How to use 'Collisions' command?

Blitz3D Forums/Blitz3D Beginners Area/How to use 'Collisions' command?

Happy Sammy

(Posted 2005) [#1]

Hi all,

I found that

Collisions Object1, Scenery, 2, r

is commonly used (ellipsoid to polygon)
However, I tried sample examples and still could notice any difference between the values of r (r=1,2,3)?

The Sample examples:

; Collisions Example 
; ------------------ 

Graphics3D 640,480 
SetBuffer BackBuffer() 

; Set collision type values 
type_ground=1 
type_character=2 
type_scenery=3 

camera=CreateCamera() 
RotateEntity camera,45,0,0 
PositionEntity camera,0,15,-10 

light=CreateLight() 
RotateEntity light,45,0,0 

; Create cube 'ground' 
cube=CreateCube() 
ScaleEntity cube,10,10,10 
EntityColor cube,0,127,0 
EntityType cube,type_ground 
PositionEntity cube,0,-5,0 

; Create sphere 'character' 
sphere=CreateSphere( 32 ) 
EntityColor sphere,127,0,0 
EntityRadius sphere,1 
EntityType sphere,type_character 
PositionEntity sphere,0,7,0 

; Enable collisions between type_character and type_ground 
Collisions type_character,type_ground,2,2 

; Create cylinder 'scenery' 
cylinder=CreateCylinder( 32 ) 
ScaleEntity cylinder,2,2,2 
EntityColor cylinder,0,0,255 
EntityRadius cylinder,2 
EntityBox cylinder,-2,-2,-2,4,4,4 
EntityType cylinder,type_scenery 
PositionEntity cylinder,-4,7,-4 

; Create cone 'scenery' 
cone=CreateCone( 32 ) 
ScaleEntity cone,2,2,2 
EntityColor cone,0,0,255 
EntityRadius cone,2 
EntityBox cone,-2,-2,-2,4,4,4 
EntityType cone,type_scenery 
PositionEntity cone,4,7,-4 

; Create prism 'scenery' 
prism=CreateCylinder( 3 ) 
ScaleEntity prism,2,2,2 
EntityColor prism,0,0,255 
EntityRadius prism,2 
EntityBox prism,-2,-2,-2,4,4,4 
EntityType prism,type_scenery 
PositionEntity prism,-4,7,4 
RotateEntity prism,0,180,0 

; Create pyramid 'scenery' 
pyramid=CreateCone( 4 ) 
ScaleEntity pyramid,2,2,2 
EntityColor pyramid,0,0,255 
EntityRadius pyramid,2 
EntityBox pyramid,-2,-2,-2,4,4,4 
EntityType pyramid,type_scenery 
RotateEntity pyramid,0,45,0 
PositionEntity pyramid,4,7,4 

; Set collision method and response values 
method=2 
response=2 

method_info$="ellipsoid-to-polygon" 
response_info$="slide1" 

While Not KeyDown( 1 ) 

x#=0 
y#=0 
z#=0 

If KeyDown( 203 )=True Then x#=-0.1 
If KeyDown( 205 )=True Then x#=0.1 
If KeyDown( 208 )=True Then z#=-0.1 
If KeyDown( 200 )=True Then z#=0.1 

MoveEntity sphere,x#,y#,z# 
MoveEntity sphere,0,-0.02,0 ; gravity 

; Change collision method 
If KeyHit( 50 )=True 
method=method+1 
If method=4 Then method=1 
If method=1 Then method_info$="ellipsoid-to-sphere" 
If method=2 Then method_info$="ellipsoid-to-polygon" 
If method=3 Then method_info$="ellipsoid-to-box" 
EndIf 

; Change collision response 
If KeyHit( 19 )=True 
response=response+1 
If response=4 Then response=1 
If response=1 Then response_info$="stop" 
If response=2 Then response_info$="slide1" 
If response=3 Then response_info$="slide2" 
EndIf 

; Enable collisions between type_character and type_scenery 
Collisions type_character,type_scenery,method,response 

; Perform collision checking 
UpdateWorld 

RenderWorld 

Text 0,0,"Use cursor keys to move sphere" 
Text 0,20,"Press M to change collision Method (currently: "+method_info$+")" 
Text 0,40,"Press R to change collision Response (currently: "+response_info$+")" 
Text 0,60,"Collisions type_character,type_scenery,"+method+","+response 

Flip 

Wend 

End

1. How to use 'Collisions' command?
2. Will ODE or Tokamak have better (or faster) collision detection than the built-in "collisions" command?

Thanks in advance.
Sammy
:)

Matty

(Posted 2005) [#2]

I don't think that sample works as it should, try this:

I've removed the collisions command from the loop and placed it outside. Change the final parameter to see how they differ. For some reason it doesn't work as you would expect when collisions is called within the loop.

