I'm working on a simple Three.js demo that uses OrbitControls.js.
I'd like to change the behavior of panning in OrbitControls. Currently, when you pan the camera, it moves the camera in a plane that is perpendicular to the viewing direction. I'd like to change it so that the camera stays a constant distance from the ground plane and moves parallel to it. Google Earth uses a similar control setup.
Edit: I should have mentioned this detail in the first place, but I'd also like the point where you click and start dragging to remain directly under the cursor throughout the entire drag. There needs to be that solid connection between the mouse movement and what the user expects to happen on the screen. Otherwise, it feels as though I'm 'slipping' when I try to move around the scene.
Can someone give me a high-level explanation of how this might be done (with or without OrbitControls.js)?
EDIT: OrbitControls now supports panning parallel to the "ground plane", and it is the default.
To pan parallel to screen-space (the legacy behavior), set:
controls.screenSpacePanning = true;
Also available is MapControls, which has an API similar to that of Google Earth.
three.js r.94
Some time ago I was working on exactly this issue, i.e. adaptation of OrbitControls.js to map navigation.
Here's the code of MapControls.js.
Here's the demo of the controls.
I figured it out. Here's the overview:
Store the mousedown event somewhere.
When the mouse moves, get the new mousedown event.
For each of those points, find the points on the plane where those clicks are located (You'll need to put the points into camera space, transform them into world space, then fire a ray from the camera through each point to find their intersections with the plane. This page explains the ray-plane intersection test).
Subtract the world-space start intersection point from the world-space end intersection point to get the offset.
Subtract that offset from the camera's target point and you're done!
In the case of OrbitControl.js, the camera always looks at the target point, and its position is relative to that point. So when you change the target, the camera moves with it. Since the target always lies on the plane, the camera moves parallel to that plane (as long as you're panning).
You should set your camera 'up' to z axe:
camera.up.set(0,0,1)
And then, the main problem with OrbitControl is its panUp() function. It should be fixed.
My pull request : https://github.com/mrdoob/three.js/pull/12727
y axe is relative to camera axes and should be relative to a fixed plan in the world. To define the expected y axe, make a 90° rotation of camera x axe, based on world z axe.
v.setFromMatrixColumn( objectMatrix, 0 ); // get X column of objectMatrix
v.applyAxisAngle( new THREE.Vector3( 0, 0, 1 ), Math.PI / 2 );
v.multiplyScalar( distance );
panOffset.add( v )
Enjoy!
Related
I'm using ThreeJS, but this is a general math question.
My end goal is to position an object in my scene using 2D screen space coordinates; however, I want a specific z position in the perspective projection.
As an example, I have a sphere that I want to place towards the bottom left of the screen while having the sphere be 5 units away from the camera. If the camera were to move, the sphere would maintain its perceived size and position.
I can't use an orthographic camera because the sphere needs to be able to move around in the perspective projection. At some point the sphere will be undocked from the screen and interact with the scene using physics.
I'm sure the solution is somewhere in the camera inverse matrix, however, that is beyond my abilities at the current moment.
Any help is greatly appreciated.
Thanks!
Your post includes too many questions, which is out of scope for StackOverflow. But I’ll try to answer just the main one:
Create a plane Mesh using PlaneGeometry.
Rotate it to face the camera, place it 5 units away from the camera.
Add it as a child with camera.add(plane); so whenever the camera moves, the plane moves with it.
Use a Raycaster’s .setfromCamera(cords, cam)
then
.intersectObject(plane)
method to convert x, y screen cords into an x, y, z world position where it
intersects the plane. You can read about it in the docs.
Once it’s working, make the plane invisible with visible = false
You can see the raycaster working in this official example: https://threejs.org/examples/#webgl_geometry_terrain_raycast
I'm trying to learn the ThreeJS positioning functions, but I'm not quite getting there.
I have a light and an animation loop. I want this light to be at a fixed angle relative to the camera pointing towards 0,0,0.
I can make the light come from the camera angle itself like so (in animation loop):
rectLight.position.copy(camera.position);
rectLight.lookAt(0,0,0);
But I don't want it to come from the viewer's perspective, I want it to come from somewhere else relative to it, and at a set distance from center.
So I think it's camera angle +/- some degrees/radians, and then a fixed distance.
I've tried adjusting the coordinates relative to the camera position, like y += 25, y *= 3, and such. Everything I try gives me some whacky light placement motion I don't understand. I'm sorry, 8th grade geometry teacher, I should have paid attention.
