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

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

Mobile Programming

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

Z-axis inverted?
Web Design

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/(f-n), -n/(f-n)],

[ 0, 0, 0,
Coding

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 on-screen size of the DisplayObject
(Cube on the above-linked image) to which PerspectiveProjection has
been applied?


A more thorough description and illustrative
code on the issue in ActionScript 3 lacks functionality

Web Design

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?

Programming Languages
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
Game Development

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