Questions tagged [perspective]
The perspective tag has no usage guidance.
85
questions
1
vote
1
answer
63
views
Is my perspective incorrect?
I am trying to implement a UVN free camera for browsing the 3D space of my OpenGL simulation and I noticed the perspective is introducing some sort of distortion. I observed it is more noticeable ...
- 121
0
votes
0
answers
32
views
Name of non-standard perspective projection where parallel lines do not meet at a single vanishing point
I have made a non-standard perspective projection for a rectangular room (see left figure), in which for stylistic reasons, I chose to make the perspective "width" of the walls equal ...
- 1
0
votes
1
answer
40
views
How are these two projection matrices related?
I have two 3D perspective projection matrices $A,B$ with standard projection parameters $k=\cot(\theta/2)$, where $\theta$ is the field of view, $n$ is the $z$-near value, $f$ is the $z$-far value, ...
- 157
1
vote
1
answer
60
views
In perspective projection matrices, why isn't $z_\text{eye}$ mapped linearly to NDC?
As far as my understanding goes, in projection matrices $x_\text{eye}$ and $y_\text{eye}$ are mapped linearly to NDC by first using proportions to find $x_n = \frac{n\cdot x_e}{-z_e}$ and $y_n = \frac{...
0
votes
1
answer
82
views
My projection matrix for OpenGL fails on non-symmetric boundaries
Assuming my viewing volume has x coordinates varies from l to r, and y varies from top to bottom, and finally z-axis varies n to f, I derived the following projection matrix:
...
- 23
3
votes
0
answers
96
views
What vergence angle is commonly used for "infinitely far away" objects in stereoscopic displays?
I think that VR / AR experts will know the answer to this.
At what vergence angle are "infinitely far away" objects such as star field textures drawn in head-mounted VR / AR displays ?
I ...
- 213
1
vote
0
answers
37
views
How to get back project point cloud from rendered rgbd images by rgbd?
Given a sequence of RGB-D images rendered by blender and the camera parameters for the blender camera(Perspective Projection camera).
How can I back project the RGB images with depth map to a RGB ...
- 11
0
votes
2
answers
113
views
Why an object becomes larger when drawn in perspective
I am following David Salomon's book "Transformations and Projections in Computer Graphics" where it is explained how to project a 3d object to the 2d canvas in perspective:
Define a point ...
- 103
1
vote
0
answers
27
views
A fresh perspective confusion about a paragraph
I am trying to re-implement the paper "A fresh perspective"
In this paper there is one paragraph on secion 2 that reads:
Usually, $z_s = z$
is the depth value of the point $P$, unchanged by ...
- 1,746
1
vote
0
answers
72
views
Inverting perspective projection doesn't yield frustum?
I have a cube with 8 vertices representing the $[-1,1]^3$ cube vulkan uses for device coordinates.
The perspective projection matrix takes a frustum and maps it onto this cube. It thus makes sense ...
- 1,746
2
votes
0
answers
95
views
Can anyone tell me why my projection perspective matrix isn't working?
I'm a beginner in WebGL and graphics programming in general. I'm trying to render procedurally generated terrain. My first stab at this seemed to work and I get the following result.
I want to add ...
1
vote
0
answers
94
views
Mapping a box to an inverse frustum
I have a non AA, non cubic, box living happily in 3D.
I have a frustum defined by 2 squares. one square is the square defined by [-1, 1]^2 and the other square can have any size, there is also a ...
- 1,746
0
votes
0
answers
72
views
Camera Perspective of 2D X/Y Plane
I'll start with the coordinate system I'm trying to use: If I were standing on the ground, facing north, the x axis is a line moving from the west to the east (positive X is east). Positive y is ...
- 101
0
votes
1
answer
119
views
OpenGL - How to increase view space coordinate range in X and Y axis
I'm trying to render some objects but apparently X and Y coordinates need to be really small in-order to get something on screen. See this example of 2 lines
The world space coordinates for these ...
- 2,478
3
votes
1
answer
84
views
Camera model for rendering the viewport as a window frame?
