CODEWITHSUNDEEP
c++opengl
Rookie
Rookie

Reputation: 3781

How to render lower resolution scene stretched to fullscreen native resolution?

I have seen this kind of functionality in DirectX apps only: when you resize the window, the rendering will also stretch accordingly, and it looks like it was actually a texture that was stretched.

How can i do this efficiently in OpenGL ? The purpose for this is to create a fullscreen application with native resolution, because its rather hard to choose lower resolution on LCD screens, and allow me to render with lower resolution to get higher FPS.

Upvotes: 2

Views: 1780

Answers (2)

Jonathan DeCarlo
Jonathan DeCarlo

Reputation: 2818

You call glViewport() to tell OpenGL what part of the window (in pixels) will ultimately be rendered by OpenGL. You use a method like glFrustum(), glOrtho(), or glOrtho2D() in order to set the parameters of the "world" in which you are drawing in.

If you handle an event to tell you when the window is being resized, then you can call glViewport() again to update the size of your viewport accordingly.

So, if your world in square (for example), and your viewport is rectangular, then it will have the effect you are referring to (it will stretch accordingly, like it was actually a texture).

Upvotes: -1

Nicol Bolas
Nicol Bolas

Reputation: 474536

You will need to render to a texture or renderbuffer, then do a glBlitFramebuffer to the actual default framebuffer. Then swap buffers as normal.

Upvotes: 2

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