The third lesson covers the workflow for generating realistic interior renderings:
- V-Ray Sun and Sky system for interior rendering
- Proper Camera Exposure
- Portal Lights to improve illumination coming from outside
- Global Illumination Engines for interior rendering
- Shading your scene using the predefined materials in the V-Ray Materials Library
- Setting up V-Ray for a High Quality render and using the Denoiser render element
You can download the lesson guide here.
Each section is annotated in the video. You can find scene files with the same names in the Lesson 3 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.
V-Ray Sun & Sky and Camera Setup
We start by adjusting the V-Ray Sun and Sky system which is the main source of light in our case. Since light is coming through the windows it is not enough to properly illuminate the scene as it is. We fix that by adjusting the Camera Exposure Value(EV). We can also adjust for the sun's warm color by using the White Balance option of the Camera.
In the case of an interior rendering we might need a wider camera lens to capture more of the room. This however results in some perspective distortion. We can use the Vertical Tilt option of the camera to adjust the rendering and create 2-point perspective.
For this scene, we switch the Sky model to CIE Clear. This model allows us to control the intensity of the sky separately from the intensity of the sun using the Horizontal Illum. parameter which gives us more control over the overall illumination
Finally, we increase the suns Size Multiplier to create softer shadows.
In this step, we use Portal Lights to improve the illumination in our scene. In day time illumination of interiors, the light usually comes from the environment, through the windows into the room. This means that a lot of the light is bounced or secondary light which requires a lot of GI calculation. We can go around that issue by using a V-Ray Plane Light with the Portal Light option enabled. When in this mode the color and intensity of the light is determined by whatever is behind the light. If we put these lights outside the windows V-Ray will sample the color and intensity of the sky and use those values to emit light from the Plane lights. This introduces direct light into the room which makes the calculations much faster and improves the quality of the final render.
In this step, we explore the different methods for calculating GI with V-Ray.
Brute Force is the most precise of all the GI methods in V-Ray. It doesn't require a pre-pass which allows us to use it in Interactive Rendering. It is suitable for Primary Rays engine when we need high precision. It may be used for Secondary Rays engine but mostly in exterior scenes where GI light doesn't bounce many times.
Irradiance Map is an adaptive version of the Brute Force. It is faster and creates very accurate results but it requires a pre-pass. It is suitable for Primary Rays engine in most cases. It cannot be used for Secondary Rays engine.
Light Cache is a special method which can quickly calculate many bounces of light but it is not extremely precise. This makes it suitable for Secondary Rays engine especially in interior scenes where light bounces a lot. It is not used as a Primary Rays engine.
Since we do not want to delve into the complex controls of the GI methods we only use the Quality Slider to adjust the settings. However, moving the slider changes a bunch of different settings in the GI engines' parameters.
For draft renderings, we use Irradiance Map + Light Cache as this is the quickest combination. For high quality rendering, we use Brute Force + Light Cache as this combines the multiple bounces of the Light Cache with the high precision of the Brute Force.
In this step, we use the materials in the V-Ray Material Library to shade the objects in the scene. We will use the available materials and adjust the material size so that the textures are tiled correctly. We can fine tune some of the materials by changing their parameters where we deem that necessary.
When we are applying materials to the V-Ray Proxies in the scene we use a Multi Material material and the proxies have proper Material IDs assigned when they were exported. This workflow is explained in Lesson 1 Extra module about Proxy Shading.
High Quality Rendering
In the final step, we setup V-Ray for high quality rendering. To do that we use high settings for the Quality slider and add the Denoiser Render Element. Once the render is complete we can further adjust the final image with the Color Corrections options of the V-Ray Frame Buffer.
This lesson comes with 3 Extra modules. For each module there is a video, and a scene file with the same name in the Lesson 3 folder.
1. Night Time Setup
In this bonus module, we switch the illumination to a night time setup. To make things faster we first lower the Quality slider and enable the Material Override. Next, we set-up the environment to look as an evening time sky. This includes disabling the V-Ray Sun and switching the Environment from a V-Ray Sky to a dark blue color. Since we are changing the illumination we also need to adjust the Camera Exposure Value (EV) parameter. This allows us to use physically accurate lights later. Finally, we add some artificial lighting to the scene using V-Ray lights.
2. Render Elements
In this module, we set up V-Ray to split the image into its composing render elements. This allows us to apply color corrections to each element independently and gives us much more control in post processing. In this scene, the elements we need are:
- Lighting - this element stores the contribution of lights to the diffuse component of the materials in the scene
- Global Illumination - this element stores the contribution of global illumination to the diffuse component of the materials in the scene
- Reflection - this render element holds all reflective parts of the scene
- Specular - this render element holds the specular reflections in the scene (the reflections of lights in blurry reflections)
- Refraction - this render elements holds all the refractive parts of the scene
- Background - this is the background or environment
In the end will add a Material ID render element. This is a custom render element which isolates objects with the same material and renders them with a unique flat color. This allows us to easily select objects with the same material in post-production and apply color corrections to them.
3. Simple Compositing
In this module, we use Photoshop to compose the render elements back to the beauty pass. To do that we use the Add (Linear Dodge) blend mode. Once the image is composed we can apply color corrections on each render element which allows us to have much more control over the final result. In the last step, we use the Material ID render element to create a selection mask and use it to apply color corrections just to the walls.