Mandelbrot: Implement subsampling

* Added subsampling. This makes the render look less noisy and generally nicer.

Change-Id: I1dd667c8799bd97fb84e1401976da12ecf74ea8c
Reviewed-on: https://review.haiku-os.org/732
Reviewed-by: waddlesplash <[email protected]>

src/apps/mandelbrot/FractalEngine.cpp

@@ -91,6 +91,9 @@ void FractalEngine::MessageReceived(BMessage* msg)
 	case MSG_SET_ITERATIONS:
 		fIterations = msg->GetUInt16("iterations", 0);
 		break;
+	case MSG_SET_SUBSAMPLING:
+		fSubsampling = msg->GetUInt8("subsampling", 1);
+		break;
 
 	case MSG_RESIZE: {
 		TRACE("Got MSG_RESIZE threads rendering\n");
@@ -251,19 +254,38 @@ void FractalEngine::RenderPixel(uint32 x, uint32 y)
 	double real = (x * fSize + fLocationX) - (fWidth / 2 * fSize);
 	double imaginary = (y * -(fSize) + fLocationY) - (fHeight / 2 * -(fSize));
 
-	int32 iterToEscape = (this->*fDoSet)(real, imaginary);
+	double subsampleDelta = fSize / fSubsampling;
-	uint16 loc = 0;
+	uint16 nSamples = fSubsampling * fSubsampling;
-	if (iterToEscape == -1)
+
+	int16 totalR = 0;
+	int16 totalG = 0;
+	int16 totalB = 0;
+	for (uint8 subX = 0; subX < fSubsampling; subX++) {
+		for (uint8 subY = 0; subY < fSubsampling; subY++) {
+			double sampleReal = real + subX * subsampleDelta;
+			double sampleImaginary = imaginary + subY * subsampleDelta;
+
+			int32 sampleIterToEscape = (this->*fDoSet)(sampleReal, sampleImaginary);
+
+			uint16 sampleLoc = 0;
+			if (sampleIterToEscape == -1)
 				// Didn't escape.
-		loc = 999;
+				sampleLoc = 999;
 			else
-		loc = 998 - (iterToEscape % 999);
+				sampleLoc = 998 - (sampleIterToEscape % 999);
+			sampleLoc *= 3;
+
+			totalR += fColorset[sampleLoc + 0];
+			totalG += fColorset[sampleLoc + 1];
+			totalB += fColorset[sampleLoc + 2];
+		}
+	}
+
 
 	uint32 offsetBase = fWidth * y * 3 + x * 3;
-	loc *= 3;
+	fRenderBuffer[offsetBase + 2] = totalR / nSamples; // fRenderBuffer is BGR
-	fRenderBuffer[offsetBase + 2] = fColorset[loc + 0]; // fRenderBuffer is BGR
+	fRenderBuffer[offsetBase + 1] = totalG / nSamples;
-	fRenderBuffer[offsetBase + 1] = fColorset[loc + 1];
+	fRenderBuffer[offsetBase + 0] = totalB / nSamples;
-	fRenderBuffer[offsetBase + 0] = fColorset[loc + 2];
 }
 
 

src/apps/mandelbrot/FractalEngine.h

@@ -25,6 +25,7 @@ public:
 		MSG_CHANGE_SET = 'Frct',
 		MSG_SET_PALETTE,
 		MSG_SET_ITERATIONS,
+		MSG_SET_SUBSAMPLING,
 		MSG_RESIZE,
 		MSG_BUFFER_CREATED,
 		MSG_RENDER,
@@ -45,6 +46,9 @@ private:
 	uint8* fRenderBuffer;
 	uint32 fRenderBufferLen;
 
