gun's initial transform in tank.gunTransform, and updating the transform in this way:
But this doesn't give the result I want it to. The pivot of the rotation seems off (which is fixable..), but also it doesn't seem to rotate more than 90 degrees, no matter where I move my mouse or tank.
What I just noticed while doing a second check is, when I rotate my mouse around the top-left corner of the window (so also outside the window), the gun does rotate 360 degrees (I'll clamp that later on).
EDIT:
I just realised that the tank's position is in world coordinates and the mouse's position is probably in screen coordinates.
I've defined a Camera class like this:
Could I calculate the tank's screen coordinates using this information?
[Edited by - Arjan B on January 18, 2010 3:21:39 AM]
Vector3 gunDirection = new Vector3(mousePosition, 0.0f) - tank.position;float gunRotation = (float)Math.Atan2(gunDirection.Y, gunDirection.X);tank.model.Bones["Gun"].Transform = tank.gunTransform * Matrix.CreateRotationZ(gunRotation);But this doesn't give the result I want it to. The pivot of the rotation seems off (which is fixable..), but also it doesn't seem to rotate more than 90 degrees, no matter where I move my mouse or tank.
What I just noticed while doing a second check is, when I rotate my mouse around the top-left corner of the window (so also outside the window), the gun does rotate 360 degrees (I'll clamp that later on).
EDIT:
I just realised that the tank's position is in world coordinates and the mouse's position is probably in screen coordinates.
I've defined a Camera class like this:
class Camera { public Matrix viewMatrix; public Matrix projectionMatrix; public Vector3 position; public Vector3 lookAt; public Camera(Vector3 position, Vector3 lookAt, float aspectRatio) { this.position = position; this.lookAt = lookAt; viewMatrix = Matrix.CreateLookAt(position, lookAt, Vector3.Up); projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, aspectRatio, 1.0f, 10000.0f); } }Could I calculate the tank's screen coordinates using this information?
[Edited by - Arjan B on January 18, 2010 3:21:39 AM]
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