camera

MoKaLux · March 2020

hope you are all doing fine.

How can I control my camera to follow the player but not every time?

function Level1:onEnterFrame(e)
	self.world:step(1/60, 1, 1)
	-- camera follow player
	local playerposx, playerposy = self.player.body:getPosition()
	local offsetX = -(playerposx - 128) * self.gamelayer:getScaleX()
	self.gamelayer:setX(offsetX)
--	local offsetY = -(playerposy - myappheight / 2 + 0) * self.gamelayer:getScaleY() -- too much camera movements
	local offsetY = -myappheight -- fixed camera ok but doesn't follow player when too low or too high
	self.gamelayer:setY(offsetY)
end

To be more precise, I want the camera to be fixed on the Y axis unless the player goes down or up above a certain limit.
Do you have any camera scripts, a website to recommend?
How did you do it?

hgy29 · March 2020

I usually do it the other way: camera keeps the player cenetered on screen unless he reaches the edges of the level. I am not sure what you want to achieve

MoKaLux · March 2020

@hgy29 thank you for your answer.
I want my camera to follow the player but not when he jumps only when he goes up/down a hill/platform... I have read that you should reposition the camera only when the player lands on a platform by putting triggers on those platforms.
I don't really know how to handle this

I have seen this page for camera in 2d games and it's just too much for me!
https://www.gamasutra.com/blogs/ItayKeren/20150511/243083/Scroll_Back_The_Theory_and_P ractice_of_Cameras_in_SideScrollers.php

A compilation of camera scripts would be awesome so we could choose the one appropriate to our game genre. They would also go straight to the wiki

MoKaLux · March 2020

@hgy29 like you did in Arthur & Aziliz at the beginning of the game, when the player jumps the camera doesn't move. The camera moves only when the player reaches a certain point. How can I do this please?

hgy29 · March 2020

Just had a try, no the camera moves when you jump in my game, even at the beginning of the game. However the camera starts following the playing horizontally only after a certain point, when there is enough level graphics around.

rrraptor · March 2020

A bit complicated xD

local random = math.random
local function clamp(v, min, max)
	return (v <> min) >< max
end
 
local function lerp(a,b,t)
	return a + (b-a) * t
end
 
 
Camera = Core.class(Sprite)
 
function Camera:init(w,h)
	self.w = w
	self.h = h
	self.minY = -1
	self.maxY = -1
 
	-- camera center
	self.dot = Pixel.new(0,0.1,64,64)
	self:addChild(self.dot)
end
 
function Camera:limitY(min,max)
	self.minY = min
	self.maxY = max
end
 
function Camera:follow(obj)
	local sx,sy = self:getPosition()
 
	local x,y = obj:getPosition()
 
	local cx = -x + self.w / 2
	local cy = -y + self.h / 2
	if self.minY >= 0 and self.maxY >= 0 then 
		cy = clamp(cy, self.minY, self.maxY)
	end
	self.dot:setPosition(-sx + self.w / 2 - 16,-sy + self.h / 2 - 16)
	self:setPosition(
		lerp(sx,cx,0.1), 
		lerp(sy,cy,0.1)
	)
end 
 
Background = Core.class(Sprite)
 
function Background:init(cam)
	self.timer = 0
	self.camera = cam
end
 
function Background:update(dt)
	self.timer += dt
	if self.timer >= 0.08 then 
		local sz = random(4, 8)
		local star = Pixel.new(random(0xffffff), 1, sz, sz)
		local cx, cy = self.camera:getPosition()
		star:setPosition(
			self.camera.w - cx,
			random(self.camera.h) - cy
		)
		star.speed = random(100,200)
		star.timer = 0
		self:addChild(star)
		self.timer = 0
	end
 
	local n = self:getNumChildren()
	for i = n, 1, -1 do
		local child = self:getChildAt(i)
		child.timer += dt
		local x,y = child:getPosition()
		x -= child.speed * dt
		child:setPosition(x, y)
		if child.timer >= 2 then 
			self:removeChild(child)
		end
	end
end
 
local W = application:getLogicalWidth()
local H = application:getLogicalHeight()
 
local camera = Camera.new(W,H)
camera:limitY(350, 500)
stage:addChild(camera)
 
local BG = Background.new(camera)
camera:addChild(BG)
 
local px = Pixel.new(0xff0000, 1, 32, 32)
camera:addChild(px)
 
 
local timer = 0
stage:addEventListener("enterFrame", function(e)
	local dt = e.deltaTime
	BG:update(dt)
 
	timer += dt
 
	local x,y = px:getPosition()
 
	x += 100 * dt
	y = math.sin(timer) * 150
 
	px:setPosition(x,y)
	camera:follow(px)
end)

MoKaLux · March 2020

@rrraptor thank you will give it a try

corona cameras:
https://github.com/Zetosoft/dynacam
https://github.com/roaminggamer/RGCamera
https://gist.github.com/GymbylCoding/8675733

and one that also looks awesome but for love2d:
https://github.com/adnzzzzZ/STALKER-X

@hgy29 do you think you can translate one of corona camera code above with your tool?

MoKaLux · March 2020

rrraptor said:
A bit complicated xD

@rrraptor MAGNIFICO you are my hero of the day

Thank you very much for your help

MoKaLux · March 2020

@rrraptor I need some more help

How do you want to call your camera class? that's for the wiki

A few suggestions (camera is to vague):
-rrraptorCamera ?

-cameraCL (for Clamp and Lerp)?

MoKaLux · March 2020

here is rrraptor's camera class:

--[[
-- rrraptor
	A camera which can follow any sprite using Clamp and Lerp functions.
	Ideal for platformers, RPG, ...
-- USAGE
self.camera = CameraCL.new(myappwidth, myappheight)
self.camera:addChild(ground)
self.camera:addChild(self.player)
function Level1:onEnterFrame(e)
	-- camera follow player
	self.camera:follow(self.player)
end
]]
 
-- functions
local function clamp(v, min, max)
	return (v <> min) >< max
end
 
local function lerp(a,b,t)
	return a + (b-a) * t
end
 
-- the class
CameraCL = Core.class(Sprite)
 
function CameraCL:init(w,h)
	self.w = w
	self.h = h
	self.minY = -1
	self.maxY = -1
	-- camera center
	self.dot = Pixel.new(0xffffff,0.5,64*2,64*2)
	self:addChild(self.dot)
end
 
function CameraCL:limitY(min,max)
	self.minY = min
	self.maxY = max
end
 
function CameraCL:follow(obj)
	local sx,sy = self:getPosition()
	local x,y = obj:getPosition()
	local cx = -x + self.w / 2
	local cy = -y + self.h / 2
	if self.minY >= 0 and self.maxY >= 0 then
		cy = clamp(cy, self.minY, self.maxY)
	end
	self.dot:setPosition(-sx + self.w / 2 - 16,-sy + self.h / 2 - 16)
	self:setPosition(lerp(sx,cx,0.1), lerp(sy,cy,0.1))
end

Hopefully we can build other cameras based on this class for different game genres.

MoKaLux · April 2020

you can see the camera class in action

Camera uses triggers put in the tiled map.
https://mokalux.itch.io/gideros-platformer-lf
Using liquidfun, tiled.
PS: liquidfun doesn't work the same on html5 (some collisions bug). The same code works fine on pc and android

I suspect this line of code:
local myleftshape = b2.PolygonShape.new()
myleftshape:setAsBox(0.1, h / 3, 0 + w / 4 - 1, h / 2, 0) -- half w, half h, centerx, centery, angle
Html5 may convert it to either 0 or 1 instead of keeping it 0.1!?

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