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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Is my perspective math correct?
I've got a homework in which I have to calculate and plot some points using a pespective transformation, but I'm not sure my results are correct, since the 3d plot using Camera coordinates looks very ...
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1
answer
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World coordinates, Normalised device coordinates and device coordinates
Can I get to know the difference between the three? A good example would add up too.
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23
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5
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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 ...
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17
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3
answers
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Why do we have graphics frameworks like OpenGL and DirectX, when games could just draw pixels directly?
Games and other graphically intensive applications use frameworks like OpenGL and DirectX. Also they require features like pixel shader and DX12.
But why would we need all these frameworks and GPU ...
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14
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2
answers
450
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Why smoothed meshes in 3D studio end up with the same number of vertices/triangles? How then can they be smoothed with the same geometry?
I am trying to understand why meshes that are smoothed in 3D studio (Modifiers/Smoother) end up having the same amount of vertices/faces before or after that process, as well as the exact same ...
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13
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5
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802
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Is there a standard specification for 3D graphic representation?
I'm reading a book on computer graphics, and at some point, it shows a 3D model, created from a .dat file.
Here are a few rules for the .dat file creation:
Made of a list of vertex positions / faces
...
- 233
13
votes
1
answer
1k
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Is this the correct way to implement Beer's Law?
When I implement Beer's law (color absorption over distance through an object), it never looks very good for some reason.
When i have the color behind the object, I calculate the adjusted color like ...
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13
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1
answer
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What's the difference between orthographic and perspective projection?
I have been studying computer graphics, from the book Fundamentals of Computer Graphic (but the third edition), and I lastly read about projections. Though, I didn't exactly understand what's the ...
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10
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1
answer
286
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Sphere intersection occlusion (for hybrid raytracing)
Thinking about hybrid raytracing, hence the following question:
Suppose I have two solid spheres $s_1$ and $s_2$. We know their centres and radii, and we know that they have some overlapping volume ...
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10
votes
2
answers
188
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Is depth of field incongruous in a 3D still image?
If rendering an image in 2D, adding depth of field effects (blurring objects further from the focal distance) adds realism and draws the eye to the object of the image. With a 3D (i.e. stereo) image, ...
10
votes
1
answer
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Pipeline to create Voronoi Meshes
I would like to implement a Maya plugin (this question is independent from Maya) to create 3D Voronoi patterns, Something like
I just know that I have to start from point sampling (I implemented the ...
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9
votes
2
answers
10k
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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 ...
9
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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 ...
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9
votes
0
answers
486
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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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8
votes
3
answers
897
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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 ...
8
votes
1
answer
1k
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Maximum number of vertices after clipping a triangle against an AABB
I clip a 3D triangle against a 3D Axis-Aligned Bounding Box (AABB) to obtain the largest planar polygon of the triangle contained in the AABB. My clipping algorithm is a (slightly modified) version of ...
- 1,044
8
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1
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294
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Human Readable/Writable 3D Representation Formats/Languages?
My goal is to create 3D meshes without the use of a 3D editor. So I want to know what representation languages and formats there are that are designed for this or otherwise that would be good for ...
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8
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2
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1k
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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 ...
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8
votes
1
answer
369
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NURBS topology classification
In what sense is it true that a NURBS surface can only have the topology of a plane, cylinder or torus?
For example I can do a NURBS sphere.
Is the sphere homeomorphic to one of the above surfaces?
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7
votes
1
answer
2k
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What is stereo about multi-view stereo?
What 3D scene reconstruction methods does the term "multi-view stereo" encompass? Is it only used for methods that apply binocular stereo algorithms (taking 2 views as input) in a pairwise manner? Or ...
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1
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After a deformation operation on polygons, how can I check for and fix inverted polys?
I'm doing a quick and dirty automated deformation routine on a polygon body. If it was a tree, and my axis was in the center of the tree, I would like to bend the body by bending the axis. I would ...
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6
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4
answers
777
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How to decide which way to triangulate a quad?
Apologies if this is a dumb question... but given four arbitrary (non-coplanar) points in 3D space, there are obviously two different ways to triangulate the quad that they form. One triangulation may ...
- 183
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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6
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1
answer
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What's the difference between Clipping and Culling?
