help with polygon collision - GameCreators Forum

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Phaelax

DBPro Master

23

Years of Service

User Offline

Joined: 16th Apr 2003

Location: Metropia

Posted: 3rd Jun 2011 22:31 Edited at: 3rd Jun 2011 22:31

Link

I'm working based on this: http://pogopixels.com/blog/2d-polygon-collision-detection/

I've gone of the code 3 times and can't find anything wrong, yet whenever the two shapes get close to intersecting, the shape controlled by the user jumps way off course. For some reason, the value of 'minIntervalDistance#' is way larger than it should be.

The website linked above provides C# code, which I compiled and the example works fine. If anyone has time to comb through this I'd appreciate a push in the right direction.

randomize timer()

n# = (2.0-2.0^-23)*2.0^127
#CONSTANT POSITIVE_INFINITY = n#

Type Vector2D
	x as float
	y as float
EndType

Type PolygonCollisionResult
	willIntersect as boolean
	intersect as boolean
	minimumTranslationVector as Vector2D
EndType

dim polygonA(6) as Vector2D
dim polygonB(7) as Vector2D

local result as PolygonCollisionResult

local v1 : v1 = make vector2(1)
local axis : axis = make vector2(2)
local translationAxis : translationAxis = make vector2(3)
local velocity : velocity = make vector2(4)
local d : d = make vector2(5)

makeRandomPolygonA(100)
makeRandomPolygonB(100)

p1x = 400
p1y = 300

p2x = 200
p2y = 200

sync on
sync rate 60

do
	cls
	
	rem controls
	vx = 0
	vy = 0
	if upkey() and flag=0 then vy = -3
	if downkey() and flag=0 then vy = 3
	if rightkey() and flag=0 then vx = 3
	if leftkey() and flag=0 then vx = -3
	
	
	mx = mousex()
	my = mousey()
	
	`ink rgb(255,255,255),0
	`line 200, 200, mx, my
	`ink rgb(255,0,0),0
	`line 200, 200, 200+(my-200), 200-(mx-200)
	
	
	ink rgb(255,255,255),0
	drawPolygonB(p2x, p2y)

rem collision 
	result.intersect = 1
	result.willIntersect = 1
	
	local edgeCountA : edgeCountA = array count(polygonA())
	local edgeCountB : edgeCountB = array count(polygonB())
	local minIntervalDistance# = POSITIVE_INFINITY
	local edge as Vector2D
	
	REM loop through all the edges of both polygons
	for i = 1 to edgeCountA+edgeCountB
		if i <= edgeCountA
			p2 = i+1
			if p2 > edgeCountA then p2 = 1
			edge.x = polygonA(p2).x - polygonA(i).x
			edge.y = polygonA(p2).y - polygonA(i).y
		else
			p2 = i+1
			if p2 > edgeCountB then p2 = edgeCountA+1
			edge.x = polygonB(p2).x - polygonB(i - edgeCountA).x
			edge.y = polygonB(p2).y - polygonB(i - edgeCountA).y
		endif
		
		
		
		REM ==== Step 1. Find if the polygons are currently intersecting ====
		
		REM Find the axis perpendicular to the current edge
		set vector2 axis, -edge.y, edge.x
		normalize vector2 axis, axis
		
	
		`ink rgb(255,0,0),0
		`x = p1x+polygonA(i).x
		`y = p1y+polygonA(i).y
		`line x, y, x+x vector2(axis)*40, y+y vector2(axis)*40
		
		
		
		REM Find the projection of the polygon on the current axis
		local minA# = 0 : local minB# = 0 : local maxA# = 0 : local maxB# = 0
		
