I'm trying to make a controllable ball in OpenGL. I'm using my own matrix class to transform the object matrix, but I can't seem to get the Rotation right. I always end up with the ball rotating around the local axis.
This is how it looks right now https://gfycat.com/LongKindBassethound . The long line are the local axis.
So when the ball moves forward the next side movement will be wrong. Theres a function in the matrix class that allows rotation around any axis:
Matrix& Matrix::rotationAxis(const Vector& Axis, float Angle) {
const float Si = sin(Angle);
const float Co = cos(Angle);
const float OMCo = 1 - Co;
Vector Ax = Axis;
Ax.normalize();
m00= (Ax.X * Ax.X) * OMCo + Co;
m01= (Ax.X * Ax.Y) * OMCo - (Ax.Z * Si);
m02= (Ax.X * Ax.Z) * OMCo + (Ax.Y * Si);
m03= 0;
m10= (Ax.Y * Ax.X) * OMCo + (Ax.Z * Si);
m11= (Ax.Y * Ax.Y) * OMCo + Co;
m12= (Ax.Y * Ax.Z) * OMCo - (Ax.X * Si);
m13= 0;
m20= (Ax.Z * Ax.X) * OMCo - (Ax.Y * Si);
m21= (Ax.Z * Ax.Y) * OMCo + (Ax.X * Si);
m22= (Ax.Z * Ax.Z) * OMCo + Co;
m23= 0;
m30= 0;
m31= 0;
m32= 0;
m33= 1;
return *this;
}
I think with this I can take the world direction vectors and transform them to the local space of the object and then rotate around the result. I don't really know how to do that though (matrix of the ball * world vector? That doesn't work). I would really like to avoid quaternions, but if I can't do that I would appreciate suggestions in that direction too.
EDIT: More Info
The transforamtion Code. As you can see I tried different methods that all do the same... So no surprise there that it doesnt work.
Matrix transM, rotX, rotZ;
rotationX = straight;
rotationZ = side;
if (velocity != Vector(0, 0, 0)) {
velocity.X = -0.0005 * DeltaTime;
velocity.X = clamp(velocity.X, 0, FLT_MAX);
velocity.Z = -0.0005 * DeltaTime;
velocity.Z = clamp(velocity.Z, 0, FLT_MAX);
}
velocity.X += speed * -side * DeltaTime;
velocity.Z += speed * straight * DeltaTime;
transM.translation(velocity.X, 0, velocity.Z);
if (velocity.Z != 0 || velocity.X != 0) {
//http://mathworld.wolfram.com/EulerAngles.html
//http://gamedev.stackexchange.com/questions/67199/how-to-rotate-an-object-around-world-aligned-axes
Vector localAxisX = m_Ball * Vector(1, 0, 0);
Vector localAxisZ = m_Ball * Vector(0, 0, 1);
rotX.rotationAxis(Vector(1, 0, 0), 0.5* M_PI * straight * DeltaTime);
rotZ.rotationAxis(Vector(0, 0, 1), 0.5* M_PI * side * DeltaTime);
//rotX.rotationX(0.5* M_PI * straight * DeltaTime * 3);
//rotZ.rotationZ(0.5* M_PI * side * DeltaTime * 3);
//Matrix fullRotation.rotationYawPitchRoll(Vector(0, 0.5* M_PI * straight * DeltaTime, 0.5* M_PI * side * DeltaTime));
m_Ball = transM * m_Ball * (rotX*rotZ);
}
else {
m_Ball = transM * m_Ball;
}
Draw code with my previous attempt trying to use glRotatef (obviously commented out right now)
void Ball::draw(float DeltaTime) {
glPushMatrix();
glMultMatrixf(m_Ball);
if(rotationX)
glRotatef(0.5* M_PI * rotationX * DeltaTime, 1.0, 0.0, 0.0);
if(rotationZ)
glRotatef(0.5* M_PI * rotationZ * DeltaTime, 0.0, 0.0, 1.0);
g_Model_ball.drawTriangles();
glPopMatrix();
drawAxis();
}
I highly suggest using quaternions to easily handle compound rotations and avoid gimbal lock.
https://en.wikipedia.org/wiki/Gimbal_lock
Ok with regards to your comments and video, You want to rotate around the ball's center. It seems you accumulate your rotations in m_Ball but do a weird transM multiplication. Also you are probably accumulating translations in transM.
