Example Image here
I am trying to find a way to calculate points on my cylinders top circle surface. My situation looks like this, I have a vector which is defining my cylinders direction in 3d room. Then I already calculated me a perpendicular vector with
Vector3.Cross(vector1, vector2)
Now I use the diameter/2 to calculate the point which is lying on the edge of the circular top surface of my cylinder. Now I want to rotate my vector always 90 degrees in order to get 4 points on the edge of the surface. All the 4 vectors defining them should be perpendicular to the cylinders direction. Can you help me how I can rotate the first perpendicular to achieve this?
I already tried:
Matrix4x4.CreateFromAxisAngle(vectorcylinderdirection, radiant)
Then I calculated again cross product but it doesnt work like I want to.
Edit:
public static void calculatePontsOnCylinder()
{
//Calculate Orthogonal Vector to Direction
Vector3 tCylinderDirection = new Vector3(1, 0, 0);
Vector3 tOrthogonal = Vector3.Cross(tCylinderDirection, new Vector3(-tCylinderDirection.Z,tCylinderDirection.X,tCylinderDirection.Y));
Vector3 tNormOrthogonal = Vector3.Normalize(tOrthogonal);
//Calculate point on surface circle of cylinder
//10mm radius
int tRadius = 10;
Vector3 tPointFinder = tNormOrthogonal * tRadius;
//tPointFinder add the cylinder start point
//not yet implemented
//now i need to rotate the vector always 90 degrees to find the 3 other points on the circular top surface of the cylinder
//don't know how to do this
// I thought this should do it
Matrix4x4.CreateFromAxisAngle(tCylinderDirection, (float)DegreeToRadian(90));
}
private static double DegreeToRadian(double angle)
{
return Math.PI * angle / 180.0;
}
In the picture you can see a example, the vector1 is what I need, always rotated 90 degrees and vector2 would be my cylinder direction vector
I possibly have found the correct formula:
Vector3 tFinal = Vector3.Multiply((float)Math.Cos(DegreeToRadian(90)), tPointFinder) + Vector3.Multiply((float)Math.Sin(DegreeToRadian(90)), Vector3.Cross(tCylinderDirection, tPointFinder));
Vector3 tFinal180 = Vector3.Multiply((float)Math.Cos(DegreeToRadian(180)), tPointFinder) + Vector3.Multiply((float)Math.Sin(DegreeToRadian(180)), Vector3.Cross(tCylinderDirection, tPointFinder));
Vector3 tFinal270= Vector3.Multiply((float)Math.Cos(DegreeToRadian(270)), tPointFinder) + Vector3.Multiply((float)Math.Sin(DegreeToRadian(270)), Vector3.Cross(tCylinderDirection, tPointFinder));
Interesting is that if I try it with (1,1,0) as cylinder direction it gives me correct directions but the length is different for 90 degrees and 270.
Here is the code that should solve your problem assuming that the input requirements are satisfied.
float zCutPlaneLocation = 20; // should not get bigger than cylinder length
float cylinderRadius = 100;
Vector3 cylinderCenter = new Vector3(0, 0, 0); // or whatever you got as cylinder center point, given as Vector3 since Point type is not defined
// will return 360 points on cylinder edge, corresponding to this z section (cut plane),
// another z section will give another 360 points and so on
List<Vector3> cylinderRotatedPointsIn3D = new List<Vector3>();
for (int angleToRotate = 0; angleToRotate < 360; angleToRotate++)
{
cylinderRotatedPointsIn3D.Add(GetRotatedPoint(zCutPlaneLocation, angleToRotate, cylinderRadius, cylinderCenter));
}
....
private static Vector3 GetRotatedPoint(
float zLocation, double rotationAngleInRadian, float cylinderRadius, Vector3 cylinderCenter)
{
Vector2 cylinderCenterInSection = new Vector2(cylinderCenter.X, cylinderCenter.Y);
float xOfRotatedPoint = cylinderRadius * (float)Math.Cos(rotationAngleInRadian);
float yOfRotatedPoint = cylinderRadius * (float)Math.Sin(rotationAngleInRadian);
Vector2 rotatedVector = new Vector2(xOfRotatedPoint, yOfRotatedPoint);
Vector2 rotatedSectionPointOnCylinder = rotatedVector + cylinderCenterInSection;
Vector3 rotatedPointOnCylinderIn3D = new Vector3(
rotatedSectionPointOnCylinder.X,
rotatedSectionPointOnCylinder.Y,
zLocation + cylinderCenter.Z);
return rotatedPointOnCylinderIn3D;
}
I just created a console app for this. First part of code should be added in main method.
Working with those matrices seems is not that easy. Also I am not sure if your solution works ok for any kind of angle.
