vertex

--[[
This is a modified vector API to include vertex information for texture mapping
(UV coordinates).

]]--
local vertex = {
        -- note that arithmetic functions return VECTORS- and lose UV info
    add = function( self, o )
        return vector.new(
            self.x + o.x,
            self.y + o.y,
            self.z + o.z
        )
    end,
    sub = function( self, o )
        return vector.new(
            self.x - o.x,
            self.y - o.y,
            self.z - o.z
        )
    end,
    -- This is not true of multiplication
    mul = function( self, m )
        return vertex.new(
            self.x * m,
            self.y * m,
            self.z * m,
            self.u, self.v
        )
    end,
    dot = function( self, o )
        return self.x*o.x + self.y*o.y + self.z*o.z
    end,
    cross = function( self, o )
        return vector.new(
            self.y*o.z - self.z*o.y,
            self.z*o.x - self.x*o.z,
            self.x*o.y - self.y*o.x
        )
    end,
    length = function( self )
        return math.sqrt( self.x*self.x + self.y*self.y + self.z*self.z )
    end,
    normalize = function( self )
        return self:mul( 1 / self:length() )
    end,
    tostring = function( self )
        return self.x..","..self.y..","..self.z..",("..self.u..","..self.v..")"
    end,
}

local vmetatable = {
    __index = vertex,
    __add = vertex.add,
    __sub = vertex.sub,
    __mul = vertex.mul,
    __unm = function( v ) return v:mul(-1) end,
    __tostring = vertex.tostring,
}

function new( x, y, z, u, v )
    local v = {
        x = x or 0,
        y = y or 0,
        z = z or 0,
        u = u or 0,
        v = v or 0
    }
    setmetatable( v, vmetatable )
    return v
end