Summary and Introduction
the perfect solution to add a natural gradient to a fog. Just pick an object and crank up the “Distance Far” value. No more rough edges that can be real eyesores!
the simplest and most organic way to introduce some nuance into the volumetric object. Play around with the scale and other settings to find out what fits you. (Keep in mind that it lacks the Corona Distance map)
Introduction to OpenVDB
OpenVDB - the master way
Part 1/4 - Absorption
Part 2/4 - Scattering
Part 3/4 - Emission
Part 4/4 - Motion Blur
OpenVDB - “Dos and Don'ts”
We start by setting the absorption to 0,4 to achieve the proper density. Then we increase directionality to 0,6 for that silver lining at the edges of the cloud. Unfortunately. Increasing the scattering “Scale” value doesn’t help to remove the dark colors because the object is too thick; we need to resolve it in a different way
There are two ways we can solve the darkness issue. Let’s use a quick cheat first. We can apply the low emission value that mimics the light being scattered inside. This solution might be sometimes acceptable and is definitely quicker to render than the next option.
The realistic approach is to disable the „Single bounce only” option. It can easily make it ten times longer to render, so we need to optimize the asset already. We increased the step size from 1 cm to 30 cm without noticeable quality deterioration. This value depends on many factors (object’s scale and placement in the scene), but we could drop the rendering a few times quicker.
You can see what happens when we go too high with the “step size.” Even though we sped up the rendering time, we lost details, and artifacts started to pop up. 1000cm is definitely too high, so we’re eventually getting back to a 30cm value
Turning off the “Single Bounce” means we can control the amount of bounciness using “Max Ray Depth” in the performance tab. We can expand it from default 25 to 100, making a huge difference. We are finally able to grasp that realistic fluffy feeling instead of harsh CG gradients. Certainly, it all happens at the expense of render times.
In our final test, we increased „Light Samples Multiplier” in the performance tab as it is suggested in the Corona Helpdesk. We didn't notice any significant differences though.
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