OOP with background()

General Discussion Other

ariane.sa..

in General Discussion • Other • 11 months ago

Newbie question. When using OOP, is it always necessary to use background to update the objects? In other words, if I created a circle object and then directed it to move to another location, would I necessarily need to use background() or a masking rectangle in order to update the display to reflect the new position of the circle?

Hope that makes sense....

Ariane

Replies(3)

asimes

Re: OOP with background()

11 months ago

It should work the same way as not having used OOP. Clear everything if something moved with background() then draw everything.

Let's say you have one visual object (a circle) that needs to be drawn wherever its position is once per frame. To do this, you clear with background() in draw() and then draw your object wherever it is supposed to be (in this case rendering the circle in draw() by calling the circle's display method). The effect this will have is "erasing" the previous frame and rendering the new frame including the updated position of your object.

ariane.sa..

Re: Re: OOP with background()

11 months ago

Thanks for the reply. I am particularly interested in the OOP approach because I have an array of objects moving on screen. I wondered if there was perhaps a way to refresh the screen without expressly resorting to using background() or rect(). Not that there is anything wrong with those, just for argument's sake I wondered if there was an alternative approach.

What comes to my mind is that if I have 10 circles, and perhaps only 2 or 3 are being updated, it seems to be that using background or rect forces me to cycle through all the circles and update. That seems to me to be wasteful.

Ariane

asimes

Re: OOP with background()

11 months ago

You are right that not all objects would need to be redrawn, but the tradeoff is a calculation of what area of the screen needs to be redrawn. A trigger could be whether or not an object moved. Given all the objects, for the ones that moved, erase them by drawing them only using the background color (assuming the background is a solid color), then redraw them normally at their new position. This might cause problems if another object was within the area of the object being erased.

Top Reply