Questions tagged [3d]
Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.
86
questions with no upvoted or accepted answers
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3D mesh segmentation simple algorithm
I am developing the algorithm reported in this article:
Least square conformal mapping.
Here is presented an algorithm to flat a 3d mesh on the parametric space, but i don't understand the ...
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5
votes
0
answers
244
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OpenSCAD Hull/Minkowski function by hand?
I am trying to model an organic object using OpenSCAD. However this will need to be ported over to older software. This restricts the primitives I can use (only cone, cylinder, torus, sphere and cubes)...
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Historically Significant 3D Bicubic Patch Data?
The little milk pitcher / jug in Martin Newell's 1975 PhD thesis “The Utilization of Procedure Models in Digital Image Synthesis”, does anybody have the bicubic patch data for it? The teapot's data (...
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185
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Generate complex (non-convex) polyhedron UV mapping
I need to find an approach to the problem of generating texture maps for non-convex polyhedrons without using a design tool like Maya. Specifically, I am mapping simulation results data onto a 3D ...
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1
answer
299
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How can I raycast with chunks?
I am attempting to implement chunks/octrees to speed up my render times. However, sometimes the walls show horizontal or vertical lines (rays hitting the inside of voxels?) or some blocks disappear ...
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84
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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,...
- 131
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votes
0
answers
75
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Why my cosine interpolation of a cube's face doesn't work?
NB please : executable use cases are available at the end of this question. I begin this question by showing you the problems of my program, then I explain how the latter works, and finally I end up ...
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answers
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Optimized 3D rendering using dots and/or line segments of different sizes in Scratch
I'm developing a 3D rendering engine in Scratch, which is a block-based visual programming language. It does not have any support for bitmap rendering, but there is a "pen" plugin that lets ...
2
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131
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Finding Camera projection matrix from known input and output
Lets say I have a rectangle with known coordinates in 3D scene, and I'm projecting it using pin point camera to the plane (screen).
You can imagine it deforms on the screen per camera transformation ...
2
votes
1
answer
143
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View rotation matrix
Im unsure about how I could describe what im trying to achieve in few words or a title so ill go on to describe it.
So I have voxel, in 3D space, represented solely by its center.
The voxel though, is ...
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2
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0
answers
161
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physics/math of lighting gradient of a 3D object
Consider a monochrome ball. The colours of the pixels is a function of the point height, the light intensity, the light angle, and the surface material (reflection).
What is the simplest formula ...
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98
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Why do materials have both an ambient color and a diffuse color?
One of the first things I learned about computer graphics lighting (and light in general) is that when a ray of light hits a surface, the surface absorbs certain colors and the light retains the rest. ...
2
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0
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82
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Atmospheric scattering band/seperation artifact
I am currently experimenting with some atmospheric scattering in glsl in my OpenGL engine.
I am experiencing a strange phenomena where a strange band / separation artifact appears along the middle of ...
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2
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0
answers
85
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Implementing monte carlo path traced refractions problem
I am writing a forward monte carlo path tracer with the added feature of specular refractions for transparent materials, I have managed to come this far but something is not quite right and I am ...
- 21
2
votes
0
answers
89
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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 ...
- 121
2
votes
0
answers
157
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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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2
votes
0
answers
379
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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 ...
- 121
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answers
182
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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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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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2
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0
answers
404
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Symmetry plane estimation for 3D point cloud
I have a question about finding the symmetry plane that separate the left and the right halves of a point cloud. We scanned an object, say a human face, with a 3D scanner, such as Kinect, which gives ...
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1
vote
0
answers
35
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How to transform face mesh?
We can use ARcore to create custom textures and 3D models for Augmented Faces, like the augmentation of a Fox ears. But aside from augmenting 3D objects, can we "transform" facemesh, for ...
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vote
0
answers
44
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How to find point on mesh at a minimum distance from ray
I'm searching for an efficient data structure and algorithm to compute the minimum distance between a ray and a set of meshes in 3D.
What I expect as a result are the coordinates of the nearest point ...
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1
vote
0
answers
45
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How to display real time 3-D orthogonal vector rotations?
I'm an embedded developer here with very little experience in computer graphics. I'm currently working on a GUI that can display a calculated inertial solution at run time. I have hardware that can ...
1
vote
0
answers
32
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help with libgil tutorial (python binding)
could you please give me some guidance on following this libgil tutorial? https://libigl.github.io/libigl-python-bindings/tut-chapter0/
The problem: When I do the first example (two yellow triangles), ...
