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CLK/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
Ryan Carsten Schmidt 5ef6b190af Fix typos
2023-12-16 03:53:07 -06:00

685 lines
23 KiB
C++

//
// ScanTargetVertexArrayAttributs.cpp
// Clock Signal
//
// Created by Thomas Harte on 11/11/2018.
// Copyright © 2018 Thomas Harte. All rights reserved.
//
#include "ScanTarget.hpp"
#include <cmath>
#ifndef M_PI
#define M_PI 3.1415926f
#endif
using namespace Outputs::Display::OpenGL;
// MARK: - State setup for compiled shaders.
void ScanTarget::set_uniforms(ShaderType type, Shader &target) const {
// Slightly over-amping rowHeight here is a cheap way to make sure that lines
// converge even allowing for the fact that they may not be spaced by exactly
// the expected distance. Cf. the stencil-powered logic for making sure all
// pixels are painted only exactly once per field.
const auto modals = BufferingScanTarget::modals();
switch(type) {
case ShaderType::Composition: break;
default:
target.set_uniform("rowHeight", GLfloat(1.05f / modals.expected_vertical_lines));
target.set_uniform("scale", GLfloat(modals.output_scale.x), GLfloat(modals.output_scale.y) * modals.aspect_ratio * (3.0f / 4.0f));
target.set_uniform("phaseOffset", GLfloat(modals.input_data_tweaks.phase_linked_luminance_offset));
const float clocks_per_angle = float(modals.cycles_per_line) * float(modals.colour_cycle_denominator) / float(modals.colour_cycle_numerator);
GLfloat texture_offsets[4];
GLfloat angles[4];
for(int c = 0; c < 4; ++c) {
GLfloat angle = (GLfloat(c) - 1.5f) / 4.0f;
texture_offsets[c] = angle * clocks_per_angle;
angles[c] = GLfloat(angle * 2.0f * M_PI);
}
target.set_uniform("textureCoordinateOffsets", 1, 4, texture_offsets);
target.set_uniform("compositeAngleOffsets", 4, 1, angles);
switch(modals.composite_colour_space) {
case ColourSpace::YIQ: {
const GLfloat rgbToYIQ[] = {0.299f, 0.596f, 0.211f, 0.587f, -0.274f, -0.523f, 0.114f, -0.322f, 0.312f};
const GLfloat yiqToRGB[] = {1.0f, 1.0f, 1.0f, 0.956f, -0.272f, -1.106f, 0.621f, -0.647f, 1.703f};
target.set_uniform_matrix("lumaChromaToRGB", 3, false, yiqToRGB);
target.set_uniform_matrix("rgbToLumaChroma", 3, false, rgbToYIQ);
} break;
case ColourSpace::YUV: {
const GLfloat rgbToYUV[] = {0.299f, -0.14713f, 0.615f, 0.587f, -0.28886f, -0.51499f, 0.114f, 0.436f, -0.10001f};
const GLfloat yuvToRGB[] = {1.0f, 1.0f, 1.0f, 0.0f, -0.39465f, 2.03211f, 1.13983f, -0.58060f, 0.0f};
target.set_uniform_matrix("lumaChromaToRGB", 3, false, yuvToRGB);
target.set_uniform_matrix("rgbToLumaChroma", 3, false, rgbToYUV);
} break;
}
break;
}
}
void ScanTarget::set_sampling_window(int output_width, int, Shader &target) {
const auto modals = BufferingScanTarget::modals();
if(modals.display_type != DisplayType::CompositeColour) {
const float one_pixel_width = float(modals.cycles_per_line) * modals.visible_area.size.width / float(output_width);
const float clocks_per_angle = float(modals.cycles_per_line) * float(modals.colour_cycle_denominator) / float(modals.colour_cycle_numerator);
GLfloat texture_offsets[4];
GLfloat angles[4];
for(int c = 0; c < 4; ++c) {
texture_offsets[c] = 1.0f * (((one_pixel_width * float(c)) / 3.0f) - (one_pixel_width * 0.5f));
angles[c] = GLfloat((texture_offsets[c] / clocks_per_angle) * 2.0f * M_PI);
}
target.set_uniform("textureCoordinateOffsets", 1, 4, texture_offsets);
target.set_uniform("compositeAngleOffsets", 4, 1, angles);
}
}
void ScanTarget::enable_vertex_attributes(ShaderType type, Shader &target) {
#define rt_offset_of(field, source) (reinterpret_cast<uint8_t *>(&source.field) - reinterpret_cast<uint8_t *>(&source))
// test_scan and test_line are here so that the byte offsets that need to be
// calculated inside a loop can be done so validly; offsetof requires constant arguments.
