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I am trying to make a module for CC: Tweaked that as one of its features uses Bressenham's Line Algorithm to draw a line between 2 points on a monitor. However when I run my program I get this error:
pixels.lua:24: attempt to index local 'y1' (a number value)
Please note that I got this code from a youtube video and it is possible that I wrote something wrong.
Here is my code:
local pixels = {}
function pixels.drawPixel(x, y, monitor, color)
monitor.setCursorPos(x, y)
monitor.setBackgroundColor(color)
monitor.write(" ")
end
function pixels.fillScreen(color)
x, y = monitor.getSize()
for j = 1,y,1
do
for i = 1,x,1
do
pixels.drawPixel(i,j,monitor,color)
end
end
end
function pixels.drawLine(x1, y1, x2, y2, monitor, color)
error = 0
slope = y2 - y1 / x2 - x1
pixels.drawPixel(x1, y1. monitor, color)
for x = x1,x2,1
do
error = error + slope
if error >= 0.5
then
y = y1 + 1
error = error - 1
end
pixels.drawPixel(x,y,monitor,color)
end
end
return pixels
Line 24:
pixels.drawPixel(x1, y1. monitor, color)
As stated in the comments above, y1 has a period instead of a comma after it, telling Lua to look for a value from y1.monitor when y1 is not a table. Thus, "Attempted to index a number".
(Also, you do not have to declare your incrementor number with your for loops if the number is 1)
New to Lua/Game dev in general here. I'm trying to write a code to draw the background of my game. I have four different spritesheets for things related to setting:
Background - which contains the drawn "background image" of the game
Platforms - which contain the platform sprites of the game
objectsBig - which contain the relatively bigger drawn objects in the background (example rocks, seaweed, etc)
objectsSmall - which contain the relatively smaller drawn objects (smaller rocks, plants, etc)
I made a function, called generateQuads() which is in my Util.lua file, which, given a spritesheet, splices it up into the different sprites in the spritesheet and returns those sprites. It is as follows:
-- Function to generate quads/cut the spritesheet
function generateQuads(atlas, tileWidth, tileHeight)
local sheetWidth = atlas:getWidth() / tileWidth
local sheetHeight = atlas:getHeight() / tileHeight
local sheetCounter = 1
local quads = {}
-- for every line of the sprite sheet
for y = 0, sheetHeight - 1 do
-- for every piece in the width
for x = 0, sheetWidth - 1 do
-- quads generated will be the ones specified by tileWidth and tileHeight
quads[sheetCounter] = love.graphics.newQuad(x * tileWidth, y * tileHeight, tileWidth,
tileHeight, atlas:getDimensions())
sheetCounter = sheetCounter + 1
end
end
return quads
end
I also have a class called Map, which is meant to contain information for the Map. The following are the functions in it:
FUNCTION TO SET UP THE CLASS
function Map:init()
-- Load the background sprite into variable
-- Each is 500x500, total is 1500x500
self.background = love.graphics.newImage('Graphics/platform/background/full.png')
-- Load all the ground platforms into variable
-- Each is 60x30, total is 240x30
self.platforms = love.graphics.newImage('Graphics/platform/ground/all.png')
-- Load all the bigger misc objects into variable
-- Each is 15x20, total is 15x120
self.objectsBig = love.graphics.newImage('Graphics/platform/objects/15x20/all.png')
-- Load all the smaller misc objects into variable
-- Each is 15x15, total is 60x15
self.objectsSmall = love.graphics.newImage('Graphics/platform/objects/15x15/all.png')
-- Setting the size for each of the variables IN PIXELS
self.backgroundWidth = 500
self.backgroundHeight = 1500
self.platformWidth = 60
self.platformHeight = 30
self.objectsBigWidth = 15
self.objectsBigHeight = 20
