{"id":116,"date":"2015-02-07T19:07:41","date_gmt":"2015-02-07T19:07:41","guid":{"rendered":"http:\/\/cpscotti.com\/blog\/?p=116"},"modified":"2015-02-24T17:03:41","modified_gmt":"2015-02-24T17:03:41","slug":"swiftris-fixing-gravity","status":"publish","type":"post","link":"http:\/\/cpscotti.com\/blog\/?p=116","title":{"rendered":"Swiftris – Fixing Gravity"},"content":{"rendered":"

As I mentioned on my previous post, Swiftris’ gravity is different than the http:\/\/en.wikipedia.org\/wiki\/Tetris#Gravity<\/a> and that annoys anyone who played Tetris enough.<\/p>\n

On the original Switris source, the gravity\/collapsing behavior is implemented in ‘removeCompletedLines()’ which is called (weirdly) from within GameViewController’s implementation of the ‘gameShapeDidLand()’. Let’s start by just reimplementing removeCompletedLines() without changing its interface.<\/p>\n

Here is the original implementation:
\n[sourcecode language=”javascript” title=”Swiftris.swift excerpt at the original removeCompletedLines()”]
\nfunc removeCompletedLines() -> (linesRemoved: Array<Array<Block>>, fallenBlocks: Array<Array<Block>>) {
\n var removedLines = Array<Array<Block>>()
\n for var row = (NumRows – 1) ; row > 0 ; row– {
\n var rowOfBlocks = Array<Block>()<\/p>\n

for column in 0..<NumColumns {
\n \/\/if block not null
\n if let block = blockArray[column, row] {
\n \/\/add to the rowOfBlocks
\n rowOfBlocks.append(block)
\n }
\n }
\n \/\/if amount of blocks equals the number of Columns
\n if rowOfBlocks.count == NumColumns {
\n removedLines.append(rowOfBlocks)
\n for block in rowOfBlocks {
\n blockArray[block.col, block.row] = nil
\n }
\n }
\n }<\/p>\n

if removedLines.count == 0 {
\n return ([],[])
\n }<\/p>\n

let pointsEarned = removedLines.count * PointsPerLine * level
\n score += pointsEarned
\n if score >= level * LevelThreshold {
\n level += 1
\n delegate?.gameDidLevelUp(self)
\n }<\/p>\n

var fallenBlocks = Array<Array<Block>>()
\n for column in 0..<NumColumns {
\n var fallenBlocksArray = Array<Block>()<\/p>\n

for var row = (removedLines[0][0]).row – 1; row > 0; row– {
\n if let block = blockArray[column, row] {
\n var newRow = row<\/p>\n

\/\/falls independently?
\n while (newRow < (NumRows-1) && blockArray[column, newRow+1] == nil) {
\n newRow++
\n }<\/p>\n

block.row = newRow
\n blockArray[column, row] = nil
\n blockArray[column, newRow] = block
\n fallenBlocksArray.append(block)
\n }
\n }<\/p>\n

if fallenBlocksArray.count > 0 {
\n fallenBlocks.append(fallenBlocksArray)
\n }
\n }<\/p>\n

return (removedLines, fallenBlocks)
\n}
\n[\/sourcecode]<\/p>\n

and this is my implementation (different name but same signatures so you can just replace in GameViewController):
\n[sourcecode language=”javascript” title=”A redesigned gravity\/collapsing lines with same signature”]
\nfunc removeFullLines() -> (linesRemoved: Array<Array<Block>>, fallenBlocks: Array<Array<Block>>) {
\n \/\/ Just so we can mock the original signature
\n var externalRemovedBlocks = Array<Array<Block>>()
\n var removedBlocks = Array<Block>()<\/p>\n

\/\/ Just so we can mock the original signature
\n var externalFallenBlocks = Array<Array<Block>>()
\n var fallenBlocks = Array<Block>()<\/p>\n

\/\/Iterating from bottom of the Tetris grid; this is the summary of that loop:
\n \/\/ -> dropHeight = 0 (number of dropped rows to that point in the loop)
\n \/\/ for rows, bottom up
\n \/\/ if row is full
\n \/\/ -> save that row’s blocks to removedBlocks
\n \/\/ -> set nil for the whole row
\n \/\/ -> incread dropHeight
\n \/\/ else (row is not full)
\n \/\/ if dropHeight > 0
\n \/\/ -> lower that row by dropHeight rows <\/p>\n

var dropHeight:Int = 0
\n for var row = (NumRows – 1) ; row > 0 ; row– {<\/p>\n

if isRowFilled(row) {
\n for column in 0..<NumColumns {
\n \/\/save row (we know its not null because its filled)
\n removedBlocks.append(blockArray[column, row]!)<\/p>\n

