Questions tagged [3d]
Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.
184
questions
0
votes
1answer
45 views
Why is the z direction away from the screen/viewer?
I wonder what is the reason that when z increase, the objects appear far away and when z is negative, the object is behind the camera?
2
votes
2answers
51 views
Visualize the interpolated unit quaternion on the surface of the unit sphere
My major is mechanical, please forgive me for asking questions that may seem trivial to you.
First, I'm reading the following paper:
Dam, Erik B., Martin Koch, and Martin Lillholm. Quaternions, ...
0
votes
1answer
68 views
Compute Speed of Spheres in 3D animation
I have created two animations:
One where a "camera" moves towards the spheres creating an optic flow (1st GIF).The code can be found here.
One where spheres move randomly in a 3D coordinates space (...
2
votes
1answer
122 views
Rendering equation for spherical lights
I am currently implementing spherical lights in my DirectX game engine. I decided to build the shading formula from the classical rendering equation. Here is what I get:
The simplifications show that ...
0
votes
0answers
19 views
Apply a pose to a 3D model/mesh
Assuming that I have pose information for a human, is there any ways/tools to apply that pose to a 3D model?
Basically, given continous pose information say from a dancing person, I like to animate a ...
1
vote
1answer
36 views
Calculating normals for vertices which aren't a vertex of all neighbouring triangles
In my procedurally generated mesh in Unity, not all vertices are vertexes of all neighbouring triangles - essentially, it's a grid with cells of varying sizes. This is messing up the calculation of ...
0
votes
0answers
17 views
Is it possible to set visible and color for all 12 edges(spines) of the figure (cube) in matplotlib?
In 2d, matplotlib plots all 4 edges(spines) of a figure.
In 3d, matplotlib plots 9 out of 12 edges of a cube.
Is it possible to set visible and color for all 12 edges(spines) of a cube in 3d?
I ...
0
votes
1answer
45 views
Why does my code generate a figure whose kurtosis looks a little higher than the one I am trying to reproduce?
this figure (fig_1) is an univariate normal distribution in 3D, the corresponding equation is in the top left hand corner
it seems that x varies from -5 to 5; sigma varies from 0 to 4.
This Python ...
1
vote
1answer
40 views
Why does my code to plot a cone actually generate a roof?
per this post, this formula
$Z = 1 - \sqrt{X^{2} + Y^{2}}$
generates a cone where the point is at (0, 0, 1) and it spreads out below that. It meets the x-y plane at the unit circle
I am trying to ...
1
vote
1answer
83 views
Could some give an explanation or hint about this kind of equation? $\left(- \sqrt{X^{2} + Y^{2}} + 1\right) \cos{\left (2 \pi X + \phi \right )}$
This is a screen shot from an animation generated by a matplotlib example
the key part in the code is
...
4
votes
2answers
65 views
Creating a Smooth 3D Mesh from a 2D Outline
I am trying to find (or maybe create) an algorithm for creating a smooth, rounded 3D mesh given a 2D outline. I'm trying to recreate a system from a Gamecube game called Amazing Island, and you can ...
1
vote
1answer
165 views
What's the difference between Clipping and Culling?
In a tutorial about OpenGL both words are mentioned, unfortunately without a good explanation.
To find out, I have read this article three times, but I fear I'm a too common man... my understanding is ...
2
votes
1answer
78 views
Calculating the angle between two polygons
For my application, I want to render models as polygonal surfaces in 3D space and have edges that are bent "outwards" to have a solid line and those who are bent "inwards" to have a dotted line. So if ...
0
votes
1answer
33 views
What is performance better - add four materials to mesh or duplicate every vertex and use packed texture?
I am making ski jumping game (in Unity) with procedurally generated hill mesh. I want to add lines on hill like this (mesh is created by script, but I've manually assigned materials in Blender)
...
1
vote
0answers
12 views
How can I detect if an edge has flipped during the UV unfold process?
I'm writing my own UV Unfold operation (similar to Maya's Optimize UV tool or 3DS Max's Relax Tool). My code works great 90% of the time but in some instances, I'm getting faces and edges that flip ...
1
vote
0answers
64 views
Help with understanding the look-at function (the view matrix)
I've been reading this article about the look-at function. I don't understand the part when they're trying to inverse the matrix N.
