CLK/Outputs/CRT/CRTOpenGL.cpp

//  CRTOpenGL.cpp
//  Clock Signal
//
//  Created by Thomas Harte on 03/02/2016.
//  Copyright © 2016 Thomas Harte. All rights reserved.
//

#include "CRT.hpp"
#include <stdlib.h>
#include <math.h>

#include "OpenGL.hpp"
#include "TextureTarget.hpp"
#include "Shader.hpp"
#include "CRTOpenGL.hpp"

using namespace Outputs;

struct CRT::OpenGLState {
	std::unique_ptr<OpenGL::Shader> rgb_shader_program;
	std::unique_ptr<OpenGL::Shader> composite_input_shader_program, composite_output_shader_program;
	GLuint arrayBuffer, vertexArray;
	size_t verticesPerSlice;

	GLint positionAttribute;
	GLint textureCoordinatesAttribute;
	GLint lateralAttribute;
	GLint timestampAttribute;

	GLint windowSizeUniform, timestampBaseUniform;
	GLint boundsOriginUniform, boundsSizeUniform;

	GLuint textureName, shadowMaskTextureName;

	GLuint defaultFramebuffer;

	std::unique_ptr<OpenGL::TextureTarget> compositeTexture;	// receives raw composite levels
	std::unique_ptr<OpenGL::TextureTarget> filteredYTexture;	// receives filtered Y in the R channel plus unfiltered I/U and Q/V in G and B
	std::unique_ptr<OpenGL::TextureTarget> filteredTexture;		// receives filtered YIQ or YUV
};

namespace {
	static const GLenum first_supplied_buffer_texture_unit = 3;
}

static GLenum formatForDepth(size_t depth)
{
	switch(depth)
	{
		default: return GL_FALSE;
		case 1: return GL_RED;
		case 2: return GL_RG;
		case 3: return GL_RGB;
		case 4: return GL_RGBA;
	}
}

void CRT::construct_openGL()
{
	_openGL_state = nullptr;
	_composite_shader = _rgb_shader = nullptr;
}

void CRT::destruct_openGL()
{
	delete _openGL_state;
	_openGL_state = nullptr;
	if(_composite_shader) free(_composite_shader);
	if(_rgb_shader) free(_rgb_shader);
}

void CRT::draw_frame(unsigned int output_width, unsigned int output_height, bool only_if_dirty)
{
	// establish essentials
	if(!_openGL_state)
	{
		_openGL_state = new OpenGLState;

		// generate and bind textures for every one of the requested buffers
		for(unsigned int buffer = 0; buffer < _buffer_builder->number_of_buffers; buffer++)
		{
			glGenTextures(1, &_openGL_state->textureName);
			glActiveTexture(GL_TEXTURE0 + first_supplied_buffer_texture_unit +  buffer);
			glBindTexture(GL_TEXTURE_2D, _openGL_state->textureName);
			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

			GLenum format = formatForDepth(_buffer_builder->buffers[buffer].bytes_per_pixel);
			glTexImage2D(GL_TEXTURE_2D, 0, (GLint)format, CRTInputBufferBuilderWidth, CRTInputBufferBuilderHeight, 0, format, GL_UNSIGNED_BYTE, _buffer_builder->buffers[buffer].data);
		}

		glGenVertexArrays(1, &_openGL_state->vertexArray);
		glGenBuffers(1, &_openGL_state->arrayBuffer);
		_openGL_state->verticesPerSlice = 0;

		prepare_composite_input_shader();
		prepare_rgb_output_shader();

		glBindBuffer(GL_ARRAY_BUFFER, _openGL_state->arrayBuffer);
		glBindVertexArray(_openGL_state->vertexArray);
		prepare_vertex_array();

		// This should return either an actual framebuffer number, if this is a target with a framebuffer intended for output,
		// or 0 if no framebuffer is bound, in which case 0 is also what we want to supply to bind the implied framebuffer. So
		// it works either way.
		glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint *)&_openGL_state->defaultFramebuffer);