I want to render as if someone is looking at a landscape through a window, adjusting for the viewer's head position. The landscape is easy enough (just a distant plane), but I'm not sure how to ...
0
votes
1
answer
518
views
Where exactly is the image plane / plane of projection
Perspective projection matrices we use map 3D coords onto some imaginary image plane in front of the cameras pinhole position by casting a ray directly from the eye position to that 3d coordinate and ...
- 125
4
votes
1
answer
1k
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 ...
- 51
0
votes
1
answer
204
views
How to translate screen coordinates of a 3d point as the viewport size changes assuming camera state remains constant?
Okay, so let's say I have a point in 3d. And I have a camera state. That is, I know the camera position, the camera target and the camera up vector.
I am using the perspective projection to get the ...
- 101
2
votes
0
answers
222
views
physics/math of lighting gradient of a 3D object
Consider a monochrome ball. The colours of the pixels is a function of the point height, the light intensity, the light angle, and the surface material (reflection).
What is the simplest formula ...
- 131
-1
votes
1
answer
173
views
Why we calculate z buffer value from plane equation $AX+BY+CZ+D=0$?
Suppose in perspective projection $(x, y, z)$ coordinate projects to point $(x_p, y_p, z_{vp})$ in projection plane $AX+BY+CZ+D=0$ where projection plane kept at $z_{vp}$ position. And the plane $AX+...
- 211
0
votes
0
answers
79
views
Using Perspective Rendering To Render A 3D Point
I am wondering how I can use perspective rendering to render a point onto a screen. An image showing perspective rendering:
Say I have a 3d point (with x, y, and z coordinates), a point for the ...
0
votes
1
answer
341
views
Perspective transformation is perspective projection? [duplicate]
I know that (
Reference )in transformation source and destination has same coordinates dimensions. But in projection destination coordinate system has fewer dimensions than the source coordinate ...
user17337
1
vote
5
answers
2k
views
Existence of vanishing point
Consider the following example of perspective projection: I have one railway track with two parallel lines meeting at the point $X$ at infinity which is the theoretical approach. This X is called the ...
user17337
1
vote
2
answers
314
views
Difference between perspective and parallel projection [closed]
We know that in orthographic Projection Projectors (projection vectors) are perpendicular to the projection plane.
And in Perspective Projection Object positions are transformed to the view plane ...
user17337
1
vote
1
answer
1k
views
Why are vanishing point and centre of projection the same [closed]
We know that in perspective projection object positions are transformed to the view plane along lines that converge to the projection reference (center) point like this:
But many websites say that COP(...
user17390
0
votes
1
answer
294
views
How do I perform a perspective transform on a straight line?
I'm trying to make a software renderer, but I want to avoid creating extra triangles with clipping. For this I want to transform lines which compose triangles, instead of individual points. However I'...
- 137
2
votes
1
answer
351
views
Deriving formula for perspective correct interpolation
I am trying to derive the formula for perspective correct texture interpolation on my own while implementing my own software rasterizer (projecting an arbitrarily rotated triangle in camera space on ...
- 164
5
votes
2
answers
351
views
Rendering Hypercentric Perspective
I came across some Non-Euclidean Games which involve Hyperbolic Spaces, Spherical Spaces, Portals, etc. And, I noticed that they give quite deep feel of what Non-Euclidean Spaces feel like. So, I was ...
4
votes
1
answer
1k
views
Why perspective division ( div by w) when applying the inverse to a perspective transformation?
For example, when you want to compute the world space position of a fragment in the fragment shader, you can construct the fragment's NDC coordinates, then multiply by the inverse of whatever ...
- 125
0
votes
1
answer
187
views
Simulate projection matrix deformation in two camera setup
For educational purposes I'm trying to simulate what a scene would look like with a perspective matrix deformation (before everything is brought to NDC) but I'm unsure how to do this.
I'd like to do ...
- 3
0
votes
1
answer
358
views
How does 3D graphic software adjust for distortion inherent in perspective projection?
