This page provides a step-by-step tutorial on rendering fog effects in your projects.
In this tutorial we’ll go over how to render the atmospheric effects: Aerial Perspective and Environment Fog in your projects.
To follow this tutorial, you will need to have the V-Ray for Revit plugin installed.
This tutorial page is a companion that goes with the QuickStart video posted on our YouTube channel and is available here:
To download the files used in this tutorial, please click on the button below.
Open the Example Scene
Open the apfog.rvt project, which you can download through the link above. In this tutorial, Revit 2017 is being used, however, you will be able to use this project with Revit versions 2015 and up.
With the project loaded, go into the V-Ray tab, and change the Current View to Render. Leave Quality to Draft and set Resolution to Crop Region with Printer set to a DPI of 96, then click Render to see the project as it’s currently setup.
The render takes a minute or so, and as it resolves, you can see a simple exterior city scene, in which we’d like to add atmosphere. Stop the render when you’re satisfied, and then click the Settings icon.
Switch to the Fog tab for the Fog Settings. There are two types of atmosphere fog: Aerial Perspective and Environment Fog.
Using Aerial Perspective
Aerial Perspective is an effect that makes objects seem farther away due to the earth’s atmosphere, by making them somewhat hazy looking. Enable Aerial Perspective, and leave Atmospheric Height value as it is now.
A View Distance value of 8000m (about 26,000 feet) provides for a look more physically accurate to our own atmosphere, however, our scene is at a smaller scale. Therefore, set the View Distance closer at 1000m (about 3280 feet). This allows us to see the fog effect sooner than we would have otherwise.
Render to see the effect in the project, especially along the length of the road and the buildings in the distance. The sky in the render is not affected by the Aerial Perspective since the sky color already takes distance into account in its color; it already has atmosphere applied.
To force the effect on the sky as well, click on Affect Environment in the Fog Settings, and render again. The fog affects the sky as well as the city itself, is a bit faster to calculate, and looks more dramatic than before because a lot of the shadows from before have become muted.
Using Environment Fog
Environment Fog is a more realistic simulation of how fog works. Disable Aerial Perspective and enable Environment Fog in the Fog Settings.
Click Render to see what the defaults look like.
The volume in the fog can be seen in the light rays and shadows cutting into the fog, making this a more accurate simulation than Aerial Perspective. It is not affecting the sky much, however. One way to see more of the effect in the sky is to switch to a solid color dome light: change the V-Ray Sun over to a Dome Light, and leave it at its defaults with a white solid color.
Now to reduce the amount of fog we have, adjust Particle Distance in the Fog Settings. The higher this value, such as 6000ft, makes the fog less dense.
Render the project with the white solid color Dome Light and the less dense fog, and you’ll see a dark result.
Since we are using fog in this more accurate manner, we are muting the amount of light in the scene. We should adjust the Camera’s Exposure to compensate, and capture more light in the render. However, as a quick solution, you can enable Post-Processing effects in the VFB to make adjustments to the rendered image directly. Click the Show corrections control icon in the bottom left corner of the VFB.
Enable, then expand Exposure to adjust the exposure value in the rendered image.
However, it’s better to use the Camera’s Exposure for a better result in the render. But the VFB’s controls do give you some nice color correction options for any rendered image in the VFB, which is great for fine-tuning. Adjust the Exposure to 1.87 and the Contrast to 0.25 to see the difference from the default values as you adjust the sliders.
Turn off Exposure in the VFB and go back to the Sun instead of the Dome Light. In the Fog Settings, click to enable the Affect Background for the Environment Fog. Set the Particle Distance to 800ft.
Render to see the results.
We have a pretty foggy scene with the fog’s brownish tinge coming from the color of the sun lighting. We can adjust the image for that quickly with the White Balance color correction in the VFB.
Adjust the image as you like using Exposure and White Balance to get something you prefer or use the settings below.
Environment Fog is a more realistic effect than Aerial Perspective, and as such, it is a bit more system intensive. Let’s do a final render. Set the Quality to Very High, and set the Printer DPI to 150 to increase the resolution, or set it to your comfort level, and render!
If you have enabled Swarm and have additional machines on your network with which to render, you can leave the render settings at a high level. If you do use Swarm, you may wish to switch Engine options.
Change from Progressive for the Image Sampler to Buckets, which works well for Swarm rendering.
For more on Swarm, check out our previous QuickStart video on how to use this distributed rendering system.