\/\/set nil
\n blockArray[column, row] = nil
\n }<\/p>\n

\/\/increase drop height
\n dropHeight += 1
\n } else {
\n if dropHeight > 0 {
\n \/\/lower row by drop height
\n for column in 0..<NumColumns {
\n if let block = blockArray[column, row] {
\n block.row += dropHeight
\n blockArray[column, row] = nil
\n blockArray[column, block.row] = block
\n fallenBlocks.append(block)
\n }
\n }
\n }
\n }
\n }
\n externalRemovedBlocks.append(removedBlocks)
\n externalFallenBlocks.append(fallenBlocks)<\/p>\n

if dropHeight == 0 {
\n return ([],[])
\n }<\/p>\n

let pointsEarned = dropHeight * PointsPerLine * level
\n score += pointsEarned
\n if score >= level * LevelThreshold {
\n level += 1
\n delegate?.gameDidLevelUp(self)
\n }<\/p>\n

return (externalRemovedBlocks, externalFallenBlocks)
\n }
\n[\/sourcecode]<\/p>\n

As you can see, the original Gravity is a lot simpler and makes the game harder & more fun. Also, note that ‘removeFullLines()’ has unnecessary complexity on its return values (Array of Arrays instead of simple Arrays) – we’ll fix that later.
\nAnd there’s a little problem with simply replacing ‘removeCompletedLines()’ by ‘removeFullLines()’; removeFullLines returns all fallen blocks in the same\/first subarray of fallenBlocks; where the original one would return on subarray for each column. This causes a problem since the blockIdx within each of the subarrays is used to time a animation on the GameScene side so everything will work fine but the game will lock for a few seconds every time you fill a line (linear to the full amount of blocks falling), I plan to provide a way better fix for this later but for now this solves the immediate problem:<\/p>\n

[sourcecode language=”javascript” title=”GameScene.swift before”]
\n\/\/ …
\n func collapsingLines(linesToRemove: Array<Array<Block>>, fallenBlocks: Array<Array<Block>>, completion:() -> ()) {
\n \/\/ …
\n \/\/ …
\n let delay = (NSTimeInterval(columnIdx) * 0.05) + (NSTimeInterval(blockIdx) * 0.05)
\n \/\/\/ …
\n}
\n[\/sourcecode]<\/p>\n

To this:
\n[sourcecode language=”javascript” title=”GameScene.swift after”]
\n\/\/ …
\n func collapsingLines(linesToRemove: Array<Array<Block>>, fallenBlocks: Array<Array<Block>>, completion:() -> ()) {
\n \/\/ …
\n \/\/ …
\n let delay = (NSTimeInterval(columnIdx) * 0.05) + (NSTimeInterval(1) * 0.05)
\n \/\/\/ …
\n}
\n[\/sourcecode]<\/p>\n

Now the game works as it should but the architecture of it is still a mess and all my fixes are basically hacks inside it. For my next post I’ll try to redesign\/cleanup.. let’s hope for the best.<\/p>\n","protected":false},"excerpt":{"rendered":"

As I mentioned on my previous post, Swiftris’ gravity is different than the http:\/\/en.wikipedia.org\/wiki\/Tetris#Gravity and that annoys anyone who played Tetris enough. On the original Switris source, the gravity\/collapsing behavior is implemented in ‘removeCompletedLines()’ which is called (weirdly) from within GameViewController’s implementation of the ‘gameShapeDidLand()’. Let’s start by just reimplementing removeCompletedLines() without changing its interface. […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,22,24],"tags":[],"class_list":["post-116","post","type-post","status-publish","format-standard","hentry","category-ios","category-swift","category-swiftris"],"_links":{"self":[{"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/116","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=116"}],"version-history":[{"count":4,"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/116\/revisions"}],"predecessor-version":[{"id":120,"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/116\/revisions\/120"}],"wp:attachment":[{"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=116"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=116"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/cpscotti.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=116"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}