Typography improvements

2026-05-06 13:16:02 +10:00
parent 3dc7af6fc0
commit e59677c212
5 changed files with 126 additions and 129 deletions
--- a/README.md
+++ b/README.md
@@ -254,3 +254,4 @@ If neither variable is set, the workflow falls back to the repo-local defaults u
 - Continue source cleanup/refactoring. Pass 1 done
 - Support a separate sound shader `.slang` file in shader packages.
 - Add WebView2
+- move to MSDF, typography rasterisation
--- a/apps/LoopThroughWithOpenGLCompositing/gl/TextRasterizer.cpp
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/TextRasterizer.cpp
@@ -13,9 +13,9 @@
 namespace
 {
 constexpr int kTextSdfSpread = 20;
-constexpr unsigned kTextSdfBlurPasses = 1;
 constexpr float kTextFontPixelSize = 144.0f;
 constexpr float kTextLayoutPadding = 48.0f;
+constexpr float kSdfInfinity = 1.0e20f;

 class GdiplusSession
 {
@@ -54,128 +54,115 @@ std::wstring Utf8ToWide(const std::string& text)
 	return wide;
 }

-std::vector<unsigned char> BuildLocalSdf(const std::vector<unsigned char>& alpha, unsigned width, unsigned height)
+void DistanceTransform1D(const std::vector<float>& input, std::vector<float>& output, unsigned count)
 {
-	std::vector<unsigned char> sdf(static_cast<std::size_t>(width) * height * 4, 0);
+	std::vector<unsigned> locations(count, 0);
+	std::vector<float> boundaries(static_cast<std::size_t>(count) + 1, 0.0f);
+
+	unsigned segment = 0;
+	locations[0] = 0;
+	boundaries[0] = -kSdfInfinity;
+	boundaries[1] = kSdfInfinity;
+
+	for (unsigned q = 1; q < count; ++q)
+	{
+		float intersection = 0.0f;
+		for (;;)
+		{
+			const unsigned location = locations[segment];
+			intersection =
+				((input[q] + static_cast<float>(q * q)) - (input[location] + static_cast<float>(location * location))) /
+				(2.0f * static_cast<float>(q) - 2.0f * static_cast<float>(location));
+			if (intersection > boundaries[segment] || segment == 0)
+				break;
+			--segment;
+		}
+
+		++segment;
+		locations[segment] = q;
+		boundaries[segment] = intersection;
+		boundaries[segment + 1] = kSdfInfinity;
+	}
+
+	segment = 0;
+	for (unsigned q = 0; q < count; ++q)
+	{
+		while (boundaries[segment + 1] < static_cast<float>(q))
+			++segment;
+		const unsigned location = locations[segment];
+		const float delta = static_cast<float>(q) - static_cast<float>(location);
+		output[q] = delta * delta + input[location];
+	}
+}
+
+std::vector<float> DistanceTransform2D(const std::vector<unsigned char>& targetMask, unsigned width, unsigned height)
+{
+	std::vector<float> rowInput(width, 0.0f);
+	std::vector<float> rowOutput(width, 0.0f);
+	std::vector<float> columnInput(height, 0.0f);
+	std::vector<float> columnOutput(height, 0.0f);
+	std::vector<float> rowDistance(static_cast<std::size_t>(width) * height, 0.0f);
+	std::vector<float> distance(static_cast<std::size_t>(width) * height, 0.0f);
+
 	for (unsigned y = 0; y < height; ++y)
 	{
 		for (unsigned x = 0; x < width; ++x)
-		{
-			const bool inside = alpha[static_cast<std::size_t>(y) * width + x] > 127;
-			int bestDistanceSq = kTextSdfSpread * kTextSdfSpread;
-			for (int oy = -kTextSdfSpread; oy <= kTextSdfSpread; ++oy)
-			{
-				const int sy = static_cast<int>(y) + oy;
-				if (sy < 0 || sy >= static_cast<int>(height))
-					continue;
-				for (int ox = -kTextSdfSpread; ox <= kTextSdfSpread; ++ox)
-				{
-					const int sx = static_cast<int>(x) + ox;
-					if (sx < 0 || sx >= static_cast<int>(width))
-						continue;
-					const bool sampleInside = alpha[static_cast<std::size_t>(sy) * width + sx] > 127;
-					if (sampleInside == inside)
-						continue;
-					const int distanceSq = ox * ox + oy * oy;
-					if (distanceSq < bestDistanceSq)
-						bestDistanceSq = distanceSq;
-				}
+			rowInput[x] = targetMask[static_cast<std::size_t>(y) * width + x] ? 0.0f : kSdfInfinity;
+		DistanceTransform1D(rowInput, rowOutput, width);
+		for (unsigned x = 0; x < width; ++x)
+			rowDistance[static_cast<std::size_t>(y) * width + x] = rowOutput[x];
 	}

