Managing a consistent framerate

[BlackBulletIV]

Ah ok. Doesn't OpenGL do some optimisations like not drawing what's not on the screen?

[Ertain]

If it cannot be done once, do it only as frequent as it really is required (eg, change the value of timer every second, not every frame)

For your example, how would one change the value of "timer" every second? Are you referring to love.timer?

And now, more comments.

If you are really sure you don't need the image any more, you can just clear all references to it, and Lua will collect it automatically.

How can I use one image for representing many enemies on the screen?

As for enemies on the screen, should I check for when they leave the screen, and stop drawing them when they leave said screen?

[Robin]

For your example, how would one change the value of "timer" every second? Are you referring to love.timer?

A "timer" is really a variable whose value you constantly update to reflect time passed:

Code: Select all

timer = 0
function love.update(dt)
 timer = timer + dt
end

How can I use one image for representing many enemies on the screen?

Use the same image to draw each enemy.

Code: Select all

img_enemy = love.graphics.newImage(...)

function love.draw()
   for i,enemy in ipairs(enemies) do
      love.graphics.draw(img_enemy, enemy.x, enemy.y)
   end
end

As for enemies on the screen, should I check for when they leave the screen, and stop drawing them when they leave said screen?

Yes.

(PS: do not use the code samples in this post as such, they are only examples.

[Taehl]

As for enemies on the screen, should I check for when they leave the screen, and stop drawing them when they leave said screen?

Absolutely. A very simple way of doing this would be something like:

Code: Select all

love.draw()
	for i,enemy in ipairs(enemies) do
		-- Draw the enemy only if it's inside the window
		if enemy.x > 0 and enemy.x < 800 and enemy.y > 0 and enemy.y < 600 then
			love.graphics.draw(img_enemy, enemy.x, enemy.y)
		end
	end
end

This assumes you don't have a moving camera. You'd need a little extra math to take into account the camera's position, in that case.

[miko]

For your example, how would one change the value of "timer" every second? Are you referring to love.timer?

A "timer" is really a variable whose value you constantly update to reflect time passed:

Code: Select all

timer = 0
function love.update(dt)
 timer = timer + dt
end

And then if you are drawing it (eg, seconds elapsed/remaining) you would do:

Code: Select all

if timer-previous_timer>=1 then
  previous_timer=timer
  renderNewTimerImage(timer)
end

Anyways, it was just an example. The main point is to avoid unnecessary work if you can.

[kikito]

Ah ok. Doesn't OpenGL do some optimisations like not drawing what's not on the screen?

It seems to me that the actual bottleneck here might be Lua, not OpenGL. Even if the graphics architecture (be it OpenGL or the GPU itself) "optimizes out" all the non-visible draw functions, the CPU will still have to interpret all those Lua function calls, transform them into C, etc. If you remove the unnecesary Lua calls, this would be an improvement - the test to see what falls into the screen and what doesn't has to be more efficient that just drawing everything, of course

[BlackBulletIV]

Absolutely. A very simple way of doing this would be something like:

Code: Select all

...

Don't forget the width and height! It's also best to use the getWidth/Height functions (or some variables), to make your code more abstract, as in, less reliant on outside conditions.

Code: Select all

function love.draw()
  for i, enemy in ipairs(enemies) do
    if enemy.x > -enemy.width and enemy.x < love.graphics.getWidth()
       and enemy.y > -enemy.height and enemy.y < love.graphics.getHeight()   
    then
      love.graphics.draw(img_enemy, enemy.x, enemy.y)
    end
  end
end

Ah ok. Doesn't OpenGL do some optimisations like not drawing what's not on the screen?

It seems to me that the actual bottleneck here might be Lua, not OpenGL. Even if the graphics architecture (be it OpenGL or the GPU itself) "optimizes out" all the non-visible draw functions, the CPU will still have to interpret all those Lua function calls, transform them into C, etc. If you remove the unnecesary Lua calls, this would be an improvement - the test to see what falls into the screen and what doesn't has to be more efficient that just drawing everything, of course

Ah ok, that's probably it. Because when I was reading about the OpenGL pipeline, I remember it saying something about OpenGL clearing out non-on-screen data.

EDIT: Hey congratulations on 1000 posts kikito!

[kikito]

EDIT: Hey congratulations on 1000 posts kikito!

Why, thank you! This is not what I planned for my 1000th post. At least I hope it was useful.

[BlackBulletIV]

No worries . Was it your thousandth post? I saw 1001 when I wrote that. It probably was, if you were going from the forums in top-to-bottom order.

[miko]

Don't forget the width and height! It's also best to use the getWidth/Height functions (or some variables), to make your code more abstract, as in, less reliant on outside conditions.

Code: Select all

function love.draw()
  for i, enemy in ipairs(enemies) do
    if enemy.x > -enemy.width and enemy.x < love.graphics.getWidth()
       and enemy.y > -enemy.height and enemy.y < love.graphics.getHeight()   
    then
      love.graphics.draw(img_enemy, enemy.x, enemy.y)
    end
  end
end

You don't want do access global variables and make a call to get*() on every iteration. So the modified example would be:

Code: Select all

function love.draw()
  local width, height=love.graphics.getWidth(), love.graphics.getHeight()
  local draw=love.graphics.draw
  for i, enemy in ipairs(enemies) do
    if enemy.x > -enemy.width and enemy.x < width
       and enemy.y > -enemy.height and enemy.y < height   
    then
      draw(img_enemy, enemy.x, enemy.y)
    end
  end
end