Scan test_scan;
Line test_line;
// Some GPUs require alignment and will need to copy vertex data to a
// shadow buffer otherwise
static_assert(sizeof(Scan) % 4 == 0);
static_assert(sizeof(Line) % 4 == 0);
switch(type) {
case ShaderType::Composition:
for(int c = 0; c < 2; ++c) {
const std::string prefix = c ? "end" : "start";
target.enable_vertex_attribute_with_pointer(
prefix + "DataX",
1, GL_UNSIGNED_SHORT, GL_FALSE,
sizeof(Scan),
reinterpret_cast<void *>(rt_offset_of(scan.end_points[c].data_offset, test_scan)),
1);
target.enable_vertex_attribute_with_pointer(
prefix + "Clock",
1, GL_UNSIGNED_SHORT, GL_FALSE,
sizeof(Scan),
reinterpret_cast<void *>(rt_offset_of(scan.end_points[c].cycles_since_end_of_horizontal_retrace, test_scan)),
1);
}
target.enable_vertex_attribute_with_pointer(
"dataY",
1, GL_UNSIGNED_SHORT, GL_FALSE,
sizeof(Scan),
reinterpret_cast<void *>(offsetof(Scan, data_y)),
1);
target.enable_vertex_attribute_with_pointer(
"lineY",
1, GL_UNSIGNED_SHORT, GL_FALSE,
sizeof(Scan),
reinterpret_cast<void *>(offsetof(Scan, line)),
1);
break;
default:
for(int c = 0; c < 2; ++c) {
const std::string prefix = c ? "end" : "start";
if(type == ShaderType::Conversion) {
target.enable_vertex_attribute_with_pointer(
prefix + "Point",
2, GL_UNSIGNED_SHORT, GL_FALSE,
sizeof(Line),
reinterpret_cast<void *>(rt_offset_of(end_points[c].x, test_line)),
1);
}
target.enable_vertex_attribute_with_pointer(
prefix + "Clock",
1, GL_UNSIGNED_SHORT, GL_FALSE,
sizeof(Line),
reinterpret_cast<void *>(rt_offset_of(end_points[c].cycles_since_end_of_horizontal_retrace, test_line)),
1);
target.enable_vertex_attribute_with_pointer(
prefix + "CompositeAngle",
1, GL_SHORT, GL_FALSE,
sizeof(Line),
reinterpret_cast<void *>(rt_offset_of(end_points[c].composite_angle, test_line)),
1);
}
target.enable_vertex_attribute_with_pointer(
"lineY",
1, GL_UNSIGNED_SHORT, GL_FALSE,
sizeof(Line),
reinterpret_cast<void *>(offsetof(Line, line)),
1);
target.enable_vertex_attribute_with_pointer(
"lineCompositeAmplitude",
1, GL_UNSIGNED_BYTE, GL_FALSE,
sizeof(Line),
reinterpret_cast<void *>(offsetof(Line, composite_amplitude)),
1);
break;
}
#undef rt_offset_of
}
std::vector<std::string> ScanTarget::bindings(ShaderType type) const {
switch(type) {
case ShaderType::Composition: return {
"startDataX",
"startClock",
"endDataX",
"endClock",
"dataY",
"lineY"
};
default: return {
"startPoint",
"endPoint",
"startClock",
"endClock",
"lineY",
"lineCompositeAmplitude",
"startCompositeAngle",
"endCompositeAngle"
};
}
}
// MARK: - Shader code.
