Taking my first baby steps in writing a game. I’ve never coded anything other than stuff that attaches to a database and gets used in an office, so it’s a little daunting. Please bear with (or just ignore) the potential barrage of early questions…
So my project to help me learn will be a simple vertical shooter and I’d really like a scrolling parallax starfield as the background.
Problem is, I have no clue where to even start, could someone help me along the way?
@RaggedTooth - funnily enough I have just been looking at starfields. Not the vertical type more the Star Trek 3D type. I’ll check through to see if I have any examples for you - the ones I have may work for you - you just need to change the direction and maintain the star size.
@RaggedTooth Here’s something I just threw together.
displayMode(FULLSCREEN)
function setup()
tab={}
for z=1,300 do -- number of stars
x=math.random(WIDTH)
y=math.random(HEIGHT)
s=math.random(8) -- size
sp=math.random(3) -- speed
c=color(math.random(255),math.random(255),math.random(255))
table.insert(tab,{x=x,y=y,s=s,sp=sp,c=c})
end
end
function draw()
background(0)
for a,b in pairs(tab) do
fill(b.c)
ellipse(b.x,b.y,b.s)
b.y=b.y-b.sp
if b.y<-10 then
b.y=HEIGHT+20
end
end
end
displayMode(FULLSCREEN)
function setup()
col={color(0, 12, 255, 255), color(107, 145, 171, 255),
color(255, 243, 0, 255), color(168, 169, 97, 255),
color(255, 255, 255, 255), color(255, 150, 0, 255),
color(255, 0, 13, 255)}
nbrStars=300
st={}
for z=1,nbrStars do
c=math.random(7) -- colored stars
--c=5 -- white stars
table.insert(st,vec4(math.random(WIDTH),math.random(HEIGHT),1,c))
end
speed=75
end
function draw()
background(40, 40, 50)
for a,b in pairs(st) do
fill(col[b.w])
ellipse(b.x,b.y,b.z)
xd=WIDTH/2-b.x
if xd<.02 and xd>-.02 then
xd=.1
end
yd=HEIGHT/2-b.y
if yd<.05 and yd>-.05 then
yd=.1
end
b.x=b.x-xd/speed
b.y=b.y-yd/speed
b.z=b.z+.1
if b.x<0 or b.x>WIDTH or b.y<0 or b.y>HEIGHT then
st[a].x=math.random(WIDTH)
st[a].y=math.random(HEIGHT)
st[a].z=1
end
end
end
I clearly need to learn about tables, I can see what the For loop in the draw is doing, but don’t understand the pairs syntax for the loop declaration.
@RaggedTooth Do you mean the “for a,b in pairs(st) do”-part?
If so, you have two variables a and b. Let’s say you have a table that stores 5 values:
myTable = {0, 3, 5, 7, 9}
The variable “a” is a count variable. So doing:
for a, b in pairs(myTable) do print(a) end
Will give you the values from 1 to 5. In the first iteration of the loop, “a” takes on the value 1. In the second one, “a” will be equal to 2 and so on.
The other variable, “b”, takes on what is stored in the table at that specific position in the table. So when you type in:
for a, b in pairs(myTable) do print(b) end
It will print out the values 0, 3, 5, 7 and 9. So in the first iteration of the loop, b takes on the value 0. In the second iteration, it will be 3 and so on.
The code-snippets above store a vec4 in the table. So e.g. the line ellipse(b.x,b.y,b.z) means that you take the x, y and z values of the vec4 that is currently stored in b.
I hope that was helpful
displayMode(FULLSCREEN)
function setup()
stars = {}
--speed = 10
bg = mesh()
bg.shader = shader("Filters:Radial Blur")
bg.shader.sampleDist = 1
bg.shader.sampleStrength = 2.2
r = bg:addRect(0, 0, 0, 0)
img = image(WIDTH, HEIGHT)
parameter.number("speed", 1, 10, 5)
for i = 1, 100 do
table.insert(stars, star())
end
end
function draw()
--background(0)
updateImage()
bg.texture = img
bg:setRect(r, WIDTH*.5, HEIGHT*.5, WIDTH, HEIGHT)
bg:draw()
--sprite(img, WIDTH*.5, HEIGHT*.5)
end
function updateImage()
setContext(img)
background(33, 33, 52, 255)
local remove = {}
for i, s in ipairs(stars) do
local m = (s.y - HEIGHT*.5) / (s.x - WIDTH*.5)
local d = math.sqrt( (s.y - HEIGHT*.5) ^ 2 + (s.x - WIDTH*.5) ^ 2 )
local isBug = d < 10 or math.abs(s.y - HEIGHT*.5) < 10 or math.abs(s.x - WIDTH*.5) < 10
local newX = s.x + speed * sign(s.y - HEIGHT*.5) * sign (m) * (d / 100) / s.distance
local newY = s.y + m * speed * sign(s.y - HEIGHT*.5) * sign (m) * (d / 100) / s.distance
if not isBug then
stroke(s.color.r, s.color.g, s.color.b, s.alpha / s.distance)
--ellipse(s.x, s.y, 5)
strokeWidth(6 - s.distance + d / 250)
line(s.x, s.y, newX, newY)
s.x = newX
s.y = newY
s.alpha = math.min(255, s.alpha + speed * 2)
end
if s.x < 0 or s.y < 0 or s.x > WIDTH or s.y > HEIGHT or isBug then
table.insert(remove, i)
end
end
if #remove > 0 then
for i = 1, #remove do
table.remove(stars, remove[i] - i + 1)
end
for i = 1, #remove do
table.insert(stars, star())
end
end
setContext()
end
function sign(n)
if n < 0 then
return -1
end
return 1
end
function star()
return {
x = math.random(1, WIDTH),
y = math.random(1, HEIGHT),
alpha = 0,
color = color(math.random(255)/50+150, math.random(255)/50+150, math.random(255)/50+150),
distance = math.random(1, 5)
}
end
@Simeon thanks for the example, again very helpful once I finally worked out how to import it from the file rather than from inside Codea which seemed the most logical way!