self.objectsSmallWidth = 15
self.objectsSmallHeight = 15
-- Setting the map size IN TILES
-- EXPERIMENTAL, CHECK AGAIN
self.mapWidth = 432
self.mapHeight = 243
-- Setting the width of the map IN PIXELS (in relation to platforms)
self.mapWidthPixels = self.backgroundWidth
self.mapHeightPixels = self.backgroundHeight
-- Storing our map features
self.tiles = {}
-- Storing the camera points, starting from the bottom
-- The 243 is the VIRTUAL_HEIGHT, which we needed to subtract to account for the
-- offset of the screen
self.camX = 0
self.camY = self.backgroundHeight - 243
-- Cutting each of the spritesheets
self.backgroundSprite = generateQuads(self.background, self.backgroundWidth, self.backgroundHeight)
self.platformSprite = generateQuads(self.platforms, self.platformWidth, self.platformHeight)
self.objectsBigSprite = generateQuads(self.objectsBig, self.objectsBigWidth, self.objectsBigHeight)
self.objectsSmallSprite = generateQuads(self.objectsSmall, self.objectsSmallWidth, self.objectsSmallHeight)
-- 'Setting' the tiles for the map to be background
for y = 1, self.mapHeight do
for x = 1, self.mapWidth do
self:setTile(x, y, BACKGROUND)
end
end
-- 'Setting' the platform tiles for where we start
for x = 1, self.mapWidth do
self:setTile(x, self.mapHeight - 303, GROUND_MIDDLE)
end
end
FUNCTION TO 'SET' WHERE IN THE X, Y COORDINATE THE TILES SHOULD BE
function Map:setTile(x, y, tile)
-- The table 'tiles' is going to store what tile should be in what x and y position
-- subtracting y by 1 so that it's 0 indexed, not 1 indexed
self.tiles[(y - 1) * self.mapWidth + x] = tile
end
FUNCTION TO RETURN WHAT TILE IS IN THE X, Y COORDINATE
function Map:getTile(x, y, tile)
-- This function is going to tell us what tile is set at this x and y position
return self.tiles[(y - 1) * self.mapWidth + x]
end
FUNCTION TO UPDATE
function Map:update(dt)
-- Moving the camera depending on the key being pressed
if love.keyboard.isDown('w') then
-- up movement, clamped between 0 and the other
self.camY = math.max(0, math.floor(self.camY - SCROLL_SPEED * dt))
elseif love.keyboard.isDown('a') then
-- left movement
self.camX = math.max(0, math.floor(self.camX - SCROLL_SPEED * dt))
elseif love.keyboard.isDown('s') then
-- down movement, subtracting VIRTUAL_HEIGHT to account for the screen offset
self.camY = math.min(self.backgroundHeight - VIRTUAL_HEIGHT, math.floor(self.camY + SCROLL_SPEED * dt))
elseif love.keyboard.isDown('d') then
-- right movement
self.camX = math.min(self.backgroundWidth - VIRTUAL_WIDTH, math.floor(self.camX + SCROLL_SPEED * dt))
end
end
FUNCTION TO RENDER
function Map:render()
for y = 1, self.mapHeight do
for x = 1, self.mapWidth do
-- Drawing the background first
love.graphics.draw(self.background, self.backgroundSprite[self:getTile(x, y)],
(x - 1) * self.backgroundWidth, (y - 1) * self.backgroundHeight)
love.graphics.draw(self.platform, self.platformSprite[self:getTile(x, y)],
(x - 1) * self.platformWidth, (y - 1) * self.platformHeight)
end
end
end
What I'm trying to do is splice up each spritesheet, and for set the background and bottom tiles so that I can see a bottom floor. I'm trying to do this through giving numbers to the components in my spritesheet, so that, for example, in a 1500x500 spritesheet for the background, the entire thing is considered 'one' sprite, and treated as such. Its number, 1, is given in a variable. Another example is a 240x30 platform spritesheet, where each 60x30 is considered 'one' sprite, and given a corresponding number, like so:
-- Know where the platforms are in the spritesheet
GROUND_LEFT = 1
GROUND_RIGHT = 2
GROUND_SMALL = 3
GROUND_MIDDLE = 4
-- Know where the backgrounds are in the spritesheet
BACKGROUND = 1
[...]