Here the idea is that the rotated points from cylinder are calculated in a section of the cylinder so in 2D than the result is moved in 3D by just adding the z where the Z section was made on cylinder. I suppose that world axis and cylinder axis are on the same directions. Also if your cylinder gets along (increases) on the X axis, instead of Z axis as in example just switch in code the Z with X.
I attached also a picture for more details. This should work if you have the cylinder center, radius, rotation angle and you know the length of the cylinder so that you create valid Z sections on cylinder. This could get tricky for clockwise/counter clock wise cases but lets see how it works for you.
If you want to handle this with matrices or whatever else I think that you will end up having this kind of result. So I think that you cannot have "all" the rotated points in just a list for the entire cylinder surface, they would depend on something like the rotated points of a Z section on the cylinder.
Related
I have this formula to rotate around a sphere
double naX = o.Node.Angle.X;
double naY = o.Node.Angle.Y;
double x = o.DrawingPosition.X - 4.0 * Math.Cos(naX) * Math.Sin(naY);
double y = o.DrawingPosition.Y - 4.0 * Math.Sin(naX) * Math.Sin(naY);
double z = o.DrawingPosition.Z - 4.0 * Math.Cos(naY);
Where 4.0 is the radius to follow and o.DrawingPosition is the center
I want it to rotate along the transform x axis (I have a quaternion and a unit vector normalized for calculated for the Z -1 normal) but if I add offsets the angles won't match
naX += _rotationTicks;
naY += _rotationTicks;
For example, it will follow a infinite shaped trajectory, how can I calculate the correct rotation so it behaves like a perfect circle?
Edit:
I found this answer on Rotating body from spherical coordinates
But the main core difference is that both the XY rotation angles and the origins are arbitrary values, there is a forward vector calculated with a quaternion to determine facing like this:
var quat = System.Numerics.Quaternion.CreateFromYawPitchRoll((float)o.Node.Angle.X, (float)o.Node.Angle.Y, 0);
var dirVec = new Vector3(0, -1, 0).ToNumerics();
var downwards = quat.Multiply(dirVec); // it can be backwards, left, right, etc, changing the unit vector from dirVec
Thanks in advance.
So... I'll try to be as clear as possible, if I let something unclear please let me know.
I have a vector that comes from origin and go to a point in space, and I have an object that I want it's transform.up (Or Y vector) to be colinear with this vector, but the Y rotation of this object is driven by another factor, and I dont want to change it.
So far, what I'm trying to do is project this vector in the local XY and local ZY planes and measure the angles and apply rotation:
float xInclination = Mathf.Atan(Vector3.ProjectOnPlane(orbitMomemtumVector, transform.right).z / Vector3.ProjectOnPlane(orbitMomemtumVector, transform.right).y)*Mathf.Rad2Deg;
float yInclination = Mathf.Atan(initialPos.z / initialPos.x) * Mathf.Rad2Deg;
float zInclination = -Mathf.Atan(Vector3.ProjectOnPlane(orbitMomemtumVector, transform.forward).x / Vector3.ProjectOnPlane(orbitMomemtumVector, transform.forward).y)*Mathf.Rad2Deg;
if (initialPos.x < 0 && initialPos.z > 0)
{
yInclination = 180f - Mathf.Abs(yInclination);
argumentPeriapsis = argumentPeriapsis - yInclination;
}
else if (initialPos.x < 0 && initialPos.z < 0)
{
yInclination = 180f + Mathf.Abs(yInclination);
argumentPeriapsis = argumentPeriapsis - yInclination;
}
else
{
argumentPeriapsis = argumentPeriapsis - yInclination;
}
transform.rotation = Quaternion.Euler(xInclination, (float)argumentPeriapsis, zInclination);
This image shows the problem, I need the Y arrow to be collinear with the blue line
Let me be clear on this, don't use Euler angles in 3d space. In fact, avoid them in 2d games as well. Unless your object truly rotates on a single axis, and you never have to get the angle between two rotations, or lerp your rotations, don't use them.
What you want is Quaternion.LookRotation(A, B).
A being a vector to which Z will be colinear, X being orthogonal to the plane defined by A and B, and Y belonging to that plane.
Followup:
To match other axis to A, there are multiple solutions. First would be to simply apply the lookRotation to a parent object, while the child object is rotated inside to match whatever rotation you want. You can also edit your entire mesh to do so.
The other way is to simply apply another rotation, so that both combined get your desired result, like so:
Quaternion zMatched = Quaternion.LookRotation(zAxisTarget, direction)
Quaternion yMatched = zMatched * Quaternion.AngleAxis(90f, Vector3.right);
transform.rotation = yMatched;
This will rotate the object so that the y axis becomes collinear to the previous z axis.
This is however nor perfect. If you reach this point, you should consider building your own clearer solution based on combining AngleAxis results. But it works well enough.