They say that R is orthogonal because all its row and column ...
0
votes
1answer
252 views
How can i create a 3D Sphere(earth) using OpenGL, GLFW, GLAD, GLM?
Please help me out with this thing and currently i am a little more than a beginner so please tell me in that context. i don't need any obsolete methods for creating this like using GLUT or GLEW.can ...
0
votes
1answer
137 views
What are the i,j,k components of a 3d mesh on plot.ly (online)?
A 3d Mesh on plot.ly online graph maker (https://plot.ly/create/#/) takes 3 mandatory variables (X, Y, Z) and 3 optional variables (I, J, K).
I understand that if I want to draw a cube that I then ...
0
votes
0answers
20 views
Newby - which computer language for video to video &/or 4-D to video
First post on forum. What's the simplest language / package for computer graphics that will do what i need?
I have two projects in mind:
One is to input a video (eg. from youtube) and process it ...
1
vote
0answers
86 views
Why don't I see tile-based 3D graphics?
As we know, tiles can make it quicker to update large portions of the display at once, as compared with a bitmap. To put, say a letter, on the screen, the Commodore 64 typically does two writes (the ...
3
votes
2answers
296 views
Programmatically generating bin files for GLTF models
I have a need to generate a series of GLB files. I have a base template for a GLTF file which I have to derive off of. The models thus generated will only have varying textures on them. The base mesh ...
0
votes
0answers
68 views
Using octree for cheking intersection of ray and meshes
I wrote the code for checking intersection of ray and meshes on scene. It consist of two parts - broad phase and narrow phase.
In broad phase I build an oriented bounding box around each mesh and ...
3
votes
1answer
260 views
Vulkan: efficient way to update VBO mesh vertices?
I would like to change/add/remove some mesh vertices in existing VBO's (while deforming and remeshing 3D objects) . With OpenGL I would have to reload whole vertex VBO's. I suppose with Vulkan there ...
0
votes
0answers
63 views
Programmatic rendering of 3D animations
Many years ago I used POV-Ray to render some 3D animations. I liked POV-Ray's Scene Description Language (SDL) as I could generate the required files programmatically using other languages (e.g. Perl)...
3
votes
2answers
259 views
Unfold a 3D mesh to a 2D plane
I'm trying to unfold a 3D mesh onto a 2D plane. My general idea to do this, would be to cycle through all the faces of the meshes and perform a hierarchical transformation.
So I would start at the ...
0
votes
1answer
109 views
Rendering 3-D point clouds obtained from depth maps as a 2.5D video
Suppose I have code to generate a bunch of frames, each of which is a depth map(I have access to the matrices which represent depth) which in turn is used to generate a point cloud. One frame would ...
1
vote
1answer
133 views
Why do animated CG characters always feel fake?
Why do animated CG characters always feel fake?
Usually if a CG character is an animal (or humanoid creature), they tend too look kinda off. Their movement tends to look oddly smooth or lightweight, ...
0
votes
2answers
140 views
transformation from cartesian coordinates to spherical coordinates without calculations
Given this graph in the 3d cartesian coordinates i should figure out the spherical coordinates representation but without the use of calculations .
I've been trying to solve this the whole day but i ...
0
votes
1answer
29 views
Can you generate your own HDRI maps without using photos?
For example, preparing a scene in Maya using standard lights and rendering out a panorama?
Could they also be made from scratch in photoshop using 32bit color?
Is there a reason why people don’t ...
2
votes
0answers
52 views
Intersecting Frusta
I am trying to determine whether two frusta intersect in 3D space and to quantify this intersection as a percentage of one frustum volume (eg. 100% intersection meaning that the two frusta occupy the ...
1
vote
1answer
62 views
If you can use subdivision surfaces for 2D curves
I've seen how subdivision surfaces are good for 3D curves/modeling, but haven't seen anything on if it's good, or even usable, in 2D.
My question is just that, if (a) you can even use subdivision ...
0
votes
1answer
91 views
Problems with Subdivision Surfaces
It sounds like Subdivision Surfaces are better than NURBS but not as good as T-splines. I would like to know some of the disadvantages of Subdivision Surfaces, what they can't do or what they do ...
