Entity Angle problem

BlitzMax Forums/MiniB3D Module/Entity Angle problem

bradford6

(Posted 2007) [#1]

not sure if this is a bug:


Import sidesign.MiniB3D
Graphics3D 800,600
cube:Tentity =CreateCube() ; cam:Tentity=CreateCamera() ; MoveEntity cam,0,0,-5
Repeat
	TurnEntity cube,0,3,0
RenderWorld
text 0,0,"EntityPitch(cube) = GLOBAL: "+EntityPitch(cube,True)+" Local: "+EntityPitch(cube)
text 0,20,"EntityYAW(cube) = Global: "+EntityYaw(cube,True)+" Local: "+EntityYaw(cube)
text 0,40,"EntityROLL(cube) = Global: "+EntityRoll(cube,True)+" Local: "+EntityRoll(cube)

Flip
Until KeyDown(KEY_ESCAPE)

should the entity pitch/yaw/roll values wrap to 360? (or 180/-180)

EDIT:
a possible solution would be to pass the ang vals to a function like this. looking through the TEntity.bmx code I am not sure where this would/could be done. It looks like ry# is acted upon in just about every rotation/translation call. I won't even pretend to know where this should go :) :

Function Wrap360:Float(angle#)
	If angle > 359.999 Then angle = angle - 360
	If angle < 0 Then angle = 360 + angle
	Return angle
End Function

LAB[au]

(Posted 2007) [#2]

Strange enough ... using the global flag EntityYaw(cube,1) it returns values similar to Blitz3D.

bradford6

(Posted 2007) [#3]

LAB[au],
I updated the test code to reflect your observations. thanks. I did not notice that.

regardless of whether you call EntityYaw or not, the ry# value increments every time turnentity is called. maybe eventually it will=NAN.

Chris C

(Posted 2007) [#4]

a number that increments *might* cause an overflow error but is as likely to simply overflow and wrap round, this depends on the math libs used and sometimes on the processor

a NAN (Not A Number) is something entirely different...

I think you might find

angle=angle mod 360

might be a little faster, but its largely a moot point, if you want to watch an object rotate till it causes an overflow error, you could be waiting a long time...

bradford6

(Posted 2007) [#5]

that's a good point Chris. I just wanted to bring this to simon's attention.

also,

angle=angle mod 360

is not really what I am looking for. the goal is to clamp the angle value between 0-360. if a large number is added or subtracted and it wraps around zero, the new angle needs to reflect that.

i.e 355+10 = 365 (out of range!)
Wrap360 returns '5' as the new wrapped angle

try this to see the difference:

Import sidesign.MiniB3D
Graphics3D 800,600
cube:Tentity =CreateCube() ; cam:Tentity=CreateCamera() ; MoveEntity cam,0,0,-5
Repeat
	' Mod method
	angle1#:-9.3
	angle1=angle1 Mod 360
	' Wrap 360 Function method
	angle2#:-9.3
	angle2# = wrap360(angle2#)
	TurnEntity cube,0,3,0
	
RenderWorld
text 0,60,"angle = angle Mod 360: "+angle1 
text 0,80,"Wrap360(angle): "+angle2
text 0,120,"                                                press a key"
Flip
WaitKey()
Until KeyDown(KEY_ESCAPE)

Function Wrap360:Float(angle#)
	If angle > 359.999 Then angle = angle - 360
	If angle < 0 Then angle = 360 + angle
	Return angle
End Function

simonh

(Posted 2007) [#6]

Yeah thanks for pointing this out.

Your function is a bit unreliable bradford as if the angle is for example 1000, simply subtracting 360 doesn't wrap the value.

bradford6

(Posted 2007) [#7]

ok. I'll work on that :) *** long pause ***

EDIT: ok, I'm back
this seems to work. (I put Chris C's Mod Angle where he probably meant for it to go all along :) )

I did a few tests: here is one.
i revved the amount up to 1006.29 with the angle at 0.0

using my trusty Google calculator I find that
http://www.google.com/search?q=1006+mod+360
=286
I press the right arrow once and my new angle = 286.29

(not sure how efficient/useful this is but it was fun)

Import sidesign.MiniB3D
Graphics3D 800,600
cube:Tentity =CreateCube() ; cam:Tentity=CreateCamera() ; MoveEntity cam,0,0,-5
EntityColor cube,200,0,0
light = CreateLight() ; MoveEntity light,-5,5,-5
Local amount:Float = 3.1
Repeat
	' Mod method
	
	angle1#=angle1# Mod 360
	' Wrap 360 Function method
	
	angle2# = wrap360(angle2#)
	
	RotateEntity cube,0,angle2#,0	
RenderWorld
text 0,40,"Step Amount: "+amount 

text 0,60,"angle = angle Mod 360: "+angle1 
text 0,80,"Wrap360(angle): "+angle2
text 0,120,"                                                press left/right keys to inc/dec angle"
text 0,140,"                                                press up/down keys to inc/dec step amount"
Flip


If Keyhit(KEY_LEFT)
	angle1:-amount
	angle2:-amount	

EndIf
If Keyhit(KEY_RIGHT)
	angle1:+amount
	angle2:+amount	
EndIf
If KeyDown(KEY_UP)
	amount:+3.3
EndIf
If KeyDown(KEY_DOWN)
	amount:-3.3
EndIf
Until KeyDown(KEY_ESCAPE)

Function Wrap360:Float(angle#)
	angle:Mod 360
	If angle > 359.999 Then angle = angle - 360
	If angle < 0 Then angle = 360 + angle
	Return angle
End Function