How multiple canvas elements affect performance?

问题:

I'm trying to make a simple game (view from above) on canvas. Please tell me, which is faster:

1) Draw everything on one <canvas> and calculate the areas that need to be redrawn.

2) Draw certain parts of the scene on different <canvas> elements and update each only if necessary. In the it variant, probably, I can also use a partial redraw.

For example, I could draw a map on one element, enemies on the second, and a cursor and etc on the third. When moving enemies, I could only redraw the second canvas.

Please explain in as much detail as possible which option is better and why. And could you please advise books that can deepen my knowledge on this issue? For beginners.

回答1:

Most canvas games will use a sort of layering that you are describing. The furthest forward layer would be the HUD, either by a seperate canvas or HTML elements and this would only change if something happened to it, such as someone upgrading their player. Then after that it depends on how they draw the canvas. The simplest way would be to simply draw the portions of the map and obstacles are on the screen.

回答2:

Use one canvas, trust me. If you have a sprite that does nothing but sit there it is still getting drawn 60 times a second so it makes no difference if it is moving or not changing or not if it exists on screen it is getting drawn regardless of change.