I want to then store each in the self.tiles list, so that I can access them at any time from the table (Do note that most of this is taken from the CS50 implementation of mario, and so I understand if I've gotten any concepts wrong). When I run this code, though, I get the following error:
Error
Error
Map.lua:135: bad argument #1 to 'draw' (Texture expected, got nil)
Traceback
[C]: in function 'draw'
Map.lua:135: in function 'render'
main.lua:48: in function 'draw'
[C]: in function 'xpcall'
Essentially, I just want to know a way in which I can set the bottom platform tiles, and then be able to iterate over the map and 'set' where the other object sprites should be. The background alone works fine, but once I added the:
-- 'Setting' the platform tiles for where we start
for x = 1, self.mapWidth do
self:setTile(x, self.mapHeight - 303, GROUND_MIDDLE)
end
and
love.graphics.draw(self.platform, self.platformSprite[self:getTile(x, y)],
(x - 1) * self.platformWidth, (y - 1) * self.platformHeight)
lines, the program wouldn't run.
Any help is appreciated!
EDIT: The line I'm getting an error on is the self.platform one.
i had the same problem before, and it turned out to be a typo when typing the variable. looking at your code, i saw that there was no self.platform, instead, there was self.platforms.
try:
love.graphics.draw(self.platforms, self.platformSprite[self:getTile(x, y)],
(x - 1) * self.platformWidth, (y - 1) * self.platformHeight)
I keep getting this error, no matter what:
function love.load() -- love.load starts any command inthe beginning
--number = 0 (old code)
button = {}
button.x = 200
button.y = 200
button.size = 50
button.score = 0
button.time = 0
newFont = love.graphics.newFont(40)
end
end
function love.update(dt) -- changes code in delta time: every frame: love runs in 60 frames per second
--number = number + 1 (old code)
end
function love.draw() -- does anything on the screen
end
function love.draw()
--love.graphics.setColor(0, 0, 255, 5)
--love.graphics.rectangle("fill", 200, 400, 200, 100) --love.graphics.rectangle(mode, x, y, width, height) Y increases downwards;
-- width increases to the right and the height increases downward assuming positive numbers
love.graphics.setColor(255,0,0,5)
--love.graphics.print(number) (old code)
--love.graphics.circle("fill", 150, 350, 100)
--love.graphics.circle(mode, x, y, radius, segments)
love.graphics.circle("fill", button.x, button.y, button.size)
love.graphics.setFont(newFont)
love.graphics.setColor(255, 255, 255, 1)
love.graphics.print(button.score)
end
function love.mousepressed( x, y, b, isTouch)
if b == 1 then
-- use the distance formula to measure the distance/n!
if distanceFormula(button.x, button.y, love.mouse.getX(), love.mouse.getY()) < button.size then
--checks whether click is in circle.
score = score + 1
end
end
function distanceBetween(x1,y1,x2,y2)
return math.sqrt((y2-y1)^2 + (x2-x1)^2)
end
Can someone help me?
The error goes like this:
Error main.lua:45: attempt to call global 'distanceFormula' (a nil value)
Traceback
main.lua:45: in function <main.lua:42>
[C]: in function 'xpcall
I'm very sure that it probably has to do with the function place or something. Can someone help me?
Most importantly can someone please help me with preventing future errors like this??? Thank you.
