According to BoxGeometry docs widthSegments, heightSegments and depthSegments are used to set a number of segmented faces along a corresponding side.
What is a real use case for these options?
One of the reason to use these options is to apply Displacement mapping.
Basically you add vertices by subdiving face into segments (rectangles for box). By default each face of a cube has only one segment. The more details you want on the face of a cube, the more segments needed.
For other reason, you can do something like this
Related
I need to run some calculations on meshes using ThreeJS.
The calculation should involve the faces of the mesh, but not the triangular ones.
for example in the attached image, I'd like to consider both of the triangles of the top faces as a single face.
Is there a way to know which triangles go together?
I've seen that the geometry has a "groups" property.
https://threejs.org/docs/#api/en/core/BufferGeometry.groups
But it just says it is used to split the rendering.
Can I rely on it to determine that the vertices in the group form the "face" that I need?
Is there any other way to get it?
I have a problem with mapping a texture in THREE.js which is possibly related to creating custom UV-Coordinates as extensive search indicates.
The following picture shows a geometry which was created from THREE.BoxGeometry by manipulating the lower vertices of the box. The texture on the side looks stretched (although this is correct I guess).
picture1
Is there a way of "projecting" the texture onto the side, e.g. by creating custom uv-coordinates to look like in the second (photoshopped) picture?
picture2
Thanks for you help!
You will need to remap your vertices manually to perform what is called a "box mapping" or a "triplanar mapping".
Here is an example I threw together: https://codesandbox.io/s/qxk8xvnrvj
It creates a cube with some subdivisions.. perturbs those vertices if they are on top... and then does the iterations through the faces uvs and vertices to remap each faces UVs with a box mapping, by finding the dominant axis the face normal points along... and then using the other 2 axis' as the U and V axis for unwrapping.
I am setting up a particle system in threejs by adapting the buffer geometry drawcalls example in threejs. I want to create a series of points, but I want them to be round.
The documentation for threejs points says it accepts geometry or buffer geometry, but I also noticed there is a circleBufferGeometry. Can I use this?
Or is there another way to make the points round besides using sprites? I'm not sure, but it seems like loading an image for each particle would cause a lot of unnecessary overhead.
So, in short, is there a more performant or simple way to make a particle system of round particles (spheres or discs) in threejs without sprites?
If you want to draw each "point"/"particle" as a geometric circle, you can use THREE.InstancedBufferGeometry or take a look at this
The geometry of a Points object defines where the points exist in 3D space. It does not define the shape of the points. Points are also drawn as quads, so they're always going to be a square, though they don't have to appear that way.
Your first option is to (as you pointed out) load a texture for each point. I don't really see how this would introduce "a lot" of overhead, because the texture would only be loaded once, and would be applied to all points. But, I'm sure you have your reasons.
Your other option is to create your own shader to draw the point as a circle. This method takes the point as a square, and discards any fragments (multiple fragments make up a pixel) outside the circle.
I want to create a series of segments of sphere which later can be combined to give a illusion of entire sphere. I want to do this so that i can use different textures.
Please follow the below link
Texturing a sphere in THREE.js
In addition to the above answer, you can accomplish this dynamically as well using different combination of the PI and theta values, so that you can decide on number of sphere to be created at run time ,based on the number of your textures.
At the moment I'm using ThreeCSG/CSG to subtract a small cube from a much larger cube. This works fine, but only the look of it changes not the actual geometry. So when using PhysiJS (Physics engine) on another cube, it doesn't fall into the hole but acts like it normally would. Click for Demo.
Is there any way I can actually remove a section from a CubeGeometry so that objects can fall into it - not just for display purposes? Thanks!
ThreeCSG does change the geometry, by which I mean geometry in the sense of Three.js -- the collection of vertices, the faces, etc. I think what you mean is that ThreeCSG does not change the physics-based properties of your object.
According to https://github.com/chandlerprall/Physijs/wiki/Basic-Shapes , it appears as though you have to use Physijs.ConcaveMesh as it "matches any concave geometry you have, i.e. arbitrary mesh", and it is the only one that has a change of supporting a non-convex physical object.