Live recursive contour plotting for Lua

contourplot.lua

local function contourPlot(func, lf, x, y, w, h, interval, offset, mindepth, maxdepth, dbg, depth, fvbr, fvbl, fvtl, fvtr)
    local wh, hh = w/2, h/2
    local v_c  =         func(x+wh, y+hh)+offset
    local v_br = fvbr or func(x+w , y+h )+offset
    local v_bl = fvbl or func(x   , y+h )+offset
    local v_tl = fvtl or func(x   , y   )+offset
    local v_tr = fvtr or func(x+w , y   )+offset
    
    local linelist, linecount, v = {}, 1
    v = math.floor(v_c /interval)
    linelist[v] = true
    v = math.floor(v_br/interval)
    if not linelist[v] then linelist[v] = true linecount = linecount+1 end
    v = math.floor(v_bl/interval)
    if not linelist[v] then linelist[v] = true linecount = linecount+1 end
    v = math.floor(v_tl/interval)
    if not linelist[v] then linelist[v] = true linecount = linecount+1 end
    v = math.floor(v_tr/interval)
    if not linelist[v] then linelist[v] = true linecount = linecount+1 end
    --if depth ~= nil then print(depth) end
    --if depth == nil then DBGMSG{v_c, v_br, v_bl, v_tl, v_tr} end
    local newdepth = (depth or 0)+1
    if linecount > 1 or newdepth < mindepth then
        if dbg then
            love_graphics.setColor(0, 255, 0, 255)
            love_graphics.setLineWidth(1)
            love_graphics.rectangle("line", x+4, y+4, w-4, h-4)
        end
        if newdepth <= maxdepth then
            local newmindepth = linecount > 1 and newdepth+2 or mindepth
            --[[br]]contourPlot(func, lf, x+wh, y+hh, wh, hh, interval, offset, newmindepth, maxdepth, dbg, newdepth, v_br, nil , v_c , nil )
            --[[bl]]contourPlot(func, lf, x   , y+hh, wh, hh, interval, offset, newmindepth, maxdepth, dbg, newdepth, nil , v_bl, nil , v_c )
            --[[tl]]contourPlot(func, lf, x   , y   , wh, hh, interval, offset, newmindepth, maxdepth, dbg, newdepth, v_c , nil , v_tl, nil )
            --[[tr]]contourPlot(func, lf, x+wh, y   , wh, hh, interval, offset, newmindepth, maxdepth, dbg, newdepth, nil , v_c , nil , v_tr)
        else
            for line, _ in pairs(linelist) do
                local v_l = line*interval
                local interest = {}
                local d_br = v_l-v_br local sign_br = d_br<0 and -1 or d_br>0 and 1 or 0
                local d_bl = v_l-v_bl local sign_bl = d_bl<0 and -1 or d_bl>0 and 1 or 0
                local d_tl = v_l-v_tl local sign_tl = d_tl<0 and -1 or d_tl>0 and 1 or 0
                local d_tr = v_l-v_tr local sign_tr = d_tr<0 and -1 or d_tr>0 and 1 or 0
                -- clockwise
                -- right edge
                if sign_tr ~= sign_br then
                    table.insert(interest, w)
                    table.insert(interest, h*(d_tr)/(v_br-v_tr))
                end
                -- bottom edge
                if sign_br ~= sign_bl then
                    table.insert(interest, w*(d_bl)/(v_br-v_bl))
                    table.insert(interest, h)
                end
                -- left edge
                if sign_bl ~= sign_tl then
                    table.insert(interest, 0)
                    table.insert(interest, h*(d_tl)/(v_bl-v_tl))
                end
                -- top edge
                if sign_tl ~= sign_tr then
                    table.insert(interest, w*(d_tl)/(v_tr-v_tl))
                    table.insert(interest, 0)
                end
                if #interest == 0 then
                    -- 
                elseif #interest == 4 then
                    lf(
                        x+interest[1], y+interest[2],
                        x+interest[3], y+interest[4]
                    )
                elseif #interest == 8 then
                    lf(
                        x+interest[1], y+interest[2],
                        x+interest[5], y+interest[6]
                    )
                    lf(
                        x+interest[2], y+interest[3],
                        x+interest[7], y+interest[8]
                    )
                else
                    error("wat: "..(#interest))
                end
            end
        end
    elseif dbg then
        love_graphics.setColor(0, 100, 0, 255)
        love_graphics.setLineWidth(1)
        love_graphics.rectangle("line", x+4, y+4, w-4, h-4)
    end
end
util.contourPlot = contourPlot