Using TileRender to save large, non-repeating image

jfred1979

Using TileRender to save large, non-repeating image

in Using Cinder • 10 months ago

I'm pretty new to Cinder and I'm trying to understand how exactly TileRender works. I'm just drawing a circle mid screen using:

gl::clear( Color( 0, 0, 0 ) );
gl::drawSolidCircle( Vec2f( 320.0f, 240.0f), 20.0f );

and then trying to save a large version to a file (my goal is to export images at print resolution) using code lifted from the forums:

//the size here doesn't matter, but it will get distorted if it's not the same ratio as your window
gl::TileRender tr( getWindowWidth()*4, getWindowHeight()*4 );
//use the default cinder view to render from
tr.setMatricesWindow(getWindowWidth(), getWindowHeight());
while( tr.nextTile() ) {
draw();
}
writeImage( getHomeDirectory() + "appFolder" + getPathSeparator() + "output.png", tr.getSurface() );
//reset window matrix back to normal (if you aren't changing it with a camera)
gl::setMatricesWindow( getWindowWidth(), getWindowHeight(), true );

The desired behavior for me is to have this saved as a larger version of exactly what's on screen, however it's currently just tiling the contents of the screen, so I basically end up with four circles in a large image. Do I need to zoom the camera in on the portion I want to render each draw iteration or something?

Replies(2)

sansumbre..

Re: Using TileRender to save large, non-repeating image

10 months ago

You are probably setting your matrices inside of your app::draw() method. The tr.nextTile() method sets up the correct matrices for the tile, so if you change the matrices after that you undo the correct tiling behavior.

A common (enough) pattern for dealing with this is to set your matrices in update(). That way, you can think of draw() as purely presenting the things you have, without regard for where they are being presented.

jfred1979

Re: Using TileRender to save large, non-repeating image

10 months ago

Got it working thanks!

Another question I have is how to save the image with an alpha channel, although perhaps this warrants another thread.

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