Some help with math and polygons

[soulaymenc]

Hello every one.
I am trying to highlight clicked objects on the screen, so basically each object can have different x,y coordinates (of course) but with different origin offsets as well (ox and oy). I highlight an object by drawing a rectangle that surrounds the object's borders.

So the issues I'm having are:

1/ How do I check if an object was clicked? (Check if the mouse click points exists in the polygon with a particular rotation)
2/ How to perfectly draw the rectangle around the rotated object

Thank you very much.

[micha]

2) Make a loop over all coordinates and collect the smallest and largest x- and y-coordinate. Then draw a rectangle using these coordinates:

Code: Select all

local minX = -math.huge
local maxX = math.huge
for i = 1, nNodes do
  minX = math.max(minX,rectangleCoordinateX[i])
  maxX = math.min(maxX,rectangleCoordinateX[i])
  minY = math.max(minY,rectangleCoordinateY[i])
  maxY = math.min(maxY,rectangleCoordinateY[i])
end
-- and in draw:
love.graphics.rectangle('line',minX,minY,maxX-minX,maxY-minY)

1) Do you need pixel-perfect clicking? If no, then I suggest using the rectangle from point 2) as a collision area. Checking a click against a rectangle is easy. If you want to do it pixel-perfect, then the math will be more involved.

[davisdude]

Check out this thing I did a while ago if you want to get REALLY deep into it. Just for you I added random-polygon generation.

[soulaymenc]

Check out this thing I did a while ago if you want to get REALLY deep into it. Just for you I added random-polygon generation.

Oh thank you! It does what I need I also found this useful http://math.stackexchange.com/questions ... d-on-angle

Thank you very much for helping! I'm working on a new project and hope to release it in few weeks, still a lot of work to do, and questions to be answered

[davisdude]

No problem! (In case you didn't know) You can read through the files by changing the extension to a .zip.
All the math is within the file MLib.lua, and the code that makes it so that you can see it is in main.lua.