[bb] Homing physics ( 2D ) by Jeppe Nielsen [ 1+ years ago ]

[BlitzBot]

Title : Homing physics ( 2D )
Author : Jeppe Nielsen
Posted : 1+ years ago

Description : Allow enemies to chase player, with velocity and acceleration.

Code :

Code: BlitzBasic

1. ;Homing example, by Jeppe Nielsen 2003
2.  
3. Global playerx#
4. Global playery#
5. Global distance#=100
6.  
7. Type enemy
8.  
9. Field x#,y#
10. Field vx#,vy#
11. Field ax#,ay#
12.  
13. Field vmax#
14. Field amax#
15.  
16. End Type
17.  
18. Graphics3D 800,600,16,2
19.  
20. ;create ten enemies at random locations
21. For n=1 To 10                          
22. ;play with last number
23. ;enemynew(x,y,vmax,amax)
24. enemynew(Rnd(800),Rnd(600),Rnd(0.5,4.5),Rnd(0.08,0.1))
25. Next
26.  
27.  
28. Repeat
29. Cls
30.  
31. Text 10,10,"Move player with mouse"
32. Text 10,30,"LMB - Resize allowed distance to player"
33. Text 10,50,"RMB - Add enemies"
34.  
35. If click=0
36.        
37.         playerx=MouseX()
38.         playery=MouseY()
39.        
40. EndIf
41.  
42. If MouseDown(1) And click=0
43.        
44.         click=1
45.         clickx=MouseX()
46.         clicky=MouseY()
47.        
48. EndIf
49.  
50. If MouseDown(1) And click=1
51.        
52.         dx=(MouseX()-clickx)
53.         dy=(MouseY()-clicky)
54.        
55.         distance#=Sqr(dx*dx+dy*dy)
56.                
57. EndIf
58.  
59. If MouseDown(1)=False And click=1
60.         click=0
61. EndIf
62.  
63. If MouseDown(2)>0
64.         enemynew(Rnd(800),Rnd(600),Rnd(2.5,2.5),Rnd(0.08,0.1))
65. EndIf
66.  
67.  
68. enemyupdate()
69. enemydraw()
70.  
71.  
72. Rect playerx-5,playery-5,10,10,0
73.  
74. Oval playerx-distance#,playery-distance#,distance#*2,distance#*2,0
75.  
76. Flip
77.  
78.  
79. Until KeyDown(1)
80. End
81.  
82. Function enemynew.enemy(x,y,vmax#,amax#)
83.  
84. e.enemy=New enemy
85.  
86. ex#=x
87. ey#=y
88.  
89. evmax#=vmax#
90. eamax#=amax#
91.  
92. Return e
93.  
94. End Function
95.  
96. Function enemyupdate()
97.  
98. For e.enemy=Each enemy
99.  
100. dx#=(playerx-ex)
101. dy#=(playery-ey)
102.  
103. l#=Sqr(dx#*dx#+dy#*dy#)
104.  
105. dx#=(dx#/l#)*eamax#
106. dy#=(dy#/l#)*eamax#
107.  
108. ;if close enough escape target
109. If l#<=distance#
110. dx#=-dx#
111. dy#=-dy#
112. EndIf
113.  
114. ;check against all other enemies, to avoid them
115. dxx#=0
116. dyy#=0
117. co=0
118. For ee.enemy=Each enemy
119.        
120.         If ee<>e
121.                
122.                 dex#=(ex-eex)
123.                 dey#=(ey-eey)
124.                
125.                 l#=Sqr(dex#*dex#+dey#*dey#)
126.                
127.                 dxx#=dxx#+(dex#/l#)*eamax#
128.                 dyy#=dyy#+(dey#/l#)*eamax#
129.                
130.                 co=co+1
131.         EndIf
132. Next
133.  
134. dxx#=dxx#/Float(co)
135. dyy#=dyy#/Float(co)
136.  
137. dx#=(dx#+dxx#)/2
138. dy#=(dy#+dyy#)/2
139.  
140. eax#=eax#+dx#
141. eay#=eay#+dy#
142.  
143. acc#=Sqr(eax#*eax#+eay#*eay#)
144.  
145. ;Check if current acceleration is more than allowed
146. If acc#>eamax#
147.        
148.         eax#=(eax#/acc#)*eamax
149.         eay#=(eay#/acc#)*eamax
150.        
151. EndIf
152.  
153. evx#=evx#+eax#
154. evy#=evy#+eay#
155.  
156. vel#=Sqr(evx#*evx#+evy#*evy#)
157.  
158. ;Check if current velocity is more than allowed
159. If vel#>evmax#
160.         evx#=(evx#/vel#)*evmax
161.         evy#=(evy#/vel#)*evmax
162. EndIf
163.  
164. ; add velocity to position
165. ex#=ex#+evx#
166. ey#=ey#+evy#
167.  
168. Next
169. End Function
170.  
171. Function enemydraw()
172. For e.enemy=Each enemy
173.         Rect ex-3,ey-3,6,6,0
174. Next
175. End Function