I am building an application in AFrame and I want to constrain the viewers movement, that is I want to limit where the camera can go in the scene. For example I have a a-plane that is the floor and I want the camera to stop moving when it reaches 0 on the Z axis to stop the camera from going through the floor or stop again if it reaches 20 on Z axis. I also wish to limit the movement in x,y directions. There are no obstacles in the scene besides the a-plane. Is creating a navigation mesh my only option or is there an easier way to constrain movement? Thanks!
I don't know of built in tools to do this, but you could do it with programming (this sounds pretty easy). You could create a custom component, attached to the camera, with a tick handler, that records the position of the camera in world space and stores in in a variable (camPosPrevFrame). Then create a function to test if the current position is outside of the bounds. If so, set the camera coordinate on the axis that has exceeded its limit, to the previously recorded boundary (camPosPrevFrame). If you are simply testing whether the camera is on one side of an orthagonal plane (say the world space xy plane), that is pretty simple math (camera.getWorldPosition.x>someAmount). If you have a more complex situation, there are ways to test if a point is on either side of any arbitrary plane (it involves the dot product).
Let's say I have a vertical list of meshes created from PlaneBufferGeometry with ShaderMaterial. The meshes are distributed vertically and evenly spaced.
The list will have two states:
Displaying the meshes as they are
Displaying meshes with each object's vertices transformed by the vertex shader to the same arbitrary value, let's say z = -50. This gives a zoomed out effect and the user can scroll through this list (in the code we do this by moving the camera y position)
In my app I'm trying to make my mouseover events work for the second state but it's tricky since the GPU transforms the vertices so the updated vertices are not reflected in the attributes on the JS side.
*Note I've looked into GPU picking and do not want to use it because I believe there should be a simpler way to do this without render targets
Attempted Solution
My current approach is to manually change the boundingBox of each plane when we are in the second state like so:
var box = new THREE.Box3().setFromObject(plane);
box.min.z = -50;
box.max.z = -50;
plane.geometry.boundingBox = box;
And then to change the boundingSphere's center to have the same z position of -50 after computing it.
I did this approach because I looked into the Raycaster and Mesh code for THREE.js and it seems like they check both boundingSphere and boundingBox for object intersections. So I thought if I modified both of them to reflect the transforms done by the GPU, the raycaster would work fine but it doesn't seem to be working for me.
The relevant raycaster code is here:
// mouse being vec2 of normalized coordinates and camera being a perspective camera
raycaster.setFromCamera( mouse, camera );
const intersects = raycaster.intersectObjects( planes );
Possible Theories
The only thing I can think of that's wrong about this approach is maybe I'm not projecting the mouse coords right? Since all the objects now lie on the plane z = -50 would I need to project those mouse coordinates to that plane?
Inspired by the link posted by #prisoner849 I found a working solution to just create additional transparent planes equal to the number of planes in the scene. In these planes, I set the z position to -50 and just intersect with these when in state #2.
A bit hacky, but works for now.
I have this simple scene with a "tooltip" entity composed of some data, I'd like to know how to position it in front of the camera. The tooltip will have to face certain points a few meters away so the user can see it. It must obey camera direction (it can be gathered by calculating it from previousPoint to nextPoint where the camera will move), but only y axis (can't be tilted or anything like that).I tried digging through math but couldn't understand good enough to employ a solution for this little project; I appreciate all the help!
setTimeout(function(){
var camera = document.getElementById("cameraS");
var tt = document.getElementById("ttS");
var cameraPos = camera.getAttribute('position');
var ttPos = tt.getAttribute('position');
tt.setAttribute('position', cameraPos);
tt.setAttribute('rotation', {'y': -90});
}, 5000);
JSFiddle
EDIT
I made an image showing what I'm after: http://imgur.com/a/eDhqE
I have point A and point B; the camera will play an animation moving from previous point to the next, and upon reaching there the tooltip will be displayed a few meters away from the point (box) so we can see it. It must take camera orientation into consideration but it must be perpendicular to the ground (can't be tilted).
There is a command THREE.Object.lookAt(THREE.Vector3); that will rotate an object (assuming (0.0,1.0,0.0) is up) to face a vector. You can use this to have it face your camera.
If you only want Y rotation, you can copy the current rotation, then do look at, then copy the rotation.x and rotation.z from the previous frame rotation copy - so that way it'll only correct the y with .lookAt because you reset x and z.