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tweak(fps): Simplify function W3DDisplay::updateAverageFPS() and remove its frame spike filter #1662

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Merged
merged 2 commits into from
Oct 7, 2025
Merged

tweak(fps): Simplify function W3DDisplay::updateAverageFPS() and remove its frame spike filter #1662

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1ab7f06
tweak(fps): Improve and simplify average fps function
xezon Oct 1, 2025
9085d6a
Replicate in Generals
xezon Oct 7, 2025
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4 changes: 2 additions & 2 deletions Generals/Code/GameEngine/Include/Common/GameEngine.h
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ class GameEngine : public SubsystemInterface

virtual void setFramesPerSecondLimit( Int fps ); ///< Set the max render and engine update fps.
virtual Int getFramesPerSecondLimit( void ); ///< Get the max render and engine update fps.
Real getUpdateTime(); ///< Get the last engine update delta time.
Real getUpdateTime(); ///< Get the last engine update delta time in seconds.
Real getUpdateFps(); ///< Get the last engine update fps.

static Bool isTimeFrozen(); ///< Returns true if a script has frozen time.
Expand Down Expand Up @@ -128,7 +128,7 @@ class GameEngine : public SubsystemInterface
Int m_maxFPS; ///< Maximum frames per second for rendering
Int m_logicTimeScaleFPS; ///< Maximum frames per second for logic time scale

Real m_updateTime; ///< Last engine update delta time
Real m_updateTime; ///< Last engine update delta time in seconds
Real m_logicTimeAccumulator; ///< Frame time accumulated towards submitting a new logic frame

Bool m_quitting; ///< true when we need to quit the game
Expand Down
2 changes: 1 addition & 1 deletion Generals/Code/GameEngineDevice/Include/W3DDevice/GameClient/W3DDisplay.h
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Expand Up @@ -161,7 +161,7 @@ class W3DDisplay : public Display
void drawCurrentDebugDisplay( void ); ///< draws current debug display
void calculateTerrainLOD(void); ///< Calculate terrain LOD.
void renderLetterBox(UnsignedInt time); ///< draw letter box border
void updateAverageFPS(void); ///< figure out the average fps over the last 30 frames.
void updateAverageFPS(void); ///< calculate the average fps over the last 30 frames.

Byte m_initialized; ///< TRUE when system is initialized
LightClass *m_myLight[LightEnvironmentClass::MAX_LIGHTS]; ///< light hack for now
Expand Down
50 changes: 15 additions & 35 deletions Generals/Code/GameEngineDevice/Source/W3DDevice/GameClient/W3DDisplay.cpp
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Expand Up @@ -34,6 +34,7 @@
static void drawFramerateBar(void);

// SYSTEM INCLUDES ////////////////////////////////////////////////////////////
#include <numeric>
#include <stdlib.h>
#include <windows.h>
#include <io.h>
Expand Down Expand Up @@ -835,21 +836,16 @@ void W3DDisplay::reset( void )

const UnsignedInt START_CUMU_FRAME = LOGICFRAMES_PER_SECOND / 2; // skip first half-sec

/** Update a moving average of the last 30 fps measurements. Also try to filter out temporary spikes.
This code is designed to be used by the GameLOD sytems to determine the correct dynamic LOD setting.
*/
void W3DDisplay::updateAverageFPS(void)
{
const Real MaximumFrameTimeCutoff = 0.5f; //largest frame interval (seconds) we accept before ignoring it as a momentary "spike"
const Int FPS_HISTORY_SIZE = 30; //keep track of the last 30 frames
constexpr const Int FPS_HISTORY_SIZE = 30;

static Int64 lastUpdateTime64 = 0;
static Int historyOffset = 0;
static Int numSamples = 0;
static double fpsHistory[FPS_HISTORY_SIZE];
static Real fpsHistory[FPS_HISTORY_SIZE] = {0};

Int64 freq64 = getPerformanceCounterFrequency();
Int64 time64 = getPerformanceCounter();
const Int64 freq64 = getPerformanceCounterFrequency();
const Int64 time64 = getPerformanceCounter();

#if defined(RTS_DEBUG)
if (TheGameLogic->getFrame() == START_CUMU_FRAME)
Expand All @@ -858,37 +854,21 @@ void W3DDisplay::updateAverageFPS(void)
}
#endif

Int64 timeDiff = time64 - lastUpdateTime64;
const Int64 timeDiff = time64 - lastUpdateTime64;

// convert elapsed time to seconds
double elapsedSeconds = (double)timeDiff/(double)(freq64);

if (elapsedSeconds <= MaximumFrameTimeCutoff) //make sure it's not a spike
{
// append new sameple to fps history.
if (historyOffset >= FPS_HISTORY_SIZE)
historyOffset = 0;
Real elapsedSeconds = (Real)timeDiff/(Real)freq64;

m_currentFPS = 1.0/elapsedSeconds;
fpsHistory[historyOffset++] = m_currentFPS;
numSamples++;
if (numSamples > FPS_HISTORY_SIZE)
numSamples = FPS_HISTORY_SIZE;
}
// append new sample to fps history.
if (historyOffset >= FPS_HISTORY_SIZE)
historyOffset = 0;

if (numSamples)
{
// determine average frame rate over our past history.
Real average=0;
for (Int i=0,j=historyOffset-1; i<numSamples; i++,j--)
{
if (j < 0)
j=FPS_HISTORY_SIZE-1; // wrap around to front of buffer
average += fpsHistory[j];
}
m_currentFPS = 1.0f/elapsedSeconds;
fpsHistory[historyOffset++] = m_currentFPS;

m_averageFPS = average / (Real)numSamples;
}
// determine average frame rate over our past history.
const Real sum = std::accumulate(fpsHistory, fpsHistory + FPS_HISTORY_SIZE, 0.0f);
m_averageFPS = sum / FPS_HISTORY_SIZE;

lastUpdateTime64 = time64;
}
Expand Down
4 changes: 2 additions & 2 deletions GeneralsMD/Code/GameEngine/Include/Common/GameEngine.h
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ class GameEngine : public SubsystemInterface

virtual void setFramesPerSecondLimit( Int fps ); ///< Set the max render and engine update fps.
virtual Int getFramesPerSecondLimit( void ); ///< Get the max render and engine update fps.
Real getUpdateTime(); ///< Get the last engine update delta time.
Real getUpdateTime(); ///< Get the last engine update delta time in seconds.
Real getUpdateFps(); ///< Get the last engine update fps.

