slang-shaders/hdr/shaders/include/scanline_generation.h

137 lines
6.5 KiB
C

#define kPi 3.1415926536f
#define kEuler 2.718281828459f
#define kMax 1.0f
#define kBeamWidth 0.5f
const vec4 kFallOffControlPoints = vec4(0.0f, 0.0f, 0.0f, 1.0f);
const vec4 kAttackControlPoints = vec4(0.0f, 1.0f, 1.0f, 1.0f);
//const vec4 kScanlineControlPoints = vec4(1.0f, 1.0f, 0.0f, 0.0f);
const mat4 kCubicBezier = mat4( 1.0f, 0.0f, 0.0f, 0.0f,
-3.0f, 3.0f, 0.0f, 0.0f,
3.0f, -6.0f, 3.0f, 0.0f,
-1.0f, 3.0f, -3.0f, 1.0f );
float Bezier(const float t0, const vec4 control_points)
{
vec4 t = vec4(1.0, t0, t0*t0, t0*t0*t0);
return dot(t, control_points * kCubicBezier);
}
vec4 BeamControlPoints(const float beam_attack, const bool falloff)
{
const float inner_attack = clamp(beam_attack, 0.0f, 1.0);
const float outer_attack = clamp(beam_attack - 1.0f, 0.0f, 1.0);
return falloff ? kFallOffControlPoints + vec4(0.0f, outer_attack, inner_attack, 0.0f) : kAttackControlPoints - vec4(0.0f, inner_attack, outer_attack, 0.0f);
}
float ScanlineColour(const uint channel,
const vec2 tex_coord,
const vec2 source_size,
const float scanline_size,
const float source_tex_coord_x,
const float narrowed_source_pixel_offset,
const float vertical_convergence,
const float beam_attack,
const float scanline_min,
const float scanline_max,
const float scanline_attack,
inout float next_prev)
{
const float current_source_position_y = ((tex_coord.y * source_size.y) - vertical_convergence) + next_prev;
const float current_source_center_y = floor(current_source_position_y) + 0.5f;
const float source_tex_coord_y = current_source_center_y / source_size.y;
const float scanline_delta = fract(current_source_position_y) - 0.5f;
// Slightly increase the beam width to get maximum brightness
float beam_distance = abs(scanline_delta - next_prev) - (kBeamWidth / scanline_size);
beam_distance = beam_distance < 0.0f ? 0.0f : beam_distance;
const float scanline_distance = beam_distance * 2.0f;
next_prev = scanline_delta > 0.0f ? 1.0f : -1.0f;
const vec2 tex_coord_0 = vec2(source_tex_coord_x, source_tex_coord_y);
const vec2 tex_coord_1 = vec2(source_tex_coord_x + (1.0f / source_size.x), source_tex_coord_y);
const float sdr_channel_0 = COMPAT_TEXTURE(SourceSDR, tex_coord_0)[channel];
const float sdr_channel_1 = COMPAT_TEXTURE(SourceSDR, tex_coord_1)[channel];
const float hdr_channel_0 = COMPAT_TEXTURE(SourceHDR, tex_coord_0)[channel];
const float hdr_channel_1 = COMPAT_TEXTURE(SourceHDR, tex_coord_1)[channel];
/* Horizontal interpolation between pixels */
const float horiz_interp = Bezier(narrowed_source_pixel_offset, BeamControlPoints(beam_attack, sdr_channel_0 > sdr_channel_1));
const float hdr_channel = mix(hdr_channel_0, hdr_channel_1, horiz_interp);
const float sdr_channel = mix(sdr_channel_0, sdr_channel_1, horiz_interp);
const float channel_scanline_distance = clamp(scanline_distance / ((sdr_channel * (scanline_max - scanline_min)) + scanline_min), 0.0f, 1.0f);
const vec4 channel_control_points = vec4(1.0f, 1.0f, sdr_channel * scanline_attack, 0.0f);
const float luminance = Bezier(channel_scanline_distance, channel_control_points);
return luminance * hdr_channel;
}
float GenerateScanline( const uint channel,
const vec2 tex_coord,
const vec2 source_size,
const float scanline_size,
const float horizontal_convergence,
const float vertical_convergence,
const float beam_sharpness,
const float beam_attack,
const float scanline_min,
const float scanline_max,
const float scanline_attack)
{
const float current_source_position_x = (tex_coord.x * source_size.x) - horizontal_convergence;
const float current_source_center_x = floor(current_source_position_x) + 0.5f;
const float source_tex_coord_x = current_source_center_x / source_size.x;
const float source_pixel_offset = fract(current_source_position_x);
const float narrowed_source_pixel_offset = clamp(((source_pixel_offset - 0.5f) * beam_sharpness) + 0.5f, 0.0f, 1.0f);
float next_prev = 0.0f;
const float scanline_colour0 = ScanlineColour( channel,
tex_coord,
source_size,
scanline_size,
source_tex_coord_x,
narrowed_source_pixel_offset,
vertical_convergence,
beam_attack,
scanline_min,
scanline_max,
scanline_attack,
next_prev);
// Optionally sample the neighbouring scanline
float scanline_colour1 = 0.0f;
if(scanline_max > 1.0f)
{
scanline_colour1 = ScanlineColour( channel,
tex_coord,
source_size,
scanline_size,
source_tex_coord_x,
narrowed_source_pixel_offset,
vertical_convergence,
beam_attack,
scanline_min,
scanline_max,
scanline_attack,
next_prev);
}
return scanline_colour0 + scanline_colour1;
}