public void DrawLine( ref PixelBuffer pb, ref RasterLine line, bool useFixed )
{
if( useFixed == true )
throw new NotImplementedException( "fixed math not implemented" );
int x0 = ( int )( line.Vertices[ line.v0 ].PX + 0.5f );
int y0 = ( int )( line.Vertices[ line.v0 ].PY + 0.5f );
int x1 = ( int )( line.Vertices[ line.v1 ].PX + 0.5f );
int y1 = ( int )( line.Vertices[ line.v1 ].PY + 0.5f );
if( ClipLine( ref pb, ref x0, ref y0, ref x1, ref y1 ) == false )
return;
if( ( line.VertexFormat & RasterVertexFormat.Color ) == RasterVertexFormat.Color )
{
#if false
this.DrawLineVaryColor( ref pb, ref line );
#else
line.Color[ 0 ] = line.Vertices[ line.v0 ].R;
line.Color[ 1 ] = line.Vertices[ line.v0 ].G;
line.Color[ 2 ] = line.Vertices[ line.v0 ].B;
line.Color[ 3 ] = line.Vertices[ line.v0 ].A;
this.DrawLineSolidColor( ref pb, ref line, x0, y0, x1, y1 );
#endif
}
else
{
this.DrawLineSolidColor( ref pb, ref line, x0, y0, x1, y1 );
}
}
private bool ClipLine( ref PixelBuffer pb, ref int x0, ref int y0, ref int x1, ref int y1 )
{
// internal clipping codes
int xc0 = x0, yc0 = y0,
xc1 = x1, yc1 = y1;
// TODO: inline
int min_clip_x = 0, min_clip_y = 0, max_clip_x = pb.Width - 1, max_clip_y = pb.Height - 1;
// determine codes for p1 and p2
int p1_code = 0;
if( y0 < min_clip_y )
p1_code |= CLIP_CODE_N;
else
if( y0 > max_clip_y )
p1_code |= CLIP_CODE_S;
if( x0 < min_clip_x )
p1_code |= CLIP_CODE_W;
else
if( x0 > max_clip_x )
p1_code |= CLIP_CODE_E;
int p2_code = 0;
if( y1 < min_clip_y )
p2_code |= CLIP_CODE_N;
else
if( y1 > max_clip_y )
p2_code |= CLIP_CODE_S;
if( x1 < min_clip_x )
p2_code |= CLIP_CODE_W;
else
if( x1 > max_clip_x )
p2_code |= CLIP_CODE_E;
// try and trivially reject
if( ( p1_code & p2_code ) != 0 )
return false;
// test for totally visible, if so leave points untouched
if( p1_code == 0 && p2_code == 0 )
return true;
// determine end clip point for p1
switch( p1_code )
{
case CLIP_CODE_C: break;
case CLIP_CODE_N:
{
yc0 = min_clip_y;
xc0 = ( int )( x0 + 0.5f + ( min_clip_y - y0 ) * ( x1 - x0 ) / ( y1 - y0 ) );
} break;
case CLIP_CODE_S:
{
yc0 = max_clip_y;
xc0 = ( int )( x0 + 0.5f + ( max_clip_y - y0 ) * ( x1 - x0 ) / ( y1 - y0 ) );
} break;
case CLIP_CODE_W:
{
xc0 = min_clip_x;
yc0 = ( int )( y0 + 0.5f + ( min_clip_x - x0 ) * ( y1 - y0 ) / ( x1 - x0 ) );
} break;
case CLIP_CODE_E:
{
xc0 = max_clip_x;
yc0 = ( int )( y0 + 0.5f + ( max_clip_x - x0 ) * ( y1 - y0 ) / ( x1 - x0 ) );
} break;
// these cases are more complex, must compute 2 intersections
case CLIP_CODE_NE:
{
// north hline intersection
yc0 = min_clip_y;
xc0 = ( int )( x0 + 0.5f + ( min_clip_y - y0 ) * ( x1 - x0 ) / ( y1 - y0 ) );
// test if intersection is valid, of so then done, else compute next
if( xc0 < min_clip_x || xc0 > max_clip_x )
{
// east vline intersection
xc0 = max_clip_x;
yc0 = ( int )( y0 + 0.5f + ( max_clip_x - x0 ) * ( y1 - y0 ) / ( x1 - x0 ) );
}
} break;
case CLIP_CODE_SE:
{
// south hline intersection
yc0 = max_clip_y;
xc0 = ( int )( x0 + 0.5f + ( max_clip_y - y0 ) * ( x1 - x0 ) / ( y1 - y0 ) );
// test if intersection is valid, of so then done, else compute next