		REM Polygon A
		set vector2 v1, p1x+polygonA(1).x, p1y+polygonA(1).y
		local dotProduct# : dotProduct# = dot product vector2(axis, v1)
		minA# = dotProduct#
		maxA# = dotProduct#
		
		for j = 1 to edgeCountA
			set vector2 v1, p1x+polygonA(j).x, p1y+polygonA(j).y
			dotProduct# = dot product vector2(v1, axis)
			if dotProduct# < minA#
				minA# = dotProduct#
			else
				if dotProduct# > maxA# then maxA# = dotProduct#
			endif
		next j
		REM Polygon B
		set vector2 v1, p2x+polygonB(1).x, p2y+polygonB(1).y
		local dotProduct# : dotProduct# = dot product vector2(axis, v1)
		minB# = dotProduct#
		maxB# = dotProduct#
		for j = 1 to edgeCountB
			set vector2 v1, p2x+polygonB(j).x, p2y+polygonB(j).y
			dotProduct# = dot product vector2(v1, axis)
			if dotProduct# < minB#
				minB# = dotProduct#
			else
				if dotProduct# > maxB# then maxB# = dotProduct#
			endif
		next j
		
		REM Check if the polygon projections are currently intersecting
		if intervalDistance(minA#, maxA#, minB#, maxB#) > 0 then result.intersect = 0
		
		REM ==== Step 2. Find if the polygons will intersect ====
		
		REM Project the velocity
		set vector2 velocity, vx, vy 
		local velocityProjection# : velocityProjection# = dot product vector2(axis, velocity)
		
		REM Get the projection of polygon A during the movement
		if velocityProjection# < 0
			inc minA#, velocityProjection#
		else
			inc maxA#, velocityProjection#
		endif
		
		REM Do same test as above for new projection
		intervalDistance# = intervalDistance(minA#, maxA#, minB#, maxB#)
		if intervalDistance# > 0 then result.willIntersect = 0
		
		REM If the polygons are not intersecting and won't intersect, exit the loop
		if result.intersect = 0 and result.willIntersect = 0 then exit
		
		REM Check if the current interval distance is the minimum one. 
		REM If so store the interval distance and the current distance.
		REM This will be used to calculate the minimum translation vector
		intervalDistance# = abs(intervalDistance#)
		if intervalDistance# < minIntervalDistance#
			minIntervalDistance# = intervalDistance#
			set vector2 translationAxis, x vector2(axis), y vector2(axis)
			
			set vector2 d, p1x-p2x, p1y-p2y
			if dot product vector2(d, translationAxis) < 0
				set vector2 translationAxis, x vector2(axis)*-1, y vector2(axis)*-1
			endif
		endif
		
		REM The minimum translation vector can be used to push the polygons apart.
		if result.willIntersect = 1
			result.minimumTranslationVector.x = x vector2(translationAxis)*minIntervalDistance#
			result.minimumTranslationVector.y = y vector2(translationAxis)*minIntervalDistance#
		endif
	next i
	
	
	
		
	if result.willIntersect
		vx = vx + result.minimumTranslationVector.x
		vy = vy + result.minimumTranslationVector.y
	endif
	
	
	p1x = p1x + vx
	p1y = p1y + vy
	
	
	ink rgb(255,255,255),0
	rem draw the two polygon shapes
	drawPolygonA(p1x, p1y)

print mousex()
	print mousey()
	
	sync
loop

function intervalDistance(minA as float, maxA as float, minB as float, maxB as float)
	if minA < minB
		n# = minB - maxA
		exitfunction n#
	endif
	n# = minA - maxB
endfunction n#

function makeRandomPolygonA(radius)
	a# = 360/6.0
	r2 = radius/2
	for i = 1 to 6
		polygonA(i).x = sin(a#*i)*(rnd(r2)+r2)
		polygonA(i).y = cos(a#*i)*(rnd(r2)+r2)
	next i
endfunction

function drawPolygonA(x, y)
	for i = 1 to 6
		x1 = x + polygonA(i).x
		y1 = y + polygonA(i).y
		if i < 6
			x2 = x + polygonA(i+1).x
			y2 = y + polygonA(i+1).y
		else
			x2 = x + polygonA(1).x
			y2 = y + polygonA(1).y
		endif
		line x1, y1, x2, y2
	next i
endfunction

function makeRandomPolygonB(radius)
	a# = 360/7.0
	r2 = radius/2
	for i = 1 to 7
		polygonB(i).x = sin(a#*i)*(rnd(r2)+r2)
		polygonB(i).y = cos(a#*i)*(rnd(r2)+r2)
	next i
endfunction

function drawPolygonB(x, y)
	for i = 1 to 7
		x1 = x + polygonB(i).x
		y1 = y + polygonB(i).y
		if i < 7
			x2 = x + polygonB(i+1).x
			y2 = y + polygonB(i+1).y
		else
			x2 = x + polygonB(1).x
			y2 = y + polygonB(1).y
		endif
		line x1, y1, x2, y2
	next i
endfunction

