The second lesson covers the workflow for generating realistic exterior renderings:
Trees and grass require lots of polygons so we use V-Ray Proxy and V-Ray Fur to generate them efficiently
We use the Override Material function to speed up the lighting process
We use the V-Ray Sun and Sky system to match the illumination at a specific place in the world at a given time and day of the year
Using the Physical camera option we adjust the exposure and white balance of the image
We switch the illumination to image based lighting – using a panoramic high dynamic range picture of an environment and V-Ray Dome Light to illuminate our scene
We show how to setup night time illumination using the Dome Light and some of the lights covered in the Extra modules of Lesson 01
We use the VFB Lens Effects to further enhance the night time setup
Each section is annotated in the video. You can find scene files with the same names in the Lesson 2 folder. These were made so that you can start at any one of these stages and follow the steps in the video to the end.
The main module begins with setting up some vegetation. Since vegetation is usually very high poly and SketchUp cannot handle that much geometry we use several V-Ray functionalities
We begin by setting up some trees and bushes using the V-Ray Proxy. The proxy allows us to store any geometry on the hard drive and load it to SketchUp without impacting the poly count and performance of SketchUp. V-Ray then loads the geometry during render times.
The geometry can be exported from any platform that supports V-Ray (into a .vrmesh file) or any platform that can export .alembic files.
The V-Ray fur is a procedurally generated geometry that can be used to simulate effects like fur, hair and grass. In this module, we use it to quickly setup some grass for the front lawn. The Length, Thickness, Bend and Taper parameters allows us to control the look of each individual strand. The Variance parameters allow us to introduce some randomness in the grass so it looks more natural - higher numbers mean greater variation from the values determined in the Basic Parameters. The Distribution parameters allow us to control the density of the grass. We can choose between controlling the number of grass strands in two ways:
- Per Face - each face has the same number of strands, if the faces have different areas the density of the grass will vary.
- Per Area - guarantees equal density of the grass across faces with different areas
When working with proxies it is better to make copies of one proxy rather than importing the same geometry multiple times with different v-ray proxies. This method saves memory by keeping only one instance of the geometry in the RAM
This option is useful when setting up the illumination of a scene in which materials are already present. It allows us to render the entire scene with a single diffuse material which speeds up the rendering. In our workflow, we enable it in each step where we adjust the illumination and then disable it in the end for the final render.
Sun and Sky
This part demonstrates the basics of setting up a V-Ray Sun and Sky System. The main point is that the illumination (color and intensity) depends on the Sun's position. Setting up the geographical position of our scene allows us to create accurate day time illumination for any given date and hour of that day. The intensity and colors of the sky will be physically accurate based on those settings.
The Size Multiplier parameter, though not actually physically accurate - the Sun has a constant size, allows us to control the softness of the shadows for artistic purposes. Higher values create softer shadows.
The Sky Model parameter allows us to choose between different methods for generating the Sky texture. We prefer using the Hosek et al method which we believe produces the most visually pleasing effect.
Finally, we discuss the Albedo options which control the color of the sky below the horizon and how this color is blended with the actual color of the sky (above the horizon).
This part of the workflow covers the usage of the V-Ray Physical Camera options to adjust the exposure and white balance of the image. We are using the camera in its "basic options" mode in which we only have one parameter - Exposure Value(EV) to set the exposure of the image. Higher EV makes the image darker and vice versa. The White Balance parameter allows us to adjust the white balance of the image to accommodate for the color of the illumination.
Once you adjust those two parameters, you can disable the Material Override to render one version of a day time illumination.
This part demonstrates another method of generating day time illumination. We will use a V-Ray Dome Light along with a high dynamic range image (.hdr) to create Image Based Lighting. The Dome Light makes IBL much faster and easier to calculate as it doesn't require high GI settings for a good result. Start by enabling the Material Override to speed up the rendering, and then once the setup is complete disable it for the final rendering.
Night time setup
In this part, we demonstrate how to set up night time illumination. We adjust the Intensity parameter of Dome Light to make it look like evening time. We change the rotation of the image so that we can bring another part of the image into view and get rid of the direct light coming from the bright sun in the image. We add several light sources and adjust their Intensity and Color to create warm artificial illumination in the scene. To speed up the process we enable the Material Override in the beginning and disable it for the final render.
