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Cycles-X: Add hysteresis to resolution divider algorithm 

Adds hysteresis to the resolution divider algorithm to avoid having the resolution bounce around when on the boundary of two resolutions.

Reviewed By: brecht, leesonw

Differential Revision: https://developer.blender.org/D12385
This commit is contained in:
Alaska 2021-12-09 09:12:24 +01:00 committed by William Leeson
parent 894269ad12
commit d8b4275162
Notes: blender-bot 2023-02-14 09:09:43 +01:00 
Referenced by commit 2229179faa, Revert "Cycles-X: Add hysteresis to resolution divider algorithm"
2 changed files with 22 additions and 10 deletions
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28
intern/cycles/integrator/render_scheduler.cpp
View File

@ -1085,14 +1085,8 @@ void RenderScheduler::update_start_resolution_divider()
first_render_time_.denoise_time +
first_render_time_.display_update_time;
/* Allow some percent of tolerance, so that if the render time is close enough to the higher
* resolution we prefer to use it instead of going way lower resolution and time way below the
* desired one. */
const int resolution_divider_for_update = calculate_resolution_divider_for_time(
desired_update_interval_in_seconds * 1.4, actual_time_per_update);
/* TODO(sergey): Need to add hysteresis to avoid resolution divider bouncing around when actual
* render time is somewhere on a boundary between two resolutions. */
desired_update_interval_in_seconds, actual_time_per_update, start_resolution_divider_);
/* Never increase resolution to higher than the pixel size (which is possible if the scene is
* simple and compute device is fast). */
@ -1179,12 +1173,14 @@ void RenderScheduler::check_time_limit_reached()
* Utility functions.
*/
int RenderScheduler::calculate_resolution_divider_for_time(double desired_time, double actual_time)
int RenderScheduler::calculate_resolution_divider_for_time(double desired_time,
double actual_time,
int previous_resolution_divider)
{
/* TODO(sergey): There should a non-iterative analytical formula here. */
int resolution_divider = 1;
double pre_division_time = actual_time;
/* This algorithm iterates through resolution dividers until a divider is found that achieves
* the desired render time. A limit of default_start_resolution_divider_ is put in place as the
* maximum resolution divider to avoid an unreadable viewport due to a low resolution.
@ -1192,12 +1188,26 @@ int RenderScheduler::calculate_resolution_divider_for_time(double desired_time,
* calculation to better predict the performance impact of changing resolution divisions as
* the sample count can also change between resolution divisions. */
while (actual_time > desired_time && resolution_divider < default_start_resolution_divider_) {
pre_division_time = actual_time;
int pre_resolution_division_samples = get_num_samples_during_navigation(resolution_divider);
resolution_divider = resolution_divider * 2;
int post_resolution_division_samples = get_num_samples_during_navigation(resolution_divider);
actual_time /= 4.0 * pre_resolution_division_samples / post_resolution_division_samples;
}
/* Hysteresis to avoid resolution divider bouncing around when actual render time is somewhere
* on a boundary between two resolutions. This system allows some percentage of tolerance so
* that the viewport tends towards remaining at higher resolutions rather than dropping to a
* lower resolution if performance is close to, but not quite reaching the target frame rate.
* This system also tends to not increase the viewport resolution unless the hardware can
* exceed the performance target by a certain percentage. This is to help ensure the viewport
* remains responsive after increasing the resolution. */
if (resolution_divider > previous_resolution_divider && pre_division_time < desired_time * 1.5) {
return resolution_divider / 2;
}
if (resolution_divider < previous_resolution_divider && pre_division_time > desired_time / 1.3) {
return resolution_divider * 2;
}
return resolution_divider;
}

4
intern/cycles/integrator/render_scheduler.h
View File

@ -462,7 +462,9 @@ class RenderScheduler {
* desired one. This call assumes linear dependency of render time from number of pixels
* (quadratic dependency from the resolution divider): resolution divider of 2 brings render time
* down by a factor of 4. */
int calculate_resolution_divider_for_time(double desired_time, double actual_time);
int calculate_resolution_divider_for_time(double desired_time,
double actual_time,
int previous_resolution_divider);
};
int calculate_resolution_divider_for_resolution(int width, int height, int resolution);