How to make a bitmap follow mouse?

plicatibu · December 2019

Hi.

I'm trying to make the bitmap follow my mouse movement. I don't want it to move if the distance to mouse where less than a treshold (say 20px).

Any snippet on how to do it?

Regards.

rrraptor · December 2019

local cos,sin=math.cos,math.sin
function angle(x1,y1, x2,y2)
	return math.atan2(y2-y1, x2-x1)
end
 
function distance(x1,y1, x2,y2)
	return (x2-x1)^2+(y2-y1)^2
end
 
function lerp(a, b, t)
	return a + t * (b - a)
end
 
FollowSprite = Core.class(Sprite)
 
function FollowSprite:init(speed, color, distance)
	self.g = Pixel.new(color, 1, 32, 32)
	self.g:setAnchorPoint(.5,.5)
	self:addChild(self.g)
	self.tx = 0
	self.ty = 0
	self.speed = speed
	self.dist = distance
end
 
function FollowSprite:follow(x, y)
	self.tx = x
	self.ty = y
end
 
function FollowSprite:update(dt)
	local x, y = self:getPosition()
	local distSq = distance(x, y, self.tx, self.ty)
 
	if (distSq > self.dist^2) then 
		local t = 0.1
		x = lerp(x, self.tx, t)
		y = lerp(y, self.ty, t)
		self:setPosition(x, y)
		local a = angle(x, y, self.tx, self.ty)
		self:setRotation(^>a)
	end
end
 
function FollowSprite:update2(dt)
	local x, y = self:getPosition()
	local distSq = distance(x, y, self.tx, self.ty)
 
	if (distSq > self.dist^2) then 
		local a = angle(x, y, self.tx, self.ty)
		local dx = cos(a) * self.speed * dt
		local dy = sin(a) * self.speed * dt
		x += dx
		y += dy
		self:setRotation(^>a)
		self:setPosition(x, y)
	end
end
 
local obj = FollowSprite.new(300, 0xff0000, 20)
stage:addChild(obj)
 
local obj2 = FollowSprite.new(300, 0x00ff00, 20)
stage:addChild(obj2)
 
stage:addEventListener(Event.ENTER_FRAME, function(e)
	local dt = e.deltaTime
	obj:update(dt)
	obj2:update2(dt)
end)
stage:addEventListener(Event.MOUSE_HOVER, function(e)
	obj:follow(e.x, e.y)
	obj2:follow(e.x, e.y)
end)

EDIT:
You can add noise to make it move "randomly" around given point

Noise code (refernce):

local tmp = {
	{1,1,0},{-1,1,0},{1,-1,0},{-1,-1,0},
	{1,0,1},{-1,0,1},{1,0,-1},{-1,0,-1},
	{0,1,1},{0,-1,1},{0,1,-1},{0,-1,-1}
}
local grad3 = {}
-- make 0 based indices
for i,t in ipairs(tmp) do
	local gr = {}
	for j = 1, 3 do 
		gr[j-1]=t[j]
	end
	grad3[i-1]=gr
end
tmp = nil
 
local p =  {151,160,137,91,90,15,
	131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
	190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
	88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
	77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
	102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
	135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
	5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
	223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
	129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
	251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
	49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
	138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
}
 
local perm = {}
for i=0, 511 do perm[i] = p[(i & 255) + 1] end
 
local function dot(g, x, y, z) 
	return g[0]*x + g[1]*y + g[2]*z;
end
 
local function mix(a, b, t)
	return (1-t)*a + t*b
end
 
local function fade(t)
	return t*t*t*(t*(t*6-15)+10);
end
 
local function noise(x, y, z)
	-- Find unit grid cell containing point
	local X = (x//1)
	local Y = (y//1)
	local Z = (z//1)
 
	-- Get relative xyz coordinates of point within that cell
	x -= X
	y -= Y
	z -= Z
 
	-- Wrap the integer cells at 255 (smaller integer period can be introduced here)
	X = X & 255
	Y = Y & 255
	Z = Z & 255
 
	-- Calculate a set of eight hashed gradient indices
	local gi000 = perm[X+perm[Y+perm[Z]]] % 12
	local gi001 = perm[X+perm[Y+perm[Z+1]]] % 12
	local gi010 = perm[X+perm[Y+1+perm[Z]]] % 12
	local gi011 = perm[X+perm[Y+1+perm[Z+1]]] % 12
	local gi100 = perm[X+1+perm[Y+perm[Z]]] % 12
	local gi101 = perm[X+1+perm[Y+perm[Z+1]]] % 12
	local gi110 = perm[X+1+perm[Y+1+perm[Z]]] % 12
	local gi111 = perm[X+1+perm[Y+1+perm[Z+1]]] % 12
 
