Three.js manipulate 3D mouse coordinates by new direction - javascript

i have a problem at setting a new mouse position. I have an Object which is moving and rotating free in a Space and following the position of the pointerlocked cursor. Targetposition is a Vector3 positioned behind the object. Now i want to make an Animation which moves the object in the opposite direction by rotating it smoothly. So I disable my mouseListener and rotate the object with the given Three.js functions. But after I enable my listener the targetPosition turns back to the mouse position and makes the move useless. So now i want to calculate the mouse Position for my new Targetposition after the animation. How can i do that ?
The function for the 3D mouse coordinates looks something like this:
enter code here
mouseY = Math.max(-85, Math.min(70, -mouseY));
phi = THREE.Math.degToRad(90 + mouseY);
theta = THREE.Math.degToRad(mouseX);
targetPosition.x = object.position.x + 100 * Math.sin(phi) * Math.cos(theta);
targetPosition.y = object.position.y + 100 * Math.cos(phi);
targetPosition.z = object.position.z + 100 * Math.sin(phi) * Math.sin(theta);
object.lookAt(targetPosition);

Related

Three.js reverse raycasting

I'm setting up a world map on a curved plane that the user can rotate and highlight countries. When a country is clicked, I determine what exactly was clicked and then show a tooltip with some information about the selected country, like on the screenshot below:
The map itself is generated in three, but the tooltip is a regular old div. The thing is, I'd like the tooltip to stay glued to that particular point of the texture, even if the plane is rotated. The original positioning of the tooltip is based on the information from the raycaster. As such, I'd want the app to return the current position of that precise point, relative to the container (or window) - based on uv coordinate for instance. How can I achieve that?
Basing on the link provided by #prisoner849, I've implemented the following solution:
a) on mouseup event I set a new tooltip 3D origin point (only if there was no significant delta in mouse position, to discern between clicking and dragging the camera)
b) every frame, the following function is fired, which converts the 3D coords to 2D and calculates the position of the tooltip:
function setTooltipOrigin( camera, renderer, tooltip, lastClickPoint ) {
var canvas = renderer.domElement,
point = new THREE.Vector3();
point.x = lastClickPoint.x,
point.y = lastClickPoint.y,
point.z = lastClickPoint.z,
point.project( camera );
point.x = Math.round(( 0.5 + point.x / 2 ) * ( canvas.width / window.devicePixelRatio ));
point.y = Math.round(( 0.5 - point.y / 2 ) * ( canvas.height / window.devicePixelRatio ));
point.x -= 14; //small adjustment to the position, so the line points to the click point
point.y -= (tooltip.scrollHeight * 0.7); //same for y
tooltip.style.transform = 'translate(' + point.x + 'px, ' + point.y + 'px)';
}

Connect two circles with a line (with DOM elements)

I am struggling with connecting two circles with a line. I am using the famo.us library.
DEMO on Codepen
a.k.a. "Two balls, one line."
The Problem
Angle and length of the line are correct, but the position is wrong.
First attempt
The important part should be lines 114-116:
connection.origin = [.5, .5];
connection.align = [.5, .5];
connection.body.setPosition([
Math.min(sourcePos.x, targetPos.x),
Math.min(sourcePos.y, targetPos.y)
]);
Appearently i am doing something wrong with the math. Playing around with those values gives me all kinds of results, but nothing is close to correct.
Intended solution
(1) The minimal solution would be to connect the centres of the circles with the line.
(2) The better solution would be a line that is only touching the surface of both circles instead of going to the center.
(3) The ideal solution would have arrows on each end of the line to look like a directed graph.
This fixes it :
connection.body.setPosition([
sourcePos.x * Math.cos(angle) + sourcePos.y * Math.sin(angle),
sourcePos.x * Math.sin(-angle)+ sourcePos.y * Math.cos(angle)
]);
Your segment is defined by its extrimity in sourceand the angle and distance to target, thus you have to set its origin to be that of source
The rotation seems to not only rotate the object, but also rotate the coordinates around the origin, so I rotated them by -angle to compensate.
There might be a more famo.usesque way to do it (maybe you can get it to rotate before setting the position, or have the position be 0,0 and add the coordinates as a translation in the transformation).
To get your better solution, still with mostly math, you may keep the same code but
with r the radius of the source ball, remove [r * distX / distance, r * distY / distance] to the coordinates of the segment, to put it in contact with the outer part of the ball
remove both balls' radius from the distance
With that, we get :
var distX = sourcePos.x - targetPos.x;
var distY = sourcePos.y - targetPos.y;
var norm = Math.sqrt(distX * distX + distY * distY);
var distance = norm - (source.size[0]+target.size[0])/2;
var angle = -Math.atan2(-distY, distX);
connection.angle = angle;
connection.size = [distance, 2, 0];
connection.align = [.5, .5];
connection.origin = [.5, .5];
var posX = sourcePos.x - source.size[0]/2 * (distX / norm);
var posY = sourcePos.y - source.size[0]/2 * (distY / norm);
connection.body.setPosition([
posX * Math.cos(angle) + posY * Math.sin(angle),
posX * Math.sin(-angle)+ posY * Math.cos(angle)
]);
result on this fork : http://codepen.io/anon/pen/qEjPLg
I think the fact that the line length is off when the balls go fast is a timing issue. Most probably you compute the segment's length and position at a moment when the ball's centres are not yet updated for that frame.