Try not to mix your translations and rotations and avoid accumulating them in your m_Ball. You can do something like this.
//transformation matrix
transM.translation(velocity.X, 0, velocity.Z);
//accumulate translations in m_BallT
m_BallT = transM * m_BallT;
//final Rotation
Matrix rotation = rotX * rotZ;
//accumulate rotations in m_BallR
m_BallR = rotation * m_BallR;
//now compute your final transformation matrix from accumulated rotations and translation
m_Ball = m_BallT * m_BallR;
note how m_BallR is just rotations accumulated. Post multiplication will ensure new rotation is applied after accumulated rotations in m_BallR. Finally translate to the final position accumulated in m_BallT. Your ball will rotate about its center and move according to m_BallT.
You could also simply replace the transformation component on your m_BallR to avoid extra matrix multiplications.
Vector newPos(m_Ball.translation().X + velocity.X, terrainNoise.GetHeight(m_Ball.translation().X, m_Ball.translation().Z) + 0.5, m_Ball.translation().Z + velocity.Z);
rotX.rotationAxis(Vector(1, 0, 0), 0.5* M_PI * straight * DeltaTime * abs(velocity.Z) * 100);
rotZ.rotationAxis(Vector(0, 0, 1), 0.5* M_PI * side * DeltaTime * abs(velocity.X) * 100);
m_Rotation = (rotX*rotZ);
m_Ball = (m_Ball.invert() * m_Rotation).invert();
m_Ball.m03 = newPos.X;
m_Ball.m13 = newPos.Y;
m_Ball.m23 = newPos.Z;
This is the solution I came up with after reading this link provided by #Spektre. Basically you just invert the ModelMatrix of the ball to get it into world position, do your rotation and then transform it back into local space.
You have to set the newPos Vector before you rotate, otherwise it would affect future transformations.
Related
I'm programming a game engine for educational purposes and I'm a bit stucked with rotations. The thing is that I have in the UI 3 squares to represent an object's orientation in Euler Angles, and from there I can change the values.
To change them, I call:
void TransformComponent::SetOrientation(glm::vec3 eulerAxAngles)
{
glm::vec3 euler_inRadians = glm::radians(eulerAxAngles);
glm::quat newRot;
double cy = cos(euler_inRadians.y * 0.5);
double sy = sin(euler_inRadians.y * 0.5);
double cp = cos(euler_inRadians.x * 0.5);
double sp = sin(euler_inRadians.x * 0.5);
double cr = cos(euler_inRadians.z * 0.5);
double sr = sin(euler_inRadians.z * 0.5);
newRot.w = cy * cp * cr + sy * sp * sr;
newRot.x = cy * cp * sr - sy * sp * cr;
newRot.y = sy * cp * sr + cy * sp * cr;
newRot.z = sy * cp * cr - cy * sp * sr;
m_Orientation = newRot * m_Orientation;
UpdateTransform();
}
m_Orientation is a quaternion storing the object's current orientation.I know all that conversion from eulers to quaternion could be handled by glm but I changed to this to debug what was happening...
Then, UpdateTransform() does the next:
void TransformComponent::UpdateTransform()
{
m_TransformationMatrix = glm::translate(glm::mat4(1.0f), m_Translation) *
glm::scale(glm::mat4(1.0f), m_Scale) * glm::mat4_cast(m_Orientation);
//Set euler angles
m_Rotation_InEulerAngles = glm::eulerAngles(m_Orientation);
}
And m_Rotation_InEulerAngles is the vec3 that can be seen from the UI to change the angles of the object's orientation.
The problem is that when I try to modify one of the 3 euler angles, the 3 are modified, I mean, if I modify the Roll angle (around Z axis), it modifies also Pitch and Yaw (not with the Z value, it's like it sets another orientation to the object).
In this gif is shown how the translation/scaling are well performed but rotation (here is seen in radians by now), is not well performed, it changes the whole orientation, not just the one in the axis I want:
https://gfycat.com/plushhonestargentineruddyduck
Does somebody sees what I'm I doing wrong?