It looks like you don't have a function called distanceFormula. Also I don't know why you are declaring your distanceBetween function inside of love.mousepressed. distanceFormula is "a nil value" because it doesn't exist. The error is referring to line 45 in your code
if distanceFormula(button.x, button.y, love.mouse.getX(), love.mouse.getY()) < button.size then
I changed your call to distanceFormula to be a call to distanceBetween and moved distance between to it's own function. I also had to move a few of your end around and got rid of your extra love.draw()
function love.load()
--number = 0 (old code)
button = {}
button.x = 200
button.y = 200
button.size = 50
button.score = 0
button.time = 0
newFont = love.graphics.newFont(40)
end
function love.update(dt) -- changes code in delta time: every frame: love runs in 60 frames per second
--number = number + 1 (old code)
end
function love.draw()
--love.graphics.setColor(0, 0, 255, 5)
--love.graphics.rectangle("fill", 200, 400, 200, 100) --love.graphics.rectangle(mode, x, y, width, height) Y increases downwards;
-- width increases to the right and the height increases downward assuming positive numbers
love.graphics.setColor(255,0,0,5)
--love.graphics.print(number) (old code)
--love.graphics.circle("fill", 150, 350, 100)
--love.graphics.circle(mode, x, y, radius, segments)
love.graphics.circle("fill", button.x, button.y, button.size)
love.graphics.setFont(newFont)
love.graphics.setColor(255, 255, 255, 1)
love.graphics.print(button.score)
end
function love.mousepressed(x, y, b, isTouch)
if b == 1 then
-- use the distance formula to measure the distance/n!
if distanceBetween(button.x, button.y, love.mouse.getX(), love.mouse.getY()) < button.size then
--checks whether click is in circle.
button.score = button.score + 1
end
end
end
function distanceBetween(x1,y1,x2,y2)
return math.sqrt((y2-y1)^2 + (x2-x1)^2)
end
I've been using some extremely bulky code to detect collision between simple objects, and I've heard about bounding boxes. I can't find any tutorials on how to use it, so I'm asking about how to use it. Here is how I detect collision:
function platform.collision()
if player.x + player.width / 2 <= platform.x + platform.width and
player.x + player.width / 2 >= platform.x and
player.y + player.height <= platform.y + platform.height and
player.y + player.height >= platform.y then
The MDN has a rather concise article on 2D collision detection. Being the MDN, the examples are in javascript, but are easily translated to, and applicable in, any language - including Lua.
Let's take a look:
Axis-Aligned Bounding Box
One of the simpler forms of collision detection is between two rectangles that are axis aligned — meaning no rotation. The algorithm works by ensuring there is no gap between any of the 4 sides of the rectangles. Any gap means a collision does not exist.
Their example, translated to Lua:
local rect1 = { x = 5, y = 5, width = 50, height = 50 }
local rect2 = { x = 20, y = 10, width = 10, height = 10 }
if
rect1.x < rect2.x + rect2.width and
rect1.x + rect1.width > rect2.x and
rect1.y < rect2.y + rect2.height and
rect1.height + rect1.y > rect2.y
then
-- collision detected!
end
-- filling in the values =>
if
5 < 30 and
55 > 20 and
5 < 20 and
55 > 10
then
-- collision detected!
end
A live example, again in JavaScript, demonstrates this well.
Here's a quick (and imperfect) Love2D example you can throw into a main.lua and play around with.
local function rect (x, y, w, h, color)
return { x = x, y = y, width = w, height = h, color = color }
end
local function draw_rect (rect)
love.graphics.setColor(unpack(rect.color))
love.graphics.rectangle('fill', rect.x, rect.y,
rect.width, rect.height)
end
local function collides (one, two)
return (
one.x < two.x + two.width and
one.x + one.width > two.x and
one.y < two.y + two.height and
one.y + one.height > two.y
)
end
local kp = love.keyboard.isDown
local red = { 255, 0, 0, 255 }
local green = { 0, 255, 0, 255 }
local blue = { 0, 0, 255, 255 }
local dim1 = rect(5, 5, 50, 50, red)
local dim2 = rect(20, 10, 60, 40, green)
function love.update ()
if kp('up') then
dim2.y = dim2.y - 1
end
if kp('down') then
dim2.y = dim2.y + 1
end
if kp('left') then
dim2.x = dim2.x - 1
end
if kp('right') then
dim2.x = dim2.x + 1
end
dim2.color = collides(dim1, dim2) and green or blue
end
function love.draw ()
draw_rect(dim1)
draw_rect(dim2)
end
Oka explained it very well. This works for everything rectangular, not rotated and axis aligned. And you even already did it that way. This is great for buttons and the like!
