Questions tagged [3d]
Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.
2
votes
1answer
41 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
25 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
116 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
63 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
51 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
46 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
58 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
33 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
92 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
40 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
1answer
82 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
142 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
68 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
168 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
109 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
48 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
56 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
53 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
77 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.
...
3
votes
1answer
1k 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
65 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
73 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
105 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
64 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
82 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 ...
3
votes
2answers
324 views
Generate mesh from pointcloud data
Given point-cloud data :
For example.
position + color and normal.
What will you use to generate mesh of this data
and keep reasonable quality for real time cases ?
Additional info to consider:
...
3
votes
1answer
77 views
Infinitely long 3D model
Let's say that I want to render something like Dimmadome's hat, a hat which has the height of infinity.
A quick answer to this would be to place the top side of the hat high enough for the crown(...
2
votes
1answer
168 views
Light field rendering for 3d software?
Is there any 3d software that supports rendering an artificial scene to a light field image?
With that I mean an image capturing light from more than one point in a scene, more lika a spherical ...
3
votes
0answers
33 views
Possible approach for product mockup creation including distortion created through perspective
I am not an expert in 3D nor computer graphics. Please forgive me if I use wrong wording.
High level problem description: For an online shop, I would like to create mockup images of apparel (t-shirts,...
0
votes
1answer
180 views
Merge multiple Point Clouds into a single 3D object [closed]
I am testing the Intel RealSense D435 camera and have been able to create multiple Point Clouds (.ply) of a certain object. Each Point Cloud is taken in a different viewing angle of the object.
Now I ...
1
vote
2answers
53 views
If a 3D scene is rendered onto a hemispherical display, will there still be warping near the edges?
When a 3D scene is rendered to a 2D display, the image is distorted near the edges of the display.
If a 3D scene is rendered onto a hemispherical display, will there still be warping?
7
votes
3answers
222 views
How do graphic engine developers debug their 3D graphics code?
I'm currently trying to create an amateur game engine, and I often run into very basic bugs (eg I change the node hierarchy code and suddenly nothing is displayed). Some of the methods I will use ...
2
votes
1answer
47 views
How to display edges in a 3D file on Facebook
I'm trying to show a 3D model on Facebook and display its edges and lines. I found that I could export a 3D model from Sketchup using glTF Export plugin to a glb file that I can drag and drop in a ...
0
votes
1answer
85 views
Which techniques do I need to animate a 3D model in my homemade engine
Suppose I am making my own C++ 3D engine; I can already load a 3D model using assimp, display it with phong lighting, and I now want to animate it.
I'd like features in my engine to, say, load a run ...
0
votes
1answer
85 views
How to compute volume of intersection of non-axis-aligned cuboids in 3D?
Given two cuboids in 3D space (8 vertex coordinates each) that are arbitrarily oriented, how can we find the volume of overlap between them in the fastest manner?
1
vote
1answer
62 views
how to draw mesh equal distance from irregular shape geometry bounding box
I am given an irregular geometry shape with its vertices, bounding box information.
How to draw a smooth mesh equal distance from that irregular geometry shape's bounding box?
Please refer to the ...
3
votes
1answer
72 views
How to remove internal geometry programmatically in all meshes in .OBJ file?
I have an .OBJ 3D model with many complex meshes shape.
The meshes are complex because each of them have multiple internal mesh located in it.
Meshes with internal geometry is defined as a mesh, ...
1
vote
1answer
154 views
How to rotate a camera?
So I am doing a simple FPS camera with openGL. I store the camera as 4 vector, a position vector, a lookAt vector, an up vector and a right vector. When the user presses a key, I create a rotation ...
1
vote
0answers
93 views
Efficient operations on polyhedra
I currently perform several operations on polyhedra with cgal. These operations include
Union of two or more polyhedra
Difference of two or more polyhedra
Intersection of two or more polyhedra
...
1
vote
0answers
67 views
Image Processing: Photogrammetry [closed]
I am new to image processing but I am currently exploring myself in 3D reconstruction during my leisure time.
I have decided to use openCV (eg. edge detection, possible?) in C++., maybe with a little ...
1
vote
1answer
249 views
How to interpolate vertex normals for Phong lighting when barycentric coordinates are negative?
I'm interpolating normals for Phong lighting models. Since I am calculating in the light of each pixel, I'm doing the interpolating after the viewport transform has been applied. So I save a version ...
1
vote
2answers
310 views
How to calculate the view vector in Phong Lighting Model?
All the books and reference I have read say that the view vector is calculated by subtracting the point where eye is at, from the point where we want to calculate light. But since, eye is at (0, 0, 0) ...
2
votes
1answer
59 views
Do normals in obj files have to be changed into eye coordinate before being used?
Obj files give pre-calculated normals which are in model coordinates. So I wonder if they have to be transformed into eye coordinate (where I use them to calculate lighting)? I'm thinking yes because ...
5
votes
2answers
209 views
How did the hard, accurate shadows, work in early 3d (2000 - 2004) games?
I've been hunting around the internet for a while now, and I can't find anything about the specific shadow technique that I'm looking for.
I can only recall one game in particular that used it, and I ...
1
vote
0answers
84 views
How to do clipping in camera space?
I don't even know where to start. So far, the only progress I have gotten is checking the z value of each vertex of each triangle. If all three vertices' z values > absolute value of far or < ...
1
vote
2answers
109 views
Is there something wrong with a column camera matrix?
I am writing a simple ray tracer. I was working on my camera matrix when I encountered a problem. When I changed the look vector, so that it headed down, the image, which was supposed to go up, ...
2
votes
3answers
198 views
What is the use of homogenous divide?
This question perhaps has been asked and answered a thousand times, and yet I haven't found any that satisfy me. The reasons are often these:
1/ You need a 4 dimensional vector to work with 4x4 ...
2
votes
1answer
2k views
How to derive a perspective projection matrix from its components?
This has been haunting me for several days now. I want to find the component that makes up of this 4x4 perspective projection matrix, with $l$(left), $r$(right), $b$(bottom), $t$(top), $n$(near), $f$(...
1
vote
0answers
59 views
How to automatically project texture from high poly mesh to low poly mesh?
I have two aligned meshes: I have exact mapping from each vertex of low poly mesh to surface of a high poly mesh. High poly (~100K vertices) mesh is non-manifold, low poly (~1K vertices) is manifold ...