In a tutorial about OpenGL both words are mentioned, unfortunately without a good explanation.
To find out, I have read this article three times, but I fear I'm a too common man... my understanding is ...
- 297
6
votes
1
answer
386
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Graphics Pipeline: Viewspace & Back face culling incorrectly
I'm attempting to model a simple graphics pipeline - using Matlab at the moment as a modelling tool to get the transformations correct. I appreciate there are software tools that would make this ...
- 243
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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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 ...
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6
votes
1
answer
275
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Why is rotating this prism in iOS Metal not rendering correctly?
I've set up a test project for learning Metal on iOS to do some rendering, but I'm a bit stumped on how to get a prism rotating correctly about its y axis.
Here is the prism rendered without depth ...
- 263
6
votes
1
answer
814
views
Perspective correct interpolation of normal values
I'm currently writing a software rasterizer and I'm at the point where I can draw arbitrary triangles with vertex colors and perspective correct texture mapping. I do point and directional lighting by ...
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5
votes
3
answers
748
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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 ...
- 53
5
votes
2
answers
4k
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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:
...
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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
2
answers
561
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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 ...
- 152
5
votes
1
answer
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What formula or algorithm can I use to draw a 3D Sphere without using OpenGL? [closed]
I know that there are 3 techniques to draw 3D objects:
(1) Wireframe Modeling and rendering
(2) Additive Modeling
(3) Subtractive Modeling
Am I correct?
What formula or algorithm can I use to draw a ...
user464
5
votes
2
answers
159
views
Is it possible to render red / blue 3d from one image and a depth buffer?
To render an image for use with red & blue 3d glasses, the usual way to do it is to render from one point of view, convert it to a single intensity (greyscale) value per pixel, and then put that ...
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1
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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 ...
- 51
5
votes
2
answers
223
views
How to get the transform amount from a screen vector and a direction vector?
I am working on the move tool in a 3D modeling software. I need to know how much to move when the user drags an axis of the gizmo (for example along the x axis).
I have the 2D vector describing how ...
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5
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1
answer
357
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Transformation Matrices
Consider the following problem and its answer:
Given 3 points in 3D: $A=(A_x,A_y,A_z); B=(B_x,B_y,B_z) ; C=(C_x,C_y,C_z)$
Find the transformation matrix (in homogeneous coordinates) that ...
- 183
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, ...
- 123
5
votes
1
answer
158
views
Where should I project a polygon corner when it is behind me?
I am creating a simple 3D engine as a learning project to get the hang on spherical trigonometry. I am using the following approach.
1. A model consists of a lot of triangular faces.
2. Each triangle ...
5
votes
3
answers
402
views
Visualize the interpolated unit quaternion on the surface of the unit sphere
My major is mechanical, please forgive me for asking questions that may seem trivial to you.
First, I'm reading the following paper:
Dam, Erik B., Martin Koch, and Martin Lillholm. Quaternions, ...
- 51
5
votes
1
answer
167
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Project quad onto ellipse in 3D
I have three points P0, P1, P2, which are located on an arbitrarily oriented ellipse in 3D space. I have a square texture map with a circle on it. I would like to render a textured quad (with the ...
- 151
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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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, ...
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4
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4
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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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4
votes
1
answer
399
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Earth curvature and horizon in modeling large scenes
If I want to model a large environment, how can I solve the problem of earth curvature and horizon?
I use an environment map for the sky, but for the ground what can I do?
Do I have to model the ...
- 433
4
votes
3
answers
9k
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How can I get a signed distance (SDF) from a mesh?
I am trying to use constructive solid geometry (CSG) and boolean operators to combine various shapes and get the outer (possibly concave) hull. This seems to work okay when using primitive shapes like ...
- 41
4
votes
2
answers
283
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Creating a Smooth 3D Mesh from a 2D Outline
I am trying to find (or maybe create) an algorithm for creating a smooth, rounded 3D mesh given a 2D outline. I'm trying to recreate a system from a Gamecube game called Amazing Island, and you can ...
4
votes
3
answers
5k
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Programmatically generating bin files for GLTF models
I have a need to generate a series of GLB files. I have a base template for a GLTF file which I have to derive off of. The models thus generated will only have varying textures on them. The base mesh ...
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4
votes
1
answer
148
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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?
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