		// Create intermediate textures and bind to slots 0, 1 and 2
		glActiveTexture(GL_TEXTURE0);
		_openGL_state->compositeTexture = std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget(CRTIntermediateBufferWidth, CRTIntermediateBufferHeight));
		glActiveTexture(GL_TEXTURE1);
		_openGL_state->filteredYTexture = std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget(CRTIntermediateBufferWidth, CRTIntermediateBufferHeight));
		glActiveTexture(GL_TEXTURE2);
		_openGL_state->filteredTexture = std::unique_ptr<OpenGL::TextureTarget>(new OpenGL::TextureTarget(CRTIntermediateBufferWidth, CRTIntermediateBufferHeight));
	}

//		glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint *)&_openGL_state->defaultFramebuffer);
//
//		printf("%d", glIsFramebuffer(_openGL_state->defaultFramebuffer));

	// lock down any further work on the current frame
	_output_mutex->lock();

	// upload more source pixel data if any; we'll always resubmit the last line submitted last
	// time as it may have had extra data appended to it
	for(unsigned int buffer = 0; buffer < _buffer_builder->number_of_buffers; buffer++)
	{
		glActiveTexture(GL_TEXTURE0 + first_supplied_buffer_texture_unit + buffer);
		GLenum format = formatForDepth(_buffer_builder->buffers[0].bytes_per_pixel);
		if(_buffer_builder->_next_write_y_position < _buffer_builder->last_uploaded_line)
		{
			glTexSubImage2D(GL_TEXTURE_2D, 0,
								0, (GLint)_buffer_builder->last_uploaded_line,
								CRTInputBufferBuilderWidth, (GLint)(CRTInputBufferBuilderHeight - _buffer_builder->last_uploaded_line),
								format, GL_UNSIGNED_BYTE,
								&_buffer_builder->buffers[0].data[_buffer_builder->last_uploaded_line * CRTInputBufferBuilderWidth * _buffer_builder->buffers[0].bytes_per_pixel]);
			_buffer_builder->last_uploaded_line = 0;
		}

		if(_buffer_builder->_next_write_y_position > _buffer_builder->last_uploaded_line)
		{
			glTexSubImage2D(GL_TEXTURE_2D, 0,
								0, (GLint)_buffer_builder->last_uploaded_line,
								CRTInputBufferBuilderWidth, (GLint)(1 + _buffer_builder->_next_write_y_position - _buffer_builder->last_uploaded_line),
								format, GL_UNSIGNED_BYTE,
								&_buffer_builder->buffers[0].data[_buffer_builder->last_uploaded_line * CRTInputBufferBuilderWidth * _buffer_builder->buffers[0].bytes_per_pixel]);
			_buffer_builder->last_uploaded_line = _buffer_builder->_next_write_y_position;
		}
	}

	// check for anything to decode from composite
	if(_composite_src_runs->number_of_vertices)
	{
		_openGL_state->composite_input_shader_program->bind();
		_composite_src_runs->reset();
	}

//	_output_mutex->unlock();
//	return;

	// reinstate the output framebuffer
//	glBindTexture(GL_TEXTURE_2D, _openGL_state->textureName);
//	glGetIntegerv(GL_VIEWPORT, results);

	// ensure array buffer is up to date
	size_t max_number_of_vertices = 0;
	for(int c = 0; c < kCRTNumberOfFields; c++)
	{
		max_number_of_vertices = std::max(max_number_of_vertices, _run_builders[c]->number_of_vertices);
	}
	if(_openGL_state->verticesPerSlice < max_number_of_vertices)
	{
		_openGL_state->verticesPerSlice = max_number_of_vertices;
		glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)(max_number_of_vertices * kCRTOutputVertexSize * kCRTOutputVertexSize), NULL, GL_STREAM_DRAW);

		for(unsigned int c = 0; c < kCRTNumberOfFields; c++)
		{
			uint8_t *data = &_run_builders[c]->_runs[0];
			glBufferSubData(GL_ARRAY_BUFFER, (GLsizeiptr)(c * _openGL_state->verticesPerSlice * kCRTOutputVertexSize), (GLsizeiptr)(_run_builders[c]->number_of_vertices * kCRTOutputVertexSize), data);
			_run_builders[c]->uploaded_vertices = _run_builders[c]->number_of_vertices;
		}
	}