Changing, or setting orientation, is not the same as rotating:
To set your orientation, you want to do it like this:
void setOrientation(glm::vec3 eular)
{
m_Orientation = glm::quat(eular); // very simple
}
void setRotation(glm::vec3 eular)
{
m_Rotation = glm::quat(eular); // very simple
}
To rotate, we want to integrate the rotation quaternion, using SLERP:
void update(float deltaTimeS)
{
glm::quat ident(1.0f);
glm::quat rotation = glm::mix(ident, m_Rotation, deltaTimeS);
m_Orientation = rotation * m_Orientation;
}
And to get your rotation matrix:
void setTransform()
{
m_RotationMatrix = glm::gtx::quaternion::toMat4(quaternion);
}
See here for more information on quaternion rotations.
I am trying to display a 360 panorama using an IMU for head tracking.
Yaw works correctly but the roll and pitch are reverse. I also notice that the pitch contains some roll (and maybe vice-versa).
I am receiving (W, X, Y, Z) coordinate from the IMU that I am storing in an array as X, Y, Z, W.
The next step is converting the quaternion to a rotation matrix. I have looked at many examples, and can't seem to find anything wrong with the following code:
static GLfloat rotation[16];
// Quaternion (x, y, z, w)
static void quaternionToRotation(float* quaternion)
{
// Normalize quaternion
float magnitude = sqrt(quaternion[0] * quaternion[0] +
quaternion[1] * quaternion[1] +
quaternion[2] * quaternion[2] +
quaternion[3] * quaternion[3]);
for (int i = 0; i < 4; ++i)
{
quaternion[i] /= magnitude;
}
double xx = quaternion[0] * quaternion[0], xy = quaternion[0] * quaternion[1],
xz = quaternion[0] * quaternion[2], xw = quaternion[0] * quaternion[3];
double yy = quaternion[1] * quaternion[1], yz = quaternion[1] * quaternion[2],
yw = quaternion[1] * quaternion[3];
double zz = quaternion[2] * quaternion[2], zw = quaternion[2] * quaternion[3];
// Column major order
rotation[0] = 1.0f - 2.0f * (yy + zz);
rotation[1] = 2.0f * (xy - zw);
rotation[2] = 2.0f * (xz + yw);
rotation[3] = 0;
rotation[4] = 2.0f * (xy + zw);
rotation[5] = 1.0f - 2.0f * (xx + zz);
rotation[6] = 2.0f * (yz - xw);
rotation[7] = 0;
rotation[8] = 2.0f * (xz - yw);
rotation[9] = 2.0f * (yz + xw);
rotation[10] = 1.0f - 2.0f * (xx + yy);
rotation[11] = 0;
rotation[12] = 0;
rotation[13] = 0;
rotation[14] = 0;
rotation[15] = 1;
}
The rotation matrix is then used in the draw call as such:
static void draw()
{
// Get IMU quaternion
float* quaternion = tracker.getTrackingData();
if (quaternion != NULL)
{
quaternionToRotation(quaternion);
}
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glPushMatrix();
// TODO: Multiply initialRotation quaternion with IMU quaternion
glMultMatrixf(initialRotation); // Initial rotation to point forward
glMultMatrixf(rotation); // Rotation based on IMU
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, texture);
gluSphere(quad, 0.1, 50, 50);
glBindTexture(GL_TEXTURE_2D, 0);
glPopMatrix();
glFlush();
glutSwapBuffers();
}
I tried to set all but one fields in the quaternion to 0, and I notice that they all work individually, except roll and pitch is swapped around. I tried swapping X and Y but this does not seem to help.
Any help would be really appreciated. Please let me know as well if you have any steps that can let me debug my issue. Thanks!
My Question
Can someone please link a good article/tutorial/anything or maybe even explain how to correctly cast a ray from the mouse coordinates to pick objects in 3D?
I already have the Ray and intersection works, now I only need to create the ray from the mouse click.
I would just like have something which I know actually should work, thats why I ask the professionals here, not something where I am unsure if it is even correct in the first place.
State right now
I have a ray class, which actually works and detects intersection if I set the origin and direction to be the same as the camera, so when I move the camera it actually selects the right thing.
Now I would like to actually have 3D picking with the mouse, not camera movement.
I have read so many other questions about this, 2 tutorials, and especially so much different math stuff, since I am really not good at it.
