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
Z-axis 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/(f-n), -n/(f-n)],
[ 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 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

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

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