I want to get the position of the sprite while its rotated,
Example
The bigger dot is the location i want to get (while rotated), and the sprite is rotated so its quite hard to get that, and im clueless of how to get it, the origin is (0,0) for anyone asking, is there any math that needs to be done to get this?
What you need to do is create a Vector2 from the origin to the rotated point before it's rotated and then rotate that vector.
For example, let's say we have a sprite with the origin point in the center and we want to know where the front point will be when the sprite is rotated.
First, create a vector from the origin to the point you want rotated on the unrotated sprite. In this case it's probably going to be something like 20 pixels to the right of the center:
var vector = new Vector2(20, 0);
Now we can rotate our vector with this simple function (borrowed from MonoGame.Extended)
public static Vector2 Rotate(Vector2 value, float radians)
{
var cos = (float) Math.Cos(radians);
var sin = (float) Math.Sin(radians);
return new Vector2(value.X*cos - value.Y*sin, value.X*sin + value.Y*cos);
}.
Now we can get our rotated vector like so:
var radians = MathHelper.ToRadians(degrees: -33);
var rotatedVector = Rotate(vector, radians);
To get this vector back into "sprite" space we can add it back to our origin point:
var point = origin + rotatedVector;
Or alternately if you want it in "world" space you can also add it to your sprites position.
var worldPoint = position + origin + rotatedVector;
Happy coding!
Related
I am trying to determine the angle where the camera forward vector intersect with an object vector.
Sorry, not straight forward to explain with my knowledge, please find attached a diagram: The camera may not be looking directly at the object (OBJ) and I'd like to know the angle ( ? in the diagram) where the camera's forward vector (V1 in red) intersects with the vector of the object (V2 in red) (if it does), e.g. point A, or B, or C, etc depending on the x-rotation of the camera.
I tried calculating a normalized vector for the red lines, v1 and v2.
Then calculate the angle between two vectors https://onlinemschool.com/math/library/vector/angl/
But the results don't match the expected values when testing.
//v1
Vector3 hypoth = Camera.main.transform.forward.normalized;
//v2
Vector3 adjacent = (new Vector3(obj.transform.position.x, obj.transform.position.y, Camera.main.transform.position.z)
-obj.transform.position).normalized;
float dotProd = Vector3.Dot(adjacent, hypoth);
float cosOfAngle = dotProd / (Vector3.Magnitude(adjacent) * Vector3.Magnitude(hypoth));
double radAngle = Math.Acos(cosOfAngle);
float angle = (float)((180 / Math.PI) * radAngle);
Finding the angle between v1 and v2 gives you this angle, which doesn't match what you mark in your diagram:
Instead, solve for the angle between v1 and the plane normal to v2:
We can do this in unity by projecting v1 to the plane normal to v2 using Vector3.ProjectOnPlane, and then finding the angle between that projection and v1 using Vector3.Angle:
Vector3 projection = Vector3.ProjectOnPlane(hypoth, adjacent);
float angle = Vector3.Angle(projection, hypoth);
I've a similar situation where I wanted to set the collidars of the terrain units on the same height of the player Jet and at the same time it must be on the line of sight of the camera, otherwise when u shoot the terrain units , the bullets will appear like moving through enemy units on the ground , this only works when you work with prospective camera, on orthongal , u may dont need to do this at all, its just set the object on the same height as the camera and everything will be aligned .
Here is my code
void SetColliderLocation()
{
// Object on the ground
A = TerrainUnit.transform.position;
// Camera location
B = cam.transform.position;
// Enemy jet height
height = mainPlayerTransform.position.y;
// Unit Vector normalized between A and B
AB_Normalized = (A - B).normalized;
// The unit vector required to move the collider to maintain its hieght and line of sight with the camera
unitVector = (height - A.y) / AB_Normalized.y;
// Setting the location of the collidar .
collidarGameObject.transform.position = (AB_Normalized * unitVector) + A;
}
I hope its some how similar of what you are looking for.
Edit:
If you applied this script and instead of collider you put a box , you will see the box location will be always between the camera on the sky and object on the ground however the camera or the object on the ground is moving.
The following function calculates the target vector of my FPS camera to put in the OpenGL LookAt method. Camera orientation (in radians) (0,0,0) means the camera is parallel to the z axis looking in the negative direction and the camera right vector is parallel to the x axis in the positive direction.
static Matrix4 GetViewMatrix()
{
Vector3 cameraup = Vector3.Transform(Vector3.UnitY,(Quaternion.FromAxisAngle(LineOfSightVector, Orientation.Z)));
LineOfSightVector.X = (float)(Math.Sin((float)Orientation.X) * Math.Cos((float)Orientation.Y));
LineOfSightVector.Y = (float)Math.Sin((float)Orientation.Y);
LineOfSightVector.Z = (float)(Math.Cos((float)Orientation.X) * Math.Cos((float)Orientation.Y));
return Matrix4.LookAt(Position, Position + LineOfSightVector, cameraup) * View; //View = createperspectivefield of view matrix4
}
It works fine when the camera y axis is (0,1,0). However I have introduced a Z value to my camera orientation (roll). I use that to get the "cameraup" vector. I now need to adjust the 3 trig equations for the LineOfSightVector to take into account the change in the "up" vector so the camera controls go in the right direction. Can someone please advise me on this.
