Fractals/Triangle.m at master · PrParadoxy/Fractals · GitHub

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function v = Triangle(v0, x, y, vertices)

% Triangle with arbitrary verticies inspired by
% https://math.stackexchange.com/questions/274712/calculate-on-which-side-of-a-straight-line-is-a-given-point-located

% v0: Triangle has value of v0 inside, and 0 outside.
% x, y: x and y axis, use linspace to set their value.
% verticies: an array containing 2d data points.
% e.g: [[1,0]; [-1, 0]; [0, 2]]

Lx = length(x);
Ly = length(y);
v = zeros(Ly, Lx);

[~, I] = sort(vertices(:,2));
vertices = vertices(I,:);

a = vertices(1, :);
b = vertices(2, :);
c = vertices(3, :);

for t = 1:6

    for p = 1:Lx
        for q = 1:Ly


            if sign( (x(p) - c(1))*(a(2)-c(2)) - (y(q) - c(2))*(a(1) - c(1)) ) <= 0

                if sign( (x(p) - c(1))*(b(2)-c(2)) - (y(q) - c(2))*(b(1) - c(1)) ) >= 0

                    if sign( (x(p) - a(1))*(b(2)-a(2)) - (y(q) - a(2))*(b(1) - a(1)) ) <= 0

                        v(q, p) = v0;

                    end

                end

            end


        end
    end

%We have no idea where is right and where is left,
%so we keep exchanging indicies until we find a solution
    if any(v,'all')
        break
    elseif t == 1
        a = vertices(2, :);
        b = vertices(1, :);
        c = vertices(3, :);
    elseif t == 2
        a = vertices(3, :);
        b = vertices(2, :);
        c = vertices(1, :);
    elseif t == 3
        a = vertices(1, :);
        b = vertices(3, :);
        c = vertices(2, :);
    elseif t == 4
        a = vertices(2, :);
        b = vertices(3, :);
        c = vertices(1, :);
    elseif t == 5
        a = vertices(3, :);
        b = vertices(1, :);
        c = vertices(2, :);
    end

end


% Plot 3 lines that makes a triangle
% m1 = ( a(2) - b(2) )/( a(1) - b(1) );
% m2 = ( a(2) - c(2) )/( a(1) - c(1) );
% m3 = ( c(2) - b(2) )/( c(1) - b(1) );
%
% if isinf(m1)
%     Xab = a(1)*ones(1,Lx);
%     Yab = y;
% else
%     Xab = x;
%     Yab = m1*(x - b(1)) + b(2);
% end
%
%
% if isinf(m2)
%     Xac = a(1)*ones(1,Lx);
%     Yac = y;
% else
%     Xac = x;
%     Yac = m2*(x - c(1)) + c(2);
% end
%
%
% if isinf(m3)
%     Xcb = b(1)*ones(1,Lx);
%     Ycb = y;
% else
%     Xcb = x;
%     Ycb = m3*(x - b(1)) + b(2);
% end
%
%
% hold on
% plot(Xab, Yab)
% plot(Xac, Yac)
% plot(Xcb, Ycb)

end