As this question and its answers point out, projecting a sphere on a flat picture plane, with perspective projection, may result in a ellipse, not a circle, and my understanding is that the only way a ...
- 129
1
vote
1
answer
2k
views
What is principal vanishing point in perspective projection?
I am unable to visualize what is principal vanishing point w.r.t to x axis ,y axis z axis do someone can post some simple diagram to understand what is it? Also I have question in my text book
' ...
- 21
1
vote
1
answer
71
views
Does angular diameter to FoV ratio equal object's image to total image ratio?
If we have an object at certain distance D in front of a camera. The object has a horizontal diameter d, giving us an angular diameter theta (2*arctan(d/2D)) of 50 degrees (converted from radians). ...
- 115
4
votes
0
answers
179
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
0
votes
1
answer
491
views
Perspective projection near plane not in world coordinates
I have a camera I have placed zunits away from a billboarded rect. My goal is to discard all other geometry that is closer to the camera/in front of this rect.
With ...
- 1,445
0
votes
2
answers
335
views
Shear(?) matrix projection along Z (depth) axis
I'm creating a primarily 2d game (platformer perspective) with 2d background parallax layers. The parallax effect falls out of the fact that I'm positioning a bunch of layers in 3d and using a ...
- 103
3
votes
1
answer
227
views
Interpolate vertex attributes with $z$ AFTER homogeneous divide
Usually, if we want to interpolate some vertex attributes, say $A_1$, $A_2$ and $A_3$, we have to first divide them by their corresponding $z$ in view space, then we interpolate them using barycentric ...
- 279
4
votes
1
answer
2k
views
Perspective correct interpolation z-buffer
While I was deriving expressions for perspective-correct linear interpolation on triangles, I reached the conclusion that the interpolation may be kept linear only if view-space $Z$ is available. ...
- 2,226
3
votes
2
answers
1k
views
Which perspective projection matrix to use
I've seen two different perspective projection matrices being used but I want to know which one of them is the best. I think that they both output the same but I'm not sure. So if anyone can help me ...
- 33
1
vote
1
answer
466
views
Is there a general rule with regard to using the inverse of the "camera" to world when using a homogeneous transform matrix?
Not sure if this is just specific to this article but it says:
We learned how to convert points from world to any local coordinate
system. If we know the local-to-world matrix, we can multiply the
...
- 113
1
vote
0
answers
48
views
How to get "Equal" (saturation, brightness) Red and Green Colours in a Web-based Application?
I am looking for a red and a green hue that are equally discernable against a gray background on any PC monitor, using HTML/CSS-based application. There are many possible solutions to balance these ...
- 11
0
votes
1
answer
178
views
Apply Projective Transformation 2D Rectangle
I want to write code from scratch about Projective Transformation in order to apply this transformation to 2d rectangular. I searched about this transformation, but I could not figure out completely. ...
user6625
0
votes
1
answer
120
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
3
answers
2k
views
perspective matrix derivation
Now there has already been an answer here in this stackexchange, but I don't understand certain aspects of it. The author has MORE DETAILED DESCRIPTION HERE(#1) but the problem is he doesn't describe ...
- 117
0
votes
0
answers
672
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
2
votes
0
answers
78
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 ...
- 121
2
votes
1
answer
489
views
Rasterizing spheres?
I want to start developing a hybrid renderer: it first applies a rasterizer, then stores for each pixel the surface pointer, normal vector, and distance to the camera.
Then it raytraces reflections, ...
- 312
0
votes
0
answers
129
views
Issue with perspective projection
I have the following problem. Perspective projection is often referred to when talking about camera models. I don’t think I understand it very well though this concept is taught when I was at junior ...
1
vote
1
answer
170
views
Change of speed but no change of size after OpenGL Perspective Projection
I am new to OpenGL and I am trying to code un optic flow with dots appearing from the background and moving towards the viewer. As a consequence of a perspective projection, the dots are faster and ...
- 113
1
vote
1
answer
207
views
WebGL Can't render anything, wrong projection? [closed]
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 ...
- 11