static Bool isTimeFrozen(); ///< Returns true if a script has frozen time.
Expand Down Expand Up @@ -127,7 +127,7 @@ class GameEngine : public SubsystemInterface
Int m_maxFPS; ///< Maximum frames per second for rendering
Int m_logicTimeScaleFPS; ///< Maximum frames per second for logic time scale

Real m_updateTime; ///< Last engine update delta time
Real m_updateTime; ///< Last engine update delta time in seconds
Real m_logicTimeAccumulator; ///< Frame time accumulated towards submitting a new logic frame

Bool m_quitting; ///< true when we need to quit the game
Expand Down
2 changes: 1 addition & 1 deletion GeneralsMD/Code/GameEngineDevice/Include/W3DDevice/GameClient/W3DDisplay.h
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Original file line number Diff line number Diff line change
Expand Up @@ -162,7 +162,7 @@ class W3DDisplay : public Display
void drawCurrentDebugDisplay( void ); ///< draws current debug display
void calculateTerrainLOD(void); ///< Calculate terrain LOD.
void renderLetterBox(UnsignedInt time); ///< draw letter box border
void updateAverageFPS(void); ///< figure out the average fps over the last 30 frames.
void updateAverageFPS(void); ///< calculate the average fps over the last 30 frames.

Byte m_initialized; ///< TRUE when system is initialized
LightClass *m_myLight[LightEnvironmentClass::MAX_LIGHTS]; ///< light hack for now
Expand Down
50 changes: 15 additions & 35 deletions GeneralsMD/Code/GameEngineDevice/Source/W3DDevice/GameClient/W3DDisplay.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
static void drawFramerateBar(void);

// SYSTEM INCLUDES ////////////////////////////////////////////////////////////
#include <numeric>
#include <stdlib.h>
#include <windows.h>
#include <io.h>
Expand Down Expand Up @@ -885,21 +886,16 @@ void W3DDisplay::reset( void )

const UnsignedInt START_CUMU_FRAME = LOGICFRAMES_PER_SECOND / 2; // skip first half-sec

/** Update a moving average of the last 30 fps measurements. Also try to filter out temporary spikes.
This code is designed to be used by the GameLOD sytems to determine the correct dynamic LOD setting.
*/
void W3DDisplay::updateAverageFPS(void)
{
const Real MaximumFrameTimeCutoff = 0.5f; //largest frame interval (seconds) we accept before ignoring it as a momentary "spike"
const Int FPS_HISTORY_SIZE = 30; //keep track of the last 30 frames
constexpr const Int FPS_HISTORY_SIZE = 30;

static Int64 lastUpdateTime64 = 0;
static Int historyOffset = 0;
static Int numSamples = 0;
static double fpsHistory[FPS_HISTORY_SIZE];
static Real fpsHistory[FPS_HISTORY_SIZE] = {0};

Int64 freq64 = getPerformanceCounterFrequency();
Int64 time64 = getPerformanceCounter();
const Int64 freq64 = getPerformanceCounterFrequency();
const Int64 time64 = getPerformanceCounter();

#if defined(RTS_DEBUG)
if (TheGameLogic->getFrame() == START_CUMU_FRAME)
Expand All @@ -908,37 +904,21 @@ void W3DDisplay::updateAverageFPS(void)
}
#endif

Int64 timeDiff = time64 - lastUpdateTime64;
const Int64 timeDiff = time64 - lastUpdateTime64;

// convert elapsed time to seconds
double elapsedSeconds = (double)timeDiff/(double)(freq64);

if (elapsedSeconds <= MaximumFrameTimeCutoff) //make sure it's not a spike
{
// append new sameple to fps history.
if (historyOffset >= FPS_HISTORY_SIZE)
historyOffset = 0;
Real elapsedSeconds = (Real)timeDiff/(Real)freq64;

m_currentFPS = 1.0/elapsedSeconds;
fpsHistory[historyOffset++] = m_currentFPS;
numSamples++;
if (numSamples > FPS_HISTORY_SIZE)
numSamples = FPS_HISTORY_SIZE;
}
// append new sample to fps history.
if (historyOffset >= FPS_HISTORY_SIZE)
historyOffset = 0;

if (numSamples)
{
// determine average frame rate over our past history.
Real average=0;
for (Int i=0,j=historyOffset-1; i<numSamples; i++,j--)
{
if (j < 0)
j=FPS_HISTORY_SIZE-1; // wrap around to front of buffer
average += fpsHistory[j];
}
m_currentFPS = 1.0f/elapsedSeconds;
fpsHistory[historyOffset++] = m_currentFPS;

m_averageFPS = average / (Real)numSamples;
}
// determine average frame rate over our past history.
const Real sum = std::accumulate(fpsHistory, fpsHistory + FPS_HISTORY_SIZE, 0.0f);
m_averageFPS = sum / FPS_HISTORY_SIZE;

lastUpdateTime64 = time64;
}
Expand Down
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