	// switch to the output shader
	if(_openGL_state->rgb_shader_program)
	{
	_openGL_state->rgb_shader_program->bind();

	// update uniforms
	push_size_uniforms(output_width, output_height);

	// Ensure we're back on the output framebuffer
	glBindFramebuffer(GL_FRAMEBUFFER, _openGL_state->defaultFramebuffer);

	// clear the buffer
	glClear(GL_COLOR_BUFFER_BIT);

	// draw all sitting frames
	unsigned int run = (unsigned int)_run_write_pointer;
//	printf("%d: %zu v %zu\n", run, _run_builders[run]->uploaded_vertices, _run_builders[run]->number_of_vertices);
	GLint total_age = 0;
	for(int c = 0; c < kCRTNumberOfFields; c++)
	{
		// update the total age at the start of this set of runs
		total_age += _run_builders[run]->duration;

		if(_run_builders[run]->number_of_vertices > 0)
		{
			glUniform1f(_openGL_state->timestampBaseUniform, (GLfloat)total_age);

			if(_run_builders[run]->uploaded_vertices != _run_builders[run]->number_of_vertices)
			{
				uint8_t *data =  &_run_builders[run]->_runs[_run_builders[run]->uploaded_vertices * kCRTOutputVertexSize];
				glBufferSubData(GL_ARRAY_BUFFER,
								(GLsizeiptr)(((run * _openGL_state->verticesPerSlice) + _run_builders[run]->uploaded_vertices) * kCRTOutputVertexSize),
								(GLsizeiptr)((_run_builders[run]->number_of_vertices - _run_builders[run]->uploaded_vertices) * kCRTOutputVertexSize), data);
				_run_builders[run]->uploaded_vertices = _run_builders[run]->number_of_vertices;
			}

			// draw this frame
			glDrawArrays(GL_TRIANGLE_STRIP, (GLint)(run * _openGL_state->verticesPerSlice), (GLsizei)_run_builders[run]->number_of_vertices);
		}

		// advance back in time
		run = (run - 1 + kCRTNumberOfFields) % kCRTNumberOfFields;
	}
	}

	_output_mutex->unlock();
}

void CRT::set_openGL_context_will_change(bool should_delete_resources)
{
	_openGL_state = nullptr;
}

void CRT::push_size_uniforms(unsigned int output_width, unsigned int output_height)
{
	if(_openGL_state->windowSizeUniform >= 0)
	{
		glUniform2f(_openGL_state->windowSizeUniform, output_width, output_height);
	}

	GLfloat outputAspectRatioMultiplier = ((float)output_width / (float)output_height) / (4.0f / 3.0f);

	Rect _aspect_ratio_corrected_bounds = _visible_area;

	GLfloat bonusWidth = (outputAspectRatioMultiplier - 1.0f) * _visible_area.size.width;
	_aspect_ratio_corrected_bounds.origin.x -= bonusWidth * 0.5f * _aspect_ratio_corrected_bounds.size.width;
	_aspect_ratio_corrected_bounds.size.width *= outputAspectRatioMultiplier;

	if(_openGL_state->boundsOriginUniform >= 0)
		glUniform2f(_openGL_state->boundsOriginUniform, (GLfloat)_aspect_ratio_corrected_bounds.origin.x, (GLfloat)_aspect_ratio_corrected_bounds.origin.y);

	if(_openGL_state->boundsSizeUniform >= 0)
		glUniform2f(_openGL_state->boundsSizeUniform, (GLfloat)_aspect_ratio_corrected_bounds.size.width, (GLfloat)_aspect_ratio_corrected_bounds.size.height);
}

void CRT::set_composite_sampling_function(const char *shader)
{
	_composite_shader = strdup(shader);
}

void CRT::set_rgb_sampling_function(const char *shader)
{
	_rgb_shader = strdup(shader);
}

