Shaking object with movement - I don't want this!

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Davey B

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Joined: 22nd Aug 2004

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Posted: 25th Aug 2010 20:23

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Hello again,

Right my problem is that as my object moves, it gradually develops a shake, which gets worse over time. If movement stops the shake stops. When I start moving again the object shakes again with the same intensity it was last at. Any idea what the problem is?

Nothing fancy used to control the player just:

_shipforces:

if shipturn# > 0 then turn object right 2,shipturn#
if shipturn# < 0 then turn object left 2,(shipturn# * -1)

if shippitch# > 0 then pitch object up 2,shippitch#
if shippitch# < 0 then pitch object down 2,(shippitch# * -1)

if shiproll# > 0 then roll object right 2,shiproll#
if shiproll# < 0 then roll object left 2,(shiproll# * -1)

if shipvel# > 0.001 or shipvel# < -0.001
	 move object 2,shipvel# 
else
	shipvel# = 0
endif

player_ship_x# = object position x (player_ship)
player_ship_y# = object position y (player_ship)
player_ship_z# = object position z (player_ship)

return

_input:

if keystate(3)=1 and shipvel# < 300 then shipvel#=shipvel# + 3
if keystate(2)=1 and shipvel# > -200 then shipvel#=shipvel# - 2
//if keystate(3)=0 and keystate(2)=0 then if shipaccel# > 0 then shipaccel#=0
//if keystate(3)=0 and keystate(2)=0 then if shipaccel# < 0 then shipaccel#=0

if keystate(30)=1 and shipturn# > -0.4 then shipturn# = shipturn# - 0.003
if keystate(32)=1 and shipturn# < 0.4 then shipturn# = shipturn# + 0.003
if keystate(30)=0 and keystate(32)=0 then shipturn# = shipturn# - (shipturn#/70)

if keystate(17) = 1 and shippitch# < 0.4 then shippitch# = shippitch# + 0.003
if keystate(31) = 1 and shippitch# > -0.4 then shippitch# = shippitch# - 0.003
if keystate(17)=0 and keystate(31)=0 then shippitch# = shippitch# - (shippitch#/70)

if keystate(16)=1 and shiproll# > -0.4 then shiproll# = shiproll# - 0.003
if keystate(18)=1 and shiproll# < 0.4 then shiproll# = shiproll# + 0.003
if keystate(16)=0 and keystate(18)=0 then shiproll# = shiproll# - (shiproll#/70)

return

+ Code Snippet

_shipforces:

if shipturn# > 0 then turn object right 2,shipturn#
if shipturn# < 0 then turn object left 2,(shipturn# * -1)

if shippitch# > 0 then pitch object up 2,shippitch#
if shippitch# < 0 then pitch object down 2,(shippitch# * -1)

if shiproll# > 0 then roll object right 2,shiproll#
if shiproll# < 0 then roll object left 2,(shiproll# * -1)

if shipvel# > 0.001 or shipvel# < -0.001
	 move object 2,shipvel# 
else
	shipvel# = 0
endif

player_ship_x# = object position x (player_ship)
player_ship_y# = object position y (player_ship)
player_ship_z# = object position z (player_ship)

return

_input:

if keystate(3)=1 and shipvel# < 300 then shipvel#=shipvel# + 3
if keystate(2)=1 and shipvel# > -200 then shipvel#=shipvel# - 2
//if keystate(3)=0 and keystate(2)=0 then if shipaccel# > 0 then shipaccel#=0
//if keystate(3)=0 and keystate(2)=0 then if shipaccel# < 0 then shipaccel#=0

if keystate(30)=1 and shipturn# > -0.4 then shipturn# = shipturn# - 0.003
if keystate(32)=1 and shipturn# < 0.4 then shipturn# = shipturn# + 0.003
if keystate(30)=0 and keystate(32)=0 then shipturn# = shipturn# - (shipturn#/70)

if keystate(17) = 1 and shippitch# < 0.4 then shippitch# = shippitch# + 0.003
if keystate(31) = 1 and shippitch# > -0.4 then shippitch# = shippitch# - 0.003
if keystate(17)=0 and keystate(31)=0 then shippitch# = shippitch# - (shippitch#/70)

