How to calculate a point with an given center, angle and radius?

Solar2D General Questions/Discussion
#21

In a nutshell do this:

  1. Calculate the ‘direction vector’ from the turret center to the target.

  2. Convert that vector to a unit vector (normalize it)

  3. Make a copy of the vector from step #2 (you’ll need it  later for step #7).

  4. Scale your original normalized vector (from step #2) by the radius of the turret.  

  5. Add the vector from step #4 to the position of the turret.  

  6. Create your bullet at the < x, y > position specified by the vector from step #5.  (Be sure to add a body)

  7. Take then vector copy from step #3 and scale by the magnitude of the bullet (i.e. how fast you want it to go in pixels per second).

  8. Call set linear velocity with the <x,y> values of the vector from step #7

#22

Thanks for the answer :slight_smile:

My idea is to create a Laser Machine that displays a laser (using the raycast function) and reflect on each obstacle.

My question is: What kind of objects can I use to make the laser beam? Drawing lines …?

#23

Lines, rectangles, image rectangles… all will work, depending on the effect you’re looking for.

#24

Hi.

What is the difference between properties and methods in corona?

For instance: https://docs.coronalabs.com/api/type/Body/index.html

thanks

#25

Is this related to the initial question?  It’s not good to add new questions to a single-topic forum post… having said that:

local bob -- a local variable \_G.bill = 10 -- a global variable billy = 9 -- a global variable local function ted() -- local function end local function sue() -- global function end function susan() -- global function end ------------------------------------------------------------ ------------------------------------------------------------ local obj = {} -- A Table obj.myName = "Bud" -- A user-defined field/property on a table function obj.doit() -- A user-defined function on a table. print("HI") end obj.doit() -- Calling the function function obj.doit2( self ) -- Another user-defined function (with explicit self as first argument) on a table. print("Hi, my name is", self.myName ) end obj.doit2() -- doit2( obj ) called as a function obj:doit2() -- doit2() called as a method function obj:doit3( ) -- A user-defined method (implied self as first argument) on a table. print("Hi, my name is", self.myName ) end obj.doit3() -- doit3( obj ) called as a function obj:doit3() -- doit3() called as a method ------------------------------------------------------------ ------------------------------------------------------------ local circ = display.newCirlce(0,0,100) -- A display object circ.myName = "Bud" -- A user defined field/property on a display object. function circ.doit() -- A user defined function on a display object. print("HI") end circ.doit() -- Calling the function function circ.doit2( self ) -- Another user defined function (with explicit self as first argument) on a display object. print("Hi, my name is", self.myName ) end circ.doit2() -- doit2( circ ) called as a function circ:doit2() -- doit2() called as a method function circ:doit3( ) -- A user defined method (implied self as first argument) on a display object. print("Hi, my name is", self.myName ) end circ.doit3() -- doit3( circ ) called as a function circ:doit3() -- doit3() called as a method
#26

Hi gyus,

When I switch (using composer) from scene1 to scene2, my display objects inserted into scene1 are visible in scene2 … ??

What i’m doing wrong? I’m using scene:insert(…) to add my display objects

Thanks

#27

@luisxpto32,

Not seeing what that has to do with the original question.