if( xc0 < min_clip_x || xc0 > max_clip_x )
{
// east vline intersection
xc0 = max_clip_x;
yc0 = ( int )( y0 + 0.5f + ( max_clip_x - x0 ) * ( y1 - y0 ) / ( x1 - x0 ) );
}
} break;
case CLIP_CODE_NW:
{
// north hline intersection
yc0 = min_clip_y;
xc0 = ( int )( x0 + 0.5f + ( min_clip_y - y0 ) * ( x1 - x0 ) / ( y1 - y0 ) );
// test if intersection is valid, of so then done, else compute next
if( xc0 < min_clip_x || xc0 > max_clip_x )
{
xc0 = min_clip_x;
yc0 = ( int )( y0 + 0.5f + ( min_clip_x - x0 ) * ( y1 - y0 ) / ( x1 - x0 ) );
}
} break;
case CLIP_CODE_SW:
{
// south hline intersection
yc0 = max_clip_y;
xc0 = ( int )( x0 + 0.5f + ( max_clip_y - y0 ) * ( x1 - x0 ) / ( y1 - y0 ) );
// test if intersection is valid, of so then done, else compute next
if( xc0 < min_clip_x || xc0 > max_clip_x )
{
xc0 = min_clip_x;
yc0 = ( int )( y0 + 0.5f + ( min_clip_x - x0 ) * ( y1 - y0 ) / ( x1 - x0 ) );
}
} break;
default: break;
}
// determine clip point for p2
switch( p2_code )
{
case CLIP_CODE_C: break;
case CLIP_CODE_N:
{
yc1 = min_clip_y;
xc1 = x1 + ( min_clip_y - y1 ) * ( x0 - x1 ) / ( y0 - y1 );
} break;
case CLIP_CODE_S:
{
yc1 = max_clip_y;
xc1 = x1 + ( max_clip_y - y1 ) * ( x0 - x1 ) / ( y0 - y1 );
} break;
case CLIP_CODE_W:
{
xc1 = min_clip_x;
yc1 = y1 + ( min_clip_x - x1 ) * ( y0 - y1 ) / ( x0 - x1 );
} break;
case CLIP_CODE_E:
{
xc1 = max_clip_x;
yc1 = y1 + ( max_clip_x - x1 ) * ( y0 - y1 ) / ( x0 - x1 );
} break;
// these cases are more complex, must compute 2 intersections
case CLIP_CODE_NE:
{
// north hline intersection
yc1 = min_clip_y;
xc1 = ( int )( x1 + 0.5f + ( min_clip_y - y1 ) * ( x0 - x1 ) / ( y0 - y1 ) );
// test if intersection is valid, of so then done, else compute next
if( xc1 < min_clip_x || xc1 > max_clip_x )
{
// east vline intersection
xc1 = max_clip_x;
yc1 = ( int )( y1 + 0.5f + ( max_clip_x - x1 ) * ( y0 - y1 ) / ( x0 - x1 ) );
}
} break;
case CLIP_CODE_SE:
{
// south hline intersection
yc1 = max_clip_y;
xc1 = ( int )( x1 + 0.5f + ( max_clip_y - y1 ) * ( x0 - x1 ) / ( y0 - y1 ) );
// test if intersection is valid, of so then done, else compute next
if( xc1 < min_clip_x || xc1 > max_clip_x )
{
// east vline intersection
xc1 = max_clip_x;
yc1 = ( int )( y1 + 0.5f + ( max_clip_x - x1 ) * ( y0 - y1 ) / ( x0 - x1 ) );
}
} break;
case CLIP_CODE_NW:
{
// north hline intersection
yc1 = min_clip_y;
xc1 = ( int )( x1 + 0.5f + ( min_clip_y - y1 ) * ( x0 - x1 ) / ( y0 - y1 ) );
// test if intersection is valid, of so then done, else compute next
if( xc1 < min_clip_x || xc1 > max_clip_x )
{
xc1 = min_clip_x;
yc1 = ( int )( y1 + 0.5f + ( min_clip_x - x1 ) * ( y0 - y1 ) / ( x0 - x1 ) );
}
} break;
case CLIP_CODE_SW:
{
// south hline intersection
yc1 = max_clip_y;
xc1 = ( int )( x1 + 0.5f + ( max_clip_y - y1 ) * ( x0 - x1 ) / ( y0 - y1 ) );
// test if intersection is valid, of so then done, else compute next
if( xc1 < min_clip_x || xc1 > max_clip_x )
{
xc1 = min_clip_x;
yc1 = ( int )( y1 + 0.5f + ( min_clip_x - x1 ) * ( y0 - y1 ) / ( x0 - x1 ) );
}
} break;
default: break;
}
// do bounds check