Comments :


TWH(Posted 1+ years ago)

 

Code: [Select]

'Blitzmax:
Strict
'Homing example, by Jeppe Nielsen 2003
'mouse position:
Global playerx#
Global playery#
Global distance#=100
Global enemylist:TList = CreateList()

Type enemy
Field x#,y#
Field vx#,vy#
Field ax#,ay#
Field vmax#
Field amax#

Function enemynew:enemy(x,y,vmax#,amax#)
Local e:enemy=New enemy
enemylist.addlast(e)
e.x#=x
e.y#=y
e.vmax#=vmax#
e.amax#=amax#
Return e
End Function

Function enemydraw()
For Local e:enemy=EachIn enemylist
SetColor 0,0,255
DrawRect e.x-3,e.y-3,6,6
Next
End Function

Function enemyupdate()
For Local e:enemy=EachIn enemylist

Local dx#=(playerx-e.x)
Local dy#=(playery-e.y)
Local l#=Sqr(dx#*dx#+dy#*dy#)
dx#=(dx#/l#)*e.amax#
dy#=(dy#/l#)*e.amax#

'If close enough escape target
If l#<=distance#
dx#=-dx#
dy#=-dy#
EndIf

'check against all other enemies, To avoid them
Local dxx#=0
Local dyy#=0
Local co=0
For Local otherEnemy:enemy=EachIn enemylist
If otherEnemy<>e
Local dex#=(e.x-otherEnemy.x)
Local dey#=(e.y-otherEnemy.y)

'Avoid other enemies. Comment out these 3 lines to remove avoidance.
l#=Sqr(dex#*dex#+dey#*dey#)
dxx#=dxx#+(dex#/l#)*e.amax#
dyy#=dyy#+(dey#/l#)*e.amax#

co=co+1
EndIf
Next

dxx#=dxx#/Float(co)
dyy#=dyy#/Float(co)
dx#=(dx#+dxx#)/2
dy#=(dy#+dyy#)/2
e.ax#=e.ax#+dx#
e.ay#=e.ay#+dy#

Local acc#=Sqr(e.ax#*e.ax#+e.ay#*e.ay#)
'Check If current acceleration is more than allowed
If acc#>e.amax#
e.ax#=(e.ax#/acc#)*e.amax
e.ay#=(e.ay#/acc#)*e.amax
EndIf

e.vx#=e.vx#+e.ax#
e.vy#=e.vy#+e.ay#

Local vel#=Sqr(e.vx#*e.vx#+e.vy#*e.vy#)

'Check If current velocity is more than allowed
If vel#>e.vmax#
e.vx#=(e.vx#/vel#)*e.vmax
e.vy#=(e.vy#/vel#)*e.vmax
EndIf

' add velocity To position
e.x#=e.x#+e.vx#
e.y#=e.y#+e.vy#

Next
End Function
End Type

'SetGraphicsDriver GLMax2DDriver()
Graphics 640,480

'Create ten enemies at random locations
Local n:Int
For n=1 To 10
'play with last number
'enemynew(x,y,vmax,amax)
enemy.enemynew(Rnd(800),Rnd(600),Rnd(5,5), 10)'Rnd(0.08,0.1))
Next

Local click:Int = 0
Local clickx:Int = 0
Local clicky:Int = 0
Repeat
Cls
DrawText "Move player with mouse",10,10
DrawText "LMB - Resize allowed distance to player",10,30
DrawText "RMB - Add enemies",10,50

If click=0
playerx=MouseX()
playery=MouseY()
EndIf

If MouseDown(1) And click=0
click=1
clickx=MouseX()
clicky=MouseY()
EndIf

If MouseDown(1) And click=1
Local dx:Int=(MouseX()-clickx)
Local dy:Int=(MouseY()-clicky)
distance#=Sqr(dx*dx+dy*dy)
EndIf

If MouseDown(1)=False And click=1
click=0
EndIf

If MouseDown(2)>0
enemy.enemynew(Rnd(800),Rnd(600),Rnd(2.5,2.5),Rnd(0.08,0.1))
EndIf


enemy.enemyupdate()
enemy.enemydraw()

'DrawRect playerx-5,playery-5,10,10

SetAlpha 0.8
SetColor 255,0,0
SetBlend(LIGHTBLEND)
DrawOval playerx-distance#,playery-distance#,distance#*2,distance#*2
SetAlpha 1

Flip
Until KeyDown(KEY_ESCAPE) Or AppTerminate()
End



markcw(Posted 1+ years ago)

 <a href="../faq/faq_entry0b30.html?id=2" target="_blank">http://www.blitzbasic.com/faq/faq_entry.php?id=2[/url]


Jesse(Posted 1+ years ago)

 Dud! I've been here many time and I had not seen the original code. Nice. [/i]