Questions tagged [3d]
Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.
309
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2
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Triangle-based and vertex-based skinning models?
I'm reading the Loper et al. 2015 paper on the Skinned Multi-Person Linear Model and I came across this:
What we would like is a vertex-based model that has the expressive
power of the triangle ...
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5
votes
1
answer
930
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why is translating in 3D space the same as shearing in 4D space?
I was reading "3D Math Primer for Computer Graphics and Game Development" and there was something the author had said that I thought was particularly interesting, he stated
It is important to ...
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0
votes
0
answers
100
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How does anti-aliasing work, in general, for raytracing? [duplicate]
I am working on a raytracing Java program for fun. Here's one rendering:
As you can see I still have to implement anti-aliasing (and there are huge geometry problems I won't get in to). How would ...
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2
votes
1
answer
174
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How do I replace a mesh's texture with vertex colours?
I have a textured 3D mesh. I want to deduce a 3D mesh without texture, but with an RGB vector color on each node of this 3D mesh. The colors have to be picked from the initial texture. Is there a way ...
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0
answers
158
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Composition of an .obj file
Using an iPhone X, I can get a mesh of the face (using ARFaceGeometry), which I can output as an .obj file using ...
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2
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453
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Does this 3D rendering method exist? How is it called? Is there any C++ algorithm for it?
I've been thinking about making my own 3D rendering engine in C++, but I don't know much about math that's required to do it. I'm not even sure if it's possible or if it even exists or how it's called....
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2
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1
answer
1k
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How can I use 3d animation to create a character that uses sign language?
I performed a quick search on programs that translate natural language to sign language (through a 3D animation character). Here are examples:
IBM SISI
ProDeaf (which is an android app)
My question ...
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5
votes
3
answers
749
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Was Evans & Sutherland CT5 really created in 1981?
A few days ago I found a video on Twitter showing the Evans & Sutherland CT5 Flight Simulator system. It was labeled as 1981 footage and looked really amazing. The first time I saw similar 3D ...
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1
vote
1
answer
62
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Stereoscopic 3D app development
I want to create an application to visualize image pairs in stereoscopic 3D. I want it to have a cursor that can move left and right, but also in and out. I think the way to achieve this is to draw a ...
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9
votes
2
answers
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Why do I need to inverse the orientation matrix of a camera to be able to translate it in the direction it is facing?
I've been going over some OpenGL learning resources and one of them is this article: Modern OpenGL 04 - Cameras, Vectors & Input in which the author presents an approach to building a ...
- 193
0
votes
2
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277
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The distance from the cube sides to the parallel projection plane
I have asked this question on ru.stackoverflow.com and have no valid answers.
Specification:
Coordinate system
Cube spins around its center on all three axes.
Turn angle is not known previously.
...
user7220
2
votes
2
answers
4k
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Inverse-Transpose of Vertex Normals
For the past month, I have been learning on my own and writing a little graphics library and am currently working on the transformation of vertex normals to soon support lighting/shading. I understand ...
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23
votes
5
answers
27k
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Why are quads used in filmmaking and triangle in gaming?
In film school, in the classes of 3D modeling, I was told that when we model something for films we maintain topology of 4 edged polygons. Any polygon which has more or less than 4 edge/vertex is ...
- 335
3
votes
3
answers
747
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Point of view and rotation
Two questions which cross over maths/3D imaging/computer science. I'm trying to describe a point of view of an item in a 3d space and subsequently its rotation in a paper I'm writing. Versions I've ...
2
votes
0
answers
381
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Rendering of large STL files
I am in the process of creating some software in Java for generating 3D gear geometry and saving it as an STL file. I am looking at a means of drawing the geometry so that the user can view the ...
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1
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0
answers
201
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Algorithm for clipping convex quadrilaterals
I'm dealing with hardware that uses quads as its polygonal primitive. Not triangles. A triangle can be expressed by setting 2 of the 4 vertices equal to each other for a degenerate quad.
For the 3D ...
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3
votes
1
answer
684
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How to correct point cloud distortion
I am using Unreal Engine to export custom render passes for the scene depth in world units. Every pixel in the render pass has a value which is the distance from the camera to that pixel in standard ...