if( ( xc0 < min_clip_x ) || ( xc0 > max_clip_x ) ||
( yc0 < min_clip_y ) || ( yc0 > max_clip_y ) ||
( xc1 < min_clip_x ) || ( xc1 > max_clip_x ) ||
( yc1 < min_clip_y ) || ( yc1 > max_clip_y ) )
return false;
x0 = xc0; y0 = yc0;
x1 = xc1; y1 = yc1;
return true;
}
private void DrawLineVaryColor( ref PixelBuffer pb, ref RasterLine line, int x0, int y0, int x1, int y1 )
{
}
private void DrawLineSolidColor( ref PixelBuffer pb, ref RasterLine line, int x0, int y0, int x1, int y1 )
{
byte[] color = new byte[ 4 ]{
( byte )( line.Color[ 0 ] * 255.0f ),
( byte )( line.Color[ 1 ] * 255.0f ),
( byte )( line.Color[ 2 ] * 255.0f ),
( byte )( line.Color[ 3 ] * 255.0f ),
};
// pre-compute first pixel address in video buffer based on 16bit data
int pbOffset = pb.Offset + ( y0 * pb.Stride ) + ( x0 * pb.BytesPerPixel );
// compute horizontal and vertical deltas
int dx = x1 - x0; // diff in x's
int dy = y1 - y0; // diff in y's
// test which direction the line is going in i.e. slope angle
int x_inc; // step along x
if( dx >= 0 )
{
// moving right
x_inc = pb.BytesPerPixel;
}
else
{
// moving left
x_inc = -pb.BytesPerPixel;
dx = -dx; // need absolute value
}
// test y component of slope
int y_inc; // step along y
if( dy >= 0 )
{
// moving down
y_inc = pb.Stride;
}
else
{
// moving up
y_inc = -pb.Stride;
dy = -dy; // need absolute value
}
// compute (dx,dy) * 2
int dx2 = dx * 2;
int dy2 = dy * 2;
// now based on which delta is greater we can draw the line
if( dx > dy )
{
int error = dy2 - dx; // the discriminant i.e. error i.e. decision variable
// draw the line
if( pb.BytesPerPixel == 3 )
{
for( int index = 0; index <= dx; index++ )
{
// set the pixel
pb.Buffer[ pbOffset ] = color[ 0 ];
pb.Buffer[ pbOffset + 1 ] = color[ 1 ];
pb.Buffer[ pbOffset + 2 ] = color[ 2 ];
// test if error has overflowed
if( error >= 0 )
{
error -= dx2;
// move to next line
pbOffset += y_inc;
}
// adjust the error term
error += dy2;
// move to the next pixel
pbOffset += x_inc;
}
}
else
{
for( int index = 0; index <= dx; index++ )
{
pb.Buffer[ pbOffset ] = color[ 0 ];
pb.Buffer[ pbOffset + 1 ] = color[ 1 ];
pb.Buffer[ pbOffset + 2 ] = color[ 2 ];
pb.Buffer[ pbOffset + 3 ] = color[ 3 ];
if( error >= 0 )
{
error -= dx2;
pbOffset += y_inc;
}
error += dy2;
pbOffset += x_inc;
}
}
}
else
{
int error = dx2 - dy; // the discriminant i.e. error i.e. decision variable
// draw the line
if( pb.BytesPerPixel == 3 )
{
for( int index = 0; index <= dy; index++ )
{
// set the pixel
pb.Buffer[ pbOffset ] = color[ 0 ];
pb.Buffer[ pbOffset + 1 ] = color[ 1 ];
pb.Buffer[ pbOffset + 2 ] = color[ 2 ];
// test if error overflowed
if( error >= 0 )
{
error -= dy2;
// move to next line
pbOffset += x_inc;
}
// adjust the error term
error += dx2;
// move to the next pixel
pbOffset += y_inc;
}
}
else
{
for( int index = 0; index <= dy; index++ )
{
pb.Buffer[ pbOffset ] = color[ 0 ];
pb.Buffer[ pbOffset + 1 ] = color[ 1 ];
pb.Buffer[ pbOffset + 2 ] = color[ 2 ];
pb.Buffer[ pbOffset + 3 ] = color[ 3 ];
if( error >= 0 )
{
error -= dy2;
pbOffset += x_inc;
}
error += dx2;
pbOffset += y_inc;
}
}
}
}
