Lets say I have an object, and that object has a quaternion representing its orientation.
Currently, I can rotate on all 3 axes without gimbal lock, however, each rotation on any axis SHOULD rotate the other 2 axes of rotation.
What I mean by this is if I pitch an object towards the camera, but then yaw the object 90 degrees away, pitching the object will still rotate it relative to where it was before, not where it is now.
Here's a visual example of my problem:
I'm using quaternions and not euler rotations because these objects can rotate on all 3 axes, and I don't want to gimbal lock/reach singularity
I rotate my object's orientation quaternion like this:
orientation = Quaternion(Vector(0,1,0),angle) * orientation;
I then trigger a rebuilding of my object's vectors, and apply it to them (after transforming the object relative to 3D space origin point):
Quaternion Point = Quaternion(( orientation * (Vertex) ) * (orientation.inverse()));
vertices[x] = QVector3D(round(Point.v.x),round(Point.v.y),round(Point.v.z));
And when I multiply my quaternions by other quaternions, this is the multiplication operator's function:
Quaternion Quaternion::operator*(Quaternion& q) const
{
Quaternion r;
//"w" is the angle, "v" is the vector
r.w = w*q.w - glm::dot(v, q.v);
r.v = v*q.w + q.v*w + glm::cross(v,q.v);
//r.normalize();
return r;
}
I swear to god, I'm only posting because this topic is confusing me to no end. Solidifying this system will be make me unfathomably happy.
Related
I'm trying to implement yaw pitch roll for visualisation camera yaw pitch roll more then 360 degree like in Maya, Blender, Unreal Engine, Unity etc. All this application can show angles in gui more then 360 degree and no have any Gimbal lock problems.
current psevdo code;
Quaternion rotation; //relative (local rotation)
Quaternion parentRotation;
//it is psevdo code where we calculate delta angle that user generate on current frame by mouse
void SetDeltaWorldRotationFromUserInput(Quaternion value)
{
SetWorldRotation(value);
}
void SetWorldRotation(Quaternion value)
{
SetLocalRotation(parentQuaternion.inverted() * value); //get/set local rotation
}
void SetLocalRotation(Quaternion value)
{
rotation = value; //this we save new local rotation but i want to save somehow more then 360 degree
auto eulersForGui = value.toEulers(); //it is current eulers but i want to accumulate and show in gui accumulate rotation. like currentRotation + delta or somehow
auto deltaEulers = (value * rotation.inverted()).toEulers(); //i can get delta eulers but i can't add it to euelers and don't know what i need to do with this value
}
I had left a link in the comment section to your question. However as a quick answer to your problem I think this quote from that webpage should point you in the right direction:
"A sequence of rotations can be represented by a series of quaternions multiplied together, producing a single resulting quaternion that encodes the combined rotations."
The quote above can refer to either multiple quaternions each rotating around a different axis to get the combined rotation in 3D, or multiple rotations about the same axis that would accumulate to a single rotation that is more than 360 degrees.
I'm having problems rotating GameObjects in my engine. I'm trying to rotate in 2 ways.
I'm using MathGeoLib to calculate maths in the engine.
First way: Rotates correctly around axis but if I want to rotate back, if I don't do it following the inverse order then rotation doesn't work properly.
e.g:
Rotate X axis 50 degrees, Rotate Y axis 30 degrees -> Rotate Y axis -50 degrees, Rotate X axis -30 degrees. Works.
Rotate X axis 50 degrees, Rotate Y axis 30 degrees -> Rotate X axis -50 degrees, Rotate Y axis -30 degrees. Doesn't.
Code:
void ComponentTransform::SetRotation(float3 euler_rotation)
{
float3 diff = euler_rotation - editor_rotation;
editor_rotation = euler_rotation;
math::Quat mod = math::Quat::FromEulerXYZ(diff.x * DEGTORAD, diff.y * DEGTORAD, diff.z * DEGTORAD);
quat_rotation = quat_rotation * mod;
UpdateMatrix();
}
Second way: Starts rotating good around axis but after rotating some times, then it stops to rotate correctly around axis, but if I rotate it back regardless of the rotation order it works, not like the first way.
