Eliminates the concept of an iCoordinate.

Real-life precision appears not to support the idea of sub-sample pixel storage.

Components/6560/6560.hpp

@@ -69,7 +69,7 @@ template <class BusHandler> class MOS6560 {
 				speaker_(audio_generator_)
 		{
 			crt_->set_svideo_sampling_function(
-				"vec2 svideo_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
+				"vec2 svideo_sample(usampler2D texID, vec2 coordinate, float phase, float amplitude)"
 				"{"
 					"vec2 yc = texture(texID, coordinate).rg / vec2(255.0);"
 

Components/9918/9918.cpp

@@ -92,7 +92,7 @@ TMS9918::TMS9918(Personality p) {
 	// Unimaginatively, this class just passes RGB through to the shader. Investigation is needed
 	// into whether there's a more natural form.
 	crt_->set_rgb_sampling_function(
-		"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
+		"vec3 rgb_sample(usampler2D sampler, vec2 coordinate)"
 		"{"
 			"return texture(sampler, coordinate).rgb / vec3(255.0);"
 		"}");

Machines/AmstradCPC/AmstradCPC.cpp

@@ -327,7 +327,7 @@ class CRTCBusHandler {
 		void setup_output(float aspect_ratio) {
 			crt_.reset(new Outputs::CRT::CRT(1024, 16, Outputs::CRT::DisplayType::PAL50, 1));
 			crt_->set_rgb_sampling_function(
-				"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
+				"vec3 rgb_sample(usampler2D sampler, vec2 coordinate)"
 				"{"
 					"uint sample = texture(texID, coordinate).r;"
 					"return vec3(float((sample >> 4) & 3u), float((sample >> 2) & 3u), float(sample & 3u)) / 2.0;"

Machines/AppleII/Video.cpp

@@ -18,7 +18,7 @@ VideoBase::VideoBase(bool is_iie, std::function<void(Cycles)> &&target) :
 	// Set a composite sampling function that assumes one byte per pixel input, and
 	// accepts any non-zero value as being fully on, zero being fully off.
 	crt_->set_composite_sampling_function(
-		"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
+		"float composite_sample(usampler2D sampler, vec2 coordinate, float phase, float amplitude)"
 		"{"
 			"return clamp(texture(sampler, coordinate).r, 0.0, 1.0);"
 		"}");

Machines/Atari2600/TIA.cpp

@@ -124,7 +124,7 @@ void TIA::set_output_mode(Atari2600::TIA::OutputMode output_mode) {
 
 	if(output_mode == OutputMode::NTSC) {
 		crt_->set_svideo_sampling_function(
-			"vec2 svideo_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
+			"vec2 svideo_sample(usampler2D texID, vec2 coordinate, float phase, float amplitude)"
 			"{"
 				"uint c = texture(texID, coordinate).r;"
 				"uint y = c & 14u;"
@@ -136,7 +136,7 @@ void TIA::set_output_mode(Atari2600::TIA::OutputMode output_mode) {
 		display_type = Outputs::CRT::DisplayType::NTSC60;
 	} else {
 		crt_->set_svideo_sampling_function(
-			"vec2 svideo_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
+			"vec2 svideo_sample(usampler2D texID, vec2 coordinate, float phase, float amplitude)"
 			"{"
 				"uint c = texture(texID, coordinate).r;"
 				"uint y = c & 14u;"

Machines/Electron/Video.cpp

@@ -52,13 +52,11 @@ VideoOutput::VideoOutput(uint8_t *memory) : ram_(memory) {
 
 	crt_.reset(new Outputs::CRT::CRT(crt_cycles_per_line, 8, Outputs::CRT::DisplayType::PAL50, 1));
 	crt_->set_rgb_sampling_function(
-		"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
+		"vec3 rgb_sample(usampler2D sampler, vec2 coordinate)"
 		"{"
 			"uint texValue = texture(sampler, coordinate).r;"
-			"texValue >>= 4 - (int(icoordinate.x) & 4);"
 			"return vec3( uvec3(texValue) & uvec3(4u, 2u, 1u));"
 		"}");
-	crt_->set_integer_coordinate_multiplier(8.0f);
 	std::unique_ptr<Outputs::CRT::TextureBuilder::Bookender> bookender(new FourBPPBookender);
 	crt_->set_bookender(std::move(bookender));
 	// TODO: as implied below, I've introduced a clock's latency into the graphics pipeline somehow. Investigate.