+ Code Snippet

randomize timer()


n# = (2.0-2.0^-23)*2.0^127
#CONSTANT POSITIVE_INFINITY = n#

Type Vector2D
	x as float
	y as float
EndType

Type PolygonCollisionResult
	willIntersect as boolean
	intersect as boolean
	minimumTranslationVector as Vector2D
EndType


dim polygonA(6) as Vector2D
dim polygonB(7) as Vector2D

local result as PolygonCollisionResult

local v1 : v1 = make vector2(1)
local axis : axis = make vector2(2)
local translationAxis : translationAxis = make vector2(3)
local velocity : velocity = make vector2(4)
local d : d = make vector2(5)

makeRandomPolygonA(100)
makeRandomPolygonB(100)

p1x = 400
p1y = 300

p2x = 200
p2y = 200

sync on
sync rate 60

do
	cls
	
	rem controls
	vx = 0
	vy = 0
	if upkey() and flag=0 then vy = -3
	if downkey() and flag=0 then vy = 3
	if rightkey() and flag=0 then vx = 3
	if leftkey() and flag=0 then vx = -3
	
	
	mx = mousex()
	my = mousey()
	
	`ink rgb(255,255,255),0
	`line 200, 200, mx, my
	`ink rgb(255,0,0),0
	`line 200, 200, 200+(my-200), 200-(mx-200)
	
	
	ink rgb(255,255,255),0
	drawPolygonB(p2x, p2y)
	

	
	rem collision 
	result.intersect = 1
	result.willIntersect = 1
	
	local edgeCountA : edgeCountA = array count(polygonA())
	local edgeCountB : edgeCountB = array count(polygonB())
	local minIntervalDistance# = POSITIVE_INFINITY
	local edge as Vector2D
	
	REM loop through all the edges of both polygons
	for i = 1 to edgeCountA+edgeCountB
		if i <= edgeCountA
			p2 = i+1
			if p2 > edgeCountA then p2 = 1
			edge.x = polygonA(p2).x - polygonA(i).x
			edge.y = polygonA(p2).y - polygonA(i).y
		else
			p2 = i+1
			if p2 > edgeCountB then p2 = edgeCountA+1
			edge.x = polygonB(p2).x - polygonB(i - edgeCountA).x
			edge.y = polygonB(p2).y - polygonB(i - edgeCountA).y
		endif
		
		
		
		REM ==== Step 1. Find if the polygons are currently intersecting ====
		
		REM Find the axis perpendicular to the current edge
		set vector2 axis, -edge.y, edge.x
		normalize vector2 axis, axis
		
	
		`ink rgb(255,0,0),0
		`x = p1x+polygonA(i).x
		`y = p1y+polygonA(i).y
		`line x, y, x+x vector2(axis)*40, y+y vector2(axis)*40
		
		
		
		REM Find the projection of the polygon on the current axis
		local minA# = 0 : local minB# = 0 : local maxA# = 0 : local maxB# = 0
		