std::string ScanTarget::sampling_function() const {
std::string fragment_shader;
const auto modals = BufferingScanTarget::modals();
const bool is_svideo = modals.display_type == DisplayType::SVideo;
if(is_svideo) {
fragment_shader +=
"vec2 svideo_sample(vec2 coordinate, float angle) {";
} else {
fragment_shader +=
"float composite_sample(vec2 coordinate, float angle) {";
}
switch(modals.input_data_type) {
case InputDataType::Luminance1:
case InputDataType::Luminance8:
// Easy, just copy across.
fragment_shader +=
is_svideo ?
"return vec2(textureLod(textureName, coordinate, 0).r, 0.0);" :
"return textureLod(textureName, coordinate, 0).r;";
break;
case InputDataType::PhaseLinkedLuminance8:
fragment_shader +=
"uint iPhase = uint(step(sign(angle), 0.0) * 3) ^ uint(abs(angle * 2.0 / 3.141592654) ) & 3u;";
fragment_shader +=
is_svideo ?
"return vec2(textureLod(textureName, coordinate, 0)[iPhase], 0.0);" :
"return textureLod(textureName, coordinate, 0)[iPhase];";
break;
case InputDataType::Luminance8Phase8:
fragment_shader +=
"vec2 yc = textureLod(textureName, coordinate, 0).rg;"
"float phaseOffset = 3.141592654 * 2.0 * 2.0 * yc.y;"
"float rawChroma = step(yc.y, 0.75) * cos(angle + phaseOffset);";
fragment_shader +=
is_svideo ?
"return vec2(yc.x, rawChroma);" :
"return mix(yc.x, rawChroma, compositeAmplitude);";
break;
case InputDataType::Red1Green1Blue1:
case InputDataType::Red2Green2Blue2:
case InputDataType::Red4Green4Blue4:
case InputDataType::Red8Green8Blue8:
fragment_shader +=
"vec3 colour = rgbToLumaChroma * textureLod(textureName, coordinate, 0).rgb;"
"vec2 quadrature = vec2(cos(angle), sin(angle));";
fragment_shader +=
is_svideo ?
"return vec2(colour.r, dot(quadrature, colour.gb));" :
"return mix(colour.r, dot(quadrature, colour.gb), compositeAmplitude);";
break;
}
fragment_shader += "}";
return fragment_shader;
}
std::unique_ptr<Shader> ScanTarget::conversion_shader() const {
const auto modals = BufferingScanTarget::modals();
// Compose a vertex shader. If the display type is RGB, generate just the proper
// geometry position, plus a solitary textureCoordinate.
//
// If the display type is anything other than RGB, also produce composite
// angle and 1/composite amplitude as outputs.
//
// If the display type is composite colour, generate four textureCoordinates,
// spanning a range of -135, -45, +45, +135 degrees.
//
// If the display type is S-Video, generate three textureCoordinates, at
// -45, 0, +45.
std::string vertex_shader =
"#version 150\n"
"uniform vec2 scale;"
"uniform float rowHeight;"
"in vec2 startPoint;"
"in vec2 endPoint;"
"in float startClock;"
"in float startCompositeAngle;"
"in float endClock;"
"in float endCompositeAngle;"
"in float lineY;"
"in float lineCompositeAmplitude;"
"uniform sampler2D textureName;"
"uniform sampler2D qamTextureName;"
"uniform vec2 origin;"
"uniform vec2 size;"
"uniform float textureCoordinateOffsets[4];"
"out vec2 textureCoordinates[4];";
std::string fragment_shader =
"#version 150\n"
"uniform sampler2D textureName;"
"uniform sampler2D qamTextureName;"
"in vec2 textureCoordinates[4];"
"out vec4 fragColour;";
if(modals.display_type != DisplayType::RGB) {
vertex_shader +=
"out float compositeAngle;"
"out float compositeAmplitude;"
"out float oneOverCompositeAmplitude;"
"uniform float angleOffsets[4];";
fragment_shader +=
"in float compositeAngle;"
"in float compositeAmplitude;"
"in float oneOverCompositeAmplitude;"
"uniform vec4 compositeAngleOffsets;";
}
if(modals.display_type == DisplayType::SVideo || modals.display_type == DisplayType::CompositeColour) {
vertex_shader += "out vec2 qamTextureCoordinates[4];";
fragment_shader += "in vec2 qamTextureCoordinates[4];";
}
// Add the code to generate a proper output position; this applies to all display types.
