How do I ensure that perspective and orthographic projection matricies show objects at the same size on the screen?


I am working on a 3d scene editor and would like to show the scene in
orthographic projection. My current problem is that I am not sure how
to calculate the orthographic projection matrix such that the objects
do not appear at a completely different size on the screen.I currently
have the following 2 functions for calculating the camera projection
matrix.Matrix4.createPerspective = function(fov, aspect, near, far,
result) { if (typeof result === 'undefined') { result = new
Matrix

Related to : How do I ensure that perspective and orthographic projection matricies show objects at the same size on the screen?

Open GL  ES 2.0 : Orthographic Projection 
Game Development 

I am trying to make some graphing libraries in opengl es 2.0 and I
have a question. I want to set the perspective to orthogonal. From the
material online, one way to use orthogonal perspective is to
set
glOrthof(1.0,
// Left 1.0,
// Right 1.0 / (rect.size.width /
rect.size.height), // Bottom 1.0 /
(rect.size.width / rect.size.height), // Top 0.01,
// Near
10000.0);
before the viewport is defined. But
when I plugge

OpenGL orthographic projection 
Game Development 

In the description of gluOrtho2d they say it's like glOrtho with
near=1 and far=1. Why is near behind the viewer. Why
does the matrix described here:
http://www.opengl.org/sdk/docs/man2/xhtml/glOrtho.xml have the
Zaxis inverted?

Orthographic projection with origin at screen bottom left 
Game Development 

I'm using the python OpenGL bindings, and trying to only use modern
opengl calls. I have a VBO with verticies, and I am trying to render
with an orthographic projection matrix passed to the vertex
shader.
At present I am calculating my projection matrix
with the following values:
from numpy import array w = float(width) h = float(height) n = 0.5 f = 3.0 matrix = array([ [2/w, 0, 0,
0], [ 0, 2/h, 0,
0], [ 0, 0, 1/(fn), n/(fn)],
[ 0, 0, 0,

How to get visible size of DisplayObject with perspective projection 
Game Development 

The following is entirely a math question.
As we know,
PerspectiveProjection delivers perspective
transformations in 3D represented by the interdependent values of
fieldOfView and focalLength according to the
following formula:
focalLength = stageWidth/2 *
(cos(fieldOfView/2) / sin(fieldOfView/2)
Q: How to get the visible onscreen size of the DisplayObject
(Cube on the abovelinked image) to which PerspectiveProjection has
been applied?
A more thorough description and illustrative
code on the issue in ActionScript 3 lacks functionality

Why orthographic projection not working exactly while using CombinedCamera.js using Three.js? 
Game Development 

I've gone through the working live example of CombinedCamera and
with inspiration I embedded combinedcamera in my work.
camera = new THREE.CombinedCamera( width /2, height/2, 45,
0.1, 1000, 1000, 1000, 1000 );
But while using
Perspective Camera, my application works fine:
But The same application, while using orthographic projection
doesn't work at all and it looks so weird.
Whats the problem in my code? I want the orthographic projection
in all x, y and z directions on the object. How to do that?

How do I ensure that perspective and orthographic projection matricies show objects at the same size on the screen? 
Game Development 

I am working on a 3d scene editor and would like to show the scene in
orthographic projection. My current problem is that I am not sure how
to calculate the orthographic projection matrix such that the objects
do not appear at a completely different size on the screen.I currently
have the following 2 functions for calculating the camera projection
matrix.Matrix4.createPerspective = function(fov, aspect, near, far,
result) { if (typeof result === 'undefined') { result = new
Matrix



