Questions tagged [perspective]

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3D engine projection distortions

I'm trying to write my own 3D engine using Python and Pygame. I have successfully implemented rotation and projection matrices to display 3D models. However I am so far unable to implement translation ...
Zoler1337's user avatar
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How can I generate a reflectance map using a perspective camera?

In simple words, a reflectance map is a function f(n) that map a surface patch with normal n to its reflected radiance given a ...
Zhe Chen's user avatar
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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: ...
Serilena's user avatar
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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 ...
Simon's user avatar
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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 ...
Goatz's user avatar
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2 answers
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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 ...
tush's user avatar
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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 ...
Makogan's user avatar
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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 ...
Makogan's user avatar
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2 votes
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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 ...
Andrew Lubrino's user avatar
1 vote
0 answers
81 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 ...
Makogan's user avatar
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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 ...
Helpful's user avatar
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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 ...
gallickgunner's user avatar
3 votes
1 answer
77 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 ...
Andrew Chatham's user avatar
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1 answer
412 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 ...
cg_guy420's user avatar
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1 answer
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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 ...
Brovidio's user avatar
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1 answer
160 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 ...
Tanay Karnik's user avatar
2 votes
0 answers
182 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 ...
Googlebot's user avatar
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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+...
S. M.'s user avatar
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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 ...
Brendan R.'s user avatar
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1 answer
320 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 ...
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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 ...
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1 vote
2 answers
248 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 ...
user avatar
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(...
user avatar
0 votes
1 answer
230 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'...
user369070's user avatar
2 votes
1 answer
256 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 ...
Sam's user avatar
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5 votes
2 answers
257 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 ...
Monster196883's user avatar
4 votes
1 answer
771 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 ...
cg_guy420's user avatar
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1 answer
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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 ...
Cattani's user avatar
0 votes
1 answer
308 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 ...
Vun-Hugh Vaw's user avatar
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 ' ...
anuj goyal's user avatar
1 vote
1 answer
60 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). ...
Physician's user avatar
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4 votes
0 answers
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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 ...
Chris's user avatar
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0 votes
1 answer
412 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 ...
J.Doe's user avatar
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0 votes
2 answers
253 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 ...
Joseph Humfrey's user avatar
3 votes
1 answer
203 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 ...
Jojolatino's user avatar
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. ...
lightxbulb's user avatar
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3 votes
2 answers
833 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 ...
Nixcc's user avatar
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1 vote
1 answer
389 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 ...
brent's user avatar
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1 vote
0 answers
46 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 ...
Kiki Kawai's user avatar
0 votes
1 answer
150 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. ...
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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 ...
Kathia's user avatar
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0 votes
3 answers
1k 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 ...
juztcode's user avatar
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0 answers
611 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 ...
juztcode's user avatar
  • 117
2 votes
0 answers
76 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 ...
Leolime's user avatar
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2 votes
1 answer
447 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, ...
AnnoyinC's user avatar
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0 answers
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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 ...
fatestayn's user avatar
1 vote
1 answer
163 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 ...
Kathia's user avatar
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1 vote
1 answer
205 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 ...
Dreik's user avatar
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5 votes
1 answer
777 views

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 ...
Owen's user avatar
  • 53
2 votes
1 answer
130 views

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. ...
Makogan's user avatar
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