VFB Lens Effects
In the final part of the workflow we use the Lens effects to further enhance the image by adding some Bloom and Glare effects. Since those are calculated very quickly once the image is rendered we can experiment freely and get the desired result quickly.
This lesson comes with 8 Extra modules. For each module there is a video, and a scene file with the same name in the Lesson 2 folder.
1. Aerial Perspective
This extra module covers the settings of the Aerial Perspective effect found in the Environment settings. It allows us to simulate volumetric effects like thin mists. It uses a simplified method of calculation which doesn’t create volumetric shadows, but creates realistic results that can be used for different artistic effects. This effect is mainly used in large scale scenes (looking at a city from far away) to simulate the effect of looking at far away objects through the earth’s atmosphere.
2. Advanced Sun & Sky Parameters
In this module, we cover more of the settings of the V-Ray Sun and Sky system. We use the filter Color, Turbidity and Ozone parameters to affect the color of the illumination coming from the sun as well as the colors of the sky. The Affect specular option is used to control the effect the sun has on specular reflections. We can use it to modify how bright specular reflections are and to fix over bright spots is the specular reflections.
3. Environment Overrides
In this module, we cover the Environment Overrides. These options allow us to have different images to act as an environment when calculating effects like reflections, refractions and GI. This allows us to have more artistic control when creating the final image. For example, we can have one environment/image in the background but another image/environment visible in the reflective or refractive objects.
4. Advanced Camera
In this module, we cover the Advanced options of the V-Ray Physical Camera settings.
- Film Sensitivity (ISO) controls the sensitivity of the virtual film/sensor - higher values make the image brighter
- Aperture (F number) controls how open the lens aperture is. Lower values mean a wider open aperture which lets more light into the lens and makes the image brighter.
- Shutter Speed (1/s) controls the speed at which the shutter opens and closes. This value is in inverse seconds which means the actual speed is 1 divided by the specified value seconds. Higher values make the shutter open and close more quickly which lets in less light and makes the image darker.
All the lights in the scene have been set with realistic intensities and the EV has been pre-set to have a reasonable exposure. Play around with each of the three parameters and note how they affect the final image. This approach is suitable for matching real-world photos to a CG image because the Physical Camera parameters match the settings of a real-world camera.
5. Mesh Light
In this module, we demonstrate the process for turning objects into light sources. The standard approach is to apply a self-illuminated material to a mesh and then rely on global illumination to gather light from it and illuminate the scene. This approach however requires high GI settings and doesn't always produce reliable results. With V-Ray you can pick any mesh and turn it into a real direct light with a few clicks shown in the video
6. Advanced Lens Effects
In this module, we demonstrate how you can control where the Bloom and/or Glare effect is applied using a selection mask based on the Intensity of the pixels in the rendered image. The Intensity masks work straight forward. The V-Ray Frame Buffer holds the image in a 32 bit floating point format. Using the intensity mask V-Ray applies the Bloom and/or Glare effect only on pixels with Intensity higher than the one specified in the Intensity parameter. This allows you to avoid "blurring" the entire image and have the Bloom/Glare effects applied only on the bright areas of the image.
7. Proxy Shading
In this module, we discuss how to apply multiple shaders to a V-Ray Proxy geometry. This is useful when we have a complex geometry that requires different materials for different parts of the geometry i.e. a tree with leaves. For this to work the original geometry should have proper face IDs setup. If that condition is met we can use the Multi Material to apply different materials based on face IDs.
8. Advanced Fur
In this module, we look at controlling some of the V-Ray Fur settings using a texture. The Length, Thickness, Gravity, Bend and Density textures can use a grayscale texture. The values in the texture are multiplied by the value set in the Basic Parameters where White = 1 and Black = 0. The Bend Direction texture and Initial Direction textures can use an RGB texture to control the direction of the bending and the initial rotation of the strand in texture space: the red channel controls the parameters along the U direction, the Green channel - along the V direction and the Blue channel along the surface normal.