Makeing reactive grass - GameCreators Forum

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Hacktank

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Posted: 27th Jun 2009 09:11

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I am trying to make reactive grass that bends when a rigid body touches it using joints, I have the joints and grass objects made but i cannot get them to spring back to an upright position. I try to use the spring paramater on sphere and 6dof joints but i cant get them to do anything atall. How would i do this? ( NVIDIA SDK example attached)

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HowDo

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Posted: 27th Jun 2009 12:22 Edited at: 27th Jun 2009 12:28

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If you are using joints then you need to change how the value is worked out.

Putting a number like 1 or 50 will not work, try something like this.

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PHY SET SPHERE JOINT SWING LIMIT jointID, 0.05*3.14, 0, 0

Also I think that will on this command

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phy set sphere joint swing spring jointID, target#, spring#

Are you doing this in basic or GDK?

this what to look for to work out how to use the command set

Quote: "Twist and Swing Decomposition in Quaternion Components"

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HowDo

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Posted: 27th Jun 2009 13:51

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Are you getting anything like this?

Rem Project: makegrassphy
Rem Created: 27/06/2009 11:07:23

Rem ***** Main Source File *****
sync on
sync rate 60
autocam off
position camera 0,5,-5
point camera 0,0,0
x#=-0.5

phy start
id=1
make object box id,100,.1,100
position object id,0,-.2,0
phy make rigid body static box id
ground=id
jointID=1
inc id
for x = 0 to 5
   for z = 0 to 5
      make object box id,.1,1.0,.1
      position object id,x#,0,z#
      phy make rigid body dynamic box id
      phy set rigid body linear damping ID, 1.0
      phy make 6dof joint jointID,id,ground
index=0
jx#=0
jy#=.1
jz#=0
      phy set 6dof joint global anchor jointID, index, jx#, jy#, jz#
value#=0.05*3.14
restitution#=0.75
spring#=0.75
damping#=1.0
      phy set 6dof joint linear limit jointID, value#, restitution#, spring#, damping#
dampingLow#=1
restitutionLow#=0.75
springLow#=0.75
valueLow#=.01
dampingHigh#=0.05*3.14
restitutionHigh#=0.05*3.14
springHigh#=.5
valueHigh#=.5
      phy set 6dof joint twist limit jointID, dampingLow#, restitutionLow#, springLow#, valueLow#, dampingHigh#, restitutionHigh#, springHigh#, valueHigh#
value#=0.05*3.14
restitution#=0.75
spring#=0.75
damping#=1.0
      phy set 6dof joint swing1 limit ID, value#, restitution#, spring#, damping#
      phy build 6dof joint jointID
      inc jointid
      inc x#,.2
      inc id
   next z
   inc z#,.2: x#=-0.5
next z
inc id
make object sphere id,.5
position object id,0,2,.2
phy make rigid body dynamic sphere id

do

phy update
sync
loop

+ Code Snippet

Rem Project: makegrassphy
Rem Created: 27/06/2009 11:07:23

Rem ***** Main Source File *****
sync on
sync rate 60
autocam off
position camera 0,5,-5
point camera 0,0,0
x#=-0.5

phy start
id=1
make object box id,100,.1,100
position object id,0,-.2,0
phy make rigid body static box id
ground=id
jointID=1
inc id
for x = 0 to 5
   for z = 0 to 5
      make object box id,.1,1.0,.1
      position object id,x#,0,z#
      phy make rigid body dynamic box id
      phy set rigid body linear damping ID, 1.0
      phy make 6dof joint jointID,id,ground
index=0
jx#=0
jy#=.1
jz#=0
      phy set 6dof joint global anchor jointID, index, jx#, jy#, jz#
value#=0.05*3.14
restitution#=0.75
spring#=0.75
damping#=1.0
      phy set 6dof joint linear limit jointID, value#, restitution#, spring#, damping#
dampingLow#=1
restitutionLow#=0.75
springLow#=0.75
valueLow#=.01
dampingHigh#=0.05*3.14
restitutionHigh#=0.05*3.14
springHigh#=.5
valueHigh#=.5
      phy set 6dof joint twist limit jointID, dampingLow#, restitutionLow#, springLow#, valueLow#, dampingHigh#, restitutionHigh#, springHigh#, valueHigh#
value#=0.05*3.14
restitution#=0.75
spring#=0.75
damping#=1.0
      phy set 6dof joint swing1 limit ID, value#, restitution#, spring#, damping#
      phy build 6dof joint jointID
      inc jointid
      inc x#,.2
      inc id
   next z
   inc z#,.2: x#=-0.5
next z
inc id
make object sphere id,.5
position object id,0,2,.2
phy make rigid body dynamic sphere id

do

phy update
sync
loop

Dark Physics makes any hot drink go cold.