Calculating relative item positions based on camera position and rotation

For a 2d game, I have these concepts:
stage: container in which items and cameras are placed.
item: a visible entity, located on a certain point in the world, anchored from center.
camera: an invisible entity, used to generate relative images of world, located on a certain point in the world, anchored from center.
In the illustrations, you can see how they are related, and what the end result should be.
Here is the code I have: (dumbed down to make it easier to read)
Note1: This is not happening on canvas, so I will not use canvas translation or rotation (and even then, I don't think it would make the problem any easier).
Note2: Item and camera positions are center coordinates.
var sin = Math.sin(rotationRad);
var cos = Math.cos(rotationRad);
var difX = item.x - camera.x;
var difY = item.y - camera.y;
var offsetX = camera.width / 2;
var offsetY = camera.height / 2;
var view.x = (cos * difX) - (sin * difY) + _Ax + _Bx;
var view.y = (sin * difX) + (cos * difY) + _Ay + _By;
This is supposed to calculate an items new position by:
calculating new position of item by rotating it around camera center
(_A*) adjusting item position by offsetting camera position
(_B*) adjusting item position by offsetting camera size
I tried several different solutions to use for _A* and _B* here, but none of them work.
What is the correct way to do this, and if possible, what is the explanation?
You first subtract new origin position from object position. You then rotate it by the inverse of the rotation. New origin can be camera position of top left corner of viewport. Of course if you know viewport center its top left corner is computed by subtracting half of its dimensions.
Like this:
var topLeft = Camera.Position - Camera.Size / 2;
var newPosition = Object.Position - topLeft;
newPosition = Rotate(newPosition, -camera.Angle);
Rotation is very simple:
rotatedX = x * cos(angle) - y * sin(angle)
rotatedY = y * cos(angle) + x * sin(angle)

Three.js Click and Drag - Object Lagging Behind Pointer

I've created a near exact implementation of the Three.js Draggable Cubes example, except that my implementation ignores the z axis for movement in 2D. The example can be found here: http://threejs.org/examples/#webgl_interactive_draggablecubes
While I am able to click and move around my object, if I move the mouse too fast, the object will lag behind; the mouse pointer will move to it's location and then the object will follow the mouses path to the location. This issue is also noticeable in the Three.js example. Try dragging one of the cubes at anything beyond a moderate speed.
I've tried a few things to get the object to be directly under the mouse pointer but none have worked. The closest I think I might have come to a solution was by changing the mouse position update in the MouseMove event. However, it appears that the Three.js implementation of the code returns values between 1 and -1 rather than the screen X and Y coordinates, which leads me to wonder if the original implementation is causing the lag.
//Original Implementation - Works With Lag
mouse.x = (event.clientX / window.innerWidth) * 2 - 1;
mouse.y = -(event.clientY / window.innerHeight) * 2 + 1;
console.log(mouse.x + "," + mouse.y); //Output: -0.9729166666666667,0.8596858638743455
//My Implementation - Does Not Work
mouse.x = event.clientX - (window.innerWidth / 2);
mouse.y = event.clientY - (window.innerHeight / 2);
console.log(mouse.x + "," + mouse.y); //Output: -934,-410.5
//Update Function
void Update()
{
var vector = new THREE.Vector3(mouse.x, mouse.y, 1);
projector.unprojectVector(vector, camera);
var raycaster = new THREE.Raycaster(camera.position, vector.sub(camera.position).normalize());
var intersects = raycaster.intersectObject(plane);
meshToMove.position.x = intersects[0].point.x;
meshToMove.position.y = intersects[0].point.y;
}
//Main Loop
function Loop()
{
Update();
Render();
requestAnimationFrame(Loop);
}
Q: How can I update the three.js Draggable Cubes example so that objects don't lag behind the mouse during a click and drag?

