[Solved] Displacement changes abruptly during video.

[andreu.taberner]

I am working on a video and the displacement seems to change during the video.
#Check the attached video#

Look at the rocks reflected on the glass.

parameters:
Corona version: 3
Displacement screen size: 2,0
UHD Cache: Animation (Flicker-free)
UHD Precomp from file at frame 75 on a slow animation of 150 frames.

Anyone know why?
Thanks in advance.

[romullus]

Displacement in Corona is adaptive, meaning that displaced mesh will be tesselated slightly differently from frame to frame, depending on your camera position. It is possible to turn adaptivity off, by setting displacement size from screen to world units, but keep in mind that it will most likely skyrocket your scene's RAM requirements and you will be forced to find compromise between displacement quality and RAM requirements.

On the other hand, since most obvious flicker in your scene is happening in reflection, it's possible that this happening because out of camera frustum optimization. You can try this trick to see if that would help: https://forum.corona-renderer.com/index.php?topic=22702.msg139540#msg139540

[andreu.taberner]

I will do some tests with world units and see how it goes.
thanks Romullus.

[andreu.taberner]

Tests with worldUnits displacement are promising;

With a value of  WorldUnits 0,03 the geometry/displacement calculation takes about the same time as ScreenSize 2,0 (About 6s). It goes up to 11s with 0,02 which is ok too.

Ram seems not to be an issue, is using around 8Gb (128Gb installed) even lowering WorldUnits to 0,02.

The quality of the displacement, at least for rocks, is as good.

I will render the animation sequence tonight and see how it performs.

[andreu.taberner]

The rocks displacement is good and consistent now.
Changing to world unit displacement (0,02) has been the solution.

Render times has been about the same.
*Animation attached.

Thanks.