#pragma mark - Input vertex shader (i.e. from source data to intermediate line layout)

char *CRT::get_input_vertex_shader()
{
	return strdup(
		"#version 150\n"

		"in vec2 inputPosition;"
		"in vec2 outputPosition;"
		"in vec2 phaseAndAmplitude;"
		"in float phaseTime;"

		"uniform vec2 outputTextureSize;"
		"uniform vec2 inputTextureSize;"
		"uniform float phaseCyclesPerTick;"

		"out vec2 inputPositionVarying;"
		"out float phaseVarying;"

		"void main(void)"
		"{"
			"inputPositionVarying = vec2(inputPositionVarying.x / inputTextureSize.x, (inputPositionVarying.y + 0.5) / inputTextureSize.y);"
			"gl_Position = vec4(outputPosition.x * 2.0 / outputTextureSize - 1.0, outputPosition.y * 2.0 / outputTextureSize - 1.0, 0.0, 1.0);"
			"phaseVarying = (phaseCyclesPerTick * phaseTime + phaseAndAmplitude.x) * 2.0 * 3.141592654;"
		"}");
}

char *CRT::get_input_fragment_shader()
{
	const char *composite_shader = _composite_shader;
	if(!composite_shader)
	{
		// TODO: synthesise an RGB -> (selected colour space) shader
	}

	return get_compound_shader(
		"#version 150\n"

		"in vec2 inputPositionVarying;"
		"in float phaseVarying;"

		"out vec4 fragColour;"

		"uniform sampler2D texID;"

		"\n%s\n"

		"void main(void)"
		"{"
			"fragColour = vec4(composite_sample(inputPositionVarying, phaseVarying), 0.0, 0.0, 1.0);"
		"}"
	, composite_shader);
}

#pragma mark - Intermediate vertex shaders (i.e. from intermediate line layout to intermediate line layout)

#pragma mark - Output vertex shader

char *CRT::get_output_vertex_shader()
{
	// the main job of the vertex shader is just to map from an input area of [0,1]x[0,1], with the origin in the
	// top left to OpenGL's [-1,1]x[-1,1] with the origin in the lower left, and to convert input data coordinates
	// from integral to floating point.

	return strdup(
		"#version 150\n"

		"in vec2 position;"
		"in vec2 srcCoordinates;"
		"in float lateral;"
		"in float timestamp;"

		"uniform vec2 boundsOrigin;"
		"uniform vec2 boundsSize;"

		"out float lateralVarying;"
		"out vec2 shadowMaskCoordinates;"
		"out float alpha;"

		"uniform vec2 textureSize;"
		"uniform float timestampBase;"
		"uniform float ticksPerFrame;"
		"uniform vec2 positionConversion;"
		"uniform vec2 scanNormal;"

		"const float shadowMaskMultiple = 600;"

		"out vec2 srcCoordinatesVarying;"

		"void main(void)"
		"{"
			"lateralVarying = lateral + 1.0707963267949;"

			"shadowMaskCoordinates = position * vec2(shadowMaskMultiple, shadowMaskMultiple * 0.85057471264368);"

			"srcCoordinatesVarying = vec2(srcCoordinates.x / textureSize.x, (srcCoordinates.y + 0.5) / textureSize.y);"
			"float age = (timestampBase - timestamp) / ticksPerFrame;"
			"alpha = min(10.0 * exp(-age * 2.0), 1.0);"