-			const float distance = std::sqrt(static_cast<float>(bestDistanceSq));
-			const float signedDistance = (inside ? 1.0f : -1.0f) * distance;
-			float normalized = 0.5f + signedDistance / static_cast<float>(kTextSdfSpread * 2);
-			const unsigned char sourceAlpha = alpha[static_cast<std::size_t>(y) * width + x];
-			if (sourceAlpha > 0 && sourceAlpha < 255)
-				normalized = static_cast<float>(sourceAlpha) / 255.0f;
-			if (normalized < 0.0f)
-				normalized = 0.0f;
-			if (normalized > 1.0f)
-				normalized = 1.0f;
+	for (unsigned x = 0; x < width; ++x)
+	{
+		for (unsigned y = 0; y < height; ++y)
+			columnInput[y] = rowDistance[static_cast<std::size_t>(y) * width + x];
+		DistanceTransform1D(columnInput, columnOutput, height);
+		for (unsigned y = 0; y < height; ++y)
+			distance[static_cast<std::size_t>(y) * width + x] = columnOutput[y];
+	}
+
+	return distance;
+}
+
+std::vector<unsigned char> BuildTextSdfTexture(const std::vector<unsigned char>& alpha, unsigned width, unsigned height)
+{
+	std::vector<unsigned char> insideMask(static_cast<std::size_t>(width) * height, 0);
+	std::vector<unsigned char> outsideMask(static_cast<std::size_t>(width) * height, 0);
+	for (std::size_t index = 0; index < alpha.size(); ++index)
+	{
+		const bool inside = alpha[index] > 127;
+		insideMask[index] = inside ? 1 : 0;
+		outsideMask[index] = inside ? 0 : 1;
+	}
+
+	const std::vector<float> distanceToInside = DistanceTransform2D(insideMask, width, height);
+	const std::vector<float> distanceToOutside = DistanceTransform2D(outsideMask, width, height);
+	std::vector<unsigned char> sdf(static_cast<std::size_t>(width) * height * 4, 0);
+
+	for (unsigned y = 0; y < height; ++y)
+	{
+		const unsigned flippedY = height - 1 - y;
+		for (unsigned x = 0; x < width; ++x)
+		{
+			const std::size_t source = static_cast<std::size_t>(y) * width + x;
+			const float signedDistance = std::sqrt(distanceToOutside[source]) - std::sqrt(distanceToInside[source]);
+			const float normalized = std::clamp(
+				0.5f + signedDistance / static_cast<float>(kTextSdfSpread * 2),
+				0.0f,
+				1.0f);
 			const unsigned char value = static_cast<unsigned char>(normalized * 255.0f + 0.5f);
-			const std::size_t out = (static_cast<std::size_t>(y) * width + x) * 4;
+			const std::size_t out = (static_cast<std::size_t>(flippedY) * width + x) * 4;
 			sdf[out + 0] = value;
 			sdf[out + 1] = value;
 			sdf[out + 2] = value;
 			sdf[out + 3] = value;
 		}
 	}
+
 	return sdf;
 }

