I have a 3D scene with a bunch of CSS object that I want to rotate so that they are all pointing towards a point in the space.
My CSS objects are simple rectangles that are a lot wider than they are high:
var element = document.createElement('div');
element.innerHTML = "test";
element.style.width = "75px";
element.style.height = "10px";
var object = new THREE.CSS3DObject(element);
object.position.x = x;
object.position.y = y;
object.position.z = z;
Per default, the created objects are defined as if they are "facing" the z-axis. This means that if I use the lookAt() function, the objects will rotate so that the "test" text face the point.
My problem is that I would rather rotate so that the "right edge" of the div is pointing towards the desired point. I've tried fiddling with the up-vector, but I feel like that wont work because I still want the up-vector to point up. I also tried rotating the object Math.PI/2 along the y axis first, but lookAt() seems to ignore any prior set rotation.
It seems like I need to redefine the objects local z-vector instead, so that it runs along with the global x-vector. That way the objects "looking at"-direction would be to the right in the scene, and then lookAt() would orient it properly.
Sorry for probably mangling terminology, newbie 3D programmer here.
Object.lookAt( point ) will orient the object so that the object's internal positive z-axis points in the direction of the desired point.
If you want the object's internal positive x-axis to point in the direction of the desired point, you can use this pattern:
object.lookAt( point );
object.rotateY( - Math.PI / 2 );
three.js r.84
Related
In Three.js, I have a group of meshes that is loaded from outside with help of FBX loader. The group has six meshes inside. My task is to make this meshes follow pointer when they get hovered. More precisely, I'd like to have a sort of magnetic effect (just like navbar items in this pen, but with meshes in Three.js).
I think, firstly, I have to detect, where currently pointer is, i.e. get position of cursor in world coordinates system, and then translate meshes towards it. But when I try to get the position of cursor, it seems to be wrong.
Having said that, I have two questions:
How to get proper cursor's position relative to the world coordinates?
How to change position of each of the group's meshes so that they get translated against the cursor?
Here is what have I done so far:
Hi everyone.
In Three.js, I have a group of meshes that is loaded from outside with help of FBX loader. The group has six meshes inside. My task is to make this meshes follow pointer when their canvas get hovered. More precisely, I'd like to have a sort of magnetic effect (just like navbar items in this pen, but with meshes of Three.js).
I think, firstly, I have to detect, where currently pointer on canvas is, i.e. get position of cursor in world coordinates system, and then translate meshes towards it. But when I try to get the position of cursor, it seems to be wrong.
Having said that, I have two questions:
How to get proper cursor's position relative to the world coordinates?
How to change position of each of the group's meshes so that they get translated against the cursor?
Here is what have I done so far. Function that translates meshes isn't written yet. Mousemove callback returns pretty big digits, though:
// Load object and play a third-party animation
loader.load("Object_001.fbx", (object) => {
mixer = new THREE.AnimationMixer(object);
const action = mixer.clipAction(object.animations[0]);
action.play();
object.traverse((child) => {
if (child.isMesh) {
child.material.map = texture;
child.material.needsUpdate = true;
}
});
scene.add(object);
});
// log coordinates of the pointer
const mouse = new THREE.Vector3();
const position = new THREE.Vector3();
function onMouseMove(event) {
mouse.set(
(event.clientX / window.innerWidth) * 2 - 1,
-(event.clientY / window.innerHeight) * 2 + 1,
0.5
);
mouse.unproject(camera);
mouse.sub(camera.position).normalize();
const distance = -camera.position.z / mouse.z;
position.copy(camera.position).add(mouse.multiplyScalar(distance));
console.log(position);
}
wrapperElement.addEventListener("mousemove", onMouseMove);
Thanks in advance.
Made a codepen here:
https://codepen.io/cdeep/pen/YzxPPZQ
The cursor only exists in the canvas dom element which is a rendering of the camera view frustum.
The easiest way to make the object follow a mouse is to get the point of intersection of the mouse with another object in the 3d scene and set the object position to the intersection point. The above codepen showcases that.
raycaster.setFromCamera( mouse, camera );
const intersects = raycaster.intersectObjects([ground]);
if(intersects.length) {
const { point } = intersects[0];
cube.position.copy(point.setY(0.5));
}
You could also position it at a fixed distance from the mouse but it looks odd in my opinion:
const distance = 10;
raycaster.setFromCamera( mouse, camera );
const { origin, direction } = raycaster.ray;
cube.position.copy(origin.clone().add(direction.multiplyScalar(distance)));
Documentation for raycaster:
https://threejs.org/docs/index.html?q=ray#api/en/core/Raycaster
Raycasting is used for mouse picking (working out what objects in the
3d space the mouse is over) amongst other things.
I'm rather new to threejs, so what I'm doing might not be the most efficient way.
I have an object in AR on a mobile device and I want to know if I intersect with it when touching on the screen.
I use the following code to generate the raycast, and it works initally.
const tempMatrix = new THREE.Matrix4();
tempMatrix.identity().extractRotation(this.controller.matrixWorld);
this.raycaster.ray.origin.setFromMatrixPosition(this.controller.matrixWorld);
this.raycaster.ray.direction.set(0, 0, -1).applyMatrix4(tempMatrix);
However, I have the ability to reposition the object (i.e. reset the position so the object is in front, relative to the current camera direction and position) by moving and rotating the whole scene.