Machines/Oric/Video.cpp

@@ -25,13 +25,13 @@ VideoOutput::VideoOutput(uint8_t *memory) :
 		v_sync_start_position_(PAL50VSyncStartPosition), v_sync_end_position_(PAL50VSyncEndPosition),
 		counter_period_(PAL50Period) {
 	crt_->set_rgb_sampling_function(
-		"vec3 rgb_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate)"
+		"vec3 rgb_sample(usampler2D sampler, vec2 coordinate)"
 		"{"
 			"uint texValue = texture(sampler, coordinate).r;"
 			"return vec3( uvec3(texValue) & uvec3(4u, 2u, 1u));"
 		"}");
 	crt_->set_composite_sampling_function(
-		"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
+		"float composite_sample(usampler2D sampler, vec2 coordinate, float phase, float amplitude)"
 		"{"
 			"uint texValue = uint(dot(texture(sampler, coordinate).rg, uvec2(1, 256)));"
 			"uint iPhase = uint((phase + 3.141592654 + 0.39269908175) * 2.0 / 3.141592654) & 3u;"

Machines/ZX8081/Video.cpp

@@ -26,7 +26,7 @@ Video::Video() :
 	// Set a composite sampling function that assumes two-level input; either a byte is 0, which is black,
 	// or it is non-zero, which is white.
 	crt_->set_composite_sampling_function(
-		"float composite_sample(usampler2D sampler, vec2 coordinate, vec2 icoordinate, float phase, float amplitude)"
+		"float composite_sample(usampler2D sampler, vec2 coordinate, float phase, float amplitude)"
 		"{"
 			"return texture(sampler, coordinate).r;"
 		"}");

Outputs/CRT/CRT.hpp

@@ -280,7 +280,7 @@ class CRT {
 		/*!	Sets a function that will map from whatever data the machine provided to a composite signal.
 
 			@param shader A GLSL fragment including a function with the signature
-			`float composite_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)`
+			`float composite_sample(usampler2D texID, vec2 coordinate, float phase, float amplitude)`
 			that evaluates to the composite signal level as a function of a source buffer, sampling location, colour
 			carrier phase and amplitude.
 		*/
@@ -290,22 +290,6 @@ class CRT {
 			});
 		}
 
-		/*!
-			Sets a multiplier applied to iCoordinate values prior to their passing to the various sampling functions.
-			This multiplier is applied outside of the interpolation loop, making for a more precise interpolation
-			than if it were applied within the sampling function.
-
-			Idiomatically, this is likely to be the number of output pixels packed into each input sample where
-			packing is in use.
-
-			The default value is 1.0.
-		*/
-		inline void set_integer_coordinate_multiplier(float multiplier) {
-			enqueue_openGL_function([=] {
-				openGL_output_builder_.set_integer_coordinate_multiplier(multiplier);
-			});
-		}
-
 		enum CompositeSourceType {
 			/// The composite function provides continuous output.
 			Continuous,

Outputs/CRT/Internals/CRTOpenGL.cpp

@@ -524,12 +524,4 @@ void OpenGLOutputBuilder::set_timing_uniforms() {
 	if(rgb_input_shader_program_) {
 		rgb_input_shader_program_->set_width_scalers(1.0f, 1.0f);
 	}
-	set_integer_coordinate_multiplier(integer_coordinate_multiplier_);
-}
-
-void OpenGLOutputBuilder::set_integer_coordinate_multiplier(float multiplier) {
-	integer_coordinate_multiplier_ = multiplier;
-	if(composite_input_shader_program_) composite_input_shader_program_->set_integer_coordinate_multiplier(multiplier);
-	if(svideo_input_shader_program_) svideo_input_shader_program_->set_integer_coordinate_multiplier(multiplier);
-	if(rgb_input_shader_program_) rgb_input_shader_program_->set_integer_coordinate_multiplier(multiplier);
 }

Outputs/CRT/Internals/CRTOpenGL.hpp

@@ -105,8 +105,6 @@ class OpenGLOutputBuilder {
 		float get_composite_output_width() const;
 		void set_output_shader_width();
 