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2
votes
2
answers
912
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How to use multithreading in 3D software renderer to speed up fetching texture values
The biggest bottleneck of my code is fetching texture RGB values from memory.
My code looks something like this:
...
1
vote
0
answers
364
views
Applying 3d transformation to cuboid
I have the 8 vertices of a cuboid (red points)(XYZvox) with known distance in millimetres (vox to mm) between each vertex which I transform in 3d space using the 4d transformation matrix (M). I am ...
- 111
0
votes
0
answers
2k
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Convert prc-file (3D PDF) to 2D file format
I have a question regarding 3D PDF files.
I have a 3D vector graphics image which is saved as a Product Representation Compact (PRC) file. The PRC file is embedded in a PDF file. I can view and ...
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2
votes
2
answers
2k
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Extract visible vertices from a 3D geometry model
Let's assume we have a 3D model consisted of XYZ-formatted vertices (such as point cloud model). My problem is given the position and normal of camera or camera ...
- 229
0
votes
0
answers
87
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3D sphere mesh with a predefined number of vertices and a given adjacency matrix of vertices
I need a 3D triangular sphere mesh with uniformly sampled vertices, say $V$, with a predefined adjacency. Is there a specific way to achieve that?
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6
votes
1
answer
670
views
3D projection that increases objects' size as they become more distant
tl;dr Is there a name for a type of (non-physical) projection that causes objects to become larger the farther they are from a camera?
With a fisheye projection, an object twice as far from the ...
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votes
1
answer
1k
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Rotation matrix for a 3D object in space
This is the follow-up question from here: Minimum requirements to uniquely represent a 3D object in space
Assume I have 3 original points in a 3D object (in 3D space) as ...
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4
votes
2
answers
1k
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Minimum requirements to uniquely represent a 3D object in space
Let's assume we have a 3D object (in 3D space). We get a single representation vertex from this whole 3D object. Given the fact that the object can be moved and rotated in the space in any direction, ...
- 229
2
votes
0
answers
182
views
Interpolation of orientations
I have a problem of linear interpolation of CRV (Conformal Rotation Vector) in which CRVs are used to parameterize the orientations.
In my knowledge, in order to derive a linear interpolation of ...
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5
votes
2
answers
229
views
What is missing in this image that stops it from looking like a photograph?
Look at this image:
This is CG, Saya, a project meant to make as real CG as possible to the point of becoming indistinguishable from reality. I would say that it is pretty believable. But, it still ...
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5
votes
1
answer
110
views
Best way to group 3d points into planes, if any
If I have some 3d points, how can I discover parallel planes within them (not just arbitrary planes).
I want to know how many "levels" or "floors" something can travel within, after it has done so, ...
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3
votes
1
answer
166
views
How does the Waves class in the book Introduction to 3D Game Programming with DirecX11 work?
I'm confused by the Waves class implementation in the source code of the book Introduction to 3D Game Programming with DirecX11:
...
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4
votes
4
answers
2k
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How to build a 3d model from 2d pictures
I have a series of MRI images. I want to build a 3D model out of it, which not only presents the surface, but also contains the inside structures. What kind of photogrammetry based method can realize ...
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1
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0
answers
98
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Advice on synthetic data generation using 3D mesh
I'm developing a deep learning algorithm to find and classify (post consumption) plastic bottles on a conveyor belt. A way to train my model is to get tons of labeled images of each bottle, which for ...
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1
vote
1
answer
381
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Final transformation matrix to transform world coordinate into vrc [duplicate]
For a 3D scene in the world coordinates, its View Reference Point $\mathrm{VRP}$ is at $(5,2,1)$, and a viewer is looking towards point $A=(1,1,1)$. Construct a transform matrix which will map world ...
- 317
1
vote
1
answer
661
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How do I implement object picking, using OBB in OpenGL?
I am trying to make 3D drawing software. I wanted to have the drag feature so I am using object picking using the OBB algorithm. I am facing problems in understanding the algorithm, and my ...
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0
votes
0
answers
376
views
Tilting a 3d object to face a camera and have it look like it's spinning on the y axis
I have a scene kit app I'm working on and at a certain point I move the camera under a list of objects and tilt it up to give a star wars type view of them. I then need to pull the objects up one at a ...
