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-- Author : Julian Andres Guarin Reyes.

-- Project : JART, Just Another Ray Tracer.

-- email : jguarin2002 at gmail.com, j.guarin at javeriana.edu.co

-- This code was entirely written by Julian Andres Guarin Reyes.

-- The following code is licensed under GNU Public License

-- http://www.gnu.org/licenses/gpl-3.0.txt.

 -- This file is part of JART (Just Another Ray Tracer).

    -- JART (Just Another Ray Tracer) is free software: you can redistribute it and/or modify

    -- it under the terms of the GNU General Public License as published by

    -- the Free Software Foundation, either version 3 of the License, or

    -- (at your option) any later version.

    -- JART (Just Another Ray Tracer) is distributed in the hope that it will be useful,

    -- but WITHOUT ANY WARRANTY; without even the implied warranty of

    -- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    -- GNU General Public License for more details.

    -- You should have received a copy of the GNU General Public License

    -- along with JART (Just Another Ray Tracer).  If not, see <http://www.gnu.org/licenses/>.

-- The following HDL is a dot product calculator.  V and D are the vectors to be processed. 

-- Vx,Vy,Vz,Dx,Dy,Dz are the vectors components.

-- vn_A7_10, vn_A7_10 are both signed fixed representations of vectorial components where 7 bits are for the integer part and

-- 10 bits are for the decimal part.

-- vd_A15_16 is the signed fixed representation of the V and D dot product operation, where 15 bits are for the integer part and 

-- 16 bits are for the decimal part. 

library ieee;

use ieee.std_logic_1164.all;

-- Fixed Point Representation :

-- 

-- A(7,10) signed 18 bits fixed point representation :

--      1 bit for sign

--      7 bits for integer part (128) numbers.

--      10 bits for decimal part (1024) numbers. 

-- Representation Range = -128, 128-(1/1024)

-- Decimal part Resolution : 1/1024 = 0.00098 aprox, 0.001

entity bl00 is

        port (

                -- <vx, vy, vz> y <dx, dy, dz> fixed point A(7,10) => 18 bits de representacion.

                vx_A7_10        : in std_logic_vector (17 downto 0);

                vy_A7_10        : in std_logic_vector (17 downto 0);

                vz_A7_10        : in std_logic_vector (17 downto 0);

                dx_A7_10 :      in std_logic_vector (17 downto 0);

                dy_A7_10 :      in std_logic_vector (17 downto 0);

                dz_A7_10 :      in std_logic_vector (17 downto 0);

                -- <vxdx + vydy + vzdz> fixed point A(15,6) => 32 bits de representacion.

                vd_A15_16 :     out std_logic_vector (31 downto 0)

        );

end entity;

architecture rtl of bl00 is

        signal px :     std_logic_vector (31 downto 0); -- Producto A(15,20), se trunca despues a A(15,16)

        signal py :     std_logic_vector (31 downto 0); -- Producto A(15,20), se trunca despues a A(15,16)

        signal pz :     std_logic_vector (31 downto 0); -- Producto A(15,20), se trunca despues a A(15,16)

        signal s0 :     std_logic_vector (31 downto 0); -- Suma : A(15,16) + A(15,16) = A(15,16) = 31 bits de representacion. 

        component mult_A15_20

        port

        (

                dataa           : in std_logic_vector(17 downto 0);

                datab           : in std_logic_vector(17 downto 0);

                result          : out std_logic_vector (35 downto 0)

        );

        end component;

        component add_A15_16

        port

        (

                dataa           : in std_logic_vector (31 downto 0);

                datab           : in std_logic_vector (31 downto 0);

                result          : out std_logic_vector(31 downto 0)

        );

        end component;

begin

        -- Productos, trunco de una vez 4 bits para performance y espacio.

        vxdx : mult_A15_20 port map (dataa=>vx_A7_10, datab=> dx_A7_10, result(35 downto 4) => px);

        vydy : mult_A15_20 port map (dataa=>vy_A7_10, datab=> dy_A7_10, result(35 downto 4) => py);

        vzdz : mult_A15_20 port map (dataa=>vz_A7_10, datab=> dz_A7_10, result(35 downto 4) => pz);

        -- Sumas de 32 bits A(21,10).

        add0 : add_A15_16 port map (dataa=> px, datab => py , result=>s0(31 downto 0));

        add1 : add_A15_16 port map (dataa=> s0, datab => pz , result=>vd_A15_16(31 downto 0));

end rtl;