vertex_shader +=
"void main(void) {"
"float lateral = float(gl_VertexID & 1);"
"float longitudinal = float((gl_VertexID & 2) >> 1);"
"vec2 centrePoint = mix(startPoint, vec2(endPoint.x, startPoint.y), lateral) / scale;"
"vec2 height = normalize(vec2(endPoint.x, startPoint.y) - startPoint).yx * (longitudinal - 0.5) * rowHeight;"
"vec2 eyePosition = vec2(-1.0, 1.0) + vec2(2.0, -2.0) * (((centrePoint + height) - origin) / size);"
"gl_Position = vec4(eyePosition, 0.0, 1.0);";
// For everything other than RGB, calculate the two composite outputs.
if(modals.display_type != DisplayType::RGB) {
vertex_shader +=
"compositeAngle = (mix(startCompositeAngle, endCompositeAngle, lateral) / 32.0) * 3.141592654;"
"compositeAmplitude = lineCompositeAmplitude / 255.0;"
"oneOverCompositeAmplitude = mix(0.0, 255.0 / lineCompositeAmplitude, step(0.95, lineCompositeAmplitude));";
}
vertex_shader +=
"float centreClock = mix(startClock, endClock, lateral);"
"textureCoordinates[0] = vec2(centreClock + textureCoordinateOffsets[0], lineY + 0.5) / textureSize(textureName, 0);"
"textureCoordinates[1] = vec2(centreClock + textureCoordinateOffsets[1], lineY + 0.5) / textureSize(textureName, 0);"
"textureCoordinates[2] = vec2(centreClock + textureCoordinateOffsets[2], lineY + 0.5) / textureSize(textureName, 0);"
"textureCoordinates[3] = vec2(centreClock + textureCoordinateOffsets[3], lineY + 0.5) / textureSize(textureName, 0);";
if((modals.display_type == DisplayType::SVideo) || (modals.display_type == DisplayType::CompositeColour)) {
vertex_shader +=
"float centreCompositeAngle = abs(mix(startCompositeAngle, endCompositeAngle, lateral)) * 4.0 / 64.0;"
"centreCompositeAngle = floor(centreCompositeAngle);"
"qamTextureCoordinates[0] = vec2(centreCompositeAngle - 1.5, lineY + 0.5) / textureSize(textureName, 0);"
"qamTextureCoordinates[1] = vec2(centreCompositeAngle - 0.5, lineY + 0.5) / textureSize(textureName, 0);"
"qamTextureCoordinates[2] = vec2(centreCompositeAngle + 0.5, lineY + 0.5) / textureSize(textureName, 0);"
"qamTextureCoordinates[3] = vec2(centreCompositeAngle + 1.5, lineY + 0.5) / textureSize(textureName, 0);";
}
vertex_shader += "}";
// Compose a fragment shader.
if(modals.display_type != DisplayType::RGB) {
fragment_shader +=
"uniform mat3 lumaChromaToRGB;"
"uniform mat3 rgbToLumaChroma;";
fragment_shader += sampling_function();
}
fragment_shader +=
"void main(void) {"
"vec3 fragColour3;";
switch(modals.display_type) {
case DisplayType::CompositeColour:
fragment_shader += R"x(
vec4 angles = compositeAngle + compositeAngleOffsets;
// Sample four times over, at proper angle offsets.