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3
votes
1
answer
73
views
What metrics are used for deciding if a 3D object is visible?
I'm wondering what metrics I could use to decide upon the visibility of a 3D object in VR or other 3D applications and what advantages each has.
- 163
0
votes
1
answer
90
views
Which 3D object properties should be affected by distance?
Which 3D object properties should be affected by distance in VR and other 3D applications and how important is it that they are changed?
For example the level of detail, colour (?)...
- 163
1
vote
1
answer
402
views
Beginner CG Research Project [closed]
This summer I will be working with a professor on a research topic of my choice, in the field of graphics & simulation. While my professor is knowledgeable in the area he is being very hands off ...
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1
vote
1
answer
2k
views
Building view transform matrices
For a 3D scene in the world coordinates, its View Reference Point $\mathrm{VRP}$ is at $(5,-2,1)$, and a viewer is looking towards point $A=(1,1,1)$. Construct a transform matrix which will map world ...
- 317
3
votes
2
answers
7k
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Correcting my "look-at" matrix so that it works on non-camera objects?
I'm familiar with the "look-at" matrix and the goal of being able to rotate a Camera at a specific location towards a specified target.
When I tell the ...
- 166
3
votes
1
answer
2k
views
Bevel/Chamfer algorithm for arbitrary 3D mesh
I can't find any paper about a bevel/chamfer algorithm for 3D mesh. Bevel has a lot of special cases (corners, different bevel profile, bevel larger than a face). I am looking for robustness.
Do you ...
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2
votes
0
answers
287
views
How to output a 32 floating value in a render buffer with fragment shader
I would like to downsample my depth buffer and my normals.
For that, I take in input of my shader, the corresponding textures (depth, normal), and I write my new values in a multi render target.
I ...
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8
votes
2
answers
1k
views
How to translate mouse movement to a rotation gizmo?
I need to implement translation, scaling and rotation gizmos and I'm having trouble with the rotation gizmo. Basically I don't know how to translate the mouse movement to determine in which direction ...
- 211
2
votes
1
answer
889
views
How to properly direct light sample GGX in path tracing
I have been trying to implement the GGX shader in my path tracer based on this paper: Microfacet Models for Refraction through Rough Surfaces
It's pretty clear how the importance sampling works, but I ...
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6
votes
1
answer
338
views
Mix shader looks wrong on my path tracer
I apologize if my methods seem way off because this is my first time trying to build a path tracer and I'm struggling quite a bit. Currently, I am trying to mimic the "mix shader" node in Blender 3D ...
- 389
4
votes
1
answer
148
views
How does a rigged model work?
What black magic is behind this?
Starting from a pile of polygons, a skeleton, and an initial conformation, how is a new conformation turned into a new pile of polygons?
- 143
6
votes
2
answers
2k
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Is there a way to draw spherical objects without triangles?
It seems that in all existing graphics libraries, 3D objects are always described in terms of triangles. Drawing triangles can be implemented very efficiently on video hardware and since any 3D object ...
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9
votes
2
answers
10k
views
How to achieve gimbal lock with Euler angles?
I was studying about Euler angles and I came across the problem gimbal lock which can occur by using Euler angles. In gimbal lock we lose one axis of rotation.
But how? And when does it happen? On ...
3
votes
1
answer
277
views
Improved Laplacian smoothing of noisy surface meshes
I have a question regarding Laplacian Smoothing of meshes and in particular the paper "Improved Laplacian smoothing of noisy surface meshes" by J. Vollmer in the early 2000's.
What is the reason for ...
- 31
1
vote
0
answers
50
views
Aligning similar surface meshes consistently
When I have a plaster cast of a mandibula and rest it upside down on a table, in most cases it will be in a stable position.
In real life, I do not have a plaster cast, but a 3D scan, i.e. a surface ...
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4
votes
1
answer
2k
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Normal 2D photo to VR-compatible spherical photo
How to turn a normal photo like this one :
into a photo that I can use in my game development platform (Unity3D). I just wrap a 3d sphere model with the photo and then it can be all around me when I ...
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