Code:
void ComponentTransform::SetRotation(float3 euler_rotation)
{
editor_rotation = euler_rotation;
quat_rotation = math::Quat::FromEulerXYZ(euler_rotation.x * DEGTORAD, euler_rotation.y * DEGTORAD, euler_rotation.z * DEGTORAD);
UpdateMatrix();
}
Rest of code:
#define DEGTORAD 0.0174532925199432957f
void ComponentTransform::UpdateMatrix()
{
if (!this->GetGameObject()->IsParent())
{
//Get parent transform component
ComponentTransform* parent_transform = (ComponentTransform*)this->GetGameObject()->GetParent()->GetComponent(Component::CompTransform);
//Create matrix from position, rotation(quaternion) and scale
transform_matrix = math::float4x4::FromTRS(position, quat_rotation, scale);
//Multiply the object transform by parent transform
transform_matrix = parent_transform->transform_matrix * transform_matrix;
//If object have childs, call this function in childs objects
for (std::list<GameObject*>::iterator it = this->GetGameObject()->childs.begin(); it != this->GetGameObject()->childs.end(); it++)
{
ComponentTransform* child_transform = (ComponentTransform*)(*it)->GetComponent(Component::CompTransform);
child_transform->UpdateMatrix();
}
}
else
{
//Create matrix from position, rotation(quaternion) and scale
transform_matrix = math::float4x4::FromTRS(position, quat_rotation, scale);
//If object have childs, call this function in childs objects
for (std::list<GameObject*>::iterator it = this->GetGameObject()->childs.begin(); it != this->GetGameObject()->childs.end(); it++)
{
ComponentTransform* child_transform = (ComponentTransform*)(*it)->GetComponent(Component::CompTransform);
child_transform->UpdateMatrix();
}
}
}
MathGeoLib:
Quat MUST_USE_RESULT Quat::FromEulerXYZ(float x, float y, float z) { return (Quat::RotateX(x) * Quat::RotateY(y) * Quat::RotateZ(z)).Normalized(); }
Quat MUST_USE_RESULT Quat::RotateX(float angle)
{
return Quat(float3(1,0,0), angle);
}
Quat MUST_USE_RESULT Quat::RotateY(float angle)
{
return Quat(float3(0,1,0), angle);
}
Quat MUST_USE_RESULT Quat::RotateZ(float angle)
{
return Quat(float3(0,0,1), angle);
}
Quat(const float3 &rotationAxis, float rotationAngleRadians) { SetFromAxisAngle(rotationAxis, rotationAngleRadians); }
void Quat::SetFromAxisAngle(const float3 &axis, float angle)
{
assume1(axis.IsNormalized(), axis);
assume1(MATH_NS::IsFinite(angle), angle);
float sinz, cosz;
SinCos(angle*0.5f, sinz, cosz);
x = axis.x * sinz;
y = axis.y * sinz;
z = axis.z * sinz;
w = cosz;
}
Any help?
Thanks.
Using Euler angles and or Quaternions adds some limitations as it creates singularities which if not handled correctly will make silly things. Sadly almost all new 3D games using it wrongly. You can detect those by the well known things like:
sometimes your view get to very different angle that should not be there
object can not rotate anymore in some direction
object start rotating around different axises than it should
view jumps around singularity pole
view is spinning or flipping until you move/turn again (not the one caused by optic mouse error)
I am using cumulative transform matrices instead:
Understanding 4x4 homogenous transform matrices
Read the whole stuff (especially difference between local and global rotations) then in last 3 links you got C++ examples of how to do this (also read all 3 especially the preserving accuracy ...).
The idea is to have matrix representing your object coordinate system. And when ever you rotate (by mouse, keyboard, NAV,AI,...) you rotate the matrix (incrementally). The same goes for movement. This way they are no limitations or singularities. But also this approach has its problems:
lose of accuracy with time (read the preserving accuracy example to deal with this)
no knowledge about the Euler angles (the angles can be computed from the matrix however)
Both are solvable relatively easily.
