Canvas initial delay issue

[Steve Hannah]

My guess is that the first time this runs, it is rasterizing the ovals and
caching them as textures on the GPU - then subsequent runs are just using
the pre-cached textures.  If this is the case, I'm not sure there is a
simple solution for speeding up the first run.


On Mon, May 12, 2014 at 8:40 AM, Renato Rodrigues <rros at icmc.usp.br> wrote:

> Hi all,
>
> I'm trying to convert some Java2D code to JavaFX and I'm stuck with an
> issue regarding the performance of the JavaFX Canvas. At some point, I'll
> have to draw thousands of small circles on the screen.
>
> My problem is on the first drawing, on which my code takes a lot of time to
> execute. But if I have to perform a second drawing, it takes only a
> fraction of the time to draw (it is at least 10 times faster).
>
> Is there anything I'm doing wrong? Is there any way to prevent that initial
> delay?
>
> I wrote this code to test it. In this code I draw 500,000 circles at random
> positions on a 1000 x 1000 canvas (built previously). I linked this code to
> a button click event, and on the first time I click it takes 10 seconds to
> execute. But if I just click again, it takes only 0.025 seconds.
>
> private void paintCanvas() {
>     long initTime = System.currentTimeMillis();
>
>     GraphicsContext cg = canvas.getGraphicsContext2D();
>     cg.setFill(Color.WHITE);
>     cg.fillRect(0, 0, canvas.getWidth(), canvas.getHeight());
>     cg.setFill(Color.rgb(0, 0, 0, 0.1));
>
>     Random rand = new Random();
>     for (int i = 0; i < 500000; i++) {
>         cg.fillOval(1000 * rand.nextFloat(), 1000 * rand.nextFloat(), 2,
> 2);
>     }
>
>     long endTime = System.currentTimeMillis();
>     System.out.println("Time spent on drawing:" + (endTime -
> initTime)/1000.0f);        }
>
>
> Can anyone help me to understand the reason of this initial paint delay?
>
> Thanks in advance,
> Renato.
>
> --
> *Renato Rodrigues Oliveira da Silva*
> VICG - Visualization, Imaging and Computer Graphics - ICMC - USP São Carlos
>



-- 
Steve Hannah
Web Lite Solutions Corp.