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HowDo

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Location: United Kingdom

Posted: 27th Jun 2009 14:50

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Here is something more like the demo using sphere joints which I was not using before.

Rem Project: makegrassphy
Rem Created: 27/06/2009 11:07:23

Rem ***** Main Source File *****
sync on
sync rate 60
autocam off
position camera 0,5,-5
point camera 0,0,0
x#=-0.5
phy enable debug
phy start
id=1
make object box id,100,.1,100
position object id,0,-.2,0
phy make rigid body static box id
ground=id
jointID=1
inc id
for x = 0 to 5
   for z = 0 to 5
      make object box id,.1,1.0,.1
      position object id,x#,0,z#
      phy make rigid body dynamic box id
      phy set rigid body linear damping ID, 10.0
   phy make sphere joint jointID,id,ground
index=1
jx#=x#
jy#=1.0
jz#=z#
   phy set sphere joint global anchor jointID, index, jx#, jy#, jz#
index=0
jx#=x#
jy#=1.0
jz#=z#
   phy set sphere joint global axis jointID, index, jx#, jy#, jz#
value#=0.05*3.14
resitution#=0.75
hardness#=.5
   phy set sphere joint swing limit jointID, value#, resitution#, hardness#
target#=0.05*3.14
spring#=.5
   phy set sphere joint spring jointID, target#, spring#
low#=0.05*3.14
high#=0.05*3.14
   phy set sphere joint twist limit jointID, low#, high#

phy build sphere joint jointID
      inc jointid
      inc x#,.2
      inc id
   next z
   inc z#,.2: x#=-0.5
next z
inc id
make object sphere id,.5
position object id,0,2,.2
phy make rigid body dynamic sphere id
mass#=2
phy set rigid body mass ID, mass#
do

phy update
sync
loop

+ Code Snippet

Rem Project: makegrassphy
Rem Created: 27/06/2009 11:07:23

Rem ***** Main Source File *****
sync on
sync rate 60
autocam off
position camera 0,5,-5
point camera 0,0,0
x#=-0.5
phy enable debug
phy start
id=1
make object box id,100,.1,100
position object id,0,-.2,0
phy make rigid body static box id
ground=id
jointID=1
inc id
for x = 0 to 5
   for z = 0 to 5
      make object box id,.1,1.0,.1
      position object id,x#,0,z#
      phy make rigid body dynamic box id
      phy set rigid body linear damping ID, 10.0
   phy make sphere joint jointID,id,ground
index=1
jx#=x#
jy#=1.0
jz#=z#
   phy set sphere joint global anchor jointID, index, jx#, jy#, jz#
index=0
jx#=x#
jy#=1.0
jz#=z#
   phy set sphere joint global axis jointID, index, jx#, jy#, jz#
value#=0.05*3.14
resitution#=0.75
hardness#=.5
   phy set sphere joint swing limit jointID, value#, resitution#, hardness#
target#=0.05*3.14
spring#=.5
   phy set sphere joint spring jointID, target#, spring#
low#=0.05*3.14
high#=0.05*3.14
   phy set sphere joint twist limit jointID, low#, high#

     phy build sphere joint jointID
      inc jointid
      inc x#,.2
      inc id
   next z
   inc z#,.2: x#=-0.5
next z
inc id
make object sphere id,.5
position object id,0,2,.2
phy make rigid body dynamic sphere id
mass#=2
phy set rigid body mass ID, mass#
do

phy update
sync
loop

Dark Physics makes any hot drink go cold.

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BMacZero

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Posted: 27th Jun 2009 17:21

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Do you think soft bodies would be a better way to accomplish this?

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A book!

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HowDo

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Posted: 27th Jun 2009 22:39 Edited at: 27th Jun 2009 22:52

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@BMacZero
Might be, if the program for doing softbodys would work.

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Oolite

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Posted: 27th Jun 2009 22:47

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I reckon soft bodies might be too slow just for grass.
I wouldn't recommend doing it through DP, just have the plain rotate away when the rigid body is near the object. Probably be quicker and as long as the pivot point is at the bottom of the object then it should work okay.

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Hacktank

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Posted: 28th Jun 2009 02:43

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Thanks guys, the problem is solved with howdo's third post, and later i will try useing a soft body and see how it goes.

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Dark Physics & Dark A.I. & Dark Dynamix / Makeing reactive grass

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