Now when you are rotating around local axises you need to take into account that with every rotation around some axis you change the other two. So if you want to get to the original state you need to reverse order of rotations because:
rotate around x by 30deg
rotate around y by 40deg
is not the same as:
rotate around y by 40deg
rotate around x by 30deg
With cumulative matrix if you want to get back you can either iteratively drive your ship until it faces desired directions or remember original matrix and compute the rotations needed to be done one axis at a time. Or convert the matrix difference into quaternion and iterate that single rotation...
I'm currently in the process of finishing the implementation for a camera that functions in the same way as the camera in Maya. The part I'm stuck in the tumble functionality.
The problem is the following: the tumble feature works fine so long as the position of the camera is not parallel with the up vector (currently defined to be (0, 1, 0)). As soon as the camera becomes parallel with this vector (so it is looking straight up or down), the camera locks in place and will only rotate around the up vector instead of continuing to roll.
This question has already been asked here, unfortunately there is no actual solution to the problem. For reference, I also tried updating the up vector as I rotated the camera, but the resulting behaviour is not what I require (the view rolls as a result of the new orientation).
Here's the code for my camera:
using namespace glm;
// point is the position of the cursor in screen coordinates from GLFW
float deltaX = point.x - mImpl->lastPos.x;
float deltaY = point.y - mImpl->lastPos.y;
// Transform from screen coordinates into camera coordinates
Vector4 tumbleVector = Vector4(-deltaX, deltaY, 0, 0);
Matrix4 cameraMatrix = lookAt(mImpl->eye, mImpl->centre, mImpl->up);
Vector4 transformedTumble = inverse(cameraMatrix) * tumbleVector;
// Now compute the two vectors to determine the angle and axis of rotation.
Vector p1 = normalize(mImpl->eye - mImpl->centre);
Vector p2 = normalize((mImpl->eye + Vector(transformedTumble)) - mImpl->centre);
// Get the angle and axis
float theta = 0.1f * acos(dot(p1, p2));
Vector axis = cross(p1, p2);
// Rotate the eye.
mImpl->eye = Vector(rotate(Matrix4(1.0f), theta, axis) * Vector4(mImpl->eye, 0));
The vector library I'm using is GLM. Here's a quick reference on the custom types used here:
typedef glm::vec3 Vector;
typedef glm::vec4 Vector4;
typedef glm::mat4 Matrix4;
typedef glm::vec2 Point2;
mImpl is a PIMPL that contains the following members:
Vector eye, centre, up;
Point2 lastPoint;
Here is what I think. It has something to do with the gimbal lock, that occurs with euler angles (and thus spherical coordinates).
If you exceed your minimal(0, -zoom,0) or maxima(0, zoom,0) you have to toggle a boolean. This boolean will tell you if you must treat deltaY positive or not.
It could also just be caused by a singularity, therefore just limit your polar angle values between 89.99° and -89.99°.
Your problem could be solved like this.
So if your camera is exactly above (0, zoom,0) or beneath (0, -zoom,0) of your object, than the camera only rolls.
(I am also assuming your object is at (0,0,0) and the up-vector is set to (0,1,0).)
There might be some mathematical trick to resolve this, I would do it with linear algebra though.
You need to introduce a new right-vector. If you make a cross product, you will get the camera-vector. Camera-vector = up-vector x camera-vector. Imagine these vectors start at (0,0,0), then easily, to get your camera position just do this subtraction (0,0,0)-(camera-vector).
So if you get some deltaX, you rotate towards the right-vector(around the up-vector) and update it.
Any influence of deltaX should not change your up-vector.
If you get some deltaY you rotate towards the up-vector(around the right-vector) and update it. (This has no influence on the right-vector).
https://en.wikipedia.org/wiki/Rotation_matrix at Rotation matrix from axis and angle you can find a important formula.
You say u is your vector you want to rotate around and theta is the amount you want to pivot. The size of theta is proportional to deltaX/Y.