	-- Calculate noise contributions from each of the eight corners
	local n000= dot(grad3[gi000], x, y, z)
	local n100= dot(grad3[gi100], x-1, y, z)
	local n010= dot(grad3[gi010], x, y-1, z)
	local n110= dot(grad3[gi110], x-1, y-1, z)
	local n001= dot(grad3[gi001], x, y, z-1)
	local n101= dot(grad3[gi101], x-1, y, z-1)
	local n011= dot(grad3[gi011], x, y-1, z-1)
	local n111= dot(grad3[gi111], x-1, y-1, z-1)
	-- Compute the fade curve value for each of x, y, z
	local u = fade(x);
	local v = fade(y);
	local w = fade(z);
	-- Interpolate along x the contributions from each of the corners
	local nx00 = mix(n000, n100, u);
	local nx01 = mix(n001, n101, u);
	local nx10 = mix(n010, n110, u);
	local nx11 = mix(n011, n111, u);
	-- Interpolate the four results along y
	local nxy0 = mix(nx00, nx10, v);
	local nxy1 = mix(nx01, nx11, v);
	-- Interpolate the two last results along z
	local nxyz = mix(nxy0, nxy1, w);
 
	return nxyz;
end
 
return noise

And thats how you can use it with code above:

-- add 
--	self.x = 0
--	self.y = 0
-- to init function of FollowSprite
function FollowSprite:update3(dt)
	local x, y = self.x,self.y--self:getPosition()
	local distSq = distance(x, y, self.tx, self.ty)
	local n1 = 0
	local n2 = 0
	local power = 20
	--self.speed = math.sqrt(distSq)  * 0.75 --< dynamic speed based on distance
	if (distSq > self.dist^2) then 
		local a = angle(x, y, self.tx, self.ty)
		local dx = cos(a) * self.speed * dt
		local dy = sin(a) * self.speed * dt
		x += dx
		y += dy
 
		--self:setRotation(^>a)
		n1 = noise(y/100, 0.1, self.zoff) * power / 2
		n2 = noise(0.1, x/100, self.zoff) * power / 2
	else
		n1 = noise(y/100, 0.1, self.zoff) * power
		n2 = noise(0.1, x/100, self.zoff) * power
	end
 
	self:setPosition(x + n1, y + n2)
	self.zoff += dt
	self.x = x
	self.y = y
end

rrraptor · December 2019

For some reason I decided to create a noise plugin

And after a few hours, its working, and its x5 times faster than lua version.
But it only works for windows, cuz idk how to build for other platforms ¯\_(ツ)_/¯

hgy29 · December 2019

if you make it public, I can add it to gideros distributon as well as port it to other platforms

rrraptor · December 2019

hgy29 said:
if you make it public, I can add it to gideros distributon as well as port it to other platforms

The question is, does someone need it? Maybe it should have more than just simplex and perlin noises

Maybe something like this: https://github.com/Auburns/FastNoise
If so, I can also create a few examples

MoKaLux · December 2019

+1 for this to happen

Apollo14 · December 2019

+1!

plicatibu · December 2019

@rrraptor That's exactly what I wanted. It is amazing.

Thank you for sharing.

And please, let your code be added to Gideros.

Regards.

antix · December 2019

Yes, Gideros needs more general purpose things like this.

rrraptor · December 2019

@hgy29 for me to create a binding of FastNoise I need to rewrite in C? Or its ok to use C++?

hgy29 · December 2019

You can use C++, it is can cooperate with C code

rrraptor · December 2019

hgy29 said:
You can use C++, it is can cooperate with C code

Ok, good

So, how to properly create a binding?

The way I did it is:
Define noise variable

static FastNoise noise;

Create instance:

static void g_initializePlugin(lua_State* L)
{
	noise = FastNoise();
	// rest of the code
}

And the binding functions like that:

static int GetNoise(lua_State* L)
{
	FN_DECIMAL x = lua_tonumber(L, -1);
	FN_DECIMAL y = lua_tonumber(L, -2);
	FN_DECIMAL z = lua_tonumber(L, -3);
 
	FN_DECIMAL v = noise.GetNoise(x, y, z);
 
	lua_pushnumber(L, v);
 
	return 1;
}

g_deinitializePlugin is empty, cuz idk how to destroy static instance, google says that it will be automatically destroyed.
Also, should I to use lua_pop every time Im getting/pushing values from/to stack?

Or I need to use g_createClass ?

hgy29 · December 2019

if You don’t need to instanciate your generator, you won’t need to create classes. For basic lua C interface, take a look at how it is done for other plugins in gideros

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