I want to render a cube similar to .
My problem is how to render the face projections.
I tried using Reflector, but it is tricky to size and position so it captures just the face that I want, and also shows the sides.
I also saw I can use a separate canvas to render (I imagine using an orthographic camera), but I wish for everything to be in the same canvas. I saw an example with multiple views, but it seems that they can't be positioned behind.
So, is there a way to achieve this?
One possible approach to solve the issue:
Setup an orthographic camera such that its frustum encloses the cube. You can then position the camera in front of each side of the cube, use lookAt( cube.position ) to orient it properly and then render the scene into a render target. You need one render target per side. You can then use it as a texture for the respective plane mesh.
There is an official live example that demonstrates how RTT (render-to-texture) is done with three.js. Try to use it as a code template for your own app.
https://threejs.org/examples/#webgl_rtt
I've been looking for a solution to this problem for a project I'm working on. I'd like to know if there is a way to click on a plane geometry and draw onto it, paint style, and have the texture update as you draw on it.
After this, is there a way to save that texture while in the browser now that you've edited it?
You could use raycasting to determine the UV texture position where the mouse intersection takes place. Raycaster.intersectObject returns an array of objects, one of its properties is .uv. You can see it in action in this demo.
You can use a 2D <canvas> as the source of the texture. Once you have the UVs from the intersection, you could use that position to draw on the canvas as demonstrated in this other demo
How do I create a three.js material/geometry which uses part of a texture?
I am first rendering a scene to a texture. This texture is used for a Mesh with a CubeGeometry and a MeshLambertMaterial. What I would like to do now is have only a part of the texture displayed on the cube face (like a window into the texture).
I've done this before using OpenGL ES directly, with shaders, but I don't see what parameters might make it possible using the standard three.js library.
That is what texture coordinates are for. See this question and answer:
http://stackoverflow.com/questions/19366991/drawing-part-of-open-gl-texture/19367844#19367844
I need to draw transparent 2D sprites in a 3D world. I tried rendering a QUAD, texturing it(using slick_util) and rotating it to face the camera, but when there are many of them the transparency doesn't really work. The sprite closest to the camera will block the ones behind it if it's rendered before them.
I think it's because OpenGL only draws the object that is closest to the viewer without checking the alpha value.
This could be fixed by sorting them from furthest away to closest but I don't know how to do that
and wouldn't I have to use math.sqrt to get the distance? (I've heard it's slow)
I wonder if there's an easy way of getting transparency in 3D to work correctly. (Enabling something in OpenGL e.g)
Disable depth testing and render transparent geometry back to front.
Or switch to additive blending and hope that looks OK.
Or use depth peeling.
Context: trying to take THREE.js and use it to display conic sections.
Method: creating a mesh of vertices and then connect face4's to all of them. Used two faces to produce a front and back side so that when the conic section rotates it won't matter from which angle the camera views it.
Problems encountered: 1. Trying to find a good way to create a intuitive mouse rotation scheme. If you think in spherical coordinates, then it feels like just making up/down change phi and left/right change phi would work. But that requires that you can move the camera. As far as I can tell, there is no way to change actively change the rotation of anything besides the objects. Does anyone know how to change the rotation of the camera or scene? 2. Is there a way to graph functions that is better than creating a mesh? If the mesh has many points then it is too slow, and if the mesh has few points then you cannot easily make out the shape of the conic sections.
Any sort of help would be most excellent.
I'm still starting to learn Three.js, so I'm not sure about the second part of your question.
For the first part, to change the camera, there is a very good way, which could also include zooming and moving the scene: the trackball camera.
For the exact code and how to use it, you can view:
https://github.com/mrdoob/three.js/blob/master/examples/webgl_trackballcamera_earth.html
At the botton of this page (http://mrdoob.com/122/Threejs) you can see the example in action (the globe in the third row from the bottom).
There is an orbit control script for the three.js camera.
I'm not sure if I understand the rotation bit. You do want to rotate an object, but you are correct, the rotation is relative.
When you rotate or move your camera, a matrix is calculated for that position/rotation, and it does indeed rotate the scene while keeping the camera static.
This is irrelevant though, because you work in model/world space, and you position your camera in it, the engine takes care of the rotations under the hood.
What you probably want is to set up an object, hook up your rotation with spherical coordinates, and link your camera as a child to this object. The translation along the cameras Z axis relative to the object should mimic your dolly (zoom is FOV change).
You can rotate the camera by changing its position. See the code I pasted here: https://gamedev.stackexchange.com/questions/79219/three-js-camera-turning-leftside-right
As others are saying OrbitControls.js is an intuitive way for users to manage the camera.
I tackled many of the same issues when building formulatoy.net. I used Morphing Geometries since I found mapping 3d math functions to a UV surface to require v little code and it allowed an easy way to implement different coordinate systems (Cartesian, spherical, cylindrical).
You could use particles instead of a mesh I suppose but a mesh seems best. The lattice material is not too useful if you're trying to understand a surface mathematically. At this point I'm thinking of drawing my own X,Y lines on the surface (or phi, theta lines etc) to better demonstrate cross-sections.
Hope that helps.
You can use trackball controls by which you can zoom in and out of an object,rotate the object,pan it.In trackball controls you are moving the camera around the object.Object still rotates with respect to the screen or renderer centre (0,0,0).