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?

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

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

about: orthographic projection 
Game Development 

Dear flashers, I am studying on the 3d articles of Renderhjs and
trying to make a orthographic projection (atleast i think it is
orthographic). The final game will have a fixed amount of
rotations (8 or 16 probably) and full rotation as a extra performance
option selectable in the settings menu. Here is a sample of a
rotation area. http://www.tiledbasedgames.com/isometric_test/Main.html Please
note: this is just a REALLY ruff testcase only focussing on the
rotation. No depth sorting or other things are done yet and the
code is far from perfect just rufly added it into my project before
this for testing. My question is:<