But what I like doing is using (invisible) circles around objects and see if these collide. This works for everything where height is about the same as the width (which is the case for many sidescrolling platformers or top-down RPGs).
It's quite handy if you want to have the object centered at the current position. And it's especially helpful to simulate a finger on a touchscreen device, because a finger is quite a bit bigger than a mouse cursor. ;)
Here's an example on how to use this method. You can copy it as an actual game, it'll work.
--[[ Some initial default settings. ]]
function love.load()
settings = {
mouseHitbox = 5, -- A diameter around the mouse cursor.
-- For a finger (thouchscreen) this could be bigger!
}
objects = {
[1] = {
x = 250, -- Initial X position of object.
y = 200, -- Initial Y position of object.
hitbox = 100, -- A diameter around the CENTER of the object.
isHit = false -- A flag for when the object has been hit.
},
[2] = {
x = 400,
y = 250,
hitbox = 250,
isHit = false
}
}
end
--[[ This is the actual function to detect collision between two objects. ]]
function collisionDetected(x1,y1,x2,y2,d1,d2)
-- Uses the x and y coordinates of two different points along with a diameter around them.
-- As long as these two diameters collide/overlap, this function returns true!
-- If d1 and/or d2 is missing, use the a default diameter of 1 instead.
local d1 = d1 or 1
local d2 = d2 or 1
local delta_x = x2 - x1
local delta_y = y2 - y1
local delta_d = (d1 / 2) + (d2 / 2)
if ( delta_x^2 + delta_y^2 < delta_d^2 ) then
return true
end
end
--[[ Now, some LÖVE functions to give the collisionDetection() some context. ]]
function love.draw()
for i=1,#objects do -- Loop through all objects and draw them.
if ( objects[i].isHit ) then
love.graphics.setColor(255, 0, 0) -- If an object is hit, it will flash red for a frame.
objects[i].isHit = false
else
love.graphics.setColor(255, 255, 255)
end
love.graphics.circle("line", objects[i].x, objects[i].y, objects[i].hitbox/2)
end
end
-- You can use the following to check, if any object has been clicked on (or tapped on a touch screen device).
function love.mousepressed(x,y,button)
if ( button == 1 ) then
local i = objectIsHit(x,y) -- Check, if an object has been hit.
if ( i ) then
-- The object number 'i' has been hit. Do something with this information!
objects[i].isHit = true
end
end
end
function objectIsHit(x,y)
for i=1,#objects do -- Loop through all objects and see, if one of them has been hit.
if ( collisionDetected(x, y, objects[i].x, objects[i].y, settings.mouseHitbox, objects[i].hitbox) ) then
return i -- This object has been hit!
end
end
end
-- For the sake of completeness: You can use something like the following to check, if the objects themselves collide.
-- This would come in handy, if the objects would move around the screen and then bounce from each other, for example.
function love.update(dt)
if ( collisionDetected(objects[1].x, objects[1].y, objects[2].x, objects[2].y, objects[1].hitbox, objects[2].hitbox) ) then
-- The objects collided. Do something with this information!
end
end
As you can see, the collisionDetection() function is quite easy and intuitive to use.
