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
Related
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.
i am quite a beginner in Gmsh and am trying to create a mesh for hydrodynamic simulation from coastlines. I used splines for the complex coastline for simplicity, but the produced mesh crossed over the coastlines. What should i do to make the mesh not cross over the bounding curves?
Image for reference
Your mesh is simply to coarse in the moment. The points of each Triangle in the mesh lie on the real geometry/coastline but the edges are linearly connected and do not care about the geometry.
In order to refine the mesh you might try to press Mesh->Refine by Splitting a couple of times and see split the few current cells. The mesh should get finer and should not violate the geometry boarder by as much as right now.
BUT by this you'll only make the "issue" less obvious to see. On a smaller scale you will always see mesh cells that are partly "outside" the geometry borders. You cannot prevent this with concave meshes like the one you have here. If you have s.th. convex like a circle all elements will strictly lie inside the geometry border.
So as a first step, make a finer mesh until you are satisfied with the match between geometry and mesh.
I understand that CalculateFrustumPlanes() in Unity3D returns an array of Plane objects, each representing a different frustum plane, but I can't find any documentation to suggest which element is which?
for example
[0] = Front
[1] = Back
etc.
I need to calculate whether a point in space (like the centre point of a Bounding volume) is in the camera frustum, for a Quad tree system.
What is exactly the order of the Planes in the returned array is not documented (and I don't know it).
Anyway I think you can figure it out without much effort: you just need to put the camera in a well know orientation and check the normal value's of each Plane.
I need to calculate whether a point in space (like the centre point of
a Bounding volume) is in the camera frustum, for a Quad tree system.
For a Quad Tree system, I think the intersection between the frustum and a GameObject's AABB is enough, so you don't even need to know exactly the order of the Plane's in the array to compute it. You can just use GeometryUtility.TestPlanesAABB.
Order: left, right, bottom, top, near, far.
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).
I'm using a 3d engine and need to translate between 3d world space and 2d screen space using perspective projection, so I can place 2d text labels on items in 3d space.
I've seen a few posts of various answers to this problem but they seem to use components I don't have.
I have a Camera object, and can only set it's current position and lookat position, it cannot roll. The camera is moving along a path and certain target object may appear in it's view then disappear.
I have only the following values
lookat position
position
vertical FOV
Z far
Z near
and obviously the position of the target object.
Can anyone please give me an algorithm that will do this using just these components?
Many thanks.
all graphics engines use matrices to transform between different coordinats systems. Indeed OpenGL and DirectX uses them, because they are the standard way.
Cameras usually construct the matrices using the parameters you have:
view matrix (transform the world to position in a way you look at it from the camera position), it uses lookat position and camera position (also the up vector which usually is 0,1,0)
projection matrix (transforms from 3D coordinates to 2D Coordinates), it uses the fov, near, far and aspect.
You could find information of how to construct the matrices in internet searching for the opengl functions that create them:
gluLookat creates a viewmatrix
gluPerspective: creates the projection matrix
But I cant imagine an engine that doesnt allow you to get these matrices, because I can ensure you they are somewhere, the engine is using it.
Once you have those matrices, you multiply them, to get the viewprojeciton matrix. This matrix transform from World coordinates to Screen Coordinates. So just multiply the matrix with the position you want to know (in vector 4 format, being the 4ยบ component 1.0).
But wait, the result will be in homogeneous coordinates, you need to divide X,Y,Z of the resulting vector by W, and then you have the position in Normalized screen coordinates (0 means the center, 1 means right, -1 means left, etc).
From here it is easy to transform multiplying by width and height.
I have some slides explaining all this here: https://docs.google.com/presentation/d/13crrSCPonJcxAjGaS5HJOat3MpE0lmEtqxeVr4tVLDs/present?slide=id.i0
Good luck :)
P.S: when you work with 3D it is really important to understand the three matrices (model, view and projection), otherwise you will stumble every time.
so I can place 2d text labels on items
in 3d space
Have you looked up "billboard" techniques? Sometimes just knowing the right term to search under is all you need. This refers to polygons (typically rectangles) that always face the camera, regardless of camera position or orientation.