Mesh position with Repulsion - javascript

Right now, my code read multiple object store into a json file. I create cube, sphere and more with different size and materials.
But I would like those mesh to have a random position around (0,0,0) base on a repulsion force to avoid overlaps like this :
This is generate with position.x = Math.random() * 20 - 10;
I would like something like this d3.js example. To have random position of my mesh without overlaping but all to be around the center of the scene.
I'm searching for something, but found nothing right now. I'm really new the WebGL/Three.js.

Related

Force camera.lookAt to maintain current Z rotation

So, I'm putting together a 3D project that will eventually make it's way onto a kiosk in the office of a client, basically shows all of their branches as points on a globe. One of the features requested is that end users be able to swipe on the screen to orbit around the globe, in addition, they should be able to rotate the camera on it's Z axis via a rotation gesture. The problem is I'm using camera.lookAt in the animation loop, which relies on the up vector being updated correctly whenever I rotate the camera in order to not "snap" back to place along the previous up vector when a user swipes, and for the life of me, I cannot get it to cooperate.
Currently, what I'm doing to update the up vector (based off of another stackoverflow thread with a similar issue) is this:
//Current full 360 degree angle of rotation, calculated earlier
let radian = THREE.Math.degToRad(full);
//Create new vector at radian angle to camera's current position
let v1 = new THREE.Vector3(_this.object.position.x + Math.cos(radian), _this.object.position.y + Math.sin(radian), _this.object.position.z).sub( _this.object.position ).normalize();
//_this.target = 0,0,0
let v2 = _this.target.clone().sub( _this.object.position ).normalize();
//Cross vectors to get the proper up
let v3 = new THREE.Vector3().crossVectors( v1, v2 ).normalize();
_this.object.up.copy( v3 );
And this works... up to the point where the camera seemingly inverts once I head near the side of the globe opposite the camera's starting position (0,0,1.75) and then negates my rotations (as far as I can tell) which causes the same "snap" to a different rotation like before.
Once I rotate the camera, I want it to maintain the rotation when using lookAt, regardless of the lookAt inverting everything.

three.js "exploding" an object in predefined pieces

This is a sort of a follow up question of my last problem. I want to explode (technical drawing style) an imported .obj geometry which contains n .obj parts.
For example a table as object, each part is one .obj, four legs and a table top.
5 files. loading them is no problem. Now each objects position is 0,0,0 that means I need to get the world position of them, which I did with this function:
function absPos( myMesh ) {
myMesh.geometry.computeBoundingBox();
var boundingBox = myMesh.geometry.boundingBox;
var position = new THREE.Vector3();
position.subVectors( boundingBox.max, boundingBox.min );
position.multiplyScalar( 0.5 );
position.add( boundingBox.min );
position.applyMatrix4( myMesh.matrixWorld );
var abspos = {x:position.x,y:position.y,z:position.z};
return abspos;
}
now I did assume that setting the object´s position to their world positions would just happen to move them to another world position but keep their relation but that is not the case. So I cannot just use the objects world position and use it to translate the objects until I mess with the world position?
As the objects position is 0,0,0 they don´t have a relation to each other and I cannot just multiply the values to "explode" the geometry.
Is there any chance to achieve this without messing with the world positions?

updating an object's geometry when camera is moving causes glitches - three.js

I have a problem updating a vertex of a line in three.js
So, I want to have a line in my scene, that its start is always at the (0,0,0) and its end is always in a specific position of the users screen (in x,y coordinates).
What I do to achieve that (and I almost succeed) is to have an invisible plane looking always to the camera and also have its position always a little bit in front of the camera. The reason I do that is because I want the line to seem like "going towards" the user's screen. So I "send" a raycaster from the desired screen position (in x,y) and I check in which point of the plane it intersect and that's my 3D point in three.js scene. Then I update one of the 2 vertices of the line.
The problem
What I do works fine, the line end is where I want to be, but something in updating the camera and the vertex is not synchronized and causes some noticeable glitches. When I move the camera, the line do not update itself quickly and smoothly, and as a result I see the line in other position before I see it in the calculated and desireable one.
Please take a look at this jsfiddle I created to emulate the problem.
What can I do to avoid these glitches?
Thanks
code i use in render function :
var cameToCenterScaled = camera.position.clone();
cameToCenterScaled.setLength(cameToCenterScaled.length()*0.9);
plane.position.set(cameToCenterScaled.x, cameToCenterScaled.y, cameToCenterScaled.z);
plane.lookAt(camera.position);
// define in pixels where in screen we want the line to end
var notePos = findNotePoint(120,30);
linemesh.geometry.vertices[ 1 ].set(notePos.x, notePos.y, notePos.z) ;
linemesh.geometry.verticesNeedUpdate = true;
when you raycast you set the raycaster from camera, you have to make sure the camera matrices are updated
simply add
camera.updateMatrixWorld();
before you call
raycaster.setFromCamera( new THREE.Vector2( x_, y_ ) , camera );
and the line will behave as you described

How do I make an object perpendicular to a face with Three.js?