But that didn't help me much, because the people there often use some "unproject" functions, which seem to actually be deprecated and which I have no idea how to use and also don't have access to.
Right now I set the ray origin to the camera position and then try to get the direction of the ray from the calculations in this tutorial.
And it works a little bit, meaning the selection works when the camera is pointed at the object and also sometimes along the whole y-axis, I have no idea what is happening.
If someone wants to take a look at my code right now:
public Ray2(Camera cam, float mouseX, float mouseY) {
origin = cam.getEye();
float height = 600;
float width = 600;
float aspect = (float) width / (float) height;
float x = (2.0f * mouseX) / width - 1.0f;
float y = 1.0f - (2.0f * mouseX) / height;
float z = 1.0f;
Vector ray_nds = vecmath.vector(x, y, z);
Vector4f clip = new Vector4f(ray_nds.x(), ray_nds.y(), -1.0f, 1.0f);
Matrix proj = vecmath.perspectiveMatrix(60f, aspect, 0.1f, 100f);
proj = proj.invertRigid();
float tempX = proj.get(0, 0) * clip.x + proj.get(1, 0) * clip.y
+ proj.get(2, 0) * clip.z + proj.get(3, 0) * clip.w;
float tempY = proj.get(0, 1) * clip.x + proj.get(1, 1) * clip.y
+ proj.get(2, 1) * clip.z + proj.get(3, 1) * clip.w;
float tempZ = proj.get(0, 2) * clip.x + proj.get(1, 2) * clip.y
+ proj.get(2, 2) * clip.z + proj.get(3, 2) * clip.w;
float tempW = proj.get(0, 3) * clip.x + proj.get(1, 3) * clip.y
+ proj.get(2, 3) * clip.z + proj.get(3, 3) * clip.w;
Vector4f ray_eye = new Vector4f(tempX, tempY, tempZ, tempW);
ray_eye = new Vector4f(ray_eye.x, ray_eye.y, -1.0f, 0.0f);
Matrix view = cam.getTransformation();
view = view.invertRigid();
tempX = view.get(0, 0) * ray_eye.x + view.get(1, 0) * ray_eye.y
+ view.get(2, 0) * ray_eye.z + view.get(3, 0) * ray_eye.w;
tempY = view.get(0, 1) * ray_eye.x + view.get(1, 1) * ray_eye.y
+ view.get(2, 1) * ray_eye.z + view.get(3, 1) * ray_eye.w;
tempZ = view.get(0, 2) * ray_eye.x + view.get(1, 2) * ray_eye.y
+ view.get(2, 2) * ray_eye.z + view.get(3, 2) * ray_eye.w;
tempW = view.get(0, 3) * ray_eye.x + view.get(1, 3) * ray_eye.y
+ view.get(2, 3) * ray_eye.z + view.get(3, 3) * ray_eye.w;
Vector ray_wor = vecmath.vector(tempX, tempY, tempZ);
// don't forget to normalise the vector at some point
ray_wor = ray_wor.normalize();
direction = ray_wor;
}
First,unproject() method is the way to go.It is not deprecated at all.You can find it implemented in GLM math library for example.Here is my implementation of Ray based 3D picking:
// let's check if this renderable's AABB is clicked:
const glm::ivec2& mCoords = _inputManager->GetMouseCoords();
int mouseY = _viewportHeight - mCoords.y;
//unproject twice to build a ray from near to far plane"
glm::vec3 v0 = glm::unProject(glm::vec3(float(mCoords.x), float(mouseY), 0.0f),_camera->Transform().GetView(),_camera->Transform().GetProjection(), _viewport);
glm::vec3 v1 = glm::unProject(glm::vec3(float(mCoords.x), float(mouseY), 1.0f),_camera->Transform().GetView(),_camera->Transform().GetProjection(), _viewport);
glm::vec3 dir = (v1 - v0);
Ray r(_camera->Transform().GetPosition(),dir);
float ishit ;
//construct AABB:
glm::mat4 aabbMatr = glm::translate(glm::mat4(1.0),renderable->Transform().GetPosition());
aabbMatr = glm::scale(aabbMatr,renderable->Transform().GetScale());
//transforms AABB vertices(need it if the origianl bbox is not axis aligned as in this case)
renderable->GetBoundBox()->RecalcVertices(aabbMatr);
//this method makes typical Ray-AABB intersection test:
if(r.CheckIntersectAABB(*renderable->GetBoundBox().get(),&ishit)){
printf("HIT!\n");
}
But I would suggest you also to take a look at color based 3d picking which is pixel perfect and even easier to implement.
