Questions tagged [projections]
Questions about the conversions of a 3D model to a 2D model.
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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 ...
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The distance from the cube sides to the parallel projection plane
I have asked this question on ru.stackoverflow.com and have no valid answers.
Specification:
Coordinate system
Cube spins around its center on all three axes.
Turn angle is not known previously.
...
user7220
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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 ...
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A way to save 360° panorama video
What is the best way to save video from faces of a cube? The render can produce 6 squares (90°x90°) of 1024x1024 resolution. Faces oriented along axies and only position is changed continuously. I ...
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Why are width and height divided by 2 in the perspective projection matrix?
I'm using OpenGL to learn computer graphics. I'm trying to understand projection matrices. The following are shown in the OpenGL 'Red Book':
I don't understand why the width and height are divided ...
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Compute area (not surface area) and perimeter of a mesh
I'm currently researching how to compute geometric properties of architectural shapes based on their 3D meshes, and am stuck for some time on the area and perimeter calculations.
First, the area: ...
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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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Why is the back of a perspective frustrum larger than the front?
I'm following this tutorial on the perspective projection.
Question: If the point of a perspective projection is to create the perspective effect (where objects faraway appear to be smaller):
then ...
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How am I able to perform perspective projection without a near plane?
I'm learning about 3D computer graphics, but I'm having a hard time understanding why the near plane of a viewing frustum can not be placed at z position $0$ (right at the camera).
I can understand ...
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Render with camera perspective off-center
So ordinarily we have this
But I'm after this!
Is it possible to do this? Ideally by changing the projection matrix?
The reasoning is kinda interesting - I am developing for mobile VR, and I have ...
- 153
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Getting from the default view volume to an image on the screen
I don't completely understand the last part of the MVP matrix (projection).
In orthographic projection we simply scale the view volume into the default view volume (+-1 on all axis).
In perspective ...
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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
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understanding glm::perspective vs glm::ortho
I'm new to computer graphics. I played around with OpenGL and now am trying out Vulkan.
Basically what I want to do, in 2D is have an 800x800 window, and I want that to represent 800 meters by 800 ...
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My perspective projection is messed up?
So I've been messing with perspective projection matrices recently. I used numpy and GTK/Cairo to make a very small Python renderer. I'm very confused with the results I'm getting though.
I took this ...
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Screen to World coordinates glm::unProject
I'm having some trouble trying to figure out how to go from a coordinate on the screen, to 3D world coordinates on a plane.
My case is as seen on the picture further down. World origin is in the ...
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Am I calculating perspective projection correctly?
If I have a point in world space: (wx, wy, wz)
and I have a centre of projection: (cx, cy, cz)
and I wanted to project that point using perspective projection
would my point on the screen be ...
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Projected points and screen coordinates
I'm trying to understand part of the contents of a slide, but I'm not really understanding. So, here's the interested part.
I've a few questions.
Are the projected points $q_1$ and $q_2$ the points ...
user4718
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Zoom in orthographic vs perspective projection
I have read through this article about perspective and orthographic projection matrices.
I started playing with the perspective matrix and as expected if I either increase/decrease the field of view ...
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Solving a problem from *Foundations of Computer Graphics*:
From Gortler's Foundations of Computer Graphics (i.e., self-study):
Let $\mathbf{\vec{e}}^t = \mathbf{\vec{w}}^t E$ and let $P$ be a camera matrix that is just some arbitrary $4$ by $4$ matrix with ...
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Creating Sparks using Code
I'm new to this area and have less knowledge. I want to create some graphics like sparks and lightning by writing some code, using my own physics. I don't want to use some engine, However I can use ...
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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 ...
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How to unproject quadrilateral into rectangle?
tl;dr: Math problem in projective geometry: How does one find some 4x4 camera matrix that gives a projection as illustrated below, such that points A,B,C,D are somewhere on the edges of the unit box (...
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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 ...
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2D projection from some points
I am going through an undocumented function that takes in three points and a Z-value that projects three points on the plane defined by Z-value. I want to understand the mathematical theory behind it ...
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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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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 ...
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Need a reputable source for the formula for the shape of Earth's horizon
What I'm asking for
I stress that I am not asking for the formula---I know the formula, and how to derive it. Several different versions of it are reproduced near the end of the post. In fact, ...
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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 ...
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How to use GetViewProjMatrix().TransformVector(LineDirection) in UE4?
I try to project a 3D vector (a direction, not a position) in screen space, but it does not return satisfying results:
...
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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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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 ...
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Materials for research on spherical projection
I am currently doing a research on projection on a sphere, specifically for NOAA's project Science on a Sphere. What I'm trying to do is to find out how exactly do you create a video material for such ...
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Does a sphere projected into 2D space always result in an ellipse?
My intuition has always been that when any sphere is projected into 2D space that the result will always mathematically be an ellipse (or a circle in degenerate cases).
In the past when I was ...
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How can I generate procedural noise on a sphere?
I would like to generate procedural noise on the surface of a sphere (e.g. to procedurally generate planets or marble-textured balls). Of course, I could just take a standard noise algorithm and map ...
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What transformations should I apply to a model to produce this 3D effect?
I saw a video on YouTube where a person uses a transparant, knotted pyramid to display "holograms" using their smartphone. (I have not been able to reproduce this yet, so I can't tell for sure if it ...