if keystate(16)=1 and shiproll# > -0.4 then shiproll# = shiproll# - 0.003
if keystate(18)=1 and shiproll# < 0.4 then shiproll# = shiproll# + 0.003
if keystate(16)=0 and keystate(18)=0 then shiproll# = shiproll# - (shiproll#/70)

return

I've seen threads about this:
http://forum.thegamecreators.com/?m=forum_view&t=58013&b=1
http://forum.thegamecreators.com/?m=forum_view&t=58013&b=1

I dont understand their solution here, and moving the origin seems kinda strange to me. Besides I'm designing a game in space so I cant really remain in the confines of a small usable coordinate range. Any one else had this / is my code at fault? Is it a bug within DBPRO?

Cheers

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IanM

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23

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Joined: 11th Sep 2002

Location: In my moon base

Posted: 25th Aug 2010 21:57

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Quote: "as my object moves, it gradually develops a shake, which gets worse over time"

You may have fallen foul of floating point limitations.

Firstly, floating point numbers take up 4 bytes of memory. 4 Bytes of memory can hold just over 4 billion different combinations of bits. However, floats can hold numbers from as small as 1x10^-38, up to 3.4x10^38 - a much larger range than can be stored in 4 bytes.

It does this by using a logarithmic scale - you always have around 7 significant digits of accuracy, and the decimal point moves around.

For example:
1.0000001 is probably OK, range-wise, but 1.0000000001 won't be.
1000001 is probably OK too, but 1000000001 won't be.

Basically, as the numbers get larger, the minimum 'steps' between representations of those numbers also become larger.

Also something to take into account is that in the same way as you can't represent 1/3 in decimal, there are numbers that can't be represented fully using floating point - 1/10 can't for example (although I believe DBPro will show you the correct result, it's 'cheating' slightly by dropping precision and rounding).

Now, how does that aid you? It doesn't. But this might...

One way to deal with this is to determine the point where the numbers become 'too large' for your program, and then reset everything back to the origin.

For example, your camera is at 10000.0, 0.0, 0.0 and what you are aiming for is at 10500.00, 0.0, 0.0 - you reset your camera back to 0.0, 0.0, 0.0, and then move your target by a like amount to 500.0, 0.0, 0.0 and do the same for all other assets in the game arena.

Utility plug-ins collection (updated 26 July 2010) and
http://www.matrix1.demon.co.uk

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Davey B

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Joined: 22nd Aug 2004

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Posted: 25th Aug 2010 23:27

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Cheers IanM, that explanation was perfect. I figured out how to achieve some way of fixing the origin and made this cheap and dirty fix for now

+ Code Snippet

if object position x (player_ship) > 10000  or object position y (player_ship) > 10000 or object position z (player_ship) > 10000
	player_ship_oldx# = object position x (player_ship)
	player_ship_oldy# = object position y (player_ship)
	player_ship_oldz# = object position z (player_ship)
	position object player_ship,0,0,0
	for n = 10 to 150
		if object exist (n) = 1
				objx# = object position x (n)
				objy# = object position y (n)
				objz# = object position z (n)
				position object n, (objx# - player_ship_oldx#) , (objy# - player_ship_oldy#), (objz# - player_ship_oldz#)
				
			else
		endif
	next n
	
player_ship_x# = object position x (player_ship)
player_ship_y# = object position y (player_ship)
player_ship_z# = object position z (player_ship)

else
endif

Thanks again!

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IanM

Retired Moderator

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Location: In my moon base

Posted: 26th Aug 2010 01:10

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That will work fine if you only travel in directions where the x/y/z coordinates increase in the positive direction.

Change this kind of thing:

+ Code Snippet

object position x(player_ship) > 10000

To something like this:

+ Code Snippet

abs(object position x(player_ship)) > 10000

That should do the job in any direction.

Utility plug-ins (26-JUL-2010)
I'm applying terms of use that require you to wear a red nose and honk a horn whenever you use the Internet

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