vec4 samples = vec4(
composite_sample(textureCoordinates[0], angles.x),
composite_sample(textureCoordinates[1], angles.y),
composite_sample(textureCoordinates[2], angles.z),
composite_sample(textureCoordinates[3], angles.w)
);
// The outer structure of the OpenGL scan target means in practice that
// compositeAmplitude will be the same value across a piece of
// geometry. I am therefore optimistic that this conditional will not
// cause a divergence in fragment execution.
if(compositeAmplitude < 0.01) {
// Compute only a luminance for use if there's no colour information.
fragColour3 = vec3(dot(samples, vec4(0.15, 0.35, 0.35, 0.15)));
} else {
// Take the average to calculate luminance, then subtract that from all four samples to
// give chrominance.
float luminance = dot(samples, vec4(0.25));
// Split and average chrominance.
vec2 chrominances[4] = vec2[4](
textureLod(qamTextureName, qamTextureCoordinates[0], 0).gb,
textureLod(qamTextureName, qamTextureCoordinates[1], 0).gb,
textureLod(qamTextureName, qamTextureCoordinates[2], 0).gb,
textureLod(qamTextureName, qamTextureCoordinates[3], 0).gb
);
vec2 channels = (chrominances[0] + chrominances[1] + chrominances[2] + chrominances[3])*0.5 - vec2(1.0);
// Apply a colour space conversion to get RGB.
fragColour3 = lumaChromaToRGB * vec3(luminance / (1.0 - compositeAmplitude), channels);
}
)x";
break;
case DisplayType::CompositeMonochrome:
fragment_shader +=
"vec4 angles = compositeAngle + compositeAngleOffsets;"
"vec4 samples = vec4("
"composite_sample(textureCoordinates[0], angles.x),"
"composite_sample(textureCoordinates[1], angles.y),"
"composite_sample(textureCoordinates[2], angles.z),"
"composite_sample(textureCoordinates[3], angles.w)"
");"
"fragColour3 = vec3(dot(samples, vec4(0.15, 0.35, 0.35, 0.25)));";
break;
case DisplayType::RGB:
fragment_shader +=
"vec3 samples[4] = vec3[4]("
"textureLod(textureName, textureCoordinates[0], 0).rgb,"
"textureLod(textureName, textureCoordinates[1], 0).rgb,"
"textureLod(textureName, textureCoordinates[2], 0).rgb,"
"textureLod(textureName, textureCoordinates[3], 0).rgb"
");"
"fragColour3 = samples[0]*0.15 + samples[1]*0.35 + samples[2]*0.35 + samples[2]*0.15;";
break;
case DisplayType::SVideo:
fragment_shader +=
// Sample the S-Video stream to obtain luminance.
"vec4 angles = compositeAngle + compositeAngleOffsets;"
"vec4 samples = vec4("
"svideo_sample(textureCoordinates[0], angles.x).x,"
"svideo_sample(textureCoordinates[1], angles.y).x,"
"svideo_sample(textureCoordinates[2], angles.z).x,"
"svideo_sample(textureCoordinates[3], angles.w).x"
");"
"float luminance = dot(samples, vec4(0.15, 0.35, 0.35, 0.25));"
// Split and average chrominance.
"vec2 chrominances[4] = vec2[4]("
"textureLod(qamTextureName, qamTextureCoordinates[0], 0).gb,"
"textureLod(qamTextureName, qamTextureCoordinates[1], 0).gb,"
"textureLod(qamTextureName, qamTextureCoordinates[2], 0).gb,"
"textureLod(qamTextureName, qamTextureCoordinates[3], 0).gb"
");"
"vec2 channels = (chrominances[0] + chrominances[1] + chrominances[2] + chrominances[3])*0.5 - vec2(1.0);"
// Apply a colour space conversion to get RGB.
