How do i make a hollow circle?

Solar2D General Questions/Discussion
#1

i want a hollow circle thats 50x50 …

like in this post… but with a circle … he was having problems that it was making it hollow and he didnt want it that way … but i need it hollow …

https://forums.coronalabs.com/topic/54837-hollow-physic-shape-instead-of-full-physic-shape/

thanks!

#2

Why not create it in an image editing software like Photoshop or The GIMP?  If you need to use display.newCircle, you could use a graphics.newMask() that would make the inner part of the circle transparent.

Rob

#3

Well I tried making transparent cricle if that’s what you mean but it doesn’t work… It just acts like a normal filled in circle…

#4

Can you explain more about what behavior you want?

#5

so i have a filled in circle and when i press it and big hollow circle appears around it and i cant move the filled in circle out of the hollow one because of the walls… then when i let go i the hollow circle disappears (see the pic i attached(i put it together real quick)) 

#6

This might be a case of simply not using physics based collision detection for this.  Physics bodies cannot detect collisions with concave shapes.  The inside of a circle is concave. You could setup a complex multi-body octagon made up of 8 rectangular bodies (or 10 or more depending on how smooth you wanted it).  But that’s a lot of work.  What might be easier is a simple math check.  Is the circle with radius R inside the larger circle.

In the Tutorial: Non-physics collision detection ( https://coronalabs.com/blog/2013/07/23/tutorial-non-physics-collision-detection/ ) there is a function to detect when two circles are touching each other.  In your case, you want them to touch. You would need to adjust the math a bit to make sure the edges stay inside.  If the function returns false, don’t let the movement happen.

Rob

#7

Why not create it in an image editing software like Photoshop or The GIMP?  If you need to use display.newCircle, you could use a graphics.newMask() that would make the inner part of the circle transparent.

Rob

#8

Well I tried making transparent cricle if that’s what you mean but it doesn’t work… It just acts like a normal filled in circle…

#9

Can you explain more about what behavior you want?

#10

so i have a filled in circle and when i press it and big hollow circle appears around it and i cant move the filled in circle out of the hollow one because of the walls… then when i let go i the hollow circle disappears (see the pic i attached(i put it together real quick)) 

#11

This might be a case of simply not using physics based collision detection for this.  Physics bodies cannot detect collisions with concave shapes.  The inside of a circle is concave. You could setup a complex multi-body octagon made up of 8 rectangular bodies (or 10 or more depending on how smooth you wanted it).  But that’s a lot of work.  What might be easier is a simple math check.  Is the circle with radius R inside the larger circle.

In the Tutorial: Non-physics collision detection ( https://coronalabs.com/blog/2013/07/23/tutorial-non-physics-collision-detection/ ) there is a function to detect when two circles are touching each other.  In your case, you want them to touch. You would need to adjust the math a bit to make sure the edges stay inside.  If the function returns false, don’t let the movement happen.

Rob