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answers
49
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Proprietary 3D Format Reverse Engineering: What Could These Numbers And Matrices Represent?
I'm trying to reverse engineer a model format from an older Russian game (Pathologic) with limited success. It is a proprietary model format not recognized by any converters/editing tools (believe me, ...
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1
vote
0
answers
50
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How to extrude a face from a selected mesh in Babylon,js using the ExtrudeShape method?
I'm trying to extrude a face from a selected mesh in Babylon.js using the ExtrudeShape but can't figure out why I got flipped faces.
The bottom extrusions always comes flipped for a reason I ignore.
...
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1
vote
0
answers
32
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Principal component analysis on 3d points and other ways of capturing variance
So, I would like to do capture on 3d pointclouds of 3d models the planes/vectors where for each object we have the highest variance (i.e. for object represented by 2000 3d points I would like to get ...
- 111
1
vote
2
answers
267
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Defining "inside" and "outside" of a 3D space
I am not sure if this is the correct SE to ask this question. However, lets say I have been given 3D models of several enclosed spaces.
I want to populate spaces with, lets say, planes flying through ...
- 113
1
vote
1
answer
946
views
Intrinsic Matrix vs Perspective projection matrix
I was going through the camera matrix explained in the wikipedia article and understand how the matrix K \begin{bmatrix}f_x&s&x_0\\0&f_y&y_0\\0&0&1\end{bmatrix} is built. The ...
- 111
1
vote
0
answers
283
views
BSP tree rendering
As a little project, I'd like to implement a BSP merging algorithm for Boolean operations on solids. But to even tell whether it works, I need some way to render the BSP tree. In other words, I have a ...
- 111
1
vote
0
answers
43
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 ...
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1
vote
0
answers
492
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 ...
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1
vote
0
answers
56
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" ...
- 111
1
vote
0
answers
100
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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
...
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1
vote
0
answers
90
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 ...
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vote
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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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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1
vote
0
answers
363
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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
1
vote
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
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0
answers
50
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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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1
vote
0
answers
229
views
Is it possible to modify a console game graphics (Xbox 360)?
There's a thing called ENB for PC which works by modifying render functions calls of the games and applying additional effects. I wonder if there is a similar way for console games.
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35
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Can STEP files contain polygon data? How do I get a smoother mesh out of a STEP file?
I am trying to work with a .STEP file I have received. Upon opening it in CAD Assistant, I find
its surface as jagged lines, like a low poly model. When I export it as OBJ from there, the edges and ...
- 1
0
votes
0
answers
16
views
How to retrieve a mask for a partially filled 3D Truncated SDF based on its ground truth?
I am trying to create a mask which is required for a 3D inpainting task. My data contains 3D truncated SDF grid of size 64*64*64 with a truncated value of ...
- 1
0
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0
answers
19
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How can I understand the logic of Fast Point Feature Histograms (FPFH) descriptor?
I have been using FPFH features quite a lot in global registration and key-point extraction a lot, I also looked pcl page that tries to explain what it is, but fails to give detail to reader in my ...
- 111
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votes
0
answers
27
views
Object appears in unintended parts of the screen when using manual WorldToScreenPoint
Hy guys I'm new to 3d graphics and i lack some Linear algebra knowledge. I tried to recreate Unity's worldToScreenPoint method with kotlin on android. I copied some code from their forum and wrote ...
- 1
0
votes
0
answers
31
views
HTML Canvas not drawing
I'm working on a 3D Renderer with the canvas element and JS but currently the cube I made is not rendering. I currently have it set to just render a wireframe of the cube and am hoping to render the ...
0
votes
0
answers
32
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Rotating a set of cameras to look at a rotated object
I'm trying to use Instant NGP on a synthetic image dataset. I have image sequences of a moving object with the following information:
I have the object's xyz and the camera's xyz positions in a void.
...
- 1
0
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0
answers
33
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3D engine projection distortions
I'm trying to write my own 3D engine using Python and Pygame.
I have successfully implemented rotation and projection matrices to display 3D models. However I am so far unable to implement translation ...
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0
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0
answers
77
views
How to setup a 3D camera
I'm trying to figure out how to setup a 3D camera in WebGL. This is my first swing at 3D so a lot of the matrix stuff is new to me.
Code
The code can be reviewed in this CodePen: https://codepen.io/...
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answers
56
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Cropping a .usdz file
I have a program that is creating usdz 3D models from real world objects. I would like to be able to crop those objects in 3D space to remove extraneous nearby objects or walls. Is there a good ...