			"vec2 floatingPosition = (position / positionConversion) + lateral*scanNormal;"
			"vec2 mappedPosition = (floatingPosition - boundsOrigin) / boundsSize;"
			"gl_Position = vec4(mappedPosition.x * 2.0 - 1.0, 1.0 - mappedPosition.y * 2.0, 0.0, 1.0);"
		"}");
}

#pragma mark - Output fragment shaders; RGB and from composite

char *CRT::get_rgb_output_fragment_shader()
{
	return get_output_fragment_shader(_rgb_shader);
}

char *CRT::get_composite_output_fragment_shader()
{
	return get_output_fragment_shader(
		"vec4 rgb_sample(vec2 coordinate)"
		"{"
			"return texture(texID, coordinate);"
		"}");
}

char *CRT::get_output_fragment_shader(const char *sampling_function)
{
	return get_compound_shader(
		"#version 150\n"

		"in float lateralVarying;"
		"in float alpha;"
		"in vec2 shadowMaskCoordinates;"
		"in vec2 srcCoordinatesVarying;"

		"out vec4 fragColour;"

		"uniform sampler2D texID;"
		"uniform sampler2D shadowMaskTexID;"

		"\n%s\n"

		"void main(void)"
		"{"
			"fragColour = rgb_sample(srcCoordinatesVarying) * vec4(1.0, 1.0, 1.0, alpha * sin(lateralVarying));" //
		"}"
	, sampling_function);
}

#pragma mark - Shader utilities

char *CRT::get_compound_shader(const char *base, const char *insert)
{
	if(!base || !insert) return nullptr;
	size_t totalLength = strlen(base) + strlen(insert) + 1;
	char *text = new char[totalLength];
	snprintf(text, totalLength, base, insert);
	return text;
}

#pragma mark - Program compilation

void CRT::prepare_composite_input_shader()
{
	char *vertex_shader = get_input_vertex_shader();
	char *fragment_shader = get_input_fragment_shader();
	if(vertex_shader && fragment_shader)
	{
		_openGL_state->composite_input_shader_program = std::unique_ptr<OpenGL::Shader>(new OpenGL::Shader(vertex_shader, fragment_shader));

		GLint texIDUniform				= _openGL_state->composite_input_shader_program->get_uniform_location("texID");
		GLint inputTextureSizeUniform	= _openGL_state->composite_input_shader_program->get_uniform_location("inputTextureSize");
		GLint outputTextureSizeUniform	= _openGL_state->composite_input_shader_program->get_uniform_location("outputTextureSize");
		GLint phaseCyclesPerTickUniform	= _openGL_state->composite_input_shader_program->get_uniform_location("phaseCyclesPerTick");

		glUniform1i(texIDUniform, first_supplied_buffer_texture_unit);
		glUniform2f(outputTextureSizeUniform, CRTIntermediateBufferWidth, CRTIntermediateBufferHeight);
		glUniform2f(inputTextureSizeUniform, CRTInputBufferBuilderWidth, CRTInputBufferBuilderHeight);
		glUniform1f(phaseCyclesPerTickUniform, (float)_colour_cycle_numerator / (float)(_colour_cycle_denominator * _cycles_per_line));
	}
	free(vertex_shader);
	free(fragment_shader);
}

void CRT::prepare_rgb_output_shader()
{
	char *vertex_shader = get_output_vertex_shader();
	char *fragment_shader = get_rgb_output_fragment_shader();

	if(vertex_shader && fragment_shader)
	{
		_openGL_state->rgb_shader_program = std::unique_ptr<OpenGL::Shader>(new OpenGL::Shader(vertex_shader, fragment_shader));

		_openGL_state->rgb_shader_program->bind();

		_openGL_state->positionAttribute			= _openGL_state->rgb_shader_program->get_attrib_location("position");
		_openGL_state->textureCoordinatesAttribute	= _openGL_state->rgb_shader_program->get_attrib_location("srcCoordinates");
		_openGL_state->lateralAttribute				= _openGL_state->rgb_shader_program->get_attrib_location("lateral");
		_openGL_state->timestampAttribute			= _openGL_state->rgb_shader_program->get_attrib_location("timestamp");

