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Questions tagged [3d]

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

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0answers
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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 - ...
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1answer
62 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 ...
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2answers
114 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:
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1answer
105 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
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1answer
39 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 ...
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1answer
47 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 ...
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1answer
39 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 ...
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1answer
44 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
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1answer
81 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...
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1answer
62 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] ...
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1answer
68 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, ...
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2answers
72 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 ...
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1answer
60 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
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1answer
66 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
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2answers
123 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
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1answer
72 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
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1answer
81 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 ...
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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,...
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0answers
42 views

Help LOD:ing a tiled 3D model of a city

I have a 3D model of a city, divided into ~7000 adjacent tiles, taking up close to 100 GB in total, including fbx files and textures. I want to convert this into a model with different levels of ...
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0answers
31 views

Dragging an object on a plane with respect to the camera

this is a long description but I hope the solution is simple: I have a 3D pointCloud with a vtk box (displayed at 0,0,0) and I want to drag the box on the XY plane with my mouse cursor (Zero movement ...
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1answer
66 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
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2answers
48 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?
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3answers
193 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
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1answer
46 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 ...
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1answer
83 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 ...
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1answer
68 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?
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1answer
55 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
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1answer
66 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, ...
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1answer
93 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 ...
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0answers
92 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 ...
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0answers
60 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
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1answer
163 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 ...
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2answers
162 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
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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
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2answers
203 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 ...
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0answers
60 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 < ...
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2answers
103 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
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3answers
157 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 ...
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1answer
42 views

How is the generalized quaternion rotation operator is drived?

enter image description here I Would Thanks if u guys help me
2
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1answer
1k 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), $f$(...
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0answers
56 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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1answer
93 views

What technique would I use to create fake 3d walls as seen in Realm of the Mad God

I wanted to make a little demo for a console with Realm of the Mad God esc graphics to brush up my C and SDL skills. One problem I'm running in to is creating the 3D walls. The console I'm ...
2
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0answers
48 views

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 ...
4
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1answer
197 views

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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0answers
47 views

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 ...
3
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1answer
67 views

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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0answers
104 views

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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2answers
158 views

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....
3
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1answer
298 views

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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1answer
162 views

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 ...