# Questions tagged [projections]

The tag has no usage guidance.

33 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
4 votes
0 answers
107 views

### Project grid on 2d plane based on camera perspective

Unsure if this is the right network to post this, but maybe someone can help... I'm working on a personal project where, with the help of AI, I want to automatically estimate the perspective of a ...
• 41
3 votes
0 answers
61 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,...
• 131
3 votes
0 answers
206 views

### Calculate Camera parameters and HandEyeCalibration

I'm trying to calculate camera paramters and a hand eye calibration (Transformation from camera to eye (display) coordinates) for rendering on a see-through HMD. I have already calculated a ...
• 131
2 votes
1 answer
95 views

### How to derive Field of View (FOV) angles from a 2D projection

I'm looking for some guidance. I'm not sure if this is possible, and I'm not sure where to start. I need to measure the FOV angles of a first-person, 3D game using only gameplay screenshots. I'm bound ...
• 21
2 votes
0 answers
74 views

### What is the best way to calculate the projected size of a point

In a particle simulation, I am rendering particles as "spheres" using GL_POINTS instead of a mesh for efficiency. With glEnable(GL_PROGRAM_POINT_SIZE) I ...
2 votes
0 answers
53 views

### Project a Square as rectangle in projection plane using perspective projection

Consider a square S with vertices (1,1,0), (1,-1,0), (-1,-1,0) and (-1,1,0) and a plane P defined by $z=1$. Let the perspective projection of S on P is denoted by S'. What coordinates of the Center ...
• 21
2 votes
0 answers
33 views

### Make 3d objects from 3 projections in 3D Studio Max

In the early 3D Studio days before it got Max in its name it was possible to make a 3d object by defining its projections in xy, xz and yz plane. 3ds would then interpolate a 3d object from the ...
• 121
2 votes
0 answers
242 views

### How to project a view frustum in an orthographic cuboid?

I know that OpenGL uses a projection matrix to project the view frustum directly into the canoical volume [-1, 1]^3. But how would I project the frustum into an orthographic cuboid, which would then ...
• 121
2 votes
1 answer
449 views

### A question about derivation in oblique view frustum

Problem Description: Reference: Oblique View Frustum Depth Projection and Clipping "Mathematics for 3D Game Programming and Computer Graphics" 3rd edition, chapter 5.6. M is the original projection ...
• 101
1 vote
1 answer
118 views

### Parallel projection is special case of perspective projection

I synchronized with @David k's first and second answer regarding perspective and parallel projection. From the first question I understand that the image on the screen is typically described in ...
1 vote
0 answers
45 views

### What should be considered the origin of a ray used for object picking with perspective projection

I need to create a ray to pick objects in 3d environment using cursor. I'm not going to go into detailed math for this question. There's tons of information on that. In short terms, for orthogonal ...
• 464
1 vote
0 answers
134 views

### Model View Projection Matrix Multiplcation Order

I'm working on a simple software renderer and have a working implementation so far. I'm curious as to why it's actually working since I would expect the multiplication ordering for my world, view and ...
1 vote
0 answers
85 views

### Why does my self-written rendering engine make further away objects look larger?

I am writing a very simple rendering engine. I have already made a few tests, but somehow the images it creates look wrong. Objects that are further away from the camera look larger than objects ...
1 vote
0 answers
530 views

### Intrinsic Matrix vs Perspective projection matrix

I was going through the camera matrix explained in the wikipedia article and understand how the matrix K \begin{bmatrix}f_x&s&x_0\\0&f_y&y_0\\0&0&1\end{bmatrix} is built. The ...
• 111
1 vote
0 answers
70 views

### How to Pan Zoom a spherical camera?

I asked this in regular SO but I think people are not understanding the question so i will try here: So, for anyone familiar with Google Maps, when you zoom, it does it around the cursor. That is to ...
• 1,447
1 vote
0 answers
25 views