"fragColour3 = lumaChromaToRGB * vec3(luminance, channels);";
break;
}
// Apply a brightness adjustment if requested.
if(fabs(modals.brightness - 1.0f) > 0.05f) {
fragment_shader += "fragColour3 = fragColour3 * " + std::to_string(modals.brightness) + ";";
}
// Apply a gamma correction if required.
if(fabs(output_gamma_ - modals.intended_gamma) > 0.05f) {
const float gamma_ratio = output_gamma_ / modals.intended_gamma;
fragment_shader += "fragColour3 = pow(fragColour3, vec3(" + std::to_string(gamma_ratio) + "));";
}
fragment_shader +=
"fragColour = vec4(fragColour3, 0.64);"
"}";
return std::make_unique<Shader>(
vertex_shader,
fragment_shader,
bindings(ShaderType::Conversion)
);
}
std::unique_ptr<Shader> ScanTarget::composition_shader() const {
const auto modals = BufferingScanTarget::modals();
const std::string vertex_shader =
R"x(#version 150
in float startDataX;
in float startClock;
in float endDataX;
in float endClock;
in float dataY;
in float lineY;
out vec2 textureCoordinate;
uniform usampler2D textureName;
void main(void) {
float lateral = float(gl_VertexID & 1);
float longitudinal = float((gl_VertexID & 2) >> 1);
textureCoordinate = vec2(mix(startDataX, endDataX, lateral), dataY + 0.5) / textureSize(textureName, 0);
vec2 eyePosition = vec2(mix(startClock, endClock, lateral), lineY + longitudinal) / vec2(2048.0, 2048.0);
gl_Position = vec4(eyePosition*2.0 - vec2(1.0), 0.0, 1.0);
}
)x";
std::string fragment_shader =
R"x(#version 150
out vec4 fragColour;
in vec2 textureCoordinate;
uniform usampler2D textureName;
void main(void) {
)x";
switch(modals.input_data_type) {
case InputDataType::Luminance1:
fragment_shader += "fragColour = textureLod(textureName, textureCoordinate, 0).rrrr;";
break;
case InputDataType::Luminance8:
fragment_shader += "fragColour = textureLod(textureName, textureCoordinate, 0).rrrr / vec4(255.0);";
break;
case InputDataType::PhaseLinkedLuminance8:
case InputDataType::Luminance8Phase8:
case InputDataType::Red8Green8Blue8:
fragment_shader += "fragColour = textureLod(textureName, textureCoordinate, 0) / vec4(255.0);";
break;
case InputDataType::Red1Green1Blue1:
fragment_shader += "fragColour = vec4(textureLod(textureName, textureCoordinate, 0).rrr & uvec3(4u, 2u, 1u), 1.0);";
break;
case InputDataType::Red2Green2Blue2:
fragment_shader +=
"uint textureValue = textureLod(textureName, textureCoordinate, 0).r;"
"fragColour = vec4(float((textureValue >> 4) & 3u), float((textureValue >> 2) & 3u), float(textureValue & 3u), 3.0) / 3.0;";
break;
case InputDataType::Red4Green4Blue4:
fragment_shader +=
"uvec2 textureValue = textureLod(textureName, textureCoordinate, 0).rg;"
"fragColour = vec4(float(textureValue.r) / 15.0, float(textureValue.g & 240u) / 240.0, float(textureValue.g & 15u) / 15.0, 1.0);";
break;
}
return std::make_unique<Shader>(
vertex_shader,
fragment_shader + "}",
bindings(ShaderType::Composition)
);
}
std::unique_ptr<Shader> ScanTarget::qam_separation_shader() const {
const auto modals = BufferingScanTarget::modals();
const bool is_svideo = modals.display_type == DisplayType::SVideo;
// Sets up texture coordinates to run between startClock and endClock, mapping to
// coordinates that correlate with four times the absolute value of the composite angle.