		_openGL_state->windowSizeUniform			= _openGL_state->rgb_shader_program->get_uniform_location("windowSize");
		_openGL_state->boundsSizeUniform			= _openGL_state->rgb_shader_program->get_uniform_location("boundsSize");
		_openGL_state->boundsOriginUniform			= _openGL_state->rgb_shader_program->get_uniform_location("boundsOrigin");
		_openGL_state->timestampBaseUniform			= _openGL_state->rgb_shader_program->get_uniform_location("timestampBase");

		GLint texIDUniform				= _openGL_state->rgb_shader_program->get_uniform_location("texID");
		GLint shadowMaskTexIDUniform	= _openGL_state->rgb_shader_program->get_uniform_location("shadowMaskTexID");
		GLint textureSizeUniform		= _openGL_state->rgb_shader_program->get_uniform_location("textureSize");
		GLint ticksPerFrameUniform		= _openGL_state->rgb_shader_program->get_uniform_location("ticksPerFrame");
		GLint scanNormalUniform			= _openGL_state->rgb_shader_program->get_uniform_location("scanNormal");
		GLint positionConversionUniform	= _openGL_state->rgb_shader_program->get_uniform_location("positionConversion");

		glUniform1i(texIDUniform, first_supplied_buffer_texture_unit);
		glUniform1i(shadowMaskTexIDUniform, 1);
		glUniform2f(textureSizeUniform, CRTInputBufferBuilderWidth, CRTInputBufferBuilderHeight);
		glUniform1f(ticksPerFrameUniform, (GLfloat)(_cycles_per_line * _height_of_display));
		glUniform2f(positionConversionUniform, _horizontal_flywheel->get_scan_period(), _vertical_flywheel->get_scan_period() / (unsigned int)_vertical_flywheel_output_divider);

		float scan_angle = atan2f(1.0f / (float)_height_of_display, 1.0f);
		float scan_normal[] = { -sinf(scan_angle), cosf(scan_angle)};
		float multiplier = (float)_horizontal_flywheel->get_standard_period() / ((float)_height_of_display * (float)_horizontal_flywheel->get_scan_period());
		scan_normal[0] *= multiplier;
		scan_normal[1] *= multiplier;
		glUniform2f(scanNormalUniform, scan_normal[0], scan_normal[1]);
	}

	free(vertex_shader);
	free(fragment_shader);
}

void CRT::prepare_vertex_array()
{
	glEnableVertexAttribArray((GLuint)_openGL_state->positionAttribute);
	glEnableVertexAttribArray((GLuint)_openGL_state->textureCoordinatesAttribute);
	glEnableVertexAttribArray((GLuint)_openGL_state->lateralAttribute);
	glEnableVertexAttribArray((GLuint)_openGL_state->timestampAttribute);

	const GLsizei vertexStride = kCRTOutputVertexSize;
	glVertexAttribPointer((GLuint)_openGL_state->positionAttribute,				2, GL_UNSIGNED_SHORT,	GL_FALSE,	vertexStride, (void *)kCRTOutputVertexOffsetOfPosition);
	glVertexAttribPointer((GLuint)_openGL_state->textureCoordinatesAttribute,	2, GL_UNSIGNED_SHORT,	GL_FALSE,	vertexStride, (void *)kCRTOutputVertexOffsetOfTexCoord);
	glVertexAttribPointer((GLuint)_openGL_state->timestampAttribute,			4, GL_UNSIGNED_INT,		GL_FALSE,	vertexStride, (void *)kCRTOutputVertexOffsetOfTimestamp);
	glVertexAttribPointer((GLuint)_openGL_state->lateralAttribute,				1, GL_UNSIGNED_BYTE,	GL_FALSE,	vertexStride, (void *)kCRTOutputVertexOffsetOfLateral);
}