### Projecting a point on a Freefrom surface

My first issue is getting a set of planes and a set of points as input, an find the projection of the those points on the nearest plane. That was pretty easy, where i just calculate the normal of the ...
• 121
1 vote
0 answers
43 views

### 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 vote
0 answers
40 views

### 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 ...
• 1,447
0 votes
0 answers
24 views

### What do the symbols in a fisheye projection stand for?

The wikipedia page on fisheye lenses provides multiple formulations: Stereographic Equidistant Equisolid angle Orthographic $f=\frac{r}{k \tan(\theta / k)}$ $f = \frac{r}{\theta}$ \$f = \frac{r}{2 \...
• 1,447
0 votes
1 answer
86 views

### mapping of a point from a sphere into UV plane

I am reading the book An introduction to raytracing by Eric Haines and it mentions an algorithm to map a point from a sphere into a UV plane, it calls it Inverse Spherical Mapping (page 49). I googled ...
0 votes
0 answers
170 views

### Projection of line which lies in an auxiliary inclined plane

A line PQ is 75 mm long and lies in an auxiliary inclined plane (A.I.P.) which makes an angle of 45° with the H.P. The front view of the line measures 55 mm and the end P is in the V.P. and 20 mm ...
0 votes
0 answers
105 views

### Mapping an image from one camera pose to another given a planar scene

I'm trying to map an image of a 3D object to another one from a different camera position. My assumption is that the pose change between two cameras is so small and the object is far enough from the ...
0 votes
0 answers
82 views

### computing sheared perspective projection matrix

is it possible to calculate a "projection matrix" which is sheared as well? the usual perspective projection matrix forms a pyramid where the near clipping plane is rectangular. I have 4 ...
• 489
0 votes
0 answers
40 views

### Can surface normal be used for obtaining points on a plane?

Excuse my wording. I will use the picture below to explain what I mean. I want to use the surface normals for each arrow shown like below to draw lines parallel to each plane like the image shown ...
0 votes
0 answers
79 views

### 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 ...
0 votes
0 answers
31 views

### Does rotating object inside unit cube [-1,1] by homogenous matrix move it outside unit cube

I am just trying to rotate my pointcloud object which is inside the unit cube ([-1,1] in all x,y,z axis). What I did is use the basic rotation matrix from wiki and extend it to homogenuous 4x4 matrix (...
• 111
0 votes
1 answer
74 views

### Keep constant number of visible circles in 3D animation

I have created a 3D animation with a perspective projection of white circles moving randomly in a fake 3D space projected on a 2D computer screen (GIF 1). Since I need to keep the same number of ...
• 113
0 votes
0 answers
316 views

### how is zooming done in computer graphics

Since a projection plane and a center of projection is used for achieving perspective projection, the shape of the view frustum doesn't change changing the focal length(which is the distance from the ...
• 117
0 votes
0 answers
50 views

### How combine multiple projections into a single pass?

We have a projector type display used in an automotive application, where a projector displays an application on the windshield. Because the projector would normally warp a flat image, we have to ...
• 333
0 votes
0 answers
160 views

### What quad will fill the screen, which can be inverse-projection-view transformed to map to the near frustum plane?

I've been experimenting with raytracing using GLSL. I had success rendering a cube which encloses the object. Now I want to do a full-screen raytrace, and I want to construct a quad which covers the ...
• 279
0 votes
0 answers
350 views

### Inverse texture mapping

I have a textured 3D object and looking for ways to transform back the texture. Effectively, I think this is an inverse texture mapping task. Do you know of anything close to this? Some papers or ...
• 101
0 votes
1 answer
171 views

### WebGL Can't render anything, wrong projection?

I'm trying to understand and learn WebGL and computer graphics from the bottom up, that is why I started to work on my own little library for that. I've spent a couple of days looking for a right ...
0 votes
2 answers
47 views

### What projection matrix and world transformation do I need to have an isometric projection?

I'm doing my own engine in college to display a wireframe on screen with an isometric projection but I literally can't find any literature about maths behind doing it by hand just for game engines ...