Suppose I created a sphere mesh, uv-unwrapped it, and created 1000 texture maps around those unwrapped coordinates. Now I realized that I want some parts of the sphere to be "untextured" and have an option to texture them with another random texture. How would I remove the uv coordinates from the sphere so they don't get textured or at least move them to another uvmap without changing the position of the unwrapped coordinates.
Related
In the pinhole camera model, is it possible to determine the rotation required from the optical/principal axis (the axis which pierces the image plane) to intersect a given pixel coordinate (u,v)?
I have an image where I am detecting a marker in space, and have the intrinsic and extrinsic camera parameters available. I am using the extrinsic parameters to cast a 2d ray into a separately constructed map (which is overhead and 2d), however I would like the ray angle to change depending on if the detected marker is to the left or right inside of the image.
My first thought was to use arctan utilizing the focal length and the u coordinate (x-axis on image plane from center of image) to determine an angle, however I don't think the units of measurement cooperate: one should be in real world meters and the other is arbitrary pixels.
I am working on a geometry editor tool and I am dealing with the way how to get manipulators vector coordinates on the screen/camera plane so I can use these for mouse dragging. I've got access to vectors world coordinates matrix (or any objects matrix), projection matrix and camera direction, position etc.
I have a Poliigon Texture Demo c4d file. The file includes a sphere with a texture which renders correctly (bottom sphere in image). However when I create a sphere (top sphere in image), convert it to a polygonal object and apply the same texture it is being stretched horizontally.
I can fix this by changing the "Length U" setting to 50% in the Texture Tag but I notice that the sphere below does not need this modification so I was wondering how to convert the top sphere to a polygonal object the same way the bottom sphere is.
Cinema 4d Example
I have included a screengrab. The only notable difference is that the sphere below has additional diagonal division.
I am quite new to 3D so hope this all makes sense.
I think you only need to change the Sphere's Type, to a triangular type, like the sphere at the bottom.
If this helps, please consider up-voting and marking you question as solved
Here's the task:
We have an Mesh, drawn in position POS with rotation ROT
Also we have a camera Which position and rotation is relative to Mesh For example camera point is CPOS and camera rotation is CROT.
How to calculate resulting angle for camera? I was assuming that it something like:
camera.rotation.x = mesh.rotation.x + viewport.rotation.x
camera.rotation.y = mesh.rotation.y + viewport.rotation.y
camera.rotation.z = mesh.rotation.z + viewport.rotation.z
That worked strange and wrong.
Then I decided to read about it on docs and completely dissapointed.
There are several kind of rotation structures (Euler, Quaternion). But What a want is something different.
Imagine, like you are on spaceship. And it moves in space. You are sitting at starboard turret and looking at objects. They seems like passing by...
Then you want to turn your head - Angel of your head is known to you (in raw opengl, I'd just multiplied head rotation matrix on ship's rotation matrix and got my projection matrix).
In other words I want only x and y axis for camera rotations, combined in matrix. Then I want to multiply it with position-rotation matrix of an object. And this final matrix would be my projection matrix.
How could I do the same in THREE.js?
-----EDIT-----
Thank you for the answer.
Which coords should I give to a camera? It should be local, mesh relative coords, or something absolute?
I understand, that this questions are obvious, but there's no any description about relative objects in THREE.JS docs (besides api description). And the answer might be ambiguous.
Add the camera as a child of the mesh like so:
mesh.add( camera );
When the camera is a child of an object, the camera's position and orientation are specified relative to the parent object.
You can set the camera's orientation by setting either the camera's quaternion or Euler rotation -- your choice.
Please note that the renderer updates the object's matrix and matrixWorld for you. You do not need to do that manually.
three.js r.63
I'm creating heightmaps using Fractal Brownian Motion. I'm then coloring it based on the heights and mapping it to a sphere. My problem is that the heightmap doesn't wrap seamlessly. I've used the Diamond Square algorithm and it's pretty easy to make things seamless using it, but I can't seem to figure out how to do it with fBm and I seem to be having trouble finding an explanation for it on the web.
To clarify, by "seamless", I mean that when I map it to a sphere, it creates a seamless map on the sphere.
Instead of calculating the heightmap per pixel on the heightmap, calculate the heightmap in 3D space based on each point on the sphere and then map that to an image pixel. You're going to have trouble wrapping a 2D, rectangular heightmap like that onto a sphere without getting ugly results at the poles unless you start your calculations from the sphere.
fBM generalizes to 3 dimensions, so given a point on the sphere you can get the height at that point, and then you can do the math to map that value to where it should be stored in the heightmap image.
Or you could use one of the traditional map projections. A cylindrical projection (x, y)->(x, sin y) would give you a seam of just one meridian, which you could rotate to the back. Or you could "antialias" the edge by one or another means.
With a stereographic projection (x,y,z)->(x/(z+1),y/(z+1)), there's only one sour point (the projection point itself).