The problem is when I face my camera down the z axis for example and pitch this works fine however, after I have finished the pitch and would like to yaw on this new axis it begins to roll for some unknown reason =s.
void FrustumCamera::xAxisRotation(float angle)
{
// angle = angle * (double)degToRad;
Vector3<float> x = m_orientation.getXAxis();
Vector3<float> y = m_orientation.getYAxis();
Vector3<float> z = m_orientation.getZAxis();
y.rotateAroundAxis(x,angle);
x = m_orientation.getXAxis();
z.rotateAroundAxis(x,angle);
m_orientation.setYAxis(y);
m_orientation.setZAxis(z);
}
void FrustumCamera::yAxisRotation(float angle)
{
// angle = angle * (double)degToRad;
Vector3<float> x = m_orientation.getXAxis();
Vector3<float> y = m_orientation.getYAxis();
Vector3<float> z = m_orientation.getZAxis();
x.rotateAroundAxis(y,angle);
y = m_orientation.getYAxis();
z.rotateAroundAxis(y,angle);
m_orientation.setXAxis(x);
m_orientation.setZAxis(z);
}
void FrustumCamera::zAxisRotation(float angle)
{
Vector3<float> x = m_orientation.getXAxis();
Vector3<float> y = m_orientation.getYAxis();
Vector3<float> z = m_orientation.getZAxis();
x.rotateAroundAxis(z,angle);
z = m_orientation.getYAxis();
y.rotateAroundAxis(z,angle);
m_orientation.setXAxis(x);
m_orientation.setYAxis(y);
}
template <class Type>
void Vector3<Type>::rotateAroundAxis(Vector3<Type> axis, const float angle)
{
float radians = static_cast<Type>(angle * degToRad);
Type sinAngle = static_cast<Type>(sin(radians));
Type cosAngle = 0.0;
if (angle == 90 || angle == -90)
cosAngle = 0.0;
else
cosAngle = cos(radians);
normalise(axis); // normalise the axis
Type oneMinusCos = 1 - cosAngle; // (1 - cos(theta))
// construct the rotation matrix
Type tempMatrix[3][3];
tempMatrix[0][0] = (axis.x * axis.x) * oneMinusCos + cosAngle;
tempMatrix[0][1] = (axis.x * axis.y) * oneMinusCos + axis.z * sinAngle;
tempMatrix[0][2] = (axis.x * axis.z) * oneMinusCos - axis.y * sinAngle;
tempMatrix[1][0] = (axis.x * axis.y) * oneMinusCos - axis.z * sinAngle;
tempMatrix[1][1] = (axis.y * axis.y) * oneMinusCos + cosAngle;
tempMatrix[1][2] = (axis.y * axis.z) * oneMinusCos + axis.x * sinAngle;
tempMatrix[2][0] = (axis.x * axis.z) * oneMinusCos + axis.y * sinAngle;
tempMatrix[2][1] = (axis.y * axis.z) * oneMinusCos - axis.x * sinAngle;
tempMatrix[2][2] = (axis.z * axis.z) * oneMinusCos + cosAngle;
Vector3<Type> temp(*this);
Vector3<Type> result;
result.x = (temp.x * tempMatrix[0][0]) + (temp.y * tempMatrix[1][0]) + (temp.z * tempMatrix[2][0]);
result.y = (temp.x * tempMatrix[0][1]) + (temp.y * tempMatrix[1][1]) + (temp.z * tempMatrix[2][1]);
result.z = (temp.x * tempMatrix[0][2]) + (temp.y * tempMatrix[1][2]) + (temp.z * tempMatrix[2][2]);
*this = result;
}
void OpenGLRenderer::startDraw(unsigned long mask)
{
//sortBuffer(); // sort draw queue
clearBuffers(mask); // clear buffers
loadIdentity();
glTranslatef(-1*m_frustumCamera->getViewMatrix().getTranslationAxis().x,-1*m_frustumCamera->getViewMatrix().getTranslationAxis().y,-1*m_frustumCamera->getViewMatrix().getTranslationAxis().z);
glMultMatrixf(m_frustumCamera->getViewMatrix().getMatrix());
glTranslatef(m_frustumCamera->getViewMatrix().getTranslationAxis().x,m_frustumCamera->getViewMatrix().getTranslationAxis().y,m_frustumCamera->getViewMatrix().getTranslationAxis().z);// load identity
//
// push matrix stack
matrixStackPush();
}
You might be experiencing Gimbal Lock; this can happen if you pitch all the way up or down so your look vector becomes parallel with your up vector, In which case a yaw will be the same as a roll.
