CODEWITHSUNDEEP
iphoneobjective-copengl-esscaleviewport
John Corbett
John Corbett

Reputation: 1615

How to resize a window in openGL

I'm making a game in OpenGL. I have a viewport that is multiplied by a transformation matrix using glOrthof(). I'm almost done with the game, but I've made a last minute decision to scale everything down a little bit to increase visibility. I have included a diagram depicting how my screen is currently set up (the black box) and how I would like to scale it (the red box).

window

given the width and height of the black box, and x and y in the diagram, would it be possible to adjust the viewport, or perhaps do some sort of matrix multiplication to increase the window size?

I don't want to actually scale the game, I just want to increase the size of the window (which I guess will ultimately scale the game, but I want to preserve the relative scale).

right now, this is how I'm setting up my view:

glViewport(0, 0, backingWidth, backingHeight);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrthof(-backingWidth/2.0, backingWidth/2.0, -backingHeight/2.0, backingHeight/2.0, -1.0f, 1.0f);

glMatrixMode(GL_MODELVIEW);

where backingWidth, and backingHeight are the width and height of the black box respectively.

I'm pretty new to OpenGL, so all help is appreciated.

Upvotes: 0

Views: 1714

Answers (1)

Tim
Tim

Reputation: 35923

If you want to see more area in the same viewport size, you can just increase the values given to glOrthof.

If you multiply the top/left/bottom/right of glOrthof to be twice as large, then you will see twice as much in each direction, and everything will be half the original size in each direction, because you're putting twice as much content into the same number of pixels.

You can multiply glOrthof by any scale factor you want.

==EDIT==

Sorry, I noticed that you want to only scale X to the right, and not about the center. In that case leave the left attribute the same, and just add more to the right value of glOrthof.

Upvotes: 1

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