Old volume behavior vs. current

[roeland]

Octane 2021.1 no longer has the Emulate old volume behavior option. In addition some problems with the new behavior got fixed. These fixes are outlined in the release post. The aim is to make the appearance of volumes more consistent for different step lengths. There is an unavoidable loss of accuracy for large step lengths, but other things like emission brightness and opacity should stay approximately the same.

The first change is the behaviour around edges of volumes and around other things intersecting volumes. For example here is one of the test images from the release post:


2020 old behavior — 2020 current behavior — 2021 behavior

This example shows what happens if step length increases to approximately 10 times the size of the cube. In general, with very large step lengths (which are often used for fog), with 2020 old behavior the fog tends to appear thinner, while with the 2020 new behavior it tends to appear thicker. In 2021 the thickness should stay consistent.

A second change is a change in volume emission. The brightness used to increase if you reduce step length. This is a problem which got fixed with the new behavior. It did not change a lot in 2021.


2020 old behavior — 2020 current behavior — 2021 behavior

[coilbook]

Octane 2021.1 no longer has the Emulate old volume behavior option. In addition some problems with the new behavior got fixed. These fixes are outlined in the release post. The aim is to make the appearance of volumes more consistent for different step lengths. There is an unavoidable loss of accuracy for large step lengths, but other things like emission brightness and opacity should stay approximately the same.

The first change is the behaviour around edges of volumes and around other things intersecting volumes. For example here is one of the test images from the release post:


2020 old behavior — 2020 current behavior — 2021 behavior

This example shows what happens if step length increases to approximately 10 times the size of the cube. In general, with very large step lengths (which are often used for fog), with 2020 old behavior the fog tends to appear thinner, while with the 2020 new behavior it tends to appear thicker. In 2021 the thickness should stay consistent.

A second change is a change in volume emission. The brightness used to increase if you reduce step length. This is a problem which got fixed with the new behavior. It did not change a lot in 2021.


2020 old behavior — 2020 current behavior — 2021 behavior

new volume behavior produces dark smokes unlike old vol beh