		REM Polygon A
		set vector2 v1, p1x+polygonA(1).x, p1y+polygonA(1).y
		local dotProduct# : dotProduct# = dot product vector2(axis, v1)
		minA# = dotProduct#
		maxA# = dotProduct#
		
		for j = 1 to edgeCountA
			set vector2 v1, p1x+polygonA(j).x, p1y+polygonA(j).y
			dotProduct# = dot product vector2(v1, axis)
			if dotProduct# < minA#
				minA# = dotProduct#
			else
				if dotProduct# > maxA# then maxA# = dotProduct#
			endif
		next j
		REM Polygon B
		set vector2 v1, p2x+polygonB(1).x, p2y+polygonB(1).y
		local dotProduct# : dotProduct# = dot product vector2(axis, v1)
		minB# = dotProduct#
		maxB# = dotProduct#
		for j = 1 to edgeCountB
			set vector2 v1, p2x+polygonB(j).x, p2y+polygonB(j).y
			dotProduct# = dot product vector2(v1, axis)
			if dotProduct# < minB#
				minB# = dotProduct#
			else
				if dotProduct# > maxB# then maxB# = dotProduct#
			endif
		next j
		
		REM Check if the polygon projections are currently intersecting
		if intervalDistance(minA#, maxA#, minB#, maxB#) > 0 then result.intersect = 0
		
		REM ==== Step 2. Find if the polygons will intersect ====
		
		REM Project the velocity
		set vector2 velocity, vx, vy 
		local velocityProjection# : velocityProjection# = dot product vector2(axis, velocity)
		
		REM Get the projection of polygon A during the movement
		if velocityProjection# < 0
			inc minA#, velocityProjection#
		else
			inc maxA#, velocityProjection#
		endif
		
		REM Do same test as above for new projection
		intervalDistance# = intervalDistance(minA#, maxA#, minB#, maxB#)
		if intervalDistance# > 0 then result.willIntersect = 0
		
		REM If the polygons are not intersecting and won't intersect, exit the loop
		if result.intersect = 0 and result.willIntersect = 0 then exit
		
		REM Check if the current interval distance is the minimum one. 
		REM If so store the interval distance and the current distance.
		REM This will be used to calculate the minimum translation vector
		intervalDistance# = abs(intervalDistance#)
		if intervalDistance# < minIntervalDistance#
			minIntervalDistance# = intervalDistance#
			set vector2 translationAxis, x vector2(axis), y vector2(axis)
			
			set vector2 d, p1x-p2x, p1y-p2y
			if dot product vector2(d, translationAxis) < 0
				set vector2 translationAxis, x vector2(axis)*-1, y vector2(axis)*-1
			endif
		endif
		
		REM The minimum translation vector can be used to push the polygons apart.
		if result.willIntersect = 1
			result.minimumTranslationVector.x = x vector2(translationAxis)*minIntervalDistance#
			result.minimumTranslationVector.y = y vector2(translationAxis)*minIntervalDistance#
		endif
	next i
	
	
	
		
	if result.willIntersect
		vx = vx + result.minimumTranslationVector.x
		vy = vy + result.minimumTranslationVector.y
	endif
	
	
	p1x = p1x + vx
	p1y = p1y + vy
	
	
	ink rgb(255,255,255),0
	rem draw the two polygon shapes
	drawPolygonA(p1x, p1y)


	print mousex()
	print mousey()
	
	sync
loop



function intervalDistance(minA as float, maxA as float, minB as float, maxB as float)
	if minA < minB
		n# = minB - maxA
		exitfunction n#
	endif
	n# = minA - maxB
endfunction n#




function makeRandomPolygonA(radius)
	a# = 360/6.0
	r2 = radius/2
	for i = 1 to 6
		polygonA(i).x = sin(a#*i)*(rnd(r2)+r2)
		polygonA(i).y = cos(a#*i)*(rnd(r2)+r2)
	next i
endfunction


function drawPolygonA(x, y)
	for i = 1 to 6
		x1 = x + polygonA(i).x
		y1 = y + polygonA(i).y
		if i < 6
			x2 = x + polygonA(i+1).x
			y2 = y + polygonA(i+1).y
		else
			x2 = x + polygonA(1).x
			y2 = y + polygonA(1).y
		endif
		line x1, y1, x2, y2
	next i
endfunction


function makeRandomPolygonB(radius)
	a# = 360/7.0
	r2 = radius/2
	for i = 1 to 7
		polygonB(i).x = sin(a#*i)*(rnd(r2)+r2)
		polygonB(i).y = cos(a#*i)*(rnd(r2)+r2)
	next i
endfunction


function drawPolygonB(x, y)
	for i = 1 to 7
		x1 = x + polygonB(i).x
		y1 = y + polygonB(i).y
		if i < 7
			x2 = x + polygonB(i+1).x
			y2 = y + polygonB(i+1).y
		else
			x2 = x + polygonB(1).x
			y2 = y + polygonB(1).y
		endif
		line x1, y1, x2, y2
	next i
endfunction

