Physics Problem

Getting Started Newbie Questions
#1 
----------------------------------------------------------------------------------------- -- -- main.lua -- ----------------------------------------------------------------------------------------- display.setStatusBar( display.HiddenStatusBar ) local width = display.actualContentWidth local height = display.actualContentHeight local background = display.newRect( width \* 0.5, height \* 0.5, width, height ) local physics = require( "physics" ) physics.start() local line = display.newRect( width \* 0.5, height - 64, width, 128 ) line:setFillColor( 0.1, 0.1, 0.1 ) physics.addBody( line, "static" ) local player = display.newRect( width \* 0.5, height \* 0.5, 64, 64 ) player:setFillColor( 0.93, 0.11, 0.14 ) physics.addBody( player ) player:setLinearVelocity( -100, 0 )

Why doesn’t player move continuously? It stops after two seconds.

#2

That’s not how it works.  Friction and/or damping will stop the body from moving over time.  setLinearVelocity() is not continuous, it is instantaneous.

If you want the object to move at a continuous rate, call setLinearVelocity OR apply a force  in an enterFrame listener .

Suggestions:

  1. Read all the guides linked at the top of this documenation page: https://docs.coronalabs.com/api/library/physics/index.html

physics_guides.png

  1. Download my old examples and play with them (impulses & forces folders in the zip file; click colored boxes to run examples):

https://github.com/roaminggamer/CoronaGeek/raw/master/Hangouts/Hangout%2081.zip

impulses.png forces.png

  1. Grab this example from my AskEd archive (in fact get the entire repository for fun):

https://github.com/roaminggamer/RG_FreeStuff/raw/master/AskEd/2015/08/impulsesForcesVelocitiesOhMy.zip

impulsesForcesVelocitiesOhMy.png

Entire RGFreeStuff repository (see AskEd folder for 400+ coded answers):

https://github.com/roaminggamer/RG_FreeStuff

The last example uses an OLD version of SSK, so if you go that route, be sure to use the latest (may not be compatible w/ example due to path/folder name changes):

https://roaminggamer.github.io/RGDocs/pages/SSK2/

You may find my actions lib useful, but honestly this is something you can do w/o anything extra like SSK.

https://roaminggamer.github.io/RGDocs/pages/SSK2/libraries/actions1/

https://roaminggamer.github.io/RGDocs/pages/SSK2/libraries/actions2/

#3

How can I disable friction and damping? I tested my code with no gravity and then player was moving continuously. But I want to achieve this by not disabling gravity. Thanks…

#4

Please read the docs/guides as suggested, it’s all there:

https://docs.coronalabs.com/api/library/physics/index.html

I keep the API docs linked on my browser bar,  (I refer to it all the time).

#5

I know it seems like a lot, but you’ll need to read it and experiment a lot to learn this stuff.  Sorry.
 
You see if I just said this: 

local crate = display.newImage( "crate.png", 100, 200 ) physics.addBody( crate, {friction=0 } ) crate.linearDamping = 0

you’d skip all the learning and soon come back with a new question, no better ready to self-help.

#6

Sorry for stealing your time… Thanks for help I will try to learn it myself.

#7

Note: I don’t think gravity is actually the focus here,but if you want gravity on for some objects and off for others, you can make a dynamic physics object ignore gravity by setting it’s gravityScale to 0.

https://docs.coronalabs.com/api/type/Body/gravityScale.html

Don’t worry.  You’re not stealing my time.  I’m giving it.  However, I answer the way I do, because I know these kinds of questions:

  • are open-ended in nature
  • lead to more questions
  • are specific to the goals you have (which are hard for me to know as I’m not a mind reader), so it is hard for me to give you the perfect answer.

So, I typically give some info, but then encourage self learning while giving samples and sources to do that learning from.

Good luck on your journey.

PS - When you get bored or tired, take a peek here (all free):

https://forums.coronalabs.com/topic/74704-template-portfolio-release/

#8

If you specify friction (to eliminate loss of linear velocity to angular velocity during “sliding” contacts) then you’ll need to specify bounce (aka restitution) also - set it to 1 to eliminate loss from non-elastic collision response.  (it’s not clear why overriding one default wipes out others, but it does, so once you start specifying one then it’s best to specify everything)

#9

That’s not how it works.  Friction and/or damping will stop the body from moving over time.  setLinearVelocity() is not continuous, it is instantaneous.

If you want the object to move at a continuous rate, call setLinearVelocity OR apply a force  in an enterFrame listener .

Suggestions:

  1. Read all the guides linked at the top of this documenation page: https://docs.coronalabs.com/api/library/physics/index.html

physics_guides.png

  1. Download my old examples and play with them (impulses & forces folders in the zip file; click colored boxes to run examples):

https://github.com/roaminggamer/CoronaGeek/raw/master/Hangouts/Hangout%2081.zip

impulses.png forces.png

  1. Grab this example from my AskEd archive (in fact get the entire repository for fun):

https://github.com/roaminggamer/RG_FreeStuff/raw/master/AskEd/2015/08/impulsesForcesVelocitiesOhMy.zip

impulsesForcesVelocitiesOhMy.png

Entire RGFreeStuff repository (see AskEd folder for 400+ coded answers):

https://github.com/roaminggamer/RG_FreeStuff

The last example uses an OLD version of SSK, so if you go that route, be sure to use the latest (may not be compatible w/ example due to path/folder name changes):

https://roaminggamer.github.io/RGDocs/pages/SSK2/

You may find my actions lib useful, but honestly this is something you can do w/o anything extra like SSK.

https://roaminggamer.github.io/RGDocs/pages/SSK2/libraries/actions1/

https://roaminggamer.github.io/RGDocs/pages/SSK2/libraries/actions2/

#10

How can I disable friction and damping? I tested my code with no gravity and then player was moving continuously. But I want to achieve this by not disabling gravity. Thanks…

#11

Please read the docs/guides as suggested, it’s all there:

https://docs.coronalabs.com/api/library/physics/index.html

I keep the API docs linked on my browser bar,  (I refer to it all the time).

#12

I know it seems like a lot, but you’ll need to read it and experiment a lot to learn this stuff.  Sorry.
 
You see if I just said this: 

local crate = display.newImage( "crate.png", 100, 200 ) physics.addBody( crate, {friction=0 } ) crate.linearDamping = 0

you’d skip all the learning and soon come back with a new question, no better ready to self-help.

#13

Sorry for stealing your time… Thanks for help I will try to learn it myself.

#14

Note: I don’t think gravity is actually the focus here,but if you want gravity on for some objects and off for others, you can make a dynamic physics object ignore gravity by setting it’s gravityScale to 0.

https://docs.coronalabs.com/api/type/Body/gravityScale.html

Don’t worry.  You’re not stealing my time.  I’m giving it.  However, I answer the way I do, because I know these kinds of questions:

  • are open-ended in nature
  • lead to more questions
  • are specific to the goals you have (which are hard for me to know as I’m not a mind reader), so it is hard for me to give you the perfect answer.

So, I typically give some info, but then encourage self learning while giving samples and sources to do that learning from.

Good luck on your journey.

PS - When you get bored or tired, take a peek here (all free):

https://forums.coronalabs.com/topic/74704-template-portfolio-release/

#15

If you specify friction (to eliminate loss of linear velocity to angular velocity during “sliding” contacts) then you’ll need to specify bounce (aka restitution) also - set it to 1 to eliminate loss from non-elastic collision response.  (it’s not clear why overriding one default wipes out others, but it does, so once you start specifying one then it’s best to specify everything)