#pragma mark - Configuration

void CRT::set_output_device(CRT::OutputDevice output_device)
{
	if (_output_device != output_device)
	{
		_output_device = output_device;

		for(int builder = 0; builder < kCRTNumberOfFields; builder++)
		{
			_run_builders[builder]->reset();
		}
		_composite_src_runs->reset();
		_composite_src_output_y = 0;
	}
}


//	const char *const ntscVertexShaderGlobals =
//		"out vec2 srcCoordinatesVarying[4];\n"
//		"out float phase;\n";
//
//	const char *const ntscVertexShaderBody =
//		"phase = srcCoordinates.x * 6.283185308;\n"
//		"\n"
//		"srcCoordinatesVarying[0] = vec2(srcCoordinates.x / textureSize.x, (srcCoordinates.y + 0.5) / textureSize.y);\n"
//		"srcCoordinatesVarying[3] = srcCoordinatesVarying[0] + vec2(0.375 / textureSize.x, 0.0);\n"
//		"srcCoordinatesVarying[2] = srcCoordinatesVarying[0] + vec2(0.125 / textureSize.x, 0.0);\n"
//		"srcCoordinatesVarying[1] = srcCoordinatesVarying[0] - vec2(0.125 / textureSize.x, 0.0);\n"
//		"srcCoordinatesVarying[0] = srcCoordinatesVarying[0] - vec2(0.325 / textureSize.x, 0.0);\n";

	// assumes y = [0, 1], i and q = [-0.5, 0.5]; therefore i components are multiplied by 1.1914 versus standard matrices, q by 1.0452
//	const char *const yiqToRGB = "const mat3 yiqToRGB = mat3(1.0, 1.0, 1.0, 1.1389784, -0.3240608, -1.3176884, 0.6490692, -0.6762444, 1.7799756);";

	// assumes y = [0,1], u and v = [-0.5, 0.5]; therefore u components are multiplied by 1.14678899082569, v by 0.8130081300813
//	const char *const yuvToRGB = "const mat3 yiqToRGB = mat3(1.0, 1.0, 1.0, 0.0, -0.75213899082569, 2.33040137614679, 0.92669105691057, -0.4720325203252, 0.0);";

//	const char *const ntscFragmentShaderGlobals =
//		"in vec2 srcCoordinatesVarying[4];\n"
//		"in float phase;\n"
//		"\n"
//		"// for conversion from i and q are in the range [-0.5, 0.5] (so i needs to be multiplied by 1.1914 and q by 1.0452)\n"
//		"const mat3 yiqToRGB = mat3(1.0, 1.0, 1.0, 1.1389784, -0.3240608, -1.3176884, 0.6490692, -0.6762444, 1.7799756);\n";

//	const char *const ntscFragmentShaderBody =
//		"vec4 angles = vec4(phase) + vec4(-2.35619449019234, -0.78539816339745, 0.78539816339745, 2.35619449019234);\n"
//		"vec4 samples = vec4("
//		"   sample(srcCoordinatesVarying[0], angles.x),"
//		"	sample(srcCoordinatesVarying[1], angles.y),"
//		"	sample(srcCoordinatesVarying[2], angles.z),"
//		"	sample(srcCoordinatesVarying[3], angles.w)"
//		");\n"
//		"\n"
//		"float y = dot(vec4(0.25), samples);\n"
//		"samples -= vec4(y);\n"
//		"\n"
//		"float i = dot(cos(angles), samples);\n"
//		"float q = dot(sin(angles), samples);\n"
//		"\n"
//		"fragColour = 5.0 * texture(shadowMaskTexID, shadowMaskCoordinates) * vec4(yiqToRGB * vec3(y, i, q), 1.0);//sin(lateralVarying));\n";

//		dot(vec3(1.0/6.0, 2.0/3.0, 1.0/6.0), vec3(sample(srcCoordinatesVarying[0]), sample(srcCoordinatesVarying[0]), sample(srcCoordinatesVarying[0])));//sin(lateralVarying));\n";
//}