examples: Added --fixed-fps and --screenshot for deterministic captures. (#3998)

examples/47-pixelformats/pixelformats.cpp

@@ -523,6 +523,8 @@ public:
 		}
 
 		imguiCreate();
+
+		m_frameTime.reset();
 	}
 
 	int32_t shutdown() override
@@ -596,8 +598,7 @@ public:
 		{
 			if (bgfx::isValid(m_checkerboard) )
 			{
-				static int64_t timeOffset = bx::getHPCounter();
-				const float time = float( (bx::getHPCounter()-timeOffset)/double(bx::getHPFrequency() ) );
+				const float time = bx::toSeconds<float>(m_frameTime.getDurationTime() );
 				const float animate = float(m_animate)*0.5f;
 				const float xx = bx::sin(time * 0.37f) * animate;
 				const float yy = bx::cos(time * 0.43f) * animate;
@@ -631,6 +632,8 @@ public:
 	{
 		if (!entry::processEvents(m_width, m_height, m_debug, m_reset, &m_mouseState) )
 		{
+			m_frameTime.frame();
+
 			imguiBeginFrame(m_mouseState.m_mx
 				,  m_mouseState.m_my
 				, (m_mouseState.m_buttons[entry::MouseButton::Left  ] ? IMGUI_MBUT_LEFT   : 0)
@@ -832,6 +835,7 @@ public:
 	}
 
 	entry::MouseState m_mouseState;
+	FrameTime m_frameTime;
 
 	uint32_t m_width;
 	uint32_t m_height;

examples/common/common.h

@@ -25,15 +25,21 @@ struct FrameTime
 	///
 	void reset()
 	{
-		m_start = m_current;
-		frame();
+		m_current = bx::getNow();
+		m_start   = m_current;
+		m_last    = m_current;
 	}
 
 	///
 	void frame()
 	{
+		const bx::Ticks step = entry::getFixedTimeStep();
+
 		m_last    = m_current;
-		m_current = bx::getNow();
+		m_current = bx::Ticks(bx::InitZero) == step
+			? bx::getNow()
+			: m_current + step
+			;
 	}
 
 	///

examples/common/entry/entry.cpp

@@ -7,6 +7,7 @@
 #include <bx/commandline.h>
 #include <bx/file.h>
 #include <bx/sort.h>
+#include <bx/timer.h>
 #include <bgfx/bgfx.h>
 
 #include <time.h>
@@ -553,6 +554,71 @@ BX_PRAGMA_DIAGNOSTIC_POP();
 		return s_numApps;
 	}
 
+	static bx::Ticks s_fixedTimeStep = bx::InitZero;
+
+	bx::Ticks getFixedTimeStep()
+	{
+		return s_fixedTimeStep;
+	}
+
+	///
+	struct TestRun
+	{
+		TestRun(int _argc, const char* const* _argv)
+			: m_frame(0)
+			, m_screenshotFrame(0)
+		{
+			bx::CommandLine cmdLine(_argc, _argv);
+
+			const char* screenshot = cmdLine.findOption("screenshot");
+			if (NULL != screenshot)
+			{
+				bx::strCopy(m_screenshot, sizeof(m_screenshot), screenshot);
+				m_screenshotFrame = 60;
+
+				const char* frame = cmdLine.findOption("screenshot-frame");
+				if (NULL != frame)
+				{
+					bx::fromString(&m_screenshotFrame, frame);
+				}
+			}
+
+			uint32_t fps = 0 != m_screenshotFrame ? 60 : 0;
+			const char* fixedFps = cmdLine.findOption("fixed-fps");
+			if (NULL != fixedFps)
+			{
+				bx::fromString(&fps, fixedFps);
+			}
+
+			s_fixedTimeStep = 0 != fps
+				? bx::Ticks(bx::Ticks::s_kFreq.ticks/fps)
+				: bx::Ticks(bx::InitZero)
+				;
+		}
+
+		///
+		bool frame()
+		{
+			if (0 == m_screenshotFrame)
+			{
+				return true;
+			}
+
+			++m_frame;
+
+			if (m_frame == m_screenshotFrame)
+			{
+				bgfx::requestScreenShot(BGFX_INVALID_HANDLE, m_screenshot);
+			}
+
+			return m_frame < m_screenshotFrame + 3;
+		}
+
+		uint32_t m_frame;
+		uint32_t m_screenshotFrame;
+		char     m_screenshot[bx::kMaxFilePath];
+	};
+
 	int runApp(AppI* _app, int _argc, const char* const* _argv)
 	{
 		setWindowSize(kDefaultWindowHandle, s_width, s_height);
@@ -564,6 +630,8 @@ BX_PRAGMA_DIAGNOSTIC_POP();
 		bx::snprintf(title, BX_COUNTOF(title), "%S - %s", &exeName, _app->getName() );
 		setWindowTitle(kDefaultWindowHandle, title);
 
