# Questions tagged [3d]

Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.

87 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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### 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 (...
188 views

### 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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### 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,...
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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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### 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 ...
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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 ...
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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 ...
210 views

### 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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### 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. ...
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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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### 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 ...
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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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### 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 ...
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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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### 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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### 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 ...
300 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 ...
412 views

### 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
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### Automating equirectangular horizon detection in 360 images

I would like to programatically identify pitch and roll numbers that will level the horizon on each frame in a series of equirectangular 360 panorama images. Here's why. I recently ended up with a ...
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1 vote
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### How to create a more photorealistic ocean?

Photorealism has many elements. Take, for instance, the figure 1 below, a shot from Dune Part One movie. Figure 1 The process of production of a image such as this one, is laborious and involve more ...
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1 vote
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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
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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
35 views

### 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), ...
1 vote
55 views

### 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
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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. ...
1 vote
129 views

### Clipping 3D Perspective matrix

I am trying to implement clipping in my simple renderer, but i have a trouble with setting the boundaries. I used the same projection matrix that is in OpenGL. The problem is, the vertices that are ...
1 vote
33 views

### 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 ...
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1 vote
310 views

### 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 ...
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1 vote
307 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 ...
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1 vote
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### 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
597 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 ...
1 vote
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### 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" ...
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1 vote
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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
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### 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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### 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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1 vote
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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
373 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 ...
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1 vote
101 views

### 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
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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1 vote
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### 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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### Measuring sphere angles to triangle

I'm looking at using multiple importance sampling for path tracing, and doing some lighting calculations relating to spherical lights. I'm trying to decide, given a triangle and a point on that ...
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### How apply 3d transformations on 3d Mesh vertcies

I have This 3D mesh class , I use helixToolKit SharpDX to display the mesh and transformations , but i want to apply these transformations to the vertcies dirctly so the mesh can be exported with ...
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### How to extract points corresponding to faces from cube map projection (CMP) of panorama from point cloud data

I am working with the standford2d3d dataset http://buildingparser.stanford.edu/dataset.html which contains panoramas of various scenes and a .mat file of the point cloud information of all the scenes. ...
47 views

### Problems with distributed ray tracing and particle system

based on the ray tracing stunning effect, I'm considering a resilient distributed ray tracing implementation, I've just finished a basic computer graphics course, and I'm currently working on directX ...
111 views

### 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 ...
21 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 ...
63 views

### 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 ...
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