Tuto tiny-ecs beatemup Part 6 ECS Components

Components

As we have seen in the previous chapter, components are abilities we add to an Entity. Entities can and will share the same components.

Let's continue adding abilities to our player1.

BODY

The Body Component adds an Entity the ability to move both on the x and y axis. You can create a file called "cBody.lua" in the "_C" folder. The code:

CBody = Core.class()

function CBody:init(xspeed, xjumpspeed)
	-- body physics properties
	self.vx = 0
	self.vy = 0
	self.speed = xspeed
	self.currspeed = self.speed
	self.jumpspeed = xjumpspeed
	self.currjumpspeed = self.jumpspeed
	self.isonfloor = true
	self.isgoingup = false
end

The CBody:init function signature has only two parameters: the speed on the x axis and the jumpspeed.

We store other variables to keep track of an Entity current state.

Components are usually small pieces of code, which is nice!

COLLISION BOX

The CollisionBox Component adds an Entity a collision box. You can create a file called "cCollisionBox.lua" in the "_C" folder. The code:

CCollisionBox = Core.class()

function CCollisionBox:init(xcollwidth, xcollheight)
	self.w = xcollwidth
	self.h = xcollheight
end

That's all we need to tell a System this Entity has a collision box. We store the Entity collision box width and height to be used by systems.

HURT BOX

Hurt boxes are not components per se, but they use the collision box size in their parameters. I use two hurt boxes for flexibility: a head hurt box and a spine hurt box.

Hurt boxes are rectangular areas the Entity will receive damage to when overlapping another Entity hit box. Hurt boxes are simply tables holding some variables:

• is it active or is the Entity in recovery mode
• its x and y position
• its size

ANIMATION

In the previous chapter we already added the Animation Component and created the basic animations: idle, walk, jump, ... . This time we add the attacks animations ("ePlayer1.lua"):

--	self.animation:createAnim(g_ANIM_PUNCH_ATTACK1_R, 50, 51) -- 28, 31, no or low anticipation / quick hit / no or low overhead is best
	self.animation.anims[g_ANIM_PUNCH_ATTACK1_R] = {}
	self.animation.anims[g_ANIM_PUNCH_ATTACK1_R][1] = self.animation.myanimsimgs[49]
	self.animation.anims[g_ANIM_PUNCH_ATTACK1_R][2] = self.animation.myanimsimgs[52]
	self.animation.anims[g_ANIM_PUNCH_ATTACK1_R][3] = self.animation.myanimsimgs[54]
	self.animation:createAnim(g_ANIM_PUNCH_ATTACK2_R, 50, 54) -- low or mid anticipation / quick hit / low or mid overhead is best
--	self.animation:createAnim(g_ANIM_KICK_ATTACK1_R, 62, 63) -- 35, 41, no or low anticipation / quick hit / no or low overhead is best
	self.animation.anims[g_ANIM_KICK_ATTACK1_R] = {}
	self.animation.anims[g_ANIM_KICK_ATTACK1_R][1] = self.animation.myanimsimgs[62]
	self.animation.anims[g_ANIM_KICK_ATTACK1_R][2] = self.animation.myanimsimgs[64]
	self.animation.anims[g_ANIM_KICK_ATTACK1_R][3] = self.animation.myanimsimgs[67]
	self.animation:createAnim(g_ANIM_KICK_ATTACK2_R, 62, 68) -- low or mid anticipation / quick hit / low or mid overhead is best
...

We give our animations a name plus the starting image and the ending image in the spritesheet. The animations names were declared in the "main.lua" file. Here it is better to have quick animations with few images.

The code just above demonstrates two ways to create animations. We can either use:

• CAnimation:createAnim function when the images are contiguous in the spritesheet (g_ANIM_PUNCH_ATTACK2_R, g_ANIM_KICK_ATTACK2_R)
• manually create the animation table when the images are not contiguous in the spritesheet (g_ANIM_PUNCH_ATTACK1_R, g_ANIM_KICK_ATTACK1_R)

This gives us maximum flexibility!

When we are done with our animations we can do some clean up.

HIT BOX

Hit boxes are not components per se, but they are somewhat related to the attacks animations. I used two kind of hit boxes: the hit boxes targeting the head and the hit boxes targeting the spine.

Depending on the attack performed, the hit box will be different in size and will target either another Entity head or spine hurt box. Hit boxes like hurt boxes are tables:

• is it active, the Entity is performing an attack or not
• the animation frame the hit box becomes active
• the animation frame the hit box is no longer active
• the damage it deals
• its x and y position
• its size

SHADOW

The Shadow Component adds an Entity a shadow to give more depth to the game. You can create a file called "cShadow.lua" in the "_C" folder. The code:

CShadow = Core.class()

function CShadow:init(xparentw, xshadowsx, xshadowsy)
	self.sprite = Bitmap.new(Texture.new("gfx/fx/shadow.png"))
	local sx = (self.sprite:getWidth()><xparentw)/(self.sprite:getWidth()<>xparentw)
	self.sprite:setScale(xshadowsx or sx, xshadowsy or sx)
	self.sprite:setAnchorPoint(0.5, 0.5)
--	self.sprite:setAlpha(0.5)
	self.sprite:setColorTransform(0, 0, 0, 0.65)
end

The CShadow Component creates a bitmap shadow below our Entity. You can give the shadow a width and a scale (optional). We will create a System to position the shadow in the next chapters.

Next?

The player1 Entity and its components are done, now using almost the same components let's create our enemies...

Prev.: Tuto tiny-ecs beatemup Part 5 ePlayer1
Next: Tuto tiny-ecs beatemup Part 7 Enemies

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