private void UpdateRenderScale()
{
if (!active)
{
SetRenderScale(1.0f, 1.0f);
return;
}
// Add latest timing to ring buffer
frameTimeRingBufferIndex = (frameTimeRingBufferIndex + 1) % frameTimeRingBuffer.Length;
frameTimeRingBuffer[frameTimeRingBufferIndex] = VRStats.gpuTimeLastFrame;
// Rendering in low resolution means adaptive quality needs to scale back the render scale target to free up gpu cycles
bool renderInLowResolution = VRTK_SDK_Bridge.ShouldAppRenderWithLowResources();
// Thresholds
float thresholdModifier = renderInLowResolution
? singleFrameDurationInMilliseconds * 0.75f
: singleFrameDurationInMilliseconds;
float lowThresholdInMilliseconds = 0.7f * thresholdModifier;
float extrapolationThresholdInMilliseconds = 0.85f * thresholdModifier;
float highThresholdInMilliseconds = 0.9f * thresholdModifier;
// Get latest 3 frames
float frameMinus0 = frameTimeRingBuffer[(frameTimeRingBufferIndex - 0 + frameTimeRingBuffer.Length) % frameTimeRingBuffer.Length];
float frameMinus1 = frameTimeRingBuffer[(frameTimeRingBufferIndex - 1 + frameTimeRingBuffer.Length) % frameTimeRingBuffer.Length];
float frameMinus2 = frameTimeRingBuffer[(frameTimeRingBufferIndex - 2 + frameTimeRingBuffer.Length) % frameTimeRingBuffer.Length];
int previousLevel = currentRenderScaleLevel;
// Always drop 2 levels except when dropping from level 2
int dropTargetLevel = previousLevel == 2 ? 1 : previousLevel - 2;
int newLevel = Mathf.Clamp(dropTargetLevel, 0, allRenderScales.Count - 1);
// Ignore frame timings if overriding
if (overrideRenderScale)
{
currentRenderScaleLevel = overrideRenderScaleLevel;
}
// Rapidly reduce quality 2 levels if last frame was critical
else if (Time.frameCount >= lastRenderScaleChangeFrameCount + 2 + 1 &&
frameMinus0 > highThresholdInMilliseconds &&
newLevel != previousLevel)
{
currentRenderScaleLevel = newLevel;
lastRenderScaleChangeFrameCount = Time.frameCount;
}
// Rapidly reduce quality 2 levels if last 3 frames are expensive
else if (Time.frameCount >= lastRenderScaleChangeFrameCount + 2 + 3 &&
frameMinus0 > highThresholdInMilliseconds &&
frameMinus1 > highThresholdInMilliseconds &&
frameMinus2 > highThresholdInMilliseconds &&
newLevel != previousLevel)
{
currentRenderScaleLevel = newLevel;
lastRenderScaleChangeFrameCount = Time.frameCount;
}
// Predict next frame's cost using linear extrapolation: max(frame-1 to frame+1, frame-2 to frame+1)
else if (Time.frameCount >= lastRenderScaleChangeFrameCount + 2 + 2 &&
frameMinus0 > extrapolationThresholdInMilliseconds)
{
float frameDelta = frameMinus0 - frameMinus1;
// Use frame-2 if it's available
if (Time.frameCount >= lastRenderScaleChangeFrameCount + 2 + 3)
{
float frameDelta2 = (frameMinus0 - frameMinus2) * 0.5f;
frameDelta = Mathf.Max(frameDelta, frameDelta2);
}
if (frameMinus0 + frameDelta > highThresholdInMilliseconds &&
newLevel != previousLevel)
{
currentRenderScaleLevel = newLevel;
lastRenderScaleChangeFrameCount = Time.frameCount;
}
}
else
{
// Increase quality 1 level if last 3 frames are cheap
newLevel = Mathf.Clamp(previousLevel + 1, 0, allRenderScales.Count - 1);
if (Time.frameCount >= lastRenderScaleChangeFrameCount + 2 + 3 &&
frameMinus0 < lowThresholdInMilliseconds &&
frameMinus1 < lowThresholdInMilliseconds &&
frameMinus2 < lowThresholdInMilliseconds &&
newLevel != previousLevel)
{
currentRenderScaleLevel = newLevel;
lastRenderScaleChangeFrameCount = Time.frameCount;
}
}
// Force on interleaved reprojection for level 0 which is just a replica of level 1 with reprojection enabled
float additionalViewportScale = 1.0f;
if (!hmdDisplayIsOnDesktop)
{
if (currentRenderScaleLevel == 0)
{
if (interleavedReprojectionEnabled && frameMinus0 < singleFrameDurationInMilliseconds * 0.85f)
{
interleavedReprojectionEnabled = false;
}
else if (frameMinus0 > singleFrameDurationInMilliseconds * 0.925f)
{
interleavedReprojectionEnabled = true;
}
}
else
{
interleavedReprojectionEnabled = false;
}
VRTK_SDK_Bridge.ForceInterleavedReprojectionOn(interleavedReprojectionEnabled);
}
// Not running in direct mode! Interleaved reprojection not supported, so scale down the viewport
else if (currentRenderScaleLevel == 0)
{
additionalViewportScale = 0.8f;
}
float newRenderScale = allRenderScales[allRenderScales.Count - 1];
float newRenderViewportScale = allRenderScales[currentRenderScaleLevel] / newRenderScale * additionalViewportScale;
SetRenderScale(newRenderScale, newRenderViewportScale);
}
