I have a hierarchy like this:
--gun
\--bullet
In unity3d and I want the bullets specific axis meet with the guns specific axis
like this:
Note the Bule(z axis)
And here is the gun's transform
And I want to rotate the ball's transform so that the Z axis of the ball coincides with the guns Y axis
like this:
So How could I do that? thanks
A simple LookAt should do the job :
bullet.transform.LookAt( bullet.transform.position + gun.transform.up ) ;
LookAt :
Rotates the transform so the forward vector points at the given world position.
You can specify an additional vector if you want the up vector of your transform to point to a specific direction.
I think using LookRotation might solve your issue.
bullet.transform.rotation = Quaternion.LookRotation(gun.transform.forward, gun.transform.up);
What this does is that it creates a rotation based on a forward and up vector. So you might want to set something different than what I have in my example, but hopefully you'll get the idea.
Related
I've got a 3d sphere which I've been able to plot a point on using longitude and latitude thanks to some work of another developer I've found online. I think I understand what its doing.
What I need to do now is rotate my planet so the point is always at the top most point (ie the north pole) but I'm not sure how to do this. I'm probably missing some important fundamentals here so I'm hoping the answer can assist in my future learning.
Here's an image showing what I have - The blue line is a line coming from the longitude and latitude I have plotted and I need to rotate the planet so that line is basically pointing directly upwards.
https://ibb.co/2y24FxS
If anyone is able to advise it'd be very much appreciated.
If I'm not mistaken, Unity uses a coordinate system where the y-axis points up.
If the point on your sphere was in the xy-plane, you'd just have to determine the angle between the radius-vector (starts in the center of the sphere, ends on the point in question) and the y-axis, and than rotate by that amount around the z-axis, so that the radius vector becomes vertical. But your point is at an arbitrary location in 3D space - see the image below. So one way to go about it is to first bring the point to the xy-plane, then continue from there.
Calculate the radius vector, which is just r = x-sphereCenter. Make a copy of it, set y to zero, so that you have (x, 0, z) - which is just the projection of the vector r on the horizontal xz-plane - let's call the copy rXZ.
Determine the signed angle between the x-axis and rXZ (use Vector3.SignedAngle(xAxis, rXZ, yAxis), see docs), and create a rotation matrix M1 that rotates the sphere in the opposite direction around the vertical (negate the angle). This should place your point in the xy-plane.
Now determine the angle between r and the y-axis (Vector3.SignedAngle(r, yAxis, zAxis)), and create a new rotation matrix M2 that rotates by that angle around the zAxis. (I think for this second one, the simpler Vector3.Angle will work as well.)
So, what you want now is to combine the two matrices (by multiplying them) into a single transform (I'm assuming this is a transformation in the local coordinate system of the sphere, where (0, 0, 0) is the sphere's center). If I'm not mistaken, Unity uses column-major matrices, so the multiplication order should be M = M2 * M1 (the rightmost matrix is applied first).
Reorient your globe using M as a local transform, and it should bring your point to the top. You can also create M3 = M1.inverse, and then do M = M3 * M2 * M1, to preserve the original angular offset from the xy-plane.
Check for edge cases, such as r already being vertical (pointing straight up, or straight down).
like the title says, i essentially want to set the y rotation of gameobject1 to gameobject2, but gameobject1 already has changed rotation to something else than 0,0,0 in degrees. Say for example the rotation is 34, 50, 16. Since the rotation has changed the axis have changed too, meaning they aren't pointing in the x, y and z directions anymore. so if we try to get the y rot, we instead end up getting the rotation of an axis on the right, because of the rotation the y axis has moved there.
Sorry if im really vague with this, cannot explain this any better as its pretty late and i've tried to solve this for three days straight. Therefore, any help is highly appreciated.
Use transform.RotateAround(target, Vector3.up, float yourRotation), where for your problem target = Vector3.zero. See the doc here : https://docs.unity3d.com/ScriptReference/Transform.RotateAround.html
Background: I am creating an AR treasure hunt app. It is simple, it has a locator that tells you where the treasure is relative to you. I have the camera being the origin and the treasure being an object in AR world.
Question: I would like to rotate my arrow according to where in space the treasure is at. but in 2d. Basically, I would ignore the relative forward plane that is camera.forward.
Example: If the camera rotation is default, the angle can be calculated as atan2(dy,dx). If the camera is looking straight down, the angle is atan2(dz,dx).
What I have tried:
Quaternion lookRot = Quaternion.LookRotation(target.transform.position - origin.transform.position);
Quaternion relativeRot = Quaternion.Inverse(origin.transform.rotation) * lookRot;
Relative rotation is correct in 3d space but I would like to convert that into 2d ignoring the camera.forward plane. So even if the treasure is in front or behind the camera, it should not change the angle.
Okay so I’m hoping this makes sense. You’re going to need some sort of if statement to determine if your character is looking along the x, y or z plane. Hopefully the diagram is clear as to what those parameters are but if not. To be looking in the “x” plane for example, the y rotation would have to be between 45° and -45° or 135° and -135° AND the z rotation would have to be between 45° and -45° or between 135° and -135°.