1
vote
0answers
39 views
Convex hull around polygon for cave mapping
For the purpose of mapping caves, we survey new passages so that we take main polygon (survey from point A to point B) and on each "node" (survey station A in example), we shoot multiple "splay shots" ...
1
vote
2answers
324 views
How to get the 3D position for the point with (0,0) UV coordinates?
I have a 3D triangular mesh(vertices, indices, uv coords) that I'm rendering to the screen. Let's assume that the UV mapping is one-to-one. I'm trying to find a way to find the 3D position of the ...
1
vote
1answer
47 views
Export Model Textures Per Face
(Note that as far as attempts go, I can't find anything that helps me)
I have a 3D polygon, and for simplicity's sake it's going to be the one below:
It is textured using the UV map below:
Side ...
2
votes
2answers
370 views
3ds max: Z-fighting when working with Large Objects
I had a z-fighting/z-clipping issue with a scene containing some very large objects yesterday in 3ds max. It can be seen in the image below:
For some reason downscaling the scene significantly (a ...
3
votes
1answer
202 views
Rendering Fluid Simulations?
I've read about Lagrangian and Eulerian fluid simulations and here's what I take from their methods:
Lagrangian - Simulating fluid particles by calculating displacement for each particle
Eulerian - ...
1
vote
1answer
84 views
Overlaying a grid on to a height map
What is the method used in overlaying a grid (agonostic of the grid type) on to a height map? It seems it's some sort of projection, but what are the technical details in how to implement it?
An ...
2
votes
2answers
512 views
How can I draw this style of grid?
I'm trying to write code (in any language) to render this 3D grid, matching the look and colors as closely as possible:
0
votes
1answer
122 views
3D scene construction and change of coordinates
My book says:
After a scene has been constructed we transfer object descriptions to the viewing-coordinate reference frame. This conversion of object descriptions is equivalent to a sequence of ...
2
votes
1answer
107 views
What is the equivalent of rotation matrix in Euler angle space for Quaternions?
I have to load a mesh in Blender (which uses Z and Y as up and forward axes), modify it and export it (with setting up and ...
1
vote
1answer
61 views
How to rotate a shape in another 3D software so that the rotation matches with the rotation in Blender?
I import a mesh in Blender, export it with setting axis_forward='-Z', axis_up='Y', import in NVIDIA's FleX, rotate it and store it on disk; I call this mesh ...
0
votes
1answer
81 views
How to compute A and B in projection matrix
I'm trying to compute a projection matrix to transform from view space to NDC with a near clip plane at -1 and far plane at +1. The general form of this matrix (disregarding aspect ratio and focal ...
0
votes
1answer
115 views
qt - view geomview (.off ) file
I want to open a .off file and view the content 3d model using libQGLViewer, qt-creator.
I don't know how to display the 3d model after opening its .off file.
...
4
votes
1answer
4k views
How to convert Euler angles to Quaternions and get the same Euler angles back from Quaternions?
I am rotating n 3D shape using Euler angles in the order of XYZ meaning that the object is first rotated along the X axis, then Y...
5
votes
1answer
79 views
How to randomly draw Quaternions within a specific range of Euler angles for rotation?
I am pretty new to Quaternions so please bear with me. I want to draw random Quaternion samples so that their Euler angle equivalent would range within [-30, +30] ...
1
vote
1answer
74 views
How are the three plane equations derived in the NVIDIA's CG Tutorial chapter 8?
I'm reading the chapter 8 of the Cg tutorial and I could not understand 8.4.1 :
Because all these coordinates lie in the plane of the same triangle, it is possible to derive plane equations for x, ...
-1
votes
2answers
139 views
Relatively new to OpenGL, need guidance/tips on an assignment with interactive user input
I'm currently taking a Computer Graphics class at university, and have been given an assignment which involves loading an obj file and manipulating it with keyboard and mouse controls (eg. arrow keys ...
1
vote
1answer
68 views
How to raytrace triangular faces when camera is not at origin?
I've watched the Pixar In A Box, Maths of Rendering Tutorial on Khan Academy. I've started writing a raytracing program and have come to the point where I must solve for ...
2
votes
1answer
97 views
Z-buffering implementation with small triangles
For research purpose, I have to implement z-buffering algorithm to render 3D face models. But I got a problem that the triangles are too small to be rendered (i.e. there is no pixel covered completely ...