I have a player position, a pointer indicating the players view direction, a distance and a horizontal and vertical angle. I want to calculate a target position:
that is distance away from the players position
that, from the players view direction, is horizontal angle to
the right and vertical angle up
It's about positioning a Hololens-Application UI in a sphere around the player. The UI should i.e. be 40 degrees to the leftand 20 degrees up from the players view direction.
Edit: Added image to clarify. Given is the Player Pos (pX|pY|pZ), the radius (= length of the black bold line) and both angles in degree.
I'm looking for how to calculate the UI Center position (x?|y?|z?).
You can use Quaternion.Euler to create a rotation based on angles in world space and then get the desired result by multiplying it with a known position.
So by using your example you could find the position like this:
float radius, x_rot, y_rot;
Vector3 forwardDirection, playerPos;
Vector3 forwardPosition = playerPos + (forwardDirection * radius);
Vector3 targetPosition = Quaternion.Euler(x_rot, y_rot, 0) * forwardPosition;
Try check out the docs on Quaternion and Quaternion.AngleAxis for more handy rotation stuff.
Answer by a mathematician:
To calculate the spherical position with the given information (distance between objects, x angle, y angle) you use trigonometry:
float x = distance * Mathf.Cos(yAngle) * Mathf.Sin(xAngle);
float z = distance * Mathf.Cos(yAngle) * Mathf.Cos(xAngle);
float y = distance * Mathf.Sin(yAngle);
ui.transform.position = player.transform.position + new Vector3(x,y,z);
// Set UI in front of player with the same orientation as the player
ui.transform.position = player.transform.position + player.transform.forward * desiredDistance;
ui.transform.rotation = player.transform.rotation;
// turn it to the left on the players up vector around the the player
ui.transform.RotateAround(player.transform.position, player.transform.up, -40);
// Turn it up on the UI's right vector around the player
ui.transform.RotateAround(player.transform.position, ui.transform.right, 20);
assuming you also want the UI to face the player, otherwise you have to set another rotation after this.
No need to calculate it yourself, the Unity API already does it for you (
see Rotate around)
If i am understanding you correctly you want to create a UI that hovers above a point. I recently did a similar thing in my game. and this is how i did it.
if (Input.GetMouseButtonDown(0)) // use the ray cast to get a vector3 of the location your ui
// you could also do this manualy of have the computer do it the main thing is to
// get the location in the world where you want your ui to be and the
// WorldTOScreenPoint() will do the rest
{
RaycastHit hit;
Vector3 pos;
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
if (Physics.Raycast(ray, out hit))
{
pos = hit.point;
pos.y += yOffset; // use the offset if you want to have it hover above the point
ui.transform.position = cam.WorldToScreenPoint(pos); // use your main cammera here
// then either make your ui vissible or instanciati it here and make sure if you instanciate it
// that you make it a child of your cnavas
}
}
I hope this solves you problem. If i am not understanding what you are trying to do let me know and i will try to help.
Note: if you want to make the ui look farther away when you move away from the point scale the ui down as you move farther away, and scale it up when you get closer.
The diagram in the question is somewhat confusing:
The axes are in the orientation of a right-handed coordinate system, but Unity uses a left-handed coordinate system.
In terms of Euler angles, the part of the image labeled "x Angle" is actually the Y angle (rotation around Y axis), and the part of the image labeled "y Angle" is actually the X angle (around X axis).
The two angles listed use a different sign convention. The Y angle (labeled "x Angle") is following the right-hand rule, while the other angle is not.
Jonas Zimmer has a great answer that follows the conventions in the image, but I'll try to do something a bit less confusing and follows more standard math conventions.
Here is some code for Unity written in C#, in YX rotation order, treating zero angle as forward (+Z), and follows Unity's conventions of a left-handed, Y-is-up, Z-is-forward coordinate system. Increasing Y angle rotates to the right, and increasing X angle rotates down.
public static Vector3 Vector3FromAngleYX(float y, float x)
{
float cosx = Mathf.Cos(x);
return new Vector3(cosx * Mathf.Sin(y), -Mathf.Sin(x), cosx * Mathf.Cos(y));
}
Also, I found this question looking to implement a Godot version, so here is a version for Godot Engine written in GDScript, in YX rotation order, treating zero angle as forward (-Z), and follows Godot's conventions of a right-handed, Y-is-up, Z-is-back coordinate system. Increasing Y angle rotates to the left, and increasing X angle rotates up.
func vector3_from_angle_yx(y, x):
var neg_cosx = -cos(x)
return Vector3(neg_cosx * sin(y), sin(x), neg_cosx * cos(y))
I have the normals of three planes which are at 90 degrees to each other and pass through the origin.
I also have the distances of a point to the three planes. How can I determine the position of the point in C#?
