[SOLVED] Get adjacent triangles from another from a return of love.math.triangulate

[Bigfoot71]

Hello everyone!

Here is the problem, I have a polygon that I triangulate with the 'love.math.triangulate' function and I am trying to get the adjacent triangles from one of them, so I wrote a function here :

Code: Select all

local function getAdjacentTris(index, tris)

    local adj = {}
    local tri2 = tris[index]

    for k, tri1 in pairs(tris) do

        if k ~= index then
            for i = 1, 6, 2 do
                local i1 = i+2<6 and i+2 or 1
                local i2 = i+3<7 and i+3 or 2
                if  (tri1[i] == tri2[i] and tri1[i+1] == tri2[i+1])
                and (tri1[i1] == tri2[i1] and tri1[i2] == tri2[i2])
                then table.insert(adj, {tri1,k}); break end
            end
        end

        if #adj == 3 then break end

    end
    
    return adj

end

This function returns a list of adjacent triangles and their index in the original table.

But when I try it on the table containing the triangles obtained by calling 'love.math.triangulate' it doesn't return any triangles, while these triangles seem to share the same points. I thought it's probably because of the floating point so I rounded them using this function:

Code: Select all

function math.round(num, decimals)
    decimals = math.pow(10, decimals or 0)
    num = num * decimals
    if num >= 0 then num = math.floor(num + 0.5) else num = math.ceil(num - 0.5) end
    return num / decimals
end

But the result remains the same, so I started to doubt my function, so I wrote my own list of triangles and Bingo, my function works!

So I'm lost with all this, how can I get another's adjacent triangles that come from 'love.math.triangulate'? Where am I making a mistake?

Here is the complete script that I used to see if my function works, it displays the polygon then tries to display the triangles adjacent to the first triangle of this polygon, then displays the triangle adjacent to the first in my list at the top left of display:

Code: Select all

local function hexagon(x,y,l)
    local i=(l/2)*3^0.5
    return {x,y,x+l,y,x+1.5*l,y+i,x+l,y+2*i,x,y+2*i,x-l*0.5,y+i}
end

local function getAdjacentTris(index, tris)

    local adj = {}
    local tri2 = tris[index]

    for k, tri1 in pairs(tris) do

        if k ~= index then
            for i = 1, 6, 2 do
                local i1 = i+2<6 and i+2 or 1 -- 1+2=3; 3+2=5; !!5+2=7
                local i2 = i+3<7 and i+3 or 2 -- 1+3=4; 3+3=6; !!5+3=8
                if  (tri1[i] == tri2[i] and tri1[i+1] == tri2[i+1])
                and (tri1[i1] == tri2[i1] and tri1[i2] == tri2[i2])
                then table.insert(adj, {tri1,k}); break end
            end
        end

        if #adj == 3 then break end

    end
    
    return adj

end

local poly = hexagon(
    (love.graphics.getWidth()-100)/2,
    (love.graphics.getHeight()-100)/2,
    100
)

local polyTris = love.math.triangulate(poly)

local testTris = {
    {1,1, 10,1, 5,10},
    {1,1, 10,1, 10,10},
    {5,10, 10,1, 10,10},
    {90,90, 300,90, 150,90} 
}

local adjacent_polyTris = getAdjacentTris(1, polyTris)
local adjacent_testTris = getAdjacentTris(1, testTris)

function love.draw()

    love.graphics.setColor(1,0,0)
    love.graphics.polygon("fill", poly)

    love.graphics.setColor(0,1,0)
    for k, tri in pairs(adjacent_polyTris) do
        love.graphics.polygon("line", tri)
    end
    
    love.graphics.push() -- I enlarged the display so that the triangle is more visible
    love.graphics.scale(10,10)

        for k, tri in pairs(adjacent_testTris) do
            love.graphics.polygon("line", tri[1])
        end
        
    love.graphics.pop()

end

Update:

To prove that the triangles obtained by 'love.math.triangulate' share at least two same points, I did this:

Code: Select all

local polyTris = love.math.triangulate(poly)

for _, tri in pairs(polyTris) do
    print("A: ", "X = "..tri[1], "Y = "..tri[2])
    print("B: ", "X = "..tri[3], "Y = "..tri[4])
    print("C: ", "X = "..tri[5], "Y = "..tri[6])
    print()
end

And I get:

Code: Select all

A: 	X = 350	Y = 250
B: 	X = 450	Y = 250
C: 	X = 500	Y = 336.6025390625

A: 	X = 350	Y = 250
B: 	X = 500	Y = 336.6025390625
C: 	X = 450	Y = 423.205078125

A: 	X = 350	Y = 250
B: 	X = 450	Y = 423.205078125
C: 	X = 350	Y = 423.205078125

A: 	X = 350	Y = 250
B: 	X = 350	Y = 423.205078125
C: 	X = 300	Y = 336.6025390625

So why is my function not finding the coordinates they have in common ?

AUTO-SOLVED:

I only checked (A==A && B==B && C==C) so if (A==C) it was not checked therefore not validated, here is the corrected function, it is very surely optimizable but it works:

Code: Select all

local function getAdjacentTris(index, tris)

    local adj = {}
    local tri2 = tris[index]

    for k, tri1 in pairs(tris) do

        if k ~= index then
            for i = 1, 6, 2 do

                local i1 = i<4 and i+2 or 1 -- 1+2=3; 3+2=5; !!5+2=7
                local i2 = i<5 and i+3 or 2 -- 1+3=4; 3+3=6; !!5+3=8
                local i3 = i1<4 and i1+2 or i<4 and i-2 or i1-2
                local i4 = i2<5 and i2+2 or i<5 and i-1 or i2-1

                if  ( (tri1[i] == tri2[i] and tri1[i+1] == tri2[i+1])
                   or (tri1[i] == tri2[i1] and tri1[i+1] == tri2[i2])
                   or (tri1[i] == tri2[i3] and tri1[i+1] == tri2[i4]) )
                and ( (tri1[i1] == tri2[i1] and tri1[i2] == tri2[i2])
                   or (tri1[i1] == tri2[i3] and tri1[i2] == tri2[i4]) )
                then
                    table.insert(adj, {tri1,k}); break
                end

            end
        end

        if #adj == 3 then break end

    end
    
    return adj

end