Rotating canvas around a point and getting new x,y offest

I am writing a multitouch jigsaw puzzle using html5 canvas in which you can rotate the pieces around a point. Each piece has their own canvas the size of their bounding box. When the rotation occurs, the canvas size must change, which I am able to calculate and is working. What I can't figure out, is how to find the new x,y offsets if I am to have this appear to be rotating around the pivot (first touch point).
Here is an image to better explain what I'm trying to achieve. Note the pivot point is not always the center, otherwise I could just halve the difference between the new bounds and the old.
So I know the original x, y, width, height, rotation angle, new bounds(rotatedWidth, rotatedHeight), and the pivot X,Y relating to original object. What I can't figure out how to get is the x/y offset for the new bounds (to make it appear that the object rotated around the pivot point)
Thanks in advance!
First we need to find the distance from pivot point to the corner.
Then calculate the angle between pivot and corner
Then calculate the absolute angle based on previous angle + new angle.
And finally calculate the new corner.
Snapshot from demo below showing a line from pivot to corner.
The red dot is calculated while the rectangle is rotated using
translations.
Here is an example using an absolute angle, but you can easily convert this into converting the difference between old and new angle for example. I kept the angles as degrees rather than radians for simplicity.
The demo first uses canvas' internal translation and rotation to rotate the rectangle. Then we use pure math to get to the same point as evidence that we have calculated the correct new x and y point for corner.
/// find distance from pivot to corner
diffX = rect[0] - mx; /// mx/my = center of rectangle (in demo of canvas)
diffY = rect[1] - my;
dist = Math.sqrt(diffX * diffX + diffY * diffY); /// Pythagoras
/// find angle from pivot to corner
ca = Math.atan2(diffY, diffX) * 180 / Math.PI; /// convert to degrees for demo
/// get new angle based on old + current delta angle
na = ((ca + angle) % 360) * Math.PI / 180; /// convert to radians for function
/// get new x and y and round it off to integer
x = (mx + dist * Math.cos(na) + 0.5)|0;
y = (my + dist * Math.sin(na) + 0.5)|0;
Initially you can verify the printed x and y by seeing that the they are exact the same value as the initial corner defined for the rectangle (50, 100).
UPDATE
It seems as I missed the word in: offset for the new bounds... sorry about that, but what you can do instead is to calculate the distance to each corner instead.
That will give you the outer limits of the bound and you just "mix and match" the corner base on those distance values using min and max.
New Live demo here
The new parts consist of a function that will give you the x and y of a corner:
///mx, my = pivot, cx, cy = corner, angle in degrees
function getPoint(mx, my, cx, cy, angle) {
var x, y, dist, diffX, diffY, ca, na;
/// get distance from center to point
diffX = cx - mx;
diffY = cy - my;
dist = Math.sqrt(diffX * diffX + diffY * diffY);
/// find angle from pivot to corner
ca = Math.atan2(diffY, diffX) * 180 / Math.PI;
/// get new angle based on old + current delta angle
na = ((ca + angle) % 360) * Math.PI / 180;
/// get new x and y and round it off to integer
x = (mx + dist * Math.cos(na) + 0.5)|0;
y = (my + dist * Math.sin(na) + 0.5)|0;
return {x:x, y:y};
}
Now it's just to run the function for each corner and then do a min/max to find the bounds:
/// offsets
c2 = getPoint(mx, my, rect[0], rect[1], angle);
c2 = getPoint(mx, my, rect[0] + rect[2], rect[1], angle);
c3 = getPoint(mx, my, rect[0] + rect[2], rect[1] + rect[3], angle);
c4 = getPoint(mx, my, rect[0], rect[1] + rect[3], angle);
/// bounds
bx1 = Math.min(c1.x, c2.x, c3.x, c4.x);
by1 = Math.min(c1.y, c2.y, c3.y, c4.y);
bx2 = Math.max(c1.x, c2.x, c3.x, c4.x);
by2 = Math.max(c1.y, c2.y, c3.y, c4.y);
to rotate around the centre point of the canvas you can use this function:
function rotate(context, rotation, canvasWidth, canvasHeight) {
// Move registration point to the center of the canvas
context.translate(canvasWidth / 2, canvasHeight/ 2);
// Rotate 1 degree
context.rotate((rotation * Math.PI) / 180);
// Move registration point back to the top left corner of canvas
context.translate(-canvasWidth / 2, -canvasHeight/ 2);
}
Here is the way that worked best for me. First I calculate what is the new width and height of that image, then I translate it by half of that amount, then I apply the rotation and finally I go back by the original width and height amount to re center the image.
var canvas = document.getElementById("canvas")
const ctx = canvas.getContext('2d')
drawRectangle(30,30,40,40,30,"black")
function drawRectangle(x,y,width,height, angle,color) {
drawRotated(x,y,width,height,angle,ctx =>{
ctx.fillStyle = color
ctx.fillRect(0,0,width,height)
})
}
function drawRotated(x,y,width,height, angle,callback)
{
angle = angle * Math.PI / 180
const newWidth = Math.abs(width * Math.cos(angle)) + Math.abs(height * Math.sin(angle));
const newHeight = Math.abs(width * Math.sin(angle)) + Math.abs(height * Math.cos(angle));
var surface = document.createElement('canvas')
var sctx = surface.getContext('2d')
surface.width = newWidth
surface.height = newHeight
// START debug magenta square
sctx.fillStyle = "magenta"
sctx.fillRect(0,0,newWidth,newHeight)
// END
sctx.translate(newWidth/2,newHeight/2)
sctx.rotate(angle)
sctx.translate(-width/2,-height/2)
callback(sctx)
ctx.drawImage(surface,x-newWidth/2,y-newHeight/2)
}
#canvas{
border:1px solid black
}
<canvas id="canvas">
</canvas>

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