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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1answer
108 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
99 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
345 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
95 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
79 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 ...
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1answer
446 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
691 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
66 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
294 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
152 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
173 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, ...
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3answers
670 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
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1answer
8k 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
70 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
199 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 ...
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0answers
98 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 ...
5
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1answer
483 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
73 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
75 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
140 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
272 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
931 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 ...
6
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2answers
402 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 ...
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1answer
58 views

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 ...
7
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2answers
5k views

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 ...
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2answers
198 views

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. ...
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2answers
2k views

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 ...
16
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5answers
14k views

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 ...
4
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3answers
669 views

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
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0answers
271 views

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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0answers
130 views

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 ...
3
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1answer
471 views

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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2answers
488 views

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: ...
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0answers
256 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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0answers
1k views

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 ...
2
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2answers
1k views

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 ...
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0answers
68 views

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?
6
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1answer
182 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 ...
4
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1answer
732 views

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 ...
4
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2answers
503 views

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, ...
2
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0answers
160 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 ...
5
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2answers
217 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 ...
5
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1answer
89 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, ...
4
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1answer
162 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: ...
5
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4answers
2k views

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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0answers
86 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 ...
1
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1answer
344 views

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 ...
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1answer
483 views

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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0answers
348 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 ...
3
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1answer
57 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.