-std::vector<unsigned char> BuildTextCoverageTexture(const std::vector<unsigned char>& alpha, unsigned width, unsigned height)
-{
-	std::vector<unsigned char> coverage(static_cast<std::size_t>(width) * height * 4, 0);
-	for (unsigned y = 0; y < height; ++y)
-	{
-		for (unsigned x = 0; x < width; ++x)
-		{
-			const unsigned char value = alpha[static_cast<std::size_t>(y) * width + x];
-			const std::size_t out = (static_cast<std::size_t>(y) * width + x) * 4;
-			coverage[out + 0] = value;
-			coverage[out + 1] = value;
-			coverage[out + 2] = value;
-			coverage[out + 3] = value;
-		}
-	}
-	return coverage;
-}
-
-std::vector<unsigned char> FlipTextTextureForShaderUv(const std::vector<unsigned char>& pixels, unsigned width, unsigned height)
-{
-	std::vector<unsigned char> flipped(pixels.size(), 0);
-	const std::size_t stride = static_cast<std::size_t>(width) * 4;
-	for (unsigned y = 0; y < height; ++y)
-	{
-		const std::size_t srcOffset = static_cast<std::size_t>(y) * stride;
-		const std::size_t dstOffset = static_cast<std::size_t>(height - 1 - y) * stride;
-		std::memcpy(flipped.data() + dstOffset, pixels.data() + srcOffset, stride);
-	}
-	return flipped;
-}
-
-std::vector<unsigned char> BlurTextSdf(const std::vector<unsigned char>& pixels, unsigned width, unsigned height, unsigned passes)
-{
-	std::vector<unsigned char> current = pixels;
-	std::vector<unsigned char> next(pixels.size(), 0);
-	for (unsigned pass = 0; pass < passes; ++pass)
-	{
-		for (unsigned y = 0; y < height; ++y)
-		{
-			for (unsigned x = 0; x < width; ++x)
-			{
-				unsigned weightedTotal = 0;
-				unsigned weightSum = 0;
-				for (int oy = -1; oy <= 1; ++oy)
-				{
-					const int sy = static_cast<int>(y) + oy;
-					if (sy < 0 || sy >= static_cast<int>(height))
-						continue;
-					for (int ox = -1; ox <= 1; ++ox)
-					{
-						const int sx = static_cast<int>(x) + ox;
-						if (sx < 0 || sx >= static_cast<int>(width))
-							continue;
-						const unsigned weight = (ox == 0 && oy == 0) ? 4u : ((ox == 0 || oy == 0) ? 2u : 1u);
-						const std::size_t sample = (static_cast<std::size_t>(sy) * width + sx) * 4;
-						weightedTotal += static_cast<unsigned>(current[sample]) * weight;
-						weightSum += weight;
-					}
-				}
-
-				const unsigned char value = static_cast<unsigned char>((weightedTotal + weightSum / 2) / weightSum);
-				const std::size_t out = (static_cast<std::size_t>(y) * width + x) * 4;
-				next[out + 0] = value;
-				next[out + 1] = value;
-				next[out + 2] = value;
-				next[out + 3] = value;
-			}
-		}
-		current.swap(next);
-	}
-	return current;
-}
-
 void WriteTextMaskDebugDump(const std::string& text, const std::vector<unsigned char>& alpha, const std::vector<unsigned char>& sdf, unsigned width, unsigned height)
 {
 	try
@@ -308,9 +295,7 @@ bool RasterizeTextSdf(const std::string& text, const std::filesystem::path& font
 			alpha[static_cast<std::size_t>(y) * kTextTextureWidth + x] = static_cast<unsigned char>(luminance);
 		}
 	}
-	sdf = BuildTextCoverageTexture(alpha, kTextTextureWidth, kTextTextureHeight);
-	sdf = BlurTextSdf(sdf, kTextTextureWidth, kTextTextureHeight, kTextSdfBlurPasses);
-	sdf = FlipTextTextureForShaderUv(sdf, kTextTextureWidth, kTextTextureHeight);
+	sdf = BuildTextSdfTexture(alpha, kTextTextureWidth, kTextTextureHeight);
 	WriteTextMaskDebugDump(text, alpha, sdf, kTextTextureWidth, kTextTextureHeight);
 	return true;
 }
--- a/apps/LoopThroughWithOpenGLCompositing/gl/TextRasterizer.h
+++ b/apps/LoopThroughWithOpenGLCompositing/gl/TextRasterizer.h
@@ -4,7 +4,7 @@
 #include <string>
 #include <vector>