std::string vertex_shader =
"#version 150\n"
"in float startClock;"
"in float startCompositeAngle;"
"in float endClock;"
"in float endCompositeAngle;"
"in float lineY;"
"in float lineCompositeAmplitude;"
"uniform sampler2D textureName;"
"uniform float textureCoordinateOffsets[4];"
"out float compositeAngle;"
"out float compositeAmplitude;"
"out float oneOverCompositeAmplitude;";
std::string fragment_shader =
"#version 150\n"
"uniform sampler2D textureName;"
"uniform mat3 rgbToLumaChroma;"
"in float compositeAngle;"
"in float compositeAmplitude;"
"in float oneOverCompositeAmplitude;"
"out vec4 fragColour;"
"uniform vec4 compositeAngleOffsets;";
if(is_svideo) {
vertex_shader += "out vec2 textureCoordinate;";
fragment_shader += "in vec2 textureCoordinate;";
} else {
vertex_shader += "out vec2 textureCoordinates[4];";
fragment_shader += "in vec2 textureCoordinates[4];";
}
vertex_shader +=
"void main(void) {"
"float lateral = float(gl_VertexID & 1);"
"float longitudinal = float((gl_VertexID & 2) >> 1);"
"float centreClock = mix(startClock, endClock, lateral);"
"compositeAngle = mix(startCompositeAngle, endCompositeAngle, lateral) / 64.0;"
"float snappedCompositeAngle = floor(abs(compositeAngle) * 4.0);"
"vec2 eyePosition = vec2(snappedCompositeAngle, lineY + longitudinal) / vec2(2048.0, 2048.0);"
"gl_Position = vec4(eyePosition*2.0 - vec2(1.0), 0.0, 1.0);"
"compositeAngle = compositeAngle * 2.0 * 3.141592654;"
"compositeAmplitude = lineCompositeAmplitude / 255.0;"
"oneOverCompositeAmplitude = mix(0.0, 255.0 / lineCompositeAmplitude, step(0.95, lineCompositeAmplitude));";
if(is_svideo) {
vertex_shader +=
"textureCoordinate = vec2(centreClock, lineY + 0.5) / textureSize(textureName, 0);";
} else {
vertex_shader +=
"textureCoordinates[0] = vec2(centreClock + textureCoordinateOffsets[0], lineY + 0.5) / textureSize(textureName, 0);"
"textureCoordinates[1] = vec2(centreClock + textureCoordinateOffsets[1], lineY + 0.5) / textureSize(textureName, 0);"
"textureCoordinates[2] = vec2(centreClock + textureCoordinateOffsets[2], lineY + 0.5) / textureSize(textureName, 0);"
"textureCoordinates[3] = vec2(centreClock + textureCoordinateOffsets[3], lineY + 0.5) / textureSize(textureName, 0);";
}
vertex_shader += "}";
fragment_shader +=
sampling_function() +
"void main(void) {";
if(modals.display_type == DisplayType::SVideo) {
fragment_shader +=
"fragColour = vec4(svideo_sample(textureCoordinate, compositeAngle).rgg * vec3(1.0, cos(compositeAngle), sin(compositeAngle)), 1.0);";
} else {
fragment_shader +=
"vec4 angles = compositeAngle + compositeAngleOffsets;"
// Sample four times over, at proper angle offsets.
"vec4 samples = vec4("
"composite_sample(textureCoordinates[0], angles.x),"
"composite_sample(textureCoordinates[1], angles.y),"
"composite_sample(textureCoordinates[2], angles.z),"
"composite_sample(textureCoordinates[3], angles.w)"
");"
// Take the average to calculate luminance, then subtract that from all four samples to
// give chrominance.
"float luminance = dot(samples, vec4(0.25));"
"float chrominance = (dot(samples.yz, vec2(0.5)) - luminance) * oneOverCompositeAmplitude;"
// Pack that all up and send it on its way.
"fragColour = vec4(luminance, vec2(cos(compositeAngle), sin(compositeAngle)) * chrominance, 1.0);";
};
fragment_shader +=
"fragColour = fragColour*0.5 + vec4(0.5);"
"}";
return std::make_unique<Shader>(
vertex_shader,
fragment_shader,
bindings(ShaderType::QAMSeparation)
);
}