-		float integer_coordinate_multiplier_ = 1.0f;
-
 		// Maintain a couple of rectangles for masking off the extreme edge of the display;
 		// this is a bit of a cheat: there's some tolerance in when a sync pulse will be
 		// generated. So it might be slightly later than expected. Which might cause a scan
@@ -174,7 +172,6 @@ class OpenGLOutputBuilder {
 		void set_rgb_sampling_function(const std::string &);
 		void set_video_signal(VideoSignal);
 		void set_timing(unsigned int input_frequency, unsigned int cycles_per_line, unsigned int height_of_display, unsigned int horizontal_scan_period, unsigned int vertical_scan_period, unsigned int vertical_period_divider);
-		void set_integer_coordinate_multiplier(float multiplier);
 };
 
 }

Outputs/CRT/Internals/Shaders/IntermediateShader.cpp

@@ -46,11 +46,9 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_shader(const std::s
 		"uniform float inputVerticalOffset;"
 		"uniform float outputVerticalOffset;"
 		"uniform float textureHeightDivisor;"
-		"uniform float iCoordinateMultiplier;"
 
 		"out vec3 phaseAndAmplitudeVarying;"
 		"out vec2 inputPositionsVarying[11];"
-		"out vec2 iInputPositionVarying;"
 		"out vec2 delayLinePositionVarying;"
 
 		"void main(void)"
@@ -75,9 +73,8 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_shader(const std::s
 			"vec2 extendedInputPosition = " << (input_is_inputPosition ? "inputPosition" : "outputPosition") << " + extensionVector;"
 			"vec2 extendedOutputPosition = outputPosition + extensionVector;"
 
-			// keep iInputPositionVarying in whole source pixels, scale mappedInputPosition to the ordinary normalised range
+			// scale mappedInputPosition to the ordinary normalised range
 			"vec2 textureSize = vec2(textureSize(texID, 0));"
-			"iInputPositionVarying = extendedInputPosition * iCoordinateMultiplier;"
 			"vec2 mappedInputPosition = extendedInputPosition / textureSize;"
 
 			// setup input positions spaced as per the supplied offsets; these are for filtering where required
@@ -120,7 +117,6 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_composite_source_sh
 		"#version 150\n"
 
 		"in vec2 inputPositionsVarying[11];"
-		"in vec2 iInputPositionVarying;"
 		"in vec3 phaseAndAmplitudeVarying;"
 
 		"out vec4 fragColour;"
@@ -132,18 +128,18 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_composite_source_sh
 		if(!svideo_shader.empty()) {
 			fragment_shader <<
 				svideo_shader <<
-				"float composite_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
+				"float composite_sample(usampler2D texID, vec2 coordinate, float phase, float amplitude)"
 				"{"
-					"vec2 svideoColour = svideo_sample(texID, coordinate, iCoordinate, phase, amplitude);"
+					"vec2 svideoColour = svideo_sample(texID, coordinate, phase, amplitude);"
 					"return mix(svideoColour.x, svideoColour.y, abs(amplitude));"
 				"}";
 		} else {
 			fragment_shader <<
 				rgb_shader <<
 				"uniform mat3 rgbToLumaChroma;"
-				"float composite_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
+				"float composite_sample(usampler2D texID, vec2 coordinate, float phase, float amplitude)"
 				"{"
-					"vec3 rgbColour = clamp(rgb_sample(texID, coordinate, iCoordinate), vec3(0.0), vec3(1.0));"
+					"vec3 rgbColour = clamp(rgb_sample(texID, coordinate), vec3(0.0), vec3(1.0));"
 					"vec3 lumaChromaColour = rgbToLumaChroma * rgbColour;"
 					"vec2 quadrature = vec2(cos(phase), sin(phase)) * vec2(abs(amplitude), amplitude);"
 					"return dot(lumaChromaColour, vec3(1.0 - abs(amplitude), quadrature));"
@@ -154,7 +150,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_composite_source_sh
 	fragment_shader <<
 		"void main(void)"
 		"{"
-			"fragColour = vec4(composite_sample(texID, inputPositionsVarying[5], iInputPositionVarying, phaseAndAmplitudeVarying.x, phaseAndAmplitudeVarying.y));"
+			"fragColour = vec4(composite_sample(texID, inputPositionsVarying[5], phaseAndAmplitudeVarying.x, phaseAndAmplitudeVarying.y));"
 		"}";
 
 	return make_shader(fragment_shader.str(), true, true);
@@ -166,7 +162,6 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_svideo_source_shade
 		"#version 150\n"
 