Hopefully I could give you some more insight. And have fun with LÖVE 2D! :)
I have the following binary clock that I grabbed from this wiki article (the one that's for v1.5.*) for the awesome WM:
binClock = wibox.widget.base.make_widget()
binClock.radius = 1.5
binClock.shift = 1.8
binClock.farShift = 2
binClock.border = 1
binClock.lineWidth = 1
binClock.colorActive = beautiful.bg_focus
binClock.fit = function(binClock, width, height)
local size = math.min(width, height)
return 6 * 2 * binClock.radius + 5 * binClock.shift + 2 * binClock.farShift + 2 * binClock.border + 2 * binClock.border, size
end
binClock.draw = function(binClock, wibox, cr, width, height)
local curTime = os.date("*t")
local column = {}
table.insert(column, string.format("%04d", binClock:dec_bin(string.sub(string.format("%02d", curTime.hour), 1, 1))))
table.insert(column, string.format("%04d", binClock:dec_bin(string.sub(string.format("%02d", curTime.hour), 2, 2))))
table.insert(column, string.format("%04d", binClock:dec_bin(string.sub(string.format("%02d", curTime.min), 1, 1))))
table.insert(column, string.format("%04d", binClock:dec_bin(string.sub(string.format("%02d", curTime.min), 2, 2))))
table.insert(column, string.format("%04d", binClock:dec_bin(string.sub(string.format("%02d", curTime.sec), 1, 1))))
table.insert(column, string.format("%04d", binClock:dec_bin(string.sub(string.format("%02d", curTime.sec), 2, 2))))
local bigColumn = 0
for i = 0, 5 do
if math.floor(i / 2) > bigColumn then
bigColumn = bigColumn + 1
end
for j = 0, 3 do
if string.sub(column[i + 1], j + 1, j + 1) == "0" then
active = false
else
active = true
end
binClock:draw_point(cr, bigColumn, i, j, active)
end
end
end
binClock.dec_bin = function(binClock, inNum)
inNum = tonumber(inNum)
local base, enum, outNum, rem = 2, "01", "", 0
while inNum > (base - 1) do
inNum, rem = math.floor(inNum / base), math.fmod(inNum, base)
outNum = string.sub(enum, rem + 1, rem + 1) .. outNum
end
outNum = inNum .. outNum
return outNum
end
binClock.draw_point = function(binClock, cr, bigColumn, column, row, active)
cr:arc(binClock.border + column * (2 * binClock.radius + binClock.shift) + bigColumn * binClock.farShift + binClock.radius,
binClock.border + row * (2 * binClock.radius + binClock.shift) + binClock.radius, 2, 0, 2 * math.pi)
if active then
cr:set_source_rgba(0, 0.5, 0, 1)
else
cr:set_source_rgba(0.5, 0.5, 0.5, 1)
end
cr:fill()
end
binClocktimer = timer { timeout = 1 }
binClocktimer:connect_signal("timeout", function() binClock:emit_signal("widget::updated") end)
binClocktimer:start()
First, if something isn't by default already in Lua that's because this is to be used in the config file for awesome. :)
OK, so what I need is some guidance actually. I am not very familiar with Lua currently, so some guidance is all I ask so I can learn. :)
OK, so first, this code outputs a normal binary clock, but every column has 4 dots (44,44,44), instead of a 23,34,34 setup for the dots, as it would be in a normal binary clock. What's controlling that in this code? So that I can pay around with it.
Next, what controls the color? Right now it's gray background and quite a dark green, I want to brighten both of those up.
And what controls the smoothing? Right now it's outputting circles, would like to see what it's like for it to output squares instead.
That's all I need help with, if you can point me to the code and some documentation for what I need, that should be more than enough. :)
Also, if somebody would be nice enough to add some comments, that also would be awesome. Don't have to be very detailed comments, but at least to the point where it gives an idea of what each thing does. :)
EDIT:
Found what modifies the colors, so figured that out. None of the first variables control if it's a square or circle BTW. :)
The draw_point function draws the dots.
The two loops in the draw function are what create the output and is where the columns come from. To do a 23/34/34 layout you would need to modify the inner loop skip the first X points based on the counter of the outer loop I believe.