Rendering and displaying different resolutions

Hey all,

I'm using JOGL and I'm trying to figure out how I can render a scene to a lower resolution than I display the scene. IE, I'd like to render the scene at, say, 256x256, and then have that image automatically scale to fill a JPanel.

Currently, I can get the image to render at the smaller resoluton by resizing the viewport, or resizing the actual GLAutoDrawable... but I can't seem to find a way to make the viewport automatically upscale a low-res render buffer.

If any of that makes sense... I just like to set a small, fixed resolution for the scene and have that scale to fill the window.

 

U have to render ur scene to some backbuffer, preferably a FBO (Frame Buffer Object).

The FBO could be any resolution (e.g. 256x256). After u rendered ur scene to the FBO u can use it as texture to render a fullscreen quad in ur "displayed" viewport (e.g. 1280x720). The lower resolution FBO will the be automatically upscaled with bilinear filtering to cover the whole screen.

Ok... thanks.

It sounds like this method would require two "render" operations... is it going to be much / any faster than just rendering the scene outright?

>is it going to be much / any faster than just rendering the scene outright?

... depends on the complexity of ur scene, but rendering to a FBO and doing a second render pass to display the fullscreen quad with the FBO as texture is basically free. U can do hundreds or even thousand of these passes per frame  on a modern GPU (as u would e.g. to achieve blur or other filter operations).

It's a fairly complex scene (tri-strip terrain models)... but it has to run on a machine with a slow processor and no GPU or graphics acceleration of any kind...