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Profile PM Email Website

Sven B

21

Years of Service

User Offline

Joined: 5th Jan 2005

Location: Belgium

Posted: 3rd Jun 2011 23:02

Link

Hi Phaelax,

I don't know if this matters, but the collision detection doesn't work as well:

randomize timer()

n# = (2.0-2.0^-23)*2.0^127
#CONSTANT POSITIVE_INFINITY = n#

Type Vector2D
        x as float
        y as float
EndType

Type PolygonCollisionResult
        willIntersect as boolean
        intersect as boolean
        minimumTranslationVector as Vector2D
EndType

dim polygonA(6) as Vector2D
dim polygonB(7) as Vector2D

local result as PolygonCollisionResult

local v1 : v1 = make vector2(1)
local axis : axis = make vector2(2)
local translationAxis : translationAxis = make vector2(3)
local velocity : velocity = make vector2(4)
local d : d = make vector2(5)

makeRandomPolygonA(100)
makeRandomPolygonB(100)

p1x = 400
p1y = 300

p2x = 200
p2y = 200

sync on
sync rate 60

do
        cls
        
        rem controls
        vx = 0
        vy = 0
        if upkey() and flag=0 then vy = -3
        if downkey() and flag=0 then vy = 3
        if rightkey() and flag=0 then vx = 3
        if leftkey() and flag=0 then vx = -3
        
        
        mx = mousex()
        my = mousey()
        
        `ink rgb(255,255,255),0
        `line 200, 200, mx, my
        `ink rgb(255,0,0),0
        `line 200, 200, 200+(my-200), 200-(mx-200)
        
        
        ink rgb(255,255,255),0
        drawPolygonB(p2x, p2y)

rem collision 
        result.intersect = 1
        result.willIntersect = 0
        
        local edgeCountA : edgeCountA = array count(polygonA())
        local edgeCountB : edgeCountB = array count(polygonB())
        local minIntervalDistance# = POSITIVE_INFINITY
        local edge as Vector2D
        
        REM loop through all the edges of both polygons
        for i = 1 to edgeCountA+edgeCountB
                if i <= edgeCountA
                        p2 = i+1
                        if p2 > edgeCountA then p2 = 1
                        edge.x = polygonA(p2).x - polygonA(i).x
                        edge.y = polygonA(p2).y - polygonA(i).y
                else
                        p2 = i+1
                        if p2 > edgeCountB then p2 = edgeCountA+1
                        edge.x = polygonB(p2).x - polygonB(i - edgeCountA).x
                        edge.y = polygonB(p2).y - polygonB(i - edgeCountA).y
                endif
                
                
                
                REM ==== Step 1. Find if the polygons are currently intersecting ====
                
                REM Find the axis perpendicular to the current edge
                set vector2 axis, -edge.y, edge.x
                normalize vector2 axis, axis
                
                REM Find the projection of the polygon on the current axis
                local minA# = 0 : local minB# = 0 : local maxA# = 0 : local maxB# = 0
                