 		"in vec2 inputPositionsVarying[11];"
-		"in vec2 iInputPositionVarying;"
 		"in vec3 phaseAndAmplitudeVarying;"
 
 		"out vec3 fragColour;"
@@ -178,9 +173,9 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_svideo_source_shade
 		fragment_shader
 			<< rgb_shader <<
 			"uniform mat3 rgbToLumaChroma;"
-			"vec2 svideo_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
+			"vec2 svideo_sample(usampler2D texID, vec2 coordinate, float phase, float amplitude)"
 			"{"
-				"vec3 rgbColour = clamp(rgb_sample(texID, coordinate, iCoordinate), vec3(0.0), vec3(1.0));"
+				"vec3 rgbColour = clamp(rgb_sample(texID, coordinate), vec3(0.0), vec3(1.0));"
 				"vec3 lumaChromaColour = rgbToLumaChroma * rgbColour;"
 				"vec2 quadrature = vec2(cos(phase), sin(phase)) * vec2(1.0, sign(amplitude));"
 				"return vec2(lumaChromaColour.x, 0.5 + dot(quadrature, lumaChromaColour.yz) * 0.5);"
@@ -190,7 +185,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_svideo_source_shade
 	fragment_shader <<
 		"void main(void)"
 		"{"
-			"vec2 sample = svideo_sample(texID, inputPositionsVarying[5], iInputPositionVarying, phaseAndAmplitudeVarying.x, phaseAndAmplitudeVarying.y);"
+			"vec2 sample = svideo_sample(texID, inputPositionsVarying[5], phaseAndAmplitudeVarying.x, phaseAndAmplitudeVarying.y);"
 			"vec2 quadrature = vec2(cos(phaseAndAmplitudeVarying.x), sin(phaseAndAmplitudeVarying.x)) * vec2(1.0, sign(phaseAndAmplitudeVarying.y)) * 0.5 * phaseAndAmplitudeVarying.z;"
 			"fragColour = vec3(sample.x, vec2(0.5) + (sample.y * quadrature));"
 		"}";
@@ -204,7 +199,6 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_rgb_source_shader(c
 		"#version 150\n"
 
 		"in vec2 inputPositionsVarying[11];"
-		"in vec2 iInputPositionVarying;"
 		"in vec3 phaseAndAmplitudeVarying;"
 
 		"out vec3 fragColour;"
@@ -215,7 +209,7 @@ std::unique_ptr<IntermediateShader> IntermediateShader::make_rgb_source_shader(c
 
 		"void main(void)"
 		"{"
-			"fragColour = rgb_sample(texID, inputPositionsVarying[5], iInputPositionVarying);"
+			"fragColour = rgb_sample(texID, inputPositionsVarying[5]);"
 		"}";
 
 	return make_shader(fragment_shader.str(), true, true);
@@ -439,7 +433,3 @@ void IntermediateShader::set_is_double_height(bool is_double_height, float input
 	set_uniform("inputVerticalOffset", input_offset);
 	set_uniform("outputVerticalOffset", output_offset);
 }
-
-void IntermediateShader::set_integer_coordinate_multiplier(float multiplier) {
-	set_uniform("iCoordinateMultiplier", multiplier);
-}

Outputs/CRT/Internals/Shaders/IntermediateShader.hpp

@@ -135,11 +135,6 @@ public:
 	*/
 	void set_is_double_height(bool is_double_height, float input_offset = 0.0f, float output_offset = 0.0f);
 
-	/*!
-		Sets the multiplier applied in the vertex shader to iCoordinates.
-	*/
-	void set_integer_coordinate_multiplier(float);
-
 private:
 	static std::unique_ptr<IntermediateShader> make_shader(const std::string &fragment_shader, bool use_usampler, bool input_is_inputPosition);
 };