Tagged Questions
9
votes
2answers
2k views
How can I rotate about an arbitrary point in 3D (instead of the origin)?
I have some models that I want to rotate using quaternions in the normal manner, except instead of rotation about the origin, I want it to be offset slightly. I know that you don't say, in 3d space, ...
6
votes
2answers
680 views
What is eigenvalue decomposition and why would it be useful in games?
In various math libraries developed for game engines, I see 2x2 and 3x3 square matrices having this function (along with some helper functions). I tried to find information regarding it but did not ...
5
votes
3answers
656 views
Why is my model's scale changing after rotating it?
I have just started a simple flight simulator and have implemented Roll and pitch. In the beginning, testing went very well; however, after about 15-20 seconds of constantly moving the thumbsticks in ...
5
votes
1answer
90 views
Rotating plane to be parallel to given normal via change of basis
I have two planes and their respective normals. I would like to rotate the second plane, planeB, so that it is parallel to the first, planeA.
To do this, I am using a change of basis to rotate each ...
3
votes
2answers
515 views
How can I implement smooth rotation from one direction to another?
I'm having a problem with animating rotations with 1Matrix.CreateRotationY() with my basic 3D game. Based on where you click the mouse, I want the 3D object to rotate to that direction and then move.
...
3
votes
2answers
274 views
3D rotation matrices deform object while rotating
I'm writing a small 3D renderer (using an orthographic projection right now).
I've run into some trouble with my 3D rotation matrices. They seem to squeeze my 3D object (a box primitive) at certain ...
3
votes
1answer
201 views
Rotating 3d plane to XY plane
I have a triangle in 3d space and would like to create a grid over the triangle, such as in the image below.
The purpose of this is to store information about each block of the grid. In order to ...
3
votes
2answers
294 views
How to derive euler angles from matrix or quaternion?
Currently working on steering behavior for my AI and just hit a little mathematical bump.
I'm in the process of writing an align function, which basically tries to match the agent's orientation with ...
3
votes
1answer
1k views
Moving a rotated model in XNA
This seems like a simple problem with an equally simple solution that is invisible to me.
I have a model that spawns at the origin and looks at my player model wherever it goes.
I would like it to ...
2
votes
2answers
609 views
What is the difference between Vector2.Transform and this method?
I've been working on some steering behaviors and ran into trouble with my logic for converting points in world space into points in local space. I had this (it's not optimized for multiple points yet, ...
2
votes
1answer
297 views
Finding a suitable axis-angle to avoid gimbal lock
In OpenGL the camera faces the -z axis with the +y axis pointing up. I am using quaternions to represent the orientation of my objects (which works well) and am trying to do the same for the camera. I ...
2
votes
2answers
413 views
Passing an objects rotation down through its children
In my topdown 2d game you have a player with a sword, like an old Zelda game.
The sword is a seperate entity, and its collision box "rotates" around the player like an orbit, but always follows the ...
2
votes
2answers
230 views
Rotating a child shape relative to its parent's orientation
When rotating a shape using a quaternion value I also wish rotate its child shape.
The parent and child shapes both start with different orientations but their relative orientations should always be ...
2
votes
1answer
682 views
Flip rotation matrix
I'm doing character control with kinect. I need to mirror the joint orientation because the character faces the player. Somehow by Googling through internet I've done it and everything works very ...
1
vote
2answers
586 views
Transformation order when dealing with Meshes
I have created a player model out of primitive types. To do this I have created a Model class and Component (mesh) class. Each model consists of one or more components my problems start when you have ...
1
vote
2answers
228 views
Matrix Rotation with three Angles
I want to rotate a form with three given angles fo each of the three axis. But the GLM rotation function takes only one angle and a vector as arguments.
How can I convert between both formats?
1
vote
3answers
213 views
Inverting matrix then decomposing gives different quaternion than decomposing then inverting the quat
I'm getting different signs when I convert a matrix to quaternion and invert that, versus when I invert a matrix and then get the quaternion from it:
Quaternion a = Quaternion.Invert(getRotation(m));
...
1
vote
2answers
552 views
Matrix rotation of a rectangle to “face” a given point in 2d
Suppose you have a rectangle centered at point (0, 0) and now I want to rotate it such that it is facing the point (100, 100), how would I do this purely with matrix math?
To give some more specifics ...
1
vote
2answers
358 views
opengl rotations for a human
I currently can rotate around a pivot point by first translating to the pivot point then performing the rotation and finally translating back to the origin. I do that easily enough for the shoulder in ...
1
vote
0answers
161 views
Getting and Setting Rotation in XNA around the Center of my Model with XNA
Alright, so I'm currently debating how I want to do this. Basically this is what I'm trying to accomplish.
I've created a system to allow me to make my environment a little bit easier. I'm ...
1
vote
4answers
1k views
Rotating a model AND translating it forward in XNA
I have this enemy class, and I want it to
1) Spawn at a certain place Vector3 pos
2) Rotate to face my player position
3) Move forward
As this code is now, it will appear at it's specified place: ...
1
vote
0answers
293 views
How can I draw a model perpendicular to a sloped surface? [duplicate]
Possible Duplicate:
How do I find rotation in 3D based on a vector/normal?
My models are axis-aligned. I know the normal of the surface I want to draw them on.
How do I compute the ...
0
votes
1answer
59 views
Getting Rotation Values From A Rotation Matrix
I'm trying to get rotation values along the x, y and z axis from a matrix that can include rotation, translation and scale data. Currently I have this function to return the y rotational value:
float ...
0
votes
0answers
44 views
Proper matrix rotation and storing rotation values
I have GameObject's transform component(position+rotation) and shape mesh(array of vertices).
On each game tick I update coordinates of vertices relatively to game object's rotation.
And my current ...
0
votes
1answer
107 views
Camera lookAt target changes when rotating parent node
have the following issue.I have a camera with lookAt method which works fine.I have a parent node to which I parent the camera.If I rotate the parent node while keeping the camera lookAt the target , ...