                REM Polygon A
                set vector2 v1, p1x+polygonA(1).x, p1y+polygonA(1).y
                local dotProduct# : dotProduct# = dot product vector2(axis, v1)
                minA# = dotProduct#
                maxA# = dotProduct#
                
                for j = 1 to edgeCountA
                        set vector2 v1, p1x+polygonA(j).x, p1y+polygonA(j).y
                        dotProduct# = dot product vector2(v1, axis)
                        if dotProduct# < minA#
                                minA# = dotProduct#
                        else
                                if dotProduct# > maxA# then maxA# = dotProduct#
                        endif
                next j
                REM Polygon B
                set vector2 v1, p2x+polygonB(1).x, p2y+polygonB(1).y
                local dotProduct# : dotProduct# = dot product vector2(axis, v1)
                minB# = dotProduct#
                maxB# = dotProduct#
                for j = 1 to edgeCountB
                        set vector2 v1, p2x+polygonB(j).x, p2y+polygonB(j).y
                        dotProduct# = dot product vector2(v1, axis)
                        if dotProduct# < minB#
                                minB# = dotProduct#
                        else
                                if dotProduct# > maxB# then maxB# = dotProduct#
                        endif
                next j
                
                REM Check if the polygon projections are currently intersecting
                if intervalDistance(minA#, maxA#, minB#, maxB#) > 0 then result.intersect = 0
        next i
        
        
        
                
        if result.willIntersect
                vx = vx + result.minimumTranslationVector.x
                vy = vy + result.minimumTranslationVector.y
        endif
        
        
        p1x = p1x + vx
        p1y = p1y + vy
        
        
        ink rgb(255,255,255),0
        rem draw the two polygon shapes
        drawPolygonA(p1x, p1y)

print mousex()
        print mousey()
        print result.intersect
        
        sync
loop

function intervalDistance(minA as float, maxA as float, minB as float, maxB as float)
        if minA < minB
                n# = minB - maxA
                exitfunction n#
        endif
        n# = minA - maxB
endfunction n#

function makeRandomPolygonA(radius)
        a# = 360/6.0
        r2 = radius/2
        for i = 1 to 6
                polygonA(i).x = sin(a#*i)*(rnd(r2)+r2)
                polygonA(i).y = cos(a#*i)*(rnd(r2)+r2)
        next i
endfunction

function drawPolygonA(x, y)
        for i = 1 to 6
                x1 = x + polygonA(i).x
                y1 = y + polygonA(i).y
                if i < 6
                        x2 = x + polygonA(i+1).x
                        y2 = y + polygonA(i+1).y
                else
                        x2 = x + polygonA(1).x
                        y2 = y + polygonA(1).y
                endif
                line x1, y1, x2, y2
        next i
endfunction

function makeRandomPolygonB(radius)
        a# = 360/7.0
        r2 = radius/2
        for i = 1 to 7
                polygonB(i).x = sin(a#*i)*(rnd(r2)+r2)
                polygonB(i).y = cos(a#*i)*(rnd(r2)+r2)
        next i
endfunction

function drawPolygonB(x, y)
        for i = 1 to 7
                x1 = x + polygonB(i).x
                y1 = y + polygonB(i).y
                if i < 7
                        x2 = x + polygonB(i+1).x
                        y2 = y + polygonB(i+1).y
                else
                        x2 = x + polygonB(1).x
                        y2 = y + polygonB(1).y
                endif
                line x1, y1, x2, y2
        next i
endfunction

+ Code Snippet

randomize timer()


n# = (2.0-2.0^-23)*2.0^127
#CONSTANT POSITIVE_INFINITY = n#

Type Vector2D
        x as float
        y as float
EndType

Type PolygonCollisionResult
        willIntersect as boolean
        intersect as boolean
        minimumTranslationVector as Vector2D
EndType


dim polygonA(6) as Vector2D
dim polygonB(7) as Vector2D

local result as PolygonCollisionResult

local v1 : v1 = make vector2(1)
local axis : axis = make vector2(2)
local translationAxis : translationAxis = make vector2(3)
local velocity : velocity = make vector2(4)
local d : d = make vector2(5)

makeRandomPolygonA(100)
makeRandomPolygonB(100)

p1x = 400
p1y = 300

p2x = 200
p2y = 200

sync on
sync rate 60

do
        cls
        
        rem controls
        vx = 0
        vy = 0
        if upkey() and flag=0 then vy = -3
        if downkey() and flag=0 then vy = 3
        if rightkey() and flag=0 then vx = 3
        if leftkey() and flag=0 then vx = -3
        
        
        mx = mousex()
        my = mousey()
        