2. I wouldn't know much about tokamak/ode so can't help there, although their use would really depend on the type of game you are writing.

; Collisions Example 
; ------------------ 

Graphics3D 640,480 
SetBuffer BackBuffer() 

; Set collision type values 
type_ground=1 
type_character=2 
type_scenery=3 

camera=CreateCamera() 
RotateEntity camera,45,0,0 
PositionEntity camera,0,15,-10 

light=CreateLight() 
RotateEntity light,45,0,0 

; Create cube 'ground' 
cube=CreateCube() 
ScaleEntity cube,10,10,10 
EntityColor cube,0,127,0 
EntityType cube,type_ground 
PositionEntity cube,0,-5,0 

; Create sphere 'character' 
sphere=CreateSphere( 32 ) 
EntityColor sphere,127,0,0 
EntityRadius sphere,1 
EntityType sphere,type_character 
PositionEntity sphere,0,7,0 

; Enable collisions between type_character and type_ground 
Collisions type_character,type_ground,2,2 

; Create cylinder 'scenery' 
cylinder=CreateCylinder( 32 ) 
ScaleEntity cylinder,2,2,2 
EntityColor cylinder,0,0,255 
EntityRadius cylinder,2 
EntityBox cylinder,-2,-2,-2,4,4,4 
EntityType cylinder,type_scenery 
PositionEntity cylinder,-4,7,-4 

; Create cone 'scenery' 
cone=CreateCone( 32 ) 
ScaleEntity cone,2,2,2 
EntityColor cone,0,0,255 
EntityRadius cone,2 
EntityBox cone,-2,-2,-2,4,4,4 
EntityType cone,type_scenery 
PositionEntity cone,4,7,-4 

; Create prism 'scenery' 
prism=CreateCylinder( 3 ) 
ScaleEntity prism,2,2,2 
EntityColor prism,0,0,255 
EntityRadius prism,2 
EntityBox prism,-2,-2,-2,4,4,4 
EntityType prism,type_scenery 
PositionEntity prism,-4,7,4 
RotateEntity prism,0,180,0 

; Create pyramid 'scenery' 
pyramid=CreateCone( 4 ) 
ScaleEntity pyramid,2,2,2 
EntityColor pyramid,0,0,255 
EntityRadius pyramid,2 
EntityBox pyramid,-2,-2,-2,4,4,4 
EntityType pyramid,type_scenery 
RotateEntity pyramid,0,45,0 
PositionEntity pyramid,4,7,4 

; Set collision method and response values 
method=2 
response=2 

method_info$="ellipsoid-to-polygon" 
response_info$="slide1" 

;Collisions type_character,type_scenery,2,3 ;slide up
;Collisions type_character,type_scenery,2,2 ;slide 
Collisions type_character,type_scenery,2,1 ;stop

;uncomment and comment the above lines to see the difference. For some reason calling the collisions command again inside the loop does not work as expected.

While Not KeyDown( 1 ) 

x#=0 
y#=0 
z#=0 

If KeyDown( 203 )=True Then x#=-0.1 
If KeyDown( 205 )=True Then x#=0.1 
If KeyDown( 208 )=True Then z#=-0.1 
If KeyDown( 200 )=True Then z#=0.1 

MoveEntity sphere,x#,y#,z# 
MoveEntity sphere,0,-0.02,0 ; gravity 

; Change collision method 
If KeyHit( 50 )=True 
method=method+1 
If method=4 Then method=1 
If method=1 Then method_info$="ellipsoid-to-sphere" 
If method=2 Then method_info$="ellipsoid-to-polygon" 
If method=3 Then method_info$="ellipsoid-to-box" 
EndIf 

; Change collision response 
If KeyHit( 19 )=True 
response=response+1 
If response=4 Then response=1 
If response=1 Then response_info$="stop" 
If response=2 Then response_info$="slide1" 
If response=3 Then response_info$="slide2" 
EndIf 

; Enable collisions between type_character and type_scenery 

; Perform collision checking 
UpdateWorld 

RenderWorld 

Text 0,0,"Use cursor keys to move sphere" 
Text 0,20,"Press M to change collision Method (currently: "+method_info$+")" 
Text 0,40,"Press R to change collision Response (currently: "+response_info$+")" 
Text 0,60,"Collisions type_character,type_scenery,"+method+","+response 

Flip 

Wend 

End

Happy Sammy

(Posted 2005) [#3]

Hi Matty,

You are absolutely right!!!
Collisions must be put outside the while loop!!!
I got it! I could see the difference now!!!

(With that changes, the messages displayed on the screen is meaningless and could be removed.)

Thanks a lot.
Sammy
:)