+	uint8 fSubsampling = 2;
+		// 1 disables subsampling.
+
 	BMessenger fMessenger;
 
 	uint8 fThreadCount;

src/apps/mandelbrot/Mandelbrot.cpp

@@ -358,7 +358,12 @@ public:
 		MSG_ITER_4096,
 		MSG_ITER_8192,
 		MSG_ITER_12288,
-		MSG_ITER_16384
+		MSG_ITER_16384,
+
+		MSG_SUBSAMPLING_1,
+		MSG_SUBSAMPLING_2,
+		MSG_SUBSAMPLING_3,
+		MSG_SUBSAMPLING_4
 	};
 				MandelbrotWindow(BRect frame);
 				~MandelbrotWindow() {}
@@ -381,6 +386,7 @@ MandelbrotWindow::MandelbrotWindow(BRect frame)
 	BMenu* setMenu;
 	BMenu* paletteMenu;
 	BMenu* iterMenu;
+	BMenu* subsamplingMenu;
 	BLayoutBuilder::Menu<>(menuBar)
 		.AddMenu(B_TRANSLATE("File"))
 			.AddItem(B_TRANSLATE("About"), B_ABOUT_REQUESTED)
@@ -417,6 +423,13 @@ MandelbrotWindow::MandelbrotWindow(BRect frame)
 			.AddItem("12288", MSG_ITER_12288)
 			.AddItem("16384", MSG_ITER_16384)
 		.End()
+		.AddMenu(B_TRANSLATE("Subsampling"))
+			.GetMenu(subsamplingMenu)
+			.AddItem(B_TRANSLATE("1 (none)"), MSG_SUBSAMPLING_1)
+			.AddItem("4", MSG_SUBSAMPLING_2)
+			.AddItem("9", MSG_SUBSAMPLING_3)
+			.AddItem("16", MSG_SUBSAMPLING_4)
+		.End()
 	.End();
 	setMenu->SetRadioMode(true);
 	setMenu->FindItem(MSG_MANDELBROT_SET)->SetMarked(true);
@@ -424,6 +437,8 @@ MandelbrotWindow::MandelbrotWindow(BRect frame)
 	paletteMenu->FindItem(MSG_ROYAL_PALETTE)->SetMarked(true);
 	iterMenu->SetRadioMode(true);
 	iterMenu->FindItem(MSG_ITER_1024)->SetMarked(true);
+	subsamplingMenu->SetRadioMode(true);
+	subsamplingMenu->FindItem(MSG_SUBSAMPLING_2)->SetMarked(true);
 
 	BLayoutBuilder::Group<>(this, B_VERTICAL, 0)
 		.SetInsets(0)
@@ -458,6 +473,14 @@ MandelbrotWindow::MandelbrotWindow(BRect frame)
 		fFractalView->RedrawFractal(); \
 		break; \
 	}
+#define HANDLE_SUBSAMPLING(uiwhat, id) \
+	case uiwhat: { \
+		BMessage msg(FractalEngine::MSG_SET_SUBSAMPLING); \
+		msg.AddUInt8("subsampling", id); \
+		fFractalView->fFractalEngine->PostMessage(&msg); \
+		fFractalView->RedrawFractal(); \
+		break; \
+	}
 void
 MandelbrotWindow::MessageReceived(BMessage* msg)
 {
@@ -487,6 +510,11 @@ MandelbrotWindow::MessageReceived(BMessage* msg)
 	HANDLE_ITER(MSG_ITER_12288, 12288)
 	HANDLE_ITER(MSG_ITER_16384, 16384)
 
+	HANDLE_SUBSAMPLING(MSG_SUBSAMPLING_1, 1)
+	HANDLE_SUBSAMPLING(MSG_SUBSAMPLING_2, 2)
+	HANDLE_SUBSAMPLING(MSG_SUBSAMPLING_3, 3)
+	HANDLE_SUBSAMPLING(MSG_SUBSAMPLING_4, 4)
+
 	case B_ABOUT_REQUESTED: {
 		BAboutWindow* wind = new BAboutWindow("Mandelbrot",
 			"application/x-vnd.Haiku-Mandelbrot");
@@ -510,6 +538,7 @@ MandelbrotWindow::MessageReceived(BMessage* msg)
 #undef HANDLE_SET
 #undef HANDLE_PALETTE
 #undef HANDLE_ITER
+#undef HANDLE_SUBSAMPLING
 
 
 bool