-constexpr unsigned kTextTextureWidth = 2048;
-constexpr unsigned kTextTextureHeight = 256;
+constexpr unsigned kTextTextureWidth = 4096;
+constexpr unsigned kTextTextureHeight = 512;

 bool RasterizeTextSdf(const std::string& text, const std::filesystem::path& fontPath, std::vector<unsigned char>& sdf, std::string& error);
--- a/shaders/text-overlay/shader.json
+++ b/shaders/text-overlay/shader.json
@@ -34,7 +34,7 @@
      "type": "float",
      "default": 0.42,
      "min": 0.1,
-      "max": 1.5,
+      "max": 3,
      "step": 0.01
    },
    {
--- a/shaders/text-overlay/shader.slang
+++ b/shaders/text-overlay/shader.slang
@@ -10,6 +10,12 @@ float4 compositeOver(float4 baseColor, float4 overColor)
 	return float4(outRgb, outAlpha);
 }

+float sdfCoverage(float2 uv, float edge, float aa)
+{
+	float distance = sampleTitleText(uv);
+	return smoothstep(edge - aa, edge + aa, distance);
+}
+
 float4 shadeVideo(ShaderContext context)
 {
 	float2 resolution = max(context.outputResolution, float2(1.0, 1.0));
@@ -19,21 +25,26 @@ float4 shadeVideo(ShaderContext context)
 	float2 textUv = (context.uv - position) / safeTextSize;
 	bool insideTextRect = textUv.x >= 0.0 && textUv.x <= 1.0 && textUv.y >= 0.0 && textUv.y <= 1.0;

-	float mask = insideTextRect ? sampleTitleText(textUv) : 0.0;
-	float edge = 0.02;
-	float aa = max(fwidth(mask) * 1.5, 0.002);
-	float fill = smoothstep(edge - aa, edge + aa, mask);
-	float shadowRadius = min((outlineWidth + softness) * 0.025, 0.018);
-	float shadow = 0.0;
-	if (shadowRadius > 0.0001)
-	{
-		shadow = max(shadow, sampleTitleText(textUv + float2(shadowRadius, shadowRadius)));
-		shadow = max(shadow, sampleTitleText(textUv + float2(-shadowRadius, shadowRadius)));
-		shadow = max(shadow, sampleTitleText(textUv + float2(shadowRadius, -shadowRadius)));
-		shadow = max(shadow, sampleTitleText(textUv + float2(-shadowRadius, -shadowRadius)));
-	}
-	shadow = smoothstep(edge - aa, edge + aa, shadow) * (0.35 + softness);
-	float outlineAlpha = saturate(shadow * (1.0 - fill)) * outlineColor.a;
+	float distance = insideTextRect ? sampleTitleText(textUv) : 0.0;
+	float edge = 0.5;
+	float aa = max(fwidth(distance) * (1.75 + softness * 5.0), 0.0025);
+	float2 pixelTextUv = (1.0 / resolution) / safeTextSize;
+	float2 sampleOffset = pixelTextUv * 0.38;
+	float fill = (
+		sdfCoverage(textUv, edge, aa) * 2.0 +
+		sdfCoverage(textUv + float2(sampleOffset.x, sampleOffset.y), edge, aa) +
+		sdfCoverage(textUv + float2(-sampleOffset.x, sampleOffset.y), edge, aa) +
+		sdfCoverage(textUv + float2(sampleOffset.x, -sampleOffset.y), edge, aa) +
+		sdfCoverage(textUv + float2(-sampleOffset.x, -sampleOffset.y), edge, aa)) / 6.0;
+	float outlineDistance = outlineWidth * 0.16;
+	float outlineEdge = edge - outlineDistance;
+	float outline = (
+		sdfCoverage(textUv, outlineEdge, aa) * 2.0 +
+		sdfCoverage(textUv + float2(sampleOffset.x, sampleOffset.y), outlineEdge, aa) +
+		sdfCoverage(textUv + float2(-sampleOffset.x, sampleOffset.y), outlineEdge, aa) +
+		sdfCoverage(textUv + float2(sampleOffset.x, -sampleOffset.y), outlineEdge, aa) +
+		sdfCoverage(textUv + float2(-sampleOffset.x, -sampleOffset.y), outlineEdge, aa)) / 6.0;
+	float outlineAlpha = saturate(outline - fill) * outlineColor.a;
 	float fillAlpha = fill * fillColor.a;
 	float textAlpha = max(fillAlpha, outlineAlpha);
 	if (textAlpha <= 0.0001)