This page provides a tutorial on using Sun and Sky and Aerial Perspective in V-Ray for SketchUp.
In this tutorial we’ll go over how to render environmental lighting using the Sun and Sky system, as well as using Aerial Perspective to simulate atmospheric haze to denote distance.
To follow this tutorial, you will need to have the V-Ray for SketchUp plugin installed. This tutorial is a companion to go along with the QuickStart video posted on our YouTube channel and available here:
To download the files used in this tutorial, please click on the button below.
Open the Example Scene
Begin by launching SketchUp. Open the project file Aerial_Staircase_Start.skp, which can be downloaded from the Tutorial Assets section above.
Start an Interactive render to arrive at the result shown below.
Adjusting the SunLight
Open SketchUp’s Shadows rollout, and adjust the sun direction and lighting by changing the time and date.
Set the Time to 2:29 PM and the Date to 12/06.
You can access more controls for the Sunlight in the Asset Editor, with the tooltips giving you a good description of each parameter as you mouse over them.
Adjust the Size Multiplier to 5.1 to get softer shadows in the Interactive render (shown below).
Then, put a tint on the lighting by adjusting the Albedo Color, which affects the sky coloration just above the horizon.
Set the Sun Albedo Color to a cyan blue as shown below.
Now use the Blend Angle to adjust the blending amount between the horizon line and sky. Lower values reduce the Albedo color effect lower and closer to the horizon, while larger numbers pull that color up higher into the sky, all of which affects the overall scene lighting, as you can see below.
= 1Blend Angle
= 20Blend Angle
Blend Angle = 60
Next, set the Blend Angle to 5 for a nice result.
The Horizon Offset allows you to manually lower the horizon line of the sky, which again affects the lighting and reflections in the scene, as you can see in the images below.
Horizon Offset = 3.5
Horizon Offset = 10
Set the Horizon Offset to a value of 8.74.
Now we want to get a different sky that has clouds in the background, but without affecting the balanced lighting that we’ve already got. This happens through the Environment section of the Asset Editor.
In the Environment section, click on the texture icon ()next to Background.
You should see the V-Ray Sky texture is currently attached as a map, and it affects both the illumination and what we see in the background of the render.
Environment background = On
Environment background = Off
Expand the Environment Override panel and then enable both GI and Reflection Overrides.
Then left-click and drag to copy and paste the texture assignment from the Background slot to both the GI and Reflection Overrides slots.
Then, disable the Background and the illumination and reflections remain intact due to the overrides we set previously.
Re-enable the Background. Now to replace the Sky texture with a Bitmap: Click on the texture icon () next to Background. Then click on the texture list icon ( ) to open the full list of textures and select Bitmap.
Choose the file called Sky.jpg found in the downloaded assets.
In the UVW rollout, change to the UVWGenEnvironment to ensure proper placement of the texture map.
Then change the Mapping Type to Screen and you’ll see the image is mapped correctly, but it appears too dark.
To fix this, simply increase the Background value to 35.
Stop the Interactive Render.
In the layer rollout, show the Environment layer to reveal trees and mountains in the scene’s background.
Click on the Top_View scene view and you can see the distance between the buildings (3 small squares on the left) and the background trees and mountains on the right in the image below.
Back to the camera view, and restart the Interactive Render, and you can see that the mountains in the back don’t seem far away at all.
In real life, the atmosphere would make the mountains look distant; we will use Aerial Perspective to simulate that visual cue.
Using Aerial Perspective
Turn on the Aerial Perspective option, and we immediately get a better sense of depth due to the added atmosphere.
In the VFB, select the Atmosphere render layer from the drop-down menu and you can see the effect by itself.
Aerial Perspective is, in short, a volumetric effect that simulates the haze created by particles in the atmosphere that essentially make objects that are further away from the camera, appear to be brighter. Open the rollout to access the settings.
However, notice that the shadows on the building are mostly gone now.
The Aerial Perspective extends too high into the sky and is scattering all the sunlight rays, essentially diffusing the shadows away. So, lower the Atmospheric Height to 250 meters and the shadows return.
Now reduce the Visibility Range to intensify the haze effect, and settle on 1600 meters.
Now since the Aerial Perspective is dependent on the sun and sky in the scene, any changes we make to the sun, such as intensity, direction, or color, will affect the atmosphere. As a matter of fact, even when the sky is disabled, and for example, you’re using a dome light for lighting, make sure to make adjustments to the disabled sky to affect the Aerial Perspective to match into your lighting.
Go ahead and move the sun direction by changing the time of day, and you can see how the atmosphere is affected.
Time = 7:14 AM
Time = 8:20 AM
Time = 4:13 PM
You can use the Inscattered Light Mult. value to separately affect the brightness of the Aerial Perspective itself, without having to adjust the sun. The default value of 1.0 is physically accurate, and is recommended.
You can also use the Filter Color to adjust the color of the atmosphere as you like it. Here, we'll add a little more blue.
Setting up the finishing touches
Aerial Perspective does a nice fast job of giving more depth and sense of distance to a scene, but when it’s fairly strong, as in this case (shown above), it can wash away some contrast in the image. However, we can easily bring that back by clicking Show Corrections Control in the VFB.
Use a Curve to punch up the image, and you shouldn't lose that sense of depth to the scene. Use a value of (0.11 ; 0.58) for the upper point and a value of (0.25 ; 0.10) for the lower point to get the curve like this:
Add some Hue/Saturation to boost the color a little bit to add some vibrancy. Set Saturation to 0.15.
Make the scene a little warmer with White Balance. Adjust the slide to see the change and we use a value of 7279.
Here is our final render: