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/*

ORSoC GFX accelerator core

Copyright 2012, ORSoC, Per Lenander, Anton Fosselius.

RASTERIZER MODULE

 This file is part of orgfx.

 orgfx is free software: you can redistribute it and/or modify

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

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

 (at your option) any later version.

 orgfx 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 Lesser General Public License for more details.

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

 along with orgfx.  If not, see <http://www.gnu.org/licenses/>.

*/

/*

This module takes a rect write or line write request and generates pixels in the span given by dest_pixel0-1.

Triangles can be declared by dest_pixel0-2, they are handled by the triangle module

The operation is clipped to the span given by clip_pixel0-1. Pixels outside the span are discarded.

If texturing is enabled, texture coordinates u (horizontal) and v (vertical) are emitted, offset and clipped by the span given by src_pixel0-1.

When all pixels have been generated and acked, the rasterizer acks the operation and returns to wait state.

*/

module gfx_rasterizer(clk_i, rst_i,

  clip_ack_i, interp_ack_i, ack_o,

  rect_write_i, line_write_i, triangle_write_i, interpolate_i, texture_enable_i,

  //source pixel 0 and pixel 1

  src_pixel0_x_i, src_pixel0_y_i, src_pixel1_x_i, src_pixel1_y_i,

  //destination point 0, 1, 2

  dest_pixel0_x_i, dest_pixel0_y_i,

  dest_pixel1_x_i, dest_pixel1_y_i,

  dest_pixel2_x_i, dest_pixel2_y_i,

  clipping_enable_i,

  //clip pixel 0 and pixel 1

  clip_pixel0_x_i, clip_pixel0_y_i, clip_pixel1_x_i, clip_pixel1_y_i,

  target_size_x_i, target_size_y_i,

  x_counter_o, y_counter_o, u_o,v_o,

  clip_write_o, interp_write_o,

  triangle_edge0_o, triangle_edge1_o, triangle_area_o

  );

parameter point_width    = 16;

parameter subpixel_width = 16;

parameter delay_width    = 5;

input clk_i;

input rst_i;

input clip_ack_i;

input interp_ack_i;

output reg ack_o;

input rect_write_i;

input line_write_i;

input triangle_write_i;

input interpolate_i;

input texture_enable_i;

//src pixels

input [point_width-1:0] src_pixel0_x_i;

input [point_width-1:0] src_pixel0_y_i;

input [point_width-1:0] src_pixel1_x_i;

input [point_width-1:0] src_pixel1_y_i;

//dest pixels

input signed [point_width-1:-subpixel_width] dest_pixel0_x_i;

input signed [point_width-1:-subpixel_width] dest_pixel0_y_i;

input signed [point_width-1:-subpixel_width] dest_pixel1_x_i;

input signed [point_width-1:-subpixel_width] dest_pixel1_y_i;

input signed [point_width-1:-subpixel_width] dest_pixel2_x_i;

input signed [point_width-1:-subpixel_width] dest_pixel2_y_i;

wire signed [point_width-1:0] p0_x = $signed(dest_pixel0_x_i[point_width-1:0]);

wire signed [point_width-1:0] p0_y = $signed(dest_pixel0_y_i[point_width-1:0]);

wire signed [point_width-1:0] p1_x = $signed(dest_pixel1_x_i[point_width-1:0]);

wire signed [point_width-1:0] p1_y = $signed(dest_pixel1_y_i[point_width-1:0]);

//clip pixels

input                   clipping_enable_i;

input [point_width-1:0] clip_pixel0_x_i;

input [point_width-1:0] clip_pixel0_y_i;

input [point_width-1:0] clip_pixel1_x_i;

input [point_width-1:0] clip_pixel1_y_i;

input [point_width-1:0] target_size_x_i;

input [point_width-1:0] target_size_y_i;

// Generated pixel coordinates

output reg [point_width-1:0] x_counter_o;

output reg [point_width-1:0] y_counter_o;

// Generated texture coordinates

output reg [point_width-1:0] u_o;

output reg [point_width-1:0] v_o;

// Write pixel output signals

output reg                   clip_write_o;

output reg                   interp_write_o;

output [2*point_width-1:0] triangle_edge0_o;

output [2*point_width-1:0] triangle_edge1_o;

output [2*point_width-1:0] triangle_area_o;

wire ack_i = interpolate_i ? interp_ack_i : clip_ack_i;

// Variables used in rect drawing

reg [point_width-1:0] rect_p0_x;

reg [point_width-1:0] rect_p0_y;

reg [point_width-1:0] rect_p1_x;

reg [point_width-1:0] rect_p1_y;

//line drawing reg & wires

wire raster_line_busy; // busy, drawing a line.

wire x_major; // is true if x is the major axis

wire valid_out;

reg  draw_line; // trigger the line drawing.

wire [point_width-1:0] major_out; // the major axis

wire [point_width-1:0] minor_out; // the minor axis

wire                   request_next_pixel;

// State machine

reg [2:0] state;

parameter wait_state           = 3'b000,

          rect_state           = 3'b001,

          line_state           = 3'b010,

          triangle_state       = 3'b011,

          triangle_final_state = 3'b100;

// Write/ack counter

reg [delay_width-1:0] ack_counter;

always @(posedge clk_i or posedge rst_i)

if(rst_i)

  ack_counter <= 1'b0;

else if(interpolate_i & ack_i & ~triangle_write_o)

  ack_counter <= ack_counter - 1'b1;

else if(interpolate_i & triangle_write_o & ~ack_i)

  ack_counter <= ack_counter + 1'b1;

// Rect drawing variables

always @(posedge clk_i or posedge rst_i)

begin

  if(rst_i)

  begin

    rect_p0_x <= 1'b0;

    rect_p0_y <= 1'b0;

    rect_p1_x <= 1'b0;

    rect_p1_y <= 1'b0;

  end

  else

  begin

    if(clipping_enable_i)

    begin

    // pixel0 x

    if(p0_x < $signed(clip_pixel0_x_i)) // check if pixel is left of screen

      rect_p0_x <= clip_pixel0_x_i;

    else if(p0_x > $signed(clip_pixel1_x_i)) // check if pixel is right of screen

      rect_p0_x <= clip_pixel1_x_i;

    else

      rect_p0_x <= p0_x;

    // pixel0 y

    if(p0_y < $signed(clip_pixel0_y_i)) // check if pixel is above the screen

      rect_p0_y <= clip_pixel0_y_i;

    else if(p0_y > $signed(clip_pixel1_y_i)) // check if pixel is below the screen

      rect_p0_y <= clip_pixel1_y_i;

    else

      rect_p0_y <= p0_y;

    // pixel1 x

    if(p1_x < $signed(clip_pixel0_x_i)) // check if pixel is left of screen

      rect_p1_x <= clip_pixel0_x_i;

    else if(p1_x > $signed(clip_pixel1_x_i -1)) // check if pixel is right of screen

      rect_p1_x <= clip_pixel1_x_i -1'b1;

    else

      rect_p1_x <= dest_pixel1_x_i[point_width-1:0] - 1;

    // pixel1 y

    if(p1_y < $signed(clip_pixel0_y_i)) // check if pixel is above the screen

      rect_p1_y <= clip_pixel0_y_i;

    else if(p1_y > $signed(clip_pixel1_y_i -1)) // check if pixel is below the screen

      rect_p1_y <= clip_pixel1_y_i -1'b1;

    else

      rect_p1_y <= p1_y - 1;

    end

    else

    begin

      rect_p0_x <= p0_x       >= 0 ? p0_x     : 1'b0;

      rect_p0_y <= p0_y       >= 0 ? p0_y     : 1'b0;

      rect_p1_x <= (p1_x - 1) >= 0 ? p1_x - 1 : 1'b0;

      rect_p1_y <= (p1_y - 1) >= 0 ? p1_y - 1 : 1'b0;

    end

  end

end

// Checks if the current line in the rect being drawn is complete

wire raster_rect_line_done = (x_counter_o >= rect_p1_x) | (texture_enable_i && (u_o >= src_pixel1_x_i-1));

// Checks if the current rect is completely drawn

// TODO: ugly fix to prevent the an extra pixel being written when texturing is enabled. Ugly.

//wire raster_rect_done = ack_i & (x_counter_o >= rect_p1_x) & ((y_counter_o >= rect_p1_y) | (texture_enable_i && (v_o >= src_pixel1_y_i-1)));

wire raster_rect_done = (ack_i | texture_enable_i) &

                        (x_counter_o >= rect_p1_x) &

                        ((y_counter_o >= rect_p1_y) | (texture_enable_i && (v_o >= src_pixel1_y_i-1)));

// Special check if there are no pixels to draw at all (send ack immediately)

wire empty_raster = (rect_p0_x > rect_p1_x) | (rect_p0_y > rect_p1_y);

wire triangle_finished = ~interpolate_i | (ack_counter == 1'b0);

// Manage states

always @(posedge clk_i or posedge rst_i)

if(rst_i)

  state <= wait_state;

else

  case (state)

    wait_state:

      if(triangle_write_i)

        state <= triangle_state;

      else if(rect_write_i & !empty_raster) // if request for drawing a rect, go to rect drawing state

        state <= rect_state;

      else if(line_write_i)

        state <= line_state; // if request for drawing a line, go to line drawing state

    rect_state:

      if(raster_rect_done) // if we are done drawing a rect, go to wait state

        state <= wait_state;

    line_state:

      if(!raster_line_busy & !draw_line)  // if we are done drawing a line, go to wait state

        state <= wait_state;

    triangle_state:

      if(triangle_ack & triangle_finished)

        state <= wait_state;

      else if(triangle_ack)

        state <= triangle_final_state;

    triangle_final_state:

      if(triangle_finished)

        state <= wait_state;

  endcase

// If interpolation is active, only write to interp module if queue is not full. 

wire interp_ready   = interpolate_i ? (ack_counter <= point_width)   & ~interp_write_o : ack_i;

wire triangle_ready = interpolate_i ? (ack_counter <= point_width-1) & ~interp_write_o : ack_i;

// Manage outputs (mealy machine)

always @(posedge clk_i or posedge rst_i)

begin

  // Reset

  if(rst_i)

  begin

    ack_o          <= 1'b0;

    x_counter_o    <= 1'b0;

    y_counter_o    <= 1'b0;

    clip_write_o   <= 1'b0;

    interp_write_o <= 1'b0;

    u_o            <= 1'b0;

    v_o            <= 1'b0;

    //reset line regs

    draw_line      <= 1'b0;

  end

  else

  begin

    case (state)

      // Wait for incoming instructions

      wait_state:

        if(rect_write_i & !empty_raster) // Start a raster rectangle operation

        begin

          ack_o        <= 1'b0;

          clip_write_o <= 1'b1;

          // Generate pixel coordinates

          x_counter_o  <= rect_p0_x;

          y_counter_o  <= rect_p0_y;

          // Generate texture coordinates

          u_o          <= (($signed(clip_pixel0_x_i) < p0_x) ? 1'b0 :

                            $signed(clip_pixel0_x_i) - p0_x) + src_pixel0_x_i;

          v_o          <= (($signed(clip_pixel0_y_i) < p0_y) ? 1'b0 :

                            $signed(clip_pixel0_y_i) - p0_y) + src_pixel0_y_i;

        end

        else if(rect_write_i & empty_raster & !ack_o) // Start a raster rectangle operation

          ack_o     <= 1'b1;

        // Start a raster line operation

        else if(line_write_i)

        begin

          draw_line <= 1'b1;

          ack_o     <= 1'b0;

        end

        else

          ack_o     <= 1'b0;

      // Rasterize a rectangle between p0 and p1 (rasterize = generate the pixels)

      rect_state:

      begin

        if(ack_i) // If our last coordinate was acknowledged by a fragment processor

        begin

          if(raster_rect_line_done) // iterate through width of rect

          begin

            x_counter_o <= rect_p0_x;

            y_counter_o <= y_counter_o + 1'b1;

            u_o         <= ($signed(clip_pixel0_x_i) < p0_x ? 1'b0 :

                            $signed(clip_pixel0_x_i) - p0_x) + $signed(src_pixel0_x_i);

            v_o         <= v_o + 1'b1;

          end

          else

          begin

            x_counter_o <= x_counter_o + 1'b1;

            u_o         <= u_o + 1'b1;

          end

        end

        if(raster_rect_done) // iterate through height of rect (are we done?)

        begin

          clip_write_o <= 1'b0; // Only send ack when we get ack_i (see wait state)

          ack_o        <= 1'b1;

        end

      end

      // Rasterize a line between dest_pixel0 and dest_pixel1 (rasterize = generate the pixels)

      line_state:

      begin

        draw_line    <= 1'b0;

        clip_write_o <= raster_line_busy & valid_out;

        x_counter_o  <= x_major ? major_out : minor_out;

        y_counter_o  <= x_major ? minor_out : major_out;

        ack_o        <= !raster_line_busy & !draw_line;

      end

      triangle_state:

      if(triangle_ack)

      begin

        interp_write_o <= 1'b0;

        clip_write_o   <= 1'b0;

        if(triangle_finished)

          ack_o <= 1'b1;

      end

      else if(~interpolate_i)

      begin

        x_counter_o    <= triangle_x_o;

        y_counter_o    <= triangle_y_o;

        clip_write_o   <= triangle_write_o ;

      end

      else if(interpolate_i & interp_ready)

      begin

        x_counter_o    <= triangle_x_o;

        y_counter_o    <= triangle_y_o;

        // edge0, edge1 and area are set by the triangle module

        interp_write_o <= triangle_write_o;

      end

      else

      begin

        interp_write_o <= 1'b0;

        clip_write_o   <= 1'b0;

      end

      triangle_final_state:

        if(triangle_finished)

          ack_o <= 1'b1;

    endcase

  end

end

// Request wire for line drawing module

assign request_next_pixel = ack_i & raster_line_busy;

// Instansiation of bresenham line drawing module

bresenham_line bresenham(

.clk_i                  ( clk_i                ),  //clock

.rst_i                  ( rst_i                ),  //rest

.pixel0_x_i             ( dest_pixel0_x_i      ),  // left pixel x

.pixel0_y_i             ( dest_pixel0_y_i      ),  // left pixel y

.pixel1_x_i             ( dest_pixel1_x_i      ),  // right pixel x

.pixel1_y_i             ( dest_pixel1_y_i      ),  // right pixel y

.draw_line_i            ( draw_line            ), // trigger for drawing a line

.read_pixel_i           ( request_next_pixel   ), // request next pixel

.busy_o                 ( raster_line_busy     ), // is true while line is drawn

.x_major_o              ( x_major              ), // is true if x is the major axis

.major_o                ( major_out            ), // the major axis pixel coordinate

.minor_o                ( minor_out            ), // the minor axis pixel coordinate

.valid_o                ( valid_out            )

);

defparam bresenham.point_width = point_width;

defparam bresenham.subpixel_width = subpixel_width;

wire                   triangle_ack;

wire [point_width-1:0] triangle_x_o;

wire [point_width-1:0] triangle_y_o;

wire                   triangle_write_o;

// Triangle module instanciated

gfx_triangle triangle(

.clk_i                  (clk_i),

.rst_i                  (rst_i),

.ack_i                  (triangle_ready),

.ack_o                  (triangle_ack),

.triangle_write_i       (triangle_write_i),

.texture_enable_i       (texture_enable_i),

.dest_pixel0_x_i        (dest_pixel0_x_i),

.dest_pixel0_y_i        (dest_pixel0_y_i),

.dest_pixel1_x_i        (dest_pixel1_x_i),

.dest_pixel1_y_i        (dest_pixel1_y_i),

.dest_pixel2_x_i        (dest_pixel2_x_i),

.dest_pixel2_y_i        (dest_pixel2_y_i),

.x_counter_o            (triangle_x_o),

.y_counter_o            (triangle_y_o),

.triangle_edge0_o       (triangle_edge0_o),

.triangle_edge1_o       (triangle_edge1_o),

.triangle_area_o        (triangle_area_o),

.write_o                (triangle_write_o)

);

defparam triangle.point_width    = point_width;

defparam triangle.subpixel_width = subpixel_width;

endmodule