For example: We got an input from deltaX, so we rotate around the up-vector.
up-vector:= (0,1,0)
right-vector:= (0,0,-1)
cam-vector:= (0,1,0)
theta:=-1*30° // -1 due to the positive mathematical direction of rotation
R={[cos(-30°),0,-sin(-30°)],[0,1,0],[sin(-30°),0,cos(-30°)]}
new-cam-vector=R*cam-vector // normal matrix multiplication
One thing is left to be done: Update the right-vector.
right-vector=camera-vector x up-vector .
I've created an object that moves towards its destination with inertia. I am having alot of trouble getting the object to face its destination. My code is simple, it calculates the angle, converts it to degrees and passes that angle to the Matrix4 Rotate function, which adjusts the localTransform (scenegraph).
The problem is that the object spawns, and then just rotates endlessly. It slowly progresses towards its target, but just keeps spinning. I've tested it without translation, it spins regardless on the spot. All I need is for the object to face its destination. My Translate/Rotate functions work correctly, I've used it to rotate an object, have an object spawn with its parent's rotation and head in that direction. They provide 1:1 results with the GLM library.
I've tried swapping the order in aTan2, removing the degrees conversion, (though that does nothing, the Rotate function takes degrees) and swapping translation/rotation order.
localTransform is the combined rotation/scale/translation matrix. row[3]column[1] is Y. [3][0] is X.
float fAngle = atan2(v3Destination[1] - localTransform.data[3][1] , v3Destination[0] - localTransform.data[3][0]);
float fAngleDegrees = fAngle * 180 / PI;
localTransform = Matrix4::Rotate(localTransform, fAngleDegrees, Vector3(0.0f, 0.0f, 1.0f));
Vector3 Movement;
Movement[0] = v3Destination[0] - localTransform.data[3][0];
Movement[1] = v3Destination[1] - localTransform.data[3][1];
Movement = Movement * fSpeed * Application.GetTimeStep();
localTransform = Matrix4::Translate(localTransform, Movement);
Any advice on how to handle this? This is all in 2D coordinates, however the rotation is done on the Z-Axis.
Just a hunch, but is the localTransform matrix completely recomputed each time step?
Or could you be adding a rotation to a matrix that's already been rotated in the previous iteration.
This could explain the continuous rotation.
I'm trying to implement a quaternion-based camera, but when moving around the X and Y axis, the camera produces an unwanted roll on the Z axis. I want to be able to look around freely on all axis.
I've read other topics about this problem (for example: http://www.flipcode.com/forums/thread/6525 ), but I'm not getting what is meant by "Fix this by continuously rebuilding the rotation matrix by rotating around the WORLD axis, i.e around <1,0,0>, <0,1,0>, <0,0,1>, not your local coordinates, whatever they might be."
//Camera.hpp
glm::quat rotation;
//Camera.cpp
void Camera::rotate(glm::vec3 vec)
{
glm::quat paramQuat = glm::quat(vec);
rotation = paramQuat * rotation;
}
I call the rotate function like this:
cam->rotate(glm::vec3(0, 0.5, 0));
This must have to do with local/world coordinates, right? I'm just not getting it, since I thought quaternions are always based on each other (thus a quaternion can't be in "world" or "local" space?).
Also, should i use more than one quaternion for a camera?
As far as I understand it, and from looking at the code you provided, what they mean is that you shouldn't store and apply the rotation incrementally by applying rotate on the rotation quat all the time, but instead keeping track of two quaternions for each axis (X and Y in world space) and calculating the rotation vector as the product of those.
[edit: some added (pseudo)code]
// Camera.cpp
void Camera::SetRotation(glm::quat value)
{
rotation = value;
}
// controller.cpp --> probably a place where you'd want to translate user input and store your rotational state
xAngle += deltaX;
yAngle += deltaY;
glm::quat rotationX = QuatAxisAngle(X_AXIS, xAngle);
glm::quat rotationY = QuatAxisAngle(Y_AXIS, yAngle);
camera.SetRotation(rotationX * rotationY);