This can be a downside of constructing rotations piecemeal via Euler angles. You may want to look into quaternions. (Note that you cant rotate with Euler angles; they are just a representation for rotation (you need to convert it to matrix or quats), but the way you are tackling it is very much an 'Euler angle' way of thinking about it)
The strength of matrix multiplication is that any sequence of multiple rotations can be represented (and concatenated) as a single rotation matrix. What you need to be doing is something like this:
void Transformable::yaw(float angle)
{
float4x4 rot; // temp rotation matrix
float3 translate(&_transform._41); // save our translation
float3 up(&_transform._21); // y axis
// build the rotation matrix for rotation around y
MatrixRotationAxis(&rot, &up, angle);
// multiply our transform by the rotation matrix
// note that order of multiplication matters and depends on
// if your matrices are column-major or row-major
MatrixMultiply(&_transform, &_transform, &rot);
// write back our original translation
memcpy(&_transform._41, &translate, sizeof(float3));
// might want to reorthogonalise every now and then
// to make sure basis vectors are orthonormal
// or you will probably get matrix creep after a few operations
}
instead of trying to rotate one basis vector at a time. In this case _transform would be a 4x4 homogenous matrix representing the transformation matrix. (rotation and translation). The topleft 3x3 submatrix is simply the basis vectors of the orientation space.
I was setting up a camera following this tutorial. My problem is that when I move it isn't fluid, it kinda jumps. I'm calculating the MVP whenever the mouse moves using this code:
void motion(int x, int y) {
static bool wrap = false;
if(!wrap) {
int ww = glutGet(GLUT_WINDOW_WIDTH);
int wh = glutGet(GLUT_WINDOW_HEIGHT);
int dx = x - ww / 2;
int dy = y - wh / 2;
const float mousespeed = 0.001;
angles.x += dx * mousespeed;
angles.y += dy * mousespeed;
if(angles.x < -M_PI)
angles.x += M_PI * 2;
else if(angles.x > M_PI)
angles.x -= M_PI * 2;
if(angles.y < -M_PI / 2)
angles.y = -M_PI / 2;
if(angles.y > M_PI / 2)
angles.y = M_PI / 2;
lookat.x = sinf(angles.x) * cosf(angles.y);
lookat.y = sinf(angles.y);
lookat.z = cosf(angles.x) * cosf(angles.y);
view = glm::lookAt(position, position + lookat, glm::vec3(0, 1, 0));
// move mouse pointer back to the center of the window
wrap = true;
glutWarpPointer(ww / 2, wh / 2);
} else {
wrap = false;
}
}
And then I'm updating the attribute on my 'OnIdele()' function:
void onIdle() {
glUseProgram(program);
glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
glm::mat4 Model = glm::mat4(1.0f);
glm::mat4 MVP = Projection * view * Model;
glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, glm::value_ptr(MVP));
glutPostRedisplay();
}
My question is, is this the right way to implement this? Is there any way to avoid the laggyness?
Also if you don't mind me asking, how exactly does this code work? I know it limits where you can look but I can't seem to make sense of it:
if(angles.x < -M_PI)
angles.x += M_PI * 2;
else if(angles.x > M_PI)
angles.x -= M_PI * 2;
if(angles.y < -M_PI / 2)
angles.y = -M_PI / 2;
if(angles.y > M_PI / 2)
angles.y = M_PI / 2;
See if increasing mousespeed makes a difference. After you find the distance the mouse has moved, stored in dx and dy, you scale the distance by mousespeed before adding it to the camera's angles. The lower the value of mousespeed the less your mouse movement will affect the angles of your camera, and vice versa.
Also the code you asked about is limiting your camera angles to between 0 and PI * 2, or 0 and 360 degrees.