I can't wrap my head around this and was hoping someone might be able to help me. I have an object3D which is being placed on a terrain (plane mesh). I create a Ray, positioned at the object but really high, and find the intersection point into the terrain (essentially the Y intersection). Once I have that I position the object on the terrain at that position.
From the intersect object function I also get the Face which contains the normal at that point. What I'd like to do is align the mesh so that it has the same rotation as the point its standing on.
Once the object is aligned with the world I also need it to face a target its heading towards. Currently I'm using the lookAt function to achieve this.
So I guess my question is two parts. The first is how to align the object with the world. And the second is, how to get that object to face a target without messing up the calculation of the first? (I guess this could be achieved with a child node? The parent node aligned to the world and the sub-mesh node looking at the target?)
Thanks guys
Mat
Related
I am trying to achieve movement of an object on walls, instead of only one plane. In this example, an object dragged on walls by using:
intersects = raycaster.intersectObjects([walls]);
object.position.copy(intersects[0].point);
However, with this method, the object jumps because the object's center moves to the mouse. There is a related question and helpful JSFiddle for dragging on one plane without jumpin Would you please help me to modify it for multiples planes (walls)? Thanks
After reading your comment, I think what you're looking for is you want the object to animate to the position. You can do this a few ways. The "threejs" way is to move it each frame (within the animate/update loop). You could do this with Vector3.lerp by storing intersects[0].point as your target location and lerping your object.position to it each frame. Another option is to use an animation library like animejs or gsap.
for a personal project, I've created a simple 3D engine in python using as little libraries as possible. I did what I wanted - I am able to render simple polygons, and have a movable camera. However, there is a problem:
I implemented a simple flat shader, but in order for it to work, I need to know the camera location (the camera is my light source). However, the problem is that I have no way of knowing the camera's location in the world space. At any point, I am able to display my view matrix, but I am unsure about how to extract the camera's location from it, especially after I rotate the camera. Here is a screenshot of my engine with the view matrix. The camera has not been rotated yet and it is very simple to extract its location (0, 1, 4).
However, upon moving the camera to a point between the X and Z axes and pointing it upwards (and staying at the same height), the view matrix changes to this:
It is obvious now that the last column cannot be taken directly to determine the camera location (it should be something like (4,1,4) on the last picture).
I have tried a lot of math, but I can't figure out the way to determine the camera x,y,z location from the view matrix. I will appreciate any and all help in solving this, as it seems to be a simple problem, yet whose solution eludes me. Thank you.
EDIT:
I was advised to transform a vertex (0,0,0,1) by my view matrix. This, however, does not work. See the example (the vertex obviously is not located at the printed coordinates):
Just take the transform of the vector (0,0,0,1) with the modelview matrix: Which is simply the rightmost column of the modelview matrix.
EDIT: #ampersander: I wonder why you're trying to work with the camera location in the first place, if you assume the source of illumination to be located at the camera's position. In that case, just be aware, that in OpenGL there is no such thing as a camera, and in fact, what the "view" transform does, is move everything in the world around so that where you assume your camera to be ends up at the coordinate origin (0,0,0).
Or in other words: After the modelview transform, the transformed vertex position is in fact the vector from the camera to the vertex, in view space. Which means that for your assumed illumination calculation the direction toward the light source, is the negative vertex position. Take that, normalize it to unit length and stick it into the illumination term.
I have some project for child http://kinosura.kiev.ua/sova/ and i need to check faceIndex of all cubes in screen.
Now i use intersections array from mouse, but is working only when user pointer at the cube.
How to make ray or rays from camera to all object to check faceIndex ?
I try to make four rays to cubes but if i set cube.position as origin of like this:
raycaster.setFromCamera( cube1.positoin , camera )
I get empty array of intersections.
I also try to set static 2d vector as origin (get coordinate from mouse) but i have relative renderer size and this coordinate all time change... its not work(
Thanks for answer anyway.
I suggest that you try another approach It appears that your cubes do not cover one another, relative to the camera view. So use the surface normals, and compare them to the view direction to determine if they are facing the camera or facing away from the camera by a simple one-per-polygon dot product.
When you are creating your geometry, before adding it a THREE.Mesh call .generateFaceNormals() on it.
Instead of ray casting, iterate through all faces, grab the surface normal of the face, transform relative to the view (inverse transpose of the object's matrix), then dot(). might sound complicated, at first, but it's actually just a couple of steps and much faster than doing a lot of raycasts (which will probably include this anyway!)
I'm quite new to three.js and lacking some basic understanding of the coordinate systems obviously.
I have an Object3D "group" that has some children (planes). I use "group" to rotate the group of planes, which works fine. Now camera can move and parent object can rotate. One can click on the planes to select them. What I want now is to let the selected plane fly into the camera.
If I just move the plane to the camera position it flys in any direction but mostly not to the camera. Certainly because "group" seems to be the "world" for the child objects. If I move a plane along the z-axis the plane move along the z-axis of the parent.
I don't understand which coordinates I need to take (or transform) to move the plane bound to "group" in front of the camera.
Basically I demoed with three.js what famo.us did, just spent some two hours on it or so. I faked the wanted effect with an additional plane that is not grouped and which I can just move to camera without transformations. The demo is available here:
http://hwg.rattat.net/famo.html.
Would be nice if somebody could tell me how to get this working. I could still live with the fake, when I would be able to place the additional plane exactly over the selected plane.
Thanks in advance,
Christian
The question of converting local coordinates to world coordinates has been addressed at THREE.js: Calculate world space position of a point on an object . There might also be helping information at how to: get the global/world position of a child object .
I have a surface to which a set of 3d objects is drawn. The task is to determine an object by the given coordinates on the surface.
For example: some objects are drawn on the desktop application, I need to determine on which object user clicked.
Could you please advise, how such task is usually resolved? Am I need to create remember a top-most object for each pixel? I don't think it is the best approach.
Any thoughts are welcome!
Thanks!
The name for this task is picking (which ought to help you Google for more help on it). There are two main approaches:
Ray-casting: find the line that starts at the camera position and passes through the surface point you are interested in. (The line "under the mouse", or "under your finger" for a touch screen.) Depending on which 3D system you are using, there may be an API call to generate this line: for example Camera.ViewportPointToRay in Unity3D, or you may have to generate it yourself by inverting the camera transform. Find all the points of intersection between this line and the objects in your scene. Which of these points is closest to the near plane of the camera? You can use space partitioning to speed this up.
Rendering: do an extra render pass, in which instead of writing textures to the frame buffer, you record which objects were drawn. You don't do the render pass for the whole screen, you just do it for the area (e.g. the pixel) you are interested in. (This is GL_SELECT mode in OpenGL: see the Picking Tutorial for details.)
If you've described the surface somehow in 3D space, then the ray, defined by your point of observation and a 3D point that is a solution for where you clicked, should intersect one or more objects in your world, if indeed you clicked on one of them.
Given the equations for the surfaces of the objects, you can determine where this ray intersects the objects, if at all, since you also know the equation for the ray in the same coordinate system.
The object that has the closest intersection point to your point of observation (assuming you're looking at the objects from above) is the winner.