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Merge pull request #854 from TomHarte/OpenGLNoColourBurst

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Avoids all risk of infinities when there is no colour burst
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Thomas Harte 2020-11-28 23:54:29 -05:00 committed by GitHub
commit 9610672615
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1 changed files with 33 additions and 31 deletions
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64
Outputs/OpenGL/ScanTargetGLSLFragments.cpp
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@ -341,7 +341,7 @@ std::unique_ptr<Shader> ScanTarget::conversion_shader() const {
vertex_shader +=
"compositeAngle = (mix(startCompositeAngle, endCompositeAngle, lateral) / 32.0) * 3.141592654;"
"compositeAmplitude = lineCompositeAmplitude / 255.0;"
"oneOverCompositeAmplitude = mix(0.0, 255.0 / lineCompositeAmplitude, step(0.01, lineCompositeAmplitude));";
"oneOverCompositeAmplitude = mix(0.0, 255.0 / lineCompositeAmplitude, step(0.95, lineCompositeAmplitude));";
}
vertex_shader +=
@ -379,40 +379,42 @@ std::unique_ptr<Shader> ScanTarget::conversion_shader() const {
switch(modals.display_type) {
case DisplayType::CompositeColour:
fragment_shader +=
"vec4 angles = compositeAngle + compositeAngleOffsets;"
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)"
");"
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)
);
// Compute a luminance for use if there's no colour information, now, before
// modifying samples.
"float mono_luminance = dot(samples, vec4(0.15, 0.35, 0.35, 0.15));"
// 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));
// 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);
// 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 = mix("
"lumaChromaToRGB * vec3(luminance / (1.0 - compositeAmplitude), channels),"
"vec3(mono_luminance),"
"step(oneOverCompositeAmplitude, 0.01)"
");";
// Apply a colour space conversion to get RGB.
fragColour3 = lumaChromaToRGB * vec3(luminance / (1.0 - compositeAmplitude), channels);
}
)x";
break;
case DisplayType::CompositeMonochrome:
@ -622,7 +624,7 @@ std::unique_ptr<Shader> ScanTarget::qam_separation_shader() const {
"compositeAngle = compositeAngle * 2.0 * 3.141592654;"
"compositeAmplitude = lineCompositeAmplitude / 255.0;"
"oneOverCompositeAmplitude = mix(0.0, 255.0 / lineCompositeAmplitude, step(0.01, lineCompositeAmplitude));";
"oneOverCompositeAmplitude = mix(0.0, 255.0 / lineCompositeAmplitude, step(0.95, lineCompositeAmplitude));";
if(is_svideo) {
vertex_shader +=