After the repositioning, the raycasting is completely offset and is not casting rays anywhere near where I touch the screen.
Repositioning is done like this (while it works, if there's a better way, let me know!) :
public handleReposition(): void {
const xRotation = Math.abs(this.camera.rotation.x) > Math.PI / 2 ? -Math.PI : 0;
const yRotation = this.camera.rotation.y;
this.scene.rotation.set(xRotation, yRotation, xRotation);
this.scene.position.set(this.camera.position.x, this.camera.position.y, this.camera.position.z);
}
How can I achieve to raycast to the correct new location?
Thanks!
Assuming this.scene is actually the main threejs Scene, it's usually a bad idea to change its rotation or position, since it will affect everything inside the scene, including the controller. I'd suggest moving your object instead, or add your object(s) to a Group and move that.
I want to get the exact intersection point of a ray and a sprite. But when I do this:
var ray = new THREE.Raycaster( camera.position, vector.sub(camera.position ).normalize());
var sprite = new THREE.Sprite(spriteMaterial);
var intersect = ray.intersectObject(sprite);
then intersect.point is just the position of the sprite, instead of the exact point that I need.
I need this so I can check if the part of the texture that has been clicked is visible or not. (Alpha value)
Is there a way to get the exact intersection, or is there a better way to achieve my goal?
This is not currently supported. See Raycaster.js if you want to try to hack your own solution. Sprites can be rotated (turned on their side), so the solution is not trivial.
A reasonable work-around is to create a Mesh from a PlaneGeometry and set
mesh.quaternion = camera.quaternion.
three.js r.64
I've just started learning THREE and have been messing about with the three.js example of controllable MD2 characters to try and fashion it into a 3rd person shooter kind of game. I've been trying to write a simple algorithm for the enemy characters and I'm pretty sure that ray-casting would be ideal.The whole idea is that the enemies should stop rotating once they're facing the player. But Here's the problem that's giving me sleepless nights! :
Let's say, the enemy object is the origin for the ray caster ray. No matter what direction I set for the direction of that ray ( even, for example (1,0,0) - the positive x-axis), the ray's direction is always pointing towards the center of the scene!!!
Please help! haven't been able to find any Example online for this kind of use for the ray caster (apart from collision detection which I really don't need at the moment).
If all you want is for enemies to stop rotating when they are looking at the player, I would consider just checking the direction between them, as it's a lot faster than casting a ray to see if it intersects:
// Assuming `enemy` is a THREE.Mesh
var targetDir = enemy.position.clone().sub(player.position).normalize();
var currentDir = (new THREE.Vector3()).applyMatrix4(enemy.matrixWorld).sub(enemy.position).normalize();
var amountToRotate = currentDir.sub(targetDir);
var offset = amountToRotate.length();
Then rotate each axis no more than the value for that axis in amountToRotate if offset is greater than some threshold.
That said, here is how you use a Raycaster, given the variables above:
var raycaster = new THREE.Raycaster(enemy.position, targetDir);
var intersections = raycaster.intersectObject(player);
Note that if you are running any of the above code in an animation loop, it will create a lot of garbage collection churn because you are constantly creating a bunch of new objects and then immediately throwing them away. A better pattern, which is used a lot in the library itself, is to initialize objects once, copy values to them if you need to, and then use those copies for computation. For example, you could create a function to do your raycasting for you like this:
var isEnemyLookingAtPlayer = (function() {
var raycaster = new THREE.Raycaster();
var pos = new THREE.Vector3();
return function(enemy) {
raycaster.ray.origin.copy(enemy.position);
raycaster.ray.direction.copy(pos.copy(enemy.position).sub(player.position).normalize());
return !!raycaster.intersectObject(player).length;
};
})();
I have some custom geometries obtained from a STEP file conversion and I use the mouse to rotate them. They rotate around the origin of the scene, but since they are far from it, they seem rotating on a virtual sphere. How can I move them to the origin so that they don't seem "floating" around (I mean that I'd like to reduce to zero the radius of the virtual sphere). This is the example I'd like to move. I've tried setting their position to (0, 0, 0) doing:
object.position.x = 0;
object.position.y = 0;
object.position.z = 0;
but it didin't work.
The typical solution to this problem is to translate the geometry right after it is created. You do that by applying a translation matrix to the geometry like so:
geometry.applyMatrix( new THREE.Matrix4().makeTranslation( distX, distY, distZ ) );
EDIT: You can simply do this, instead:
geometry.translate( distX, distY, distZ ); // three.js r.72
The function geometry.computeBoundingBox() may be of help to you in determining an amount to translate.
However, I see in your case, you have multiple geometries, so it it a bit more complicated, but doable. You will need to translate each geometry by the same amount.
EDIT
Tip: Instead of adding each object to the scene, create a parent object, add it to the scene, and then add the objects to the parent.
var parent;
parent = new THREE.Object3D();
scene.add( parent );
parent.add( object1 );
parent.add( object2 );
// and so on...
Then in your render function, just rotate the parent, not the individual objects.