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Simplifies in-Metal transform logic, loading responsibility for setup onto the CPU.

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I think I've also finally excised whatever order-of-operations issue I was having with regard to non-4:3 displays.
This commit is contained in:
Thomas Harte 2020-09-10 20:32:58 -04:00
parent d7b405c6f8
commit bcaceff378
2 changed files with 44 additions and 24 deletions
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53
OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm
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@ -113,9 +113,7 @@ struct Uniforms {
float cyclesMultiplier;
float lineWidth;
float aspectRatioMultiplier;
float zoom;
simd::float2 offset;
simd::float3x3 sourcetoDisplay;
HalfConverter<simd::float3x3> toRGB;
HalfConverter<simd::float3x3> fromRGB;
@ -505,18 +503,49 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
- (void)setAspectRatio {
const auto modals = _scanTarget.modals();
const auto viewAspectRatio = (_view.bounds.size.width / _view.bounds.size.height);
simd::float3x3 sourceToDisplay{1.0f};
// Set the aspect ratio multiplier.
uniforms()->aspectRatioMultiplier = float(modals.aspect_ratio / viewAspectRatio);
// The starting coordinate space is [0, 1].
// Also work out the proper zoom.
const double fitWidthZoom = (viewAspectRatio / modals.aspect_ratio) / modals.visible_area.size.width;
const double fitHeightZoom = 1.0 / modals.visible_area.size.height;
uniforms()->zoom = float(std::min(fitWidthZoom, fitHeightZoom));
// Move the centre of the cropping rectangle to the centre of the display.
{
simd::float3x3 recentre{1.0f};
recentre.columns[2][0] = 0.5f - (modals.visible_area.origin.x + modals.visible_area.size.width * 0.5f);
recentre.columns[2][1] = 0.5f - (modals.visible_area.origin.y + modals.visible_area.size.height * 0.5f);
sourceToDisplay = recentre * sourceToDisplay;
}
// Store the offset.
uniforms()->offset.x = -modals.visible_area.origin.x;
uniforms()->offset.y = -modals.visible_area.origin.y;
// Convert from the internal [0, 1] to centred [-1, 1] (i.e. Metal's eye coordinates, though also appropriate
// for the zooming step that follows).
{
simd::float3x3 convertToEye;
convertToEye.columns[0][0] = 2.0f;
convertToEye.columns[1][1] = -2.0f;
convertToEye.columns[2][0] = -1.0f;
convertToEye.columns[2][1] = 1.0f;
convertToEye.columns[2][2] = 1.0f;
sourceToDisplay = convertToEye * sourceToDisplay;
}
// Determine the correct zoom level. This is a combination of (i) the necessary horizontal stretch to produce a proper
// aspect ratio; and (ii) the necessary zoom from there to either fit the visible area width or height as per a decision
// on letterboxing or pillarboxing.
const float aspectRatioStretch = float(modals.aspect_ratio / viewAspectRatio);
const float fitWidthZoom = 1.0f / (float(modals.visible_area.size.width) * aspectRatioStretch);
const float fitHeightZoom = 1.0f / float(modals.visible_area.size.height);
const float zoom = std::min(fitWidthZoom, fitHeightZoom);
// Convert from there to the proper aspect ratio by stretching or compressing width.
// After this the output is exactly centred, filling the vertical space and being as wide or slender as it likes.
{
simd::float3x3 applyAspectRatio{1.0f};
applyAspectRatio.columns[0][0] = aspectRatioStretch * zoom;
applyAspectRatio.columns[1][1] = zoom;
sourceToDisplay = applyAspectRatio * sourceToDisplay;
}
// Store.
uniforms()->sourcetoDisplay = sourceToDisplay;
}
- (void)setModals:(const Outputs::Display::ScanTarget::Modals &)modals {

15
OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal
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@ -21,12 +21,8 @@ struct Uniforms {
// This provides the intended height of a scan, in eye-coordinate terms.
float lineWidth;
// Provides a scaling factor in order to preserve 4:3 central content.
float aspectRatioMultiplier;
// Provides zoom and offset to scale the source data.
float zoom;
float2 offset;
float3x3 sourceToDisplay;
// Provides conversions to and from RGB for the active colour space.
half3x3 toRGB;
@ -152,13 +148,8 @@ template <typename Input> SourceInterpolator toDisplay(
// Hence determine this quad's real shape, using vertexID to pick a corner.
// position2d is now in the range [0, 1].
float2 position2d = start + (float(vertexID&2) * 0.5f) * tangent + (float(vertexID&1) - 0.5f) * normal * uniforms.lineWidth;
// Apply the requested offset and zoom, to map the desired area to the range [0, 1].
position2d = (position2d + uniforms.offset) * uniforms.zoom;
// Remap from [0, 1] to Metal's [-1, 1] and then apply the aspect ratio correction.
position2d = (position2d * float2(2.0f, -2.0f) + float2(-1.0f, 1.0f)) * float2(uniforms.aspectRatioMultiplier, 1.0f);
const float2 sourcePosition = start + (float(vertexID&2) * 0.5f) * tangent + (float(vertexID&1) - 0.5f) * normal * uniforms.lineWidth;
const float2 position2d = (uniforms.sourceToDisplay * float3(sourcePosition, 1.0f)).xy;
output.position = float4(
position2d,