Thanks
Having
lineOfSight = vec3(sin(phi)*cos(ksi), sin(ksi), cos(phi)*cos(ksi));
you could compute right and up directions as follows:
right = vec3(cos(phi)*cos(ksi), 0, -sin(phi)*cos(ksi));
up = cross(lineOfSight, right);
up = normalize(up);
Notice that in such model cases of cos(ksi) == 0 should be handled separately.
I have a point in space represented by a 4x4 matrix. I'd like to get the screen coordinates for the point. Picking appears to be the exact opposite fo what I need. I'm using the screen coordinate to determine where to draw text.
Currently the text I draw is floating in space far in front of the points. I've attached a screenshot of zoomed-in and zoomed-out to better explain. As you can see in the screenshot, the distance between each point is the same when zoomed in, when it should be smaller.
Am I missing a transformation? World coordinates consider 0,0,0 to be the center of the grid. I'm using SlimDX.
var viewProj = mMainCamera.View * mMainCamera.Projection;
//Convert 4x4 matrix for point to Vector4
var originalXyz = Vector3.Transform(Vector3.Zero, matrix);
//Vector4 to Vector3
Vector3 worldSpaceCoordinates = new Vector3(originalXyz.X, originalXyz.Y, originalXyz.Z);
//Transform point by view projection matrix
var transformedCoords = Vector3.Transform(worldSpaceCoordinates, viewProj);
Vector3 clipSpaceCoordinates = new Vector3(transformedCoords.X, transformedCoords.Y, transformedCoords.Z);
Vector2 pixelPosition = new Vector2((float)(0.5 * (clipSpaceCoordinates.X + 1) * ActualWidth), (float)(0.5 * (clipSpaceCoordinates.Y + 1) * ActualHeight));
Turns out I was way overthinking this. Just project the point to the screen by passing Vector3.Project your viewport information. It's a 3 line solution.
var viewProj = mMainCamera.View * mMainCamera.Projection;
var vp = mDevice.ImmediateContext.Rasterizer.GetViewports()[0];
var screenCoords = Vector3.Project(worldSpaceCoordinates, vp.X, vp.Y, vp.Width, vp.Height, vp.MinZ, vp.MaxZ, viewProj);
I am trying to the get the x and y coordinates inside a transformed sprite. I have a simple 200x200 sprite which rotates in the middle of the screen - with an origin of (0,0) to keep things simple.
I have written a piece of code that can transform the mouse coordinates but only with a specified x OR y value.
int ox = (int)(MousePos.X - Position.X);
int oy = (int)(MousePos.Y - Position.Y);
Relative.X = (float)((ox - (Math.Sin(Rotation) * Y /* problem here */)) / Math.Cos(Rotation));
Relative.Y = (float)((oy + (Math.Sin(Rotation) * X /* problem here */)) / Math.Cos(Rotation));
How can I achieve this? Or how can I fix my equation?
The most general way is to express the transformation as a matrix. This way, you can add any other transformation later, if you find you need it.
For the given transformation, the matrix is:
var mat = Matrix.CreateRotationZ(Rotation) * Matrix.CreateTranslation(Position);
This matrix can be interpreted as the system transformation from sprite space to world space. You want the inverse transformation - the system transformation from world space to sprite space.
var inv = Matrix.Invert(mat);
You can transform the mouse coordinates with this matrix:
var mouseInSpriteSpace = Vector2.Transform(MousePos, inv);
And you get the mouse position in the sprite's local system.
You can check if you have the correct matrix mat by using the overload of Spritebatch.Begin() that takes a matrix. If you pass the matrix, draw the sprite at (0, 0) with no rotation.
I want to know how to work out the new co-ordinates for a point when rotated by an angle relative to another point.
I have a block arrow and want to rotate it by an angle theta relative to a point in the middle of the base of the arrow.
This is required to allow me to draw a polygon between 2 onscreen controls. I can't use and rotate an image.
From what I have considered so far what complicates the matter further is that the origin of a screen is in the top left hand corner.
If you rotate point (px, py) around point (ox, oy) by angle theta you'll get:
p'x = cos(theta) * (px-ox) - sin(theta) * (py-oy) + ox
p'y = sin(theta) * (px-ox) + cos(theta) * (py-oy) + oy
If you are using GDI+ to do that, you can use Transform methods of the Graphics object:
graphics.TranslateTransform(point of origin);
graphics.RotateTransform(rotation angle);
Then draw the actual stuff.
If you have the System.Windows.Media namespace available, then you can use the built in transformations:
using System.Windows.Media;
var transform = new RotateTransform() {Angle = angleInDegrees, CenterX = center.X, CenterY = center.Y};
var transformedPoint = transform.Transform(point);
This takes a layout transform command on your image in the WPF, and rotates it the degree you want.
progress_image.LayoutTransform = new RotateTransform(90);