How do I compete the transformation matrix needed to transform a rectangle into a trapezium?

Posted by Rich Bradshaw on Stack Overflow See other posts from Stack Overflow or by Rich Bradshaw
Published on 2010-03-20T17:47:26Z Indexed on 2010/03/20 17:51 UTC
Read the original article Hit count: 338

Filed under:

matrix

|

perspective

I'm playing around with css transforms and the equivalent filters in IE, and want to simulate perspective by transforming a 2d rectangle into a trapezium.

Specifically, I want the right hand side of the rectangle to stay the same height, and the left hand side to be say 80% of the height, so that the mid points of both sides are horizontally in line with each other.

I'm familiar with matrix algebra, but can't think how to determine what matrix will do that.

© Stack Overflow or respective owner

Related posts about matrix

Find the "largest" dense sub matrix in a large sparse matrix

as seen on Stack Overflow - Search for 'Stack Overflow'
Given a large sparse matrix (say 10k+ by 1M+) I need to find a subset, not necessarily continuous, of the rows and columns that form a dense matrix (all non-zero elements). I want this sub matrix to be as large as possible (not the largest sum, but the largest number of elements) within some aspect… >>> More
How does a template class inherit another template class?

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a "SquareMatrix" template class which inherits "Matrix" template class, like below: SquareMatrix.h: #ifndef SQUAREMATRIX_H #define SQUAREMATRIX_H #include "Matrix.h" template <class T> class SquareMatrix : public Matrix<T> { public: T GetDeterminant(); }; template… >>> More
iPhone OpenGL ES: How do I use gravity vector to correctly transform scene for augmented reality

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying figure out how to get an OpenGL specified object to be displayed correctly according to the device orientation (ie. according to the gravity vector from the accelerometer, and heading from compass). The GLGravity sample project has an example which is almost like this (despite ignoring… >>> More
How do I use the gravity vector to correctly transform scene for augmented reality?

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying figure out how to get an OpenGL specified object to be displayed correctly according to the device orientation (ie. according to the gravity vector from the accelerometer, and heading from compass). The GLGravity sample project has an example which is almost like this (despite ignoring… >>> More
C++ templates - matrix class

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi I'm learning templates in C++ so I decied to write matrix class which would be a template class. In Matrix.h file I wrote #pragma once #include "stdafx.h" #include <vector> using namespace std; template<class T> class Matrix { public: Matrix(); ~Matrix(); GetDataVector(); … >>> More

Related posts about perspective

PeopleSoft Customer Gives User Perspective and the Benefits of Joining a Regional User Group

as seen on Oracle Blogs - Search for 'Oracle Blogs'
Tim Johnson, Portal and Web Systems Administrator at Herff Jones, Inc. and the Ohio PeopleSoft JD Edwards Regional User Group President, discusses the continuation of PeopleSoft releases thanks to Applications Unlimited. Johnson also talks about some of the customer benefits of communication to Oracle… >>> More
How to fix OpenGL Co-ordinate System in SFML?

as seen on Game Development - Search for 'Game Development'
My OpenGL setup is somehow configured to work like so: (-1, 1) (0, 1) (1, 1) (-1, 0) (0, 0) (1, 0) (-1, -1) (0, -1) (1, -1) How do I configure it so that it works like so: (0, 0) (SW/2, 0) (SW, 0) (0, SH/2) (SW/2, SH/2) (SW, SH/2) (0, SH) (SW/2, SH) (SW/2, SH) SW as Screen Width. SH as Screen… >>> More
How do you calculate UVW coordinates?

as seen on Game Development - Search for 'Game Development'
I'm working on a 3d engine and I'm calculating UVT coordinates, where U and V represent pixels on the texture measured in 0-1, and T is: T = perspective / Z But I'm trying to use this perspective-correct triangle rasteriser, which requires a W, per vertex. How do I calculate the W for each vertex… >>> More
Facebook s'ouvre à la géolocalisation, activée par l'utilisateur elle ouvre de nouvelles perspective

as seen on Developper.com - Search for 'Developper.com'
Facebook va bientôt offrir la géolocalisation de ses membres. A l'heure où les services de proximité n'ont jamais été aussi présent dans les moteurs de recherches. Coïncidence ou un voeu inavoué ?? Facebook va mettre en ligne une solution pour géolocaliser ses membres. Voici déjà un an que… >>> More
3D/perspective Top down shooter bullet issues

as seen on Game Development - Search for 'Game Development'
I'm developing a top-down shooter with multiple levels (ground for ground units, middle level for buildings, top level for air unity). The problem is the collision. Though I can make the collider box of a bullet be long enough to reach the ground (and collide with it), the real issue is optical… >>> More