Relevant codepen:
http://codepen.io/OpherV/pen/yNebep
In my game I have a model of an alien tree.
For each face of this tree I generate a pyramid (CylinderGeometry with 4 faces), and position it at the center of the face. Then I wish for this pyramid to be perpendicular to the face, so that I'll get a tree with spikes.
I've tried achieving this with object.lookAt and point it at the face normal, but weird things happen. For example:
If I add
cylinderGeometry.applyMatrix( new THREE.Matrix4().makeRotationX( - Math.PI / 2 ) );
The shape in the middle works as expected, but the rest is still distorted
What is the proper way to get my spiked tree?
Bonus question
How would I go about merging these spikes to the original geometry after proper creation and orientation so that I don't have so many separate objects?
You want to create cylinder and point it in a particular direction. One way to do that is to use the following pattern:
Create the geometry.
var cylinderGeometry = new THREE.CylinderGeometry( 1, 10, 25, 4, 1 );
Translate the geometry so the base sits at the origin.
cylinderGeometry.translate( 0, 12.5, 0 );
Rotate the geometry so the top points in the direction of the positive-Z axis.
cylinderGeometry.rotateX( Math.PI / 2 );
Create the mesh.
var cylinder = new THREE.Mesh( cylinderGeometry , characterSkinMaterial );
Objects in three.js are by default "looking" in the direction of their local positive-Z axis. (Except the camera, which looks down its negative-Z axis.)
Tell the cylinder to "look" in the direction you want. Since we have transformed the geometry, this will make the top of the cylinder point in the desired direction.
cylinder.lookAt( face.normal );
Now place the cylinder wherever you want it.
cylinder.position.copy( centerPoint );
obj.add( cylinder );
three.js r.91

How do I 'wrap' a plane over a sphere with three.js?

I am relatively new to three.js and am trying to position and manipulate a plane object to have the effect of laying over the surface of a sphere object (or any for that matter), so that the plane takes the form of the object surface. The intention is to be able to move the plane on the surface later on.
I position the plane in front of the sphere and index through the plane's vertices casting a ray towards the sphere to detect the intersection with the sphere. I then try to change the z position of said vertices, but it does not achieve the desired result. Can anyone give me some guidance on how to get this working, or indeed suggest another method?
This is how I attempt to change the vertices (with an offset of 1 to be visible 'on' the sphere surface);
planeMesh.geometry.vertices[vertexIndex].z = collisionResults[0].distance - 1;
Making sure to set the following before rendering;
planeMesh.geometry.verticesNeedUpdate = true;
planeMesh.geometry.normalsNeedUpdate = true;
I have a fiddle that shows where I am, here I cast my rays in z and I do not get intersections (collisions) with the sphere, and cannot change the plane in the manner I wish.
http://jsfiddle.net/stokewoggle/vuezL/
You can rotate the camera around the scene with the left and right arrows (in chrome anyway) to see the shape of the plane. I have made the sphere see through as I find it useful to see the plane better.
EDIT: Updated fiddle and corrected description mistake.
Sorry for the delay, but it took me a couple of days to figure this one out. The reason why the collisions were not working was because (like we had suspected) the planeMesh vertices are in local space, which is essentially the same as starting in the center of the sphere and not what you're expecting. At first, I thought a quick-fix would be to apply the worldMatrix like stemkoski did on his github three.js collision example I linked to, but that didn't end up working either because the plane itself is defined in x and y coordinates, up and down, left and right - but no z information (depth) is made locally when you create a flat 2D planeMesh.
What ended up working is manually setting the z component of each vertex of the plane. You had originaly wanted the plane to be at z = 201, so I just moved that code inside the loop that goes through each vertex and I manually set each vertex to z = 201; Now, all the ray start-positions were correct (globally) and having a ray direction of (0,0,-1) resulted in correct collisions.
var localVertex = planeMesh.geometry.vertices[vertexIndex].clone();
localVertex.z = 201;
One more thing was in order to make the plane-wrap absolutely perfect in shape, instead of using (0,0,-1) as each ray direction, I manually calculated each ray direction by subtracting each vertex from the sphere's center position location and normalizing the resulting vector. Now, the collisionResult intersection point will be even better.
var directionVector = new THREE.Vector3();
directionVector.subVectors(sphereMesh.position, localVertex);
directionVector.normalize();
var ray = new THREE.Raycaster(localVertex, directionVector);
Here is a working example:
http://jsfiddle.net/FLyaY/1/
As you can see, the planeMesh fits snugly on the sphere, kind of like a patch or a band-aid. :)
Hope this helps. Thanks for posting the question on three.js's github page - I wouldn't have seen it here. At first I thought it was a bug in THREE.Raycaster but in the end it was just user (mine) error. I learned a lot about collision code from working on this problem and I will be using it later down the line in my own 3D game projects. You can check out one of my games at: https://github.com/erichlof/SpacePong3D
Best of luck to you!
-Erich
Your ray start position is not good. Probably due to vertex coordinates being local to the plane. You start the raycast from inside the sphere so it never hits anything.
I changed the ray start position like this as a test and get 726 collisions:
var rayStart = new THREE.Vector3(0, 0, 500);
var ray = new THREE.Raycaster(rayStart, new THREE.Vector3(0, 0, -1));
Forked jsfiddle: http://jsfiddle.net/H5YSL/
I think you need to transform the vertex coordinates to world coordinates to get the position correctly. That should be easy to figure out from docs and examples.

Categories