+		TestRun test(_argc, _argv);
+
 		_app->init(_argc, _argv, s_width, s_height);
 		bgfx::frame();
 
@@ -573,7 +641,8 @@ BX_PRAGMA_DIAGNOSTIC_POP();
 #else
 		while (_app->update() )
 		{
-			if (0 != bx::strLen(s_restartApp) )
+			if (0 != bx::strLen(s_restartApp)
+			||  !test.frame() )
 			{
 				break;
 			}

examples/common/entry/entry.h

@@ -373,6 +373,9 @@ namespace entry
 	///
 	void setRestartArgs(const char* _args);
 
+	///
+	bx::Ticks getFixedTimeStep();
+
 } // namespace entry
 
 #endif // ENTRY_H_HEADER_GUARD

examples/common/example-glue.cpp

@@ -417,7 +417,11 @@ void showExampleDialog(entry::AppI* _app, const char* _errorText)
 	const bgfx::Stats* stats = bgfx::getStats();
 	const double toMsCpu = 1000.0/stats->cpuTimerFreq;
 	const double toMsGpu = 1000.0/stats->gpuTimerFreq;
-	const double frameMs = double(stats->cpuTimeFrame)*toMsCpu;
+	const bool   fixedTime = bx::Ticks(bx::InitZero) != entry::getFixedTimeStep();
+	const double frameMs   = fixedTime
+		? bx::toMilliseconds<double>(entry::getFixedTimeStep() )
+		: double(stats->cpuTimeFrame)*toMsCpu
+		;
 
 	s_frameTime.pushSample(float(frameMs) );
 
@@ -444,8 +448,8 @@ void showExampleDialog(entry::AppI* _app, const char* _errorText)
 	ImGui::PopStyleColor();
 
 	ImGui::Text("Submit CPU %0.3f, GPU %0.3f (L: %d)"
-		, double(stats->cpuTimeEnd - stats->cpuTimeBegin)*toMsCpu
-		, double(stats->gpuTimeEnd - stats->gpuTimeBegin)*toMsGpu
+		, fixedTime ? 0.0 : double(stats->cpuTimeEnd - stats->cpuTimeBegin)*toMsCpu
+		, fixedTime ? 0.0 : double(stats->gpuTimeEnd - stats->gpuTimeBegin)*toMsGpu
 		, stats->maxGpuLatency
 		);
 

examples/common/imgui/imgui.cpp

@@ -531,6 +531,14 @@ struct OcornutImguiContext
 		const double freq = double(bx::getHPFrequency() );
 		io.DeltaTime = float(frameTime/freq);
 
+#if USE_ENTRY
+		const bx::Ticks step = entry::getFixedTimeStep();
+		if (bx::Ticks(bx::InitZero) != step)
+		{
+			io.DeltaTime = bx::toSeconds<float>(step);
+		}
+#endif // USE_ENTRY
+
 		io.AddMousePosEvent( (float)_mx, (float)_my);
 		io.AddMouseButtonEvent(ImGuiMouseButton_Left,   0 != (_button & IMGUI_MBUT_LEFT  ) );
 		io.AddMouseButtonEvent(ImGuiMouseButton_Right,  0 != (_button & IMGUI_MBUT_RIGHT ) );