        `ink rgb(255,255,255),0
        `line 200, 200, mx, my
        `ink rgb(255,0,0),0
        `line 200, 200, 200+(my-200), 200-(mx-200)
        
        
        ink rgb(255,255,255),0
        drawPolygonB(p2x, p2y)
        

        
        rem collision 
        result.intersect = 1
        result.willIntersect = 0
        
        local edgeCountA : edgeCountA = array count(polygonA())
        local edgeCountB : edgeCountB = array count(polygonB())
        local minIntervalDistance# = POSITIVE_INFINITY
        local edge as Vector2D
        
        REM loop through all the edges of both polygons
        for i = 1 to edgeCountA+edgeCountB
                if i <= edgeCountA
                        p2 = i+1
                        if p2 > edgeCountA then p2 = 1
                        edge.x = polygonA(p2).x - polygonA(i).x
                        edge.y = polygonA(p2).y - polygonA(i).y
                else
                        p2 = i+1
                        if p2 > edgeCountB then p2 = edgeCountA+1
                        edge.x = polygonB(p2).x - polygonB(i - edgeCountA).x
                        edge.y = polygonB(p2).y - polygonB(i - edgeCountA).y
                endif
                
                
                
                REM ==== Step 1. Find if the polygons are currently intersecting ====
                
                REM Find the axis perpendicular to the current edge
                set vector2 axis, -edge.y, edge.x
                normalize vector2 axis, axis
                
                REM Find the projection of the polygon on the current axis
                local minA# = 0 : local minB# = 0 : local maxA# = 0 : local maxB# = 0
                
                REM Polygon A
                set vector2 v1, p1x+polygonA(1).x, p1y+polygonA(1).y
                local dotProduct# : dotProduct# = dot product vector2(axis, v1)
                minA# = dotProduct#
                maxA# = dotProduct#
                
                for j = 1 to edgeCountA
                        set vector2 v1, p1x+polygonA(j).x, p1y+polygonA(j).y
                        dotProduct# = dot product vector2(v1, axis)
                        if dotProduct# < minA#
                                minA# = dotProduct#
                        else
                                if dotProduct# > maxA# then maxA# = dotProduct#
                        endif
                next j
                REM Polygon B
                set vector2 v1, p2x+polygonB(1).x, p2y+polygonB(1).y
                local dotProduct# : dotProduct# = dot product vector2(axis, v1)
                minB# = dotProduct#
                maxB# = dotProduct#
                for j = 1 to edgeCountB
                        set vector2 v1, p2x+polygonB(j).x, p2y+polygonB(j).y
                        dotProduct# = dot product vector2(v1, axis)
                        if dotProduct# < minB#
                                minB# = dotProduct#
                        else
                                if dotProduct# > maxB# then maxB# = dotProduct#
                        endif
                next j
                
                REM Check if the polygon projections are currently intersecting
                if intervalDistance(minA#, maxA#, minB#, maxB#) > 0 then result.intersect = 0
        next i
        
        
        
                
        if result.willIntersect
                vx = vx + result.minimumTranslationVector.x
                vy = vy + result.minimumTranslationVector.y
        endif
        
        
        p1x = p1x + vx
        p1y = p1y + vy
        
        
        ink rgb(255,255,255),0
        rem draw the two polygon shapes
        drawPolygonA(p1x, p1y)


        print mousex()
        print mousey()
        print result.intersect
        
        sync
loop



function intervalDistance(minA as float, maxA as float, minB as float, maxB as float)
        if minA < minB
                n# = minB - maxA
                exitfunction n#
        endif
        n# = minA - maxB
endfunction n#




function makeRandomPolygonA(radius)
        a# = 360/6.0
        r2 = radius/2
        for i = 1 to 6
                polygonA(i).x = sin(a#*i)*(rnd(r2)+r2)
                polygonA(i).y = cos(a#*i)*(rnd(r2)+r2)
        next i
endfunction