Essentially what you’ve got is a sphere split into six parts, two parts for each plane along which the character could look. Once you’ve determined which plane the character is looking in you can determine the direction by finding the difference in position between the character and the treasure along the two planes the character isn’t looking along. Then use trig to calculate the angle
Replying to an old thread, but I was struggling with the same problem and found a relatively simple solution:
Project the position of the target (relative to the origin) on a plane defined by the forward vector of the camera. Then just rotate towards the projected point:
Vector3 diff = target.transform.position - origin.transform.position;
Vector3 projected = Vector3.ProjectOnPlane(diff, Camera.main.transform.forward);
origin.transform.rotation = Quaternion.LookRotation(projected);
Calculate the difference in x and y coordinates simply by subtracting transform.x for one object by transform.x of another object and the same process for y coordinates and then use Mathf.atan(difference in y/difference in x) to calculate the angle. Then put the z rotation to this angle and assign the x and y rotation to what they already were.
Turns out there is a very simple way to get relative X and Y of the target.
Vector2 ExtractRelativeXY(Transform origin, Transform target) {
// Get the absolute look rotation from origin to target.
Quaternion lookRot = Quaternion.LookRotation(target.transform.position - origin.transform.position);
// Create a relative look rotation with respect to origin's forward.
Quaternion relativeRot = Quaternion.Inverse(origin.transform.rotation) * lookRot;
// Obtain Matrix 4x4 from the rotation.
Matrix4x4 m = Matrix4x4.Rotate(relativeRot);
// Get the 3rd column (which is the forward vector of the rotation).
Vector4 mForward = m.GetColumn(2);
// Simply extract the x and y.
return new Vector2(mForward.x, mForward.y);
}
Once obtained x and y, turn it into angle using angle = atan2(y,x) as suggested by both MBo and Tom.
This works because of the matrix components of the quaternion can be demonstrated in multiple vectors. Better illustration is found here https://stackoverflow.com/a/26724912.
Using Matlab, how can I calculate a two points in Equilateral triangle if there are known one point and the Center of Gravity in a 3D ?
I know there is a infinite solutions but i need just a random one.
Thank you.
Take the vector pointing from the center of gravity to the point.
Create an orthogonal vector (this can be done in a few ways, I usually take the first vector, add 1.0 to each component until it is not parallel, then take the cross product with the original vector).
Rotate your vector 120 degrees about the orthogonal vector. (look up the rotation matrix about an arbitrary vector)
Create your second point by adding that vector to your center of gravity.
Create your third point by rotating it again or in the opposite direction.
I am trying to solve a tricky math problem, in a cocos2d for iphone context.
Basically I have a roullette wheel which is rotating over time.
I want to have a Sprite latch onto the wheel at certain points (like compass ordinal points N, S, E, W) and bounce off at all other points.
I have the image of the wheel rotating, and just need to solve the part where I can test for whether a sprite has intersected with the circle at the right point on the circle as it is rotating.
I think this question is going in the right direction, but I can't get my head around it. Can anyone help explain?
Best way to find a point on a circle closest to a given point
If I understand correctly:
First check the distance between the sprite and the centre of the roulette wheel. This will tell you if the sprite is at the edge of the wheel. (If not, nothing happens, right?)
Then, find the angle that the sprite makes from the "x-axis" of the roulette wheel.
spriteAngle = atan2(sprite.x - rouletteCentre.x, sprite.y - rouletteCentre.y)
You'll need to find the equivalent of the atan2() function. It usually returns an answer in radians; you may want to convert it to degrees or quarter-turns or something if you prefer.
Then, subtract the angle that the roulette wheel itself is rotated by (if the wheel itself is rotating, if not then you're already done). Make sure your angle measurement is consistent.
actualAngle = spriteAngle - rouletteRotationAngle
Note that actualAngle may be outside the range 0-360 degrees, and you will need to make it "wrap around".
Lastly, you will want to allow a small range of values as acceptable (e.g. 98 degrees to 102 might count as "North").
So you have a circle of radius r, with center (x0,y0).
A point lies outside of the circle, at coordinates (x,y). Your question is to find the closest point on the circle itself to the point (x,y).
The solution is simple. The closest projection of a point onto a circle is accomplished by a simple scaling. Thus,
d = sqrt((x-x0)^2 + (y-y0)^2)
xp = x0 + (x - x0)*r/d
yp = y0 + (y - y0)*r/d
The new point (xp,yp) will lie on the circle itself. To be honest, you would be better off to work in polar coordinates, with the origin at the center of the circle. Then everything gets much easier.
Your next question will be where did it hit on the circle? Don't forget the points of the compass on the circle are rotating with time. An atan2 function will give you the angle that the point (xp-x0,yp-y0) lies at. Most toolsets will have that functionality. See that I've subtracted off the origin here.