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I am new to openGL and wondering how to redimension a window in opengl without resizing objects in it (for example a quad drawn in opengl). I currently have a simple C++ function such as : 

void ProjectionOrtho::redimensionWindow(int width, int height) 
{
    glViewport(0, 0, width, height); 
}

Here is a simple image to illustrate the problem: enter image description here

Note : I have tried glViewPort(0,0, 665, 365) which are the initial height and weight of myBlueQuad, but that is not what i want since i want to be able to see the rest of the 3d universe to the right (for instance if i translate the quad to the right, i want to be able to see it)

Based on this thread: the difference between glOrtho and glViewPort in openGL I am pretty sure I need to use glOrtho but not sure how.. ive tried the following as @tkausl suggested:

glViewport(0, 0, width, height); 
glOrtho(0, width, height, 0, -1.0, 1.0); //width and height of window panel

But unfortunately, i get the same result as before. It seems that glOrtho is never applied, i've also tried calling glLoadIdentity() before my glOrtho call, it has no effect on the end result.

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  • You need to fix your projection matrix. – tkausl Oct 03 '16 at 00:46
  • @tkausl: thanks for answering :) could you be a little more specific please – Rose Oct 03 '16 at 00:50
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    You've already edited in the part you're missing. If you don't do vector-math yourself you need to use `glOrtho`. `glViewport` sets up your window-region OpenGL is allowed to draw in, `glOrtho` sets which virtual size this region has. Check the [Docs](https://www.khronos.org/opengles/sdk/1.1/docs/man/glOrtho.xml) on how to call the function, It'd probably the easiest to start with `left` and `top` as 0.0, `right` as your window-width, `bottom` as your window-height, `zNear` as `-1.0` and `zFar` as `1.0`. – tkausl Oct 03 '16 at 01:32
  • @tkausl: thanks very much for your help.. ive tried exactly what you've suggested and unfortuntately i still get the same problem (edited my first post with your suggestion in mind). also tried glOrtho(0, 675, 0, 365, -1.0,1.0); did not work as well. What am I doing wrong ? :( – Rose Oct 03 '16 at 03:02
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    You need to use the windows width and height, not the quads ones. So the same parameters you pass to `glViewport` – tkausl Oct 03 '16 at 03:25
  • @tkausl: Thanks I appreciate your help, ive tried both : glOrtho(0,width, height, 0,-1.0,1.0) //width and height of my window as youve just suggested and glOrtho(0,675, 365, 0, -1.0,1.0) //my quad dimension (the dimension that i want the quad to keep) Both are not working.. i am going crazy ! lol the quad keeps resizing almost as big as the window (as seen in the image posted) – Rose Oct 03 '16 at 03:32
  • Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/124757/discussion-between-rose-and-tkausl). – Rose Oct 03 '16 at 03:49

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