All Questions
Tagged with projections geometry
13
questions
0
votes
1
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75
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What are applications of 3D geometry to 2D geometry projection and occlusion handling?
As a layperson in the field of computer graphics, I rarely see practical applications of algorithms that take 3D geometry as the input (along with some camera and lighting parameters) and output the ...
- 103
1
vote
2
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388
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Clever projection of point onto triangle?
I know of at leas tone way to project a point onto a triangle.
Project onto the plane, check barycentric coordinates, if outisde triangle, project onto the 3 segments, check distance, retain closest ...
- 1,736
2
votes
1
answer
82
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When fitting 3d cuboids into a box, how to find the order of drawing (in a 2D projection) so that the cuboids don't appear to overlap?
I am working on a 3D packing algorithm (MIT-licensed). The box and the cuboids it contains are displayed as a 2D projection. The order of drawing the cuboids (now represented as polygons) is important:...
3
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2
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277
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$(x, y, 1)$ is 2D homogenous coordinates or 3D homogenous coordinates?
We know that $(x, y, 1)$ are the homogenous coordinates of a 2D point $(x, y)$. $(x, y, 1)$ has 2 degrees of freedom. That's why we should call it 2D homogenous coordinates. But many websites say it's ...
- 211
2
votes
1
answer
109
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Finding a texture pixel (X,Y) on a Sphere
I'm using three.js combined with face recognition, I want to rotate a sphere that displays my input video according to the detected eye location,
the face recognition gives me a X,Y on the texture ...
- 23
0
votes
1
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66
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Moving a vertex through the cursor
There is a way to move a selected point in a mesh with a cursor(assuming a camera that doesn;t change between frames).
The way I remember the algorithm (but seems to be wrong) is:
Unproject the ...
- 1,736
0
votes
0
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91
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Consistent Video Depth Estimation from Monocular Lens to approximate LiDAR?
If the iPhone had LiDAR sensors, it would be possible to generate a 3D point cloud that you could theoretically use to furnish a 3D AR reconstruction of your surroundings. E.g. you could create an AR ...
- 101
5
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1
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842
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Do straight lines always remain straight when projected with a perspective camera?
If I have a straight line in 3D space and I use a camera matrix to do a perspective projection into a 2D plane/screen will the resulting line always be straight too? If I project the start point and ...
- 53
2
votes
1
answer
131
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Computing perspective directly
Assume the screen is axis aligned with origin at 0 and there is absolutely no view transformation.
in other words we will simply try to project the model onto the screen plane following perspective. ...
- 1,736
1
vote
0
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45
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3D reconstruction using 2D matched points
I have 2 images, called left and right images. I have some matched points $[c_l,r_l]$ and $[c_r,r_r]$ in both of them (these points are in pixel coordinates).
For a 3D point in the real world, they ...
- 11
1
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40
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Program to visualize geodesics and linear projection of an ellipsoid simultaneously
I am trying to solve a problem in computer graphics but to do it I need to be able to see a comparison of geodesic lines and straigth line projections on the ellipsoid.
I have not been able to ...
- 1,736
5
votes
1
answer
163
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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 ...
9
votes
1
answer
1k
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Calculate aspect ratio from 2D shape in 3D space
Given the 4 coordinates of a 2D shape in a 3D space I want to calculate its aspect ratio.
The 3D space is created with 2 vanishing points.
The 4 coordinates - marked blue - are the 2D coordinates on ...
- 193