How do I slice physic object and measure its amount ?

Get help using Construct 2

Post » Mon Feb 06, 2017 5:30 am

So i wanted to make a clone of this game : http://www.physicsgames.net/game/3_Slices.html
someone can give me a hint how to make it works ?
B
15
S
2
Posts: 9
Reputation: 695

Post » Mon Feb 06, 2017 6:41 pm

The core part is being able to slice a polygon by a line into two polygons. This can be done by calculating the intersection between the line and the edges, as well as finding which side of the line a point is.
Here's one possible psuedcode of the algorithm to do it:
Code: Select all
for each edge clockwise
   if edge.point0 is on left side of line
      add point to poly1
   else
      add point to poly2
   if edge intersects line
      add intersection to poly1
      add intersection to poly2


Next we have the issue of drawing an arbitrary polygon and changing the collision polygon. Vanilla C2 plugins won't help here. I don't use it but the third party polygon plugin by yann probably could work since it both lets you draw arbitrary polygons at runtime and it makes it's collision polygon match.

The rough psuedocode for that could be:
Code: Select all
get the list of edges of a polygon
try to slice the polygon in two with a line
destroy the old polygon and create two new polygons from the sliced polygons


Also on a side note you'll want to set the new polygons' velocities the same as the old polygon otherwise the pieces will go at a complete stop after slicing.

At least that's a general idea how to do it. There might be some issues that need to be ironed out, such as I don't know how well the polygon plugin works with the physics behavior.
B
94
S
33
G
114
Posts: 5,361
Reputation: 73,783

Post » Wed Feb 08, 2017 8:18 am

R0J0hound wrote:The core part is being able to slice a polygon by a line into two polygons. This can be done by calculating the intersection between the line and the edges, as well as finding which side of the line a point is.
Here's one possible psuedcode of the algorithm to do it:
Code: Select all
for each edge clockwise
   if edge.point0 is on left side of line
      add point to poly1
   else
      add point to poly2
   if edge intersects line
      add intersection to poly1
      add intersection to poly2


Next we have the issue of drawing an arbitrary polygon and changing the collision polygon. Vanilla C2 plugins won't help here. I don't use it but the third party polygon plugin by yann probably could work since it both lets you draw arbitrary polygons at runtime and it makes it's collision polygon match.

The rough psuedocode for that could be:
Code: Select all
get the list of edges of a polygon
try to slice the polygon in two with a line
destroy the old polygon and create two new polygons from the sliced polygons


Also on a side note you'll want to set the new polygons' velocities the same as the old polygon otherwise the pieces will go at a complete stop after slicing.

At least that's a general idea how to do it. There might be some issues that need to be ironed out, such as I don't know how well the polygon plugin works with the physics behavior.


wow that a lot of explanation, thanks rojo
i will look forward to try this
B
15
S
2
Posts: 9
Reputation: 695


Return to How do I....?

Who is online

Users browsing this forum: Google [Bot] and 13 guests