Heres what I have so far...
public static Vector3 RealWorldSpaceToOtherSpace(Vector3 realspace, Vector4 clipplane)
{
// Work out the normal vectors of 3 imaginary planes
Vector3 floor = new Vector3(clipplane.X, clipplane.Y, clipplane.Z);
Vector3 centre = new Vector3(1f, -clipplane.X / clipplane.Y, 0f);
Vector3 wall = Vector3.Cross(floor, centre);
// Get distances from the planes
float distanceToFloor = realspace.y;
float distanceToCentre = realspace.x;
float distanceToWall = realspace.z;
// ?
// ? do stuff here
// ?
// return ????
}
Since the planes are at 90 degrees to each other, and pass through the origin, their normals form an orthogonal coordinate system with the same origin. Thus the distance to each plane is the coordinate of the point along the axis corresponding to the plane's (normalized) normal, in the new coordinate system.
Hence find the normalized normals of each plane, multiply by the corresponding distance to the plane, and add up to find the point.
A caveat is that you need to know which side of each plane the point is on; if it is on the other side of the normal, put a minus sign in front of the corresponding distance.
When given the distance from the point to one plane. The point can now be at any one point inside a plane that is at the defined distance from your first plane, so you have narrowed down the position from anywhere within the 3 dimensions to anywhere with these subset of the 3rd dimension which only has 2 dimensions..
When you are given the distance from the point to a second plane. You now have that same information, a plane at which the point can be. You will notice that both of these plains intersect and form a line. There's no need to store this line. Just know that you have narrowed down the possible point's position to 1 dimension.
Finally you are given the distance from the point to the third plane. You can create the new plane at the defined distance from the original plane , and this plane should intersect the other 2 new planes. All three planes will intersect at one point, which will be the position of the point.
Thankfully we can add the distance to the planes vector in order to create the new planes. And then we can finally get the point's position by using each of the plane's relevant dimensions in order to get the point's position.
public static Vector3 RealWorldSpaceToOtherSpace(Vector3 realspace, Vector4 clipplane)
{
// Work out the normal vectors of 3 imaginary planes
Vector3 floor = new Vector3(clipplane.X, clipplane.Y, clipplane.Z);
Vector3 centre = new Vector3(1f, -clipplane.X / clipplane.Y, 0f);
Vector3 wall = Vector3.Cross(floor, centre);
// Get distances from the planes
// Distance is represented as a Vector, since it needs to hold
// the direction in 3d space.
Vector3 distanceToFloor = new Vector3(0f, realspace.y ,0f,);
Vector3 distanceToCentre = new Vector3( realspace.x ,0f,0f,);
Vector3 distanceToWall = new Vector3(0f,0f, realspace.z );
// Create planes that contain all the possible positions of the point
// based on the distance from point to the corresponding plane.
Vector3 pointY = floor + distanceToFloor;
Vector3 pointX = centre + distanceToCentre;
Vector3 pointZ = wall + distanceToWall;
// Now that we have all 3 point's dimensions, we can create a new vector that will hold its position.
Vector3 point = new Vector3(pointX.x,pointY.y, pointZ.z);
return point
}
Note that there is a plane struct in Unity.
I'm making an XNA game and have run into a small problem figuring out a bit of vector math.
I have a class representing a 2D object with X and Y integer coordinates and a Rotation float. What I need is to have a Vector2 property for Position that gets and sets X and Y as a Vector2 that has been transformed using the Rotation float. This way I can just do something like;
Position += new Vector2((thumbstick.X * scrollSpeed), -(thumbstick.Y * scrollSpeed));
and the object will move in it's own upward direction, rather than the View's upward direction.
So far this is what I have...I think the set is right, but for += changes it needs a get as well and the answer just isn't coming to me right now... >.>
public Vector2 Position
{
get
{
// What goes here? :S
}
set
{
X = value.X * (int)Math.Cos(this.Rotation);
Y = value.Y * (int)Math.Cos(this.Rotation);
}
}
No, both are incorrect.
A 2D vector transforms like this:
x' = x*cos(angle) - y*sin(angle)
y' = x*sin(angle) + y*cos(angle)
where the angle is measured in radians, zero angle is along the positive x-axis, and increases in the counterclockwise direction as you rotate around the z-axis out of plane. The center of rotation is at the end of the vector being transformed, so imagine the vector with origin at (0,0), end at (x,y) rotation through an angle until it becomes a vector with origin at (0,0) and end at (x', y').
You can also use the Matrix helper methods to create a Z rotation matrix then multiply your vector by this to rotate it. Something like this:
Vector v1;
Matrix rot = Matrix.CreateRotationZ(angle);
Vector v2 = v1 * rot;
I think this is a bad idea. Keep all of your objects' X and Y co-ordinates in the same planes instead of each having their own axes. By all means have a Position and Heading properties and consider having a Move method which takes your input vector and does the maths to update position and heading.