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//=======================================================================

// Project Monophony

//   Wire-Frame 3D Graphics Accelerator IP Core

//

// File:

//   fm_ras_state.v

//

// Abstract:

//  line distribution

//  line is rejected when:

//    both vertices are outside +-X, or +-Y plane

//

// Author:

//   Kenji Ishimaru (info.info.wf3d@gmail.com)

//

//======================================================================

//

// Copyright (c) 2015, Kenji Ishimaru

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

//  -Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

//  -Redistributions in binary form must reproduce the above copyright notice,

//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR

// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;

// OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,

// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

// Revision History

`include "fm_3d_define.v"

module fm_ras_state (

  // system

  input         clk_core,

  input         rst_x,

  // Register Configuration

  input [15:0] i_scr_w_m1,  // Screen Width-1

  input [15:0] i_scr_h_m1,  // Screen Height-1

  // Vertex input

  input         i_en,

  output        o_ack,

  input  [`D3D_FTOI_WIDTH-1:0] i_v0_x,

  input  [`D3D_FTOI_WIDTH-1:0] i_v0_y,

  input  [`D3D_FTOI_WIDTH-1:0] i_v1_x,

  input  [`D3D_FTOI_WIDTH-1:0] i_v1_y,

  input  [`D3D_FTOI_WIDTH-1:0] i_v2_x,

  input  [`D3D_FTOI_WIDTH-1:0] i_v2_y,

  output        o_ras_state,

  // Current Line

  output        o_en,

  input         i_ack,

  output [`D3D_FTOI_WIDTH-1:0] o_v0_x,

  output [`D3D_FTOI_WIDTH-1:0] o_v0_y,

  output [`D3D_FTOI_WIDTH-1:0] o_v1_x,

  output [`D3D_FTOI_WIDTH-1:0] o_v1_y,

  input         i_state

);

localparam P_IDLE = 'd0;

localparam P_LINE_0 = 'd1;

localparam P_LINE_1 = 'd2;

localparam P_LINE_2 = 'd3;

//////////////////////////////////

// reg

//////////////////////////////////

reg [2:0]  r_state;

reg [`D3D_FTOI_WIDTH-1:0] r_v0_x;

reg [`D3D_FTOI_WIDTH-1:0] r_v0_y;

reg [`D3D_FTOI_WIDTH-1:0] r_v1_x;

reg [`D3D_FTOI_WIDTH-1:0] r_v1_y;

reg [`D3D_FTOI_WIDTH-1:0] r_v2_x;

reg [`D3D_FTOI_WIDTH-1:0] r_v2_y;

//////////////////////////////////

// wire

//////////////////////////////////

wire w_set_vtx;

wire w_reject_l0;

wire w_reject_l1;

wire w_reject_l2;

//////////////////////////////////

// assign

//////////////////////////////////

assign o_en = ((r_state == P_LINE_0) & ~w_reject_l0) |

              ((r_state == P_LINE_1) & ~w_reject_l1) |

              ((r_state == P_LINE_2) & ~w_reject_l2);

assign o_ack = (r_state == P_IDLE);

// LINE 0: v0,v1

// LINE 1: v1,v2

// LINE 2: v2,v0

assign o_v0_x = (r_state == P_LINE_0) ? r_v0_x :

                (r_state == P_LINE_1) ? r_v1_x : r_v2_x;

assign o_v0_y = (r_state == P_LINE_0) ? r_v0_y :

                (r_state == P_LINE_1) ? r_v1_y : r_v2_y;

assign o_v1_x = (r_state == P_LINE_0) ? r_v1_x :

                (r_state == P_LINE_1) ? r_v2_x : r_v0_x;

assign o_v1_y = (r_state == P_LINE_0) ? r_v1_y :

                (r_state == P_LINE_1) ? r_v2_y : r_v0_y;

assign w_set_vtx = (r_state == P_IDLE) & i_en;

assign o_ras_state = (r_state == P_IDLE) & i_state;

assign w_reject_l0 = f_reject(r_v0_x,r_v0_y,r_v1_x,r_v1_y,i_scr_w_m1,i_scr_h_m1);

assign w_reject_l1 = f_reject(r_v1_x,r_v1_y,r_v2_x,r_v2_y,i_scr_w_m1,i_scr_h_m1);

assign w_reject_l2 = f_reject(r_v2_x,r_v2_y,r_v0_x,r_v0_y,i_scr_w_m1,i_scr_h_m1);

//////////////////////////////////

// always

//////////////////////////////////

always @(posedge clk_core) begin

  if (w_set_vtx) begin

    r_v0_x <= i_v0_x;

    r_v0_y <= i_v0_y;

    r_v1_x <= i_v1_x;

    r_v1_y <= i_v1_y;

    r_v2_x <= i_v2_x;

    r_v2_y <= i_v2_y;

  end

end

`ifdef D3D_SYNC_RESET

always @(posedge clk_core) begin

`else

always @(posedge clk_core or negedge rst_x) begin

`endif

  if (rst_x == `D3D_RESET_POL) begin

    r_state <= P_IDLE;

  end else begin

    case (r_state)

      P_IDLE: begin

        if (i_en) r_state <= P_LINE_0;

      end

      P_LINE_0: begin

        if (i_ack | w_reject_l0) r_state <= P_LINE_1;

      end

      P_LINE_1: begin

        if (i_ack | w_reject_l1) r_state <= P_LINE_2;

      end

      P_LINE_2: begin

        if (i_ack | w_reject_l2) r_state <= P_IDLE;

      end

    endcase

  end

end

function f_reject;

  input [`D3D_FTOI_WIDTH-1:0] v0_x;

  input [`D3D_FTOI_WIDTH-1:0] v0_y;

  input [`D3D_FTOI_WIDTH-1:0] v1_x;

  input [`D3D_FTOI_WIDTH-1:0] v1_y;

  input [15:0] scr_w;

  input [15:0] scr_h;

  reg result;

  begin

    result = 1'b0;

    if (v0_x[`D3D_FTOI_WIDTH-1] & v1_x[`D3D_FTOI_WIDTH-1]) result = 1'b1;  // negative

    if (v0_y[`D3D_FTOI_WIDTH-1] & v1_y[`D3D_FTOI_WIDTH-1]) result = 1'b1;

    if ((~v0_x[`D3D_FTOI_WIDTH-1] & (v0_x[`D3D_FTOI_WIDTH-2:0] > scr_w))&

        (~v1_x[`D3D_FTOI_WIDTH-1] & (v1_x[`D3D_FTOI_WIDTH-2:0] > scr_w))) result = 1'b1;

    if ((~v0_y[`D3D_FTOI_WIDTH-1] & (v0_y[`D3D_FTOI_WIDTH-2:0] > scr_h))&

        (~v1_y[`D3D_FTOI_WIDTH-1] & (v1_y[`D3D_FTOI_WIDTH-2:0] > scr_h))) result = 1'b1;

    f_reject = result;

  end

endfunction

endmodule