function drawPolygonA(x, y)
        for i = 1 to 6
                x1 = x + polygonA(i).x
                y1 = y + polygonA(i).y
                if i < 6
                        x2 = x + polygonA(i+1).x
                        y2 = y + polygonA(i+1).y
                else
                        x2 = x + polygonA(1).x
                        y2 = y + polygonA(1).y
                endif
                line x1, y1, x2, y2
        next i
endfunction


function makeRandomPolygonB(radius)
        a# = 360/7.0
        r2 = radius/2
        for i = 1 to 7
                polygonB(i).x = sin(a#*i)*(rnd(r2)+r2)
                polygonB(i).y = cos(a#*i)*(rnd(r2)+r2)
        next i
endfunction


function drawPolygonB(x, y)
        for i = 1 to 7
                x1 = x + polygonB(i).x
                y1 = y + polygonB(i).y
                if i < 7
                        x2 = x + polygonB(i+1).x
                        y2 = y + polygonB(i+1).y
                else
                        x2 = x + polygonB(1).x
                        y2 = y + polygonB(1).y
                endif
                line x1, y1, x2, y2
        next i
endfunction

Unless I changed something wrong there. I removed the second part of the for loop, and added a line with the print statements.

Sven B

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tiresius

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Joined: 13th Nov 2002

Location: MA USA

Posted: 4th Jun 2011 03:19 Edited at: 4th Jun 2011 03:19

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Is it okay to declare locals within a loop like that? I've never seen that done.

+ Code Snippet

local edgeCountA : edgeCountA = array count(polygonA())
local edgeCountB : edgeCountB = array count(polygonB())
local minIntervalDistance# = POSITIVE_INFINITY
local edge as Vector2D

And is the array count() off because of silly DBPro arrays which go 0..(X) instead of 0..(X-1) ? Sorry I can't run the code right now, but I find this interesting.

A 3D marble platformer using Newton physics.

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Phaelax

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Location: Metropia

Posted: 5th Jun 2011 02:47

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The array count actually goes from 1 to X, but you can use the 0 index if you want.

If it was just an array issue, most likely some edges wouldn't be checked for the collision, but that's not the case.

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Neuro Fuzzy

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Posted: 5th Jun 2011 10:36 Edited at: 5th Jun 2011 10:37

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Heheh, I might be mistaken, but doesn't "make vector2(n)" return 0 all the time? It for sure doesn't create a unique handle. I don't know if vector2(0) is a valid vector, but if it is, this is likely the problem.

So I think when you say:
v1 = make vector2(1)

you want to say:
arbitrarynum = make vector2(1)
v1=1

[edit]

yup. Unless it was updated:

Quote: "You may well have spotted that the make vector commands all return an integer but rest assured this does not fulfil the function of a vector exist() command. I've experimented at length with this integer but it never returns anything but a 1. I am, in fact, totally baffled as to the purpose of this integer!"

http://www.neurofuzzydev.com/V/D/22a.htm

Tell me if there's a broken link to images in a thread I post, and I'll fix 'em.

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Phaelax

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Posted: 5th Jun 2011 10:55 Edited at: 5th Jun 2011 10:55

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Quote: "Heheh, I might be mistaken, but doesn't "make vector2(n)" return 0 all the time? "

Umm, you know what, you might be right! Doh!

I feel dumb, it's been so long since i used the vector commands. I'll update my code and see what happens.

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Sven B

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Posted: 5th Jun 2011 11:06

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Quote: "yup. Unless it was updated:"

You have access to the source code if you're in doubt. The vector creation commands is eg for Vector2:

+ Code Snippet

DARKSDK SDK_BOOL MakeVector2 ( int iID )
{
    if (iID < 1 || iID > MAXIMUMVALUE)
    {
        RunTimeError ( RUNTIMEERROR_VECTORNUMBERILLEGAL );
        return false;
    }

    m_DataManager.Add( new Vector2, iID );
    return true;
}

In other words, it will only return a 0 if the vector number is illegal. This is quite useless, since DBP will return an error and stop in that case...

Cheers!
Sven B

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DarkBASIC Professional Discussion / help with polygon collision