This article is a demonstration of how water caustics can be created and used to generate the effect in a swimming pool. The topics will include the creation of the water material and the lighting setup, which are the two components that must interact with each other for the desired effect, then finally - the render settings needed for this interaction to take place will be shown.
An example of the final result of adding caustics to a swimming pool.
- An archive of the project file for this guide can be found here.
- Some Cosmos assets may be missing. The V-Ray Asset Editor > Geometries menu will allow you to download them, after which, you will have to restart SketchUp for the effects to take place.
- While this guide was created in SketchUp, the approach shown here is entirely usable in V-Ray for Rhino as well.
Refractive caustics are a fascinating phenomenon that occurs when light passes through a transparent or translucent object, such as a glass or a water surface and forms bright and focused patterns on surrounding surfaces. Caustics are everywhere in the real world. Caustics can be observed throughout the natural world, with many associating them as the result of light being refracted through materials such as glass or water. In the context of computer graphics, caustics are any light contribution that goes from a light source to specular (reflective or refractive) to diffuse surface and ultimately reaches the camera or observer's eye.
Here is an example of this:
To learn more about what are caustics and how to render them - please check this page.
Creating the required objects
The focus of this tutorial is on creating caustics suitable for a body of water, a pool in this case. To achieve this, appropriate geometry for both the pool and water needs to be established. The water geometry will consist of a basic plane with displacement applied to it, using a Noise texture or a custom wave texture for the irregularities.
Here is an example:
In general, the following items will be needed to generate the pool:
- Refractive material
- Light source
- An object that will catch the caustics
Note: Adding Displacement is not required for the Caustics to work. Displacement is used in this case to turn the simple plane into an irregular water surface, but regular geometry shaped like water’s surface can be used as well.
The process of creating the Displacement is relatively simple. Apart from selecting an appropriate texture, the only adjustment that may be necessary is modifying the Amount value to achieve the desired intensity of the displacement effect. Apply the Displacement to the water plane after selecting it:
In this example, the procedural Noise A texture will be used, which is readily available in V-Ray:
Creating the materials
In this example, the materials used for the pool body itself, such as the blue tiles, are taken from the Chaos Cosmos Browser. The materials for the pool body are up to personal preference.
As for the water itself, a simple Generic VRayMtl material will be used as a starting point:
Once the Generic material is created, the Advanced Settings must be enabled. This will open up additional parameters, which are crucial for the creation of a water material:
In the Diffuse rollout, the Color will be set to black:
The Reflection rollout contains two important properties - the Reflection Color, which must be set to pure white and the Reflection IOR. The IOR for water is 1.33:
In the Refraction rollout, the same process will be repeated for the Refraction Color. It will be set to pure white and the IOR to 1.33.
The Depth (cm), will be left at 0. However, this is a value which you can experiment with depending on the objective. Another parameter, which offers even more creative freedom is the Fog Color, which can be used to add a “tint” to the water. The Fog Color and the Depth (cm) parameters are tied together - the Depth (cm) will intensify the Fog Color when its value is increased.
The last option that needs to be altered is the “Affect Shadows” parameter. This parameter is of extreme importance and it must be disabled in order for the water caustics to work:
The default Sun can be used to illuminate the scene. However, the V-Ray’s Light Gen tool will be used in this example, as it will generate a unique and interesting environment. The Exterior option will be appropriate for the goals of this demonstration. The sun rays will have to hit the water directly in order for the caustics to be generated, so the Light Gen variant must be chosen with this in mind.
Double-clicking on the chosen Light Gen variant will add a V-Ray Dome Light to the scene and this action will automatically adjust the Exposure Value of the render settings accordingly.
What needs to adjusted next is the Caustic Photons rollout of the Dome Light:
- Caustics Subdivs - The higher the value, the sharper and more defined the caustics will be. This will have a negative effect on the rendering times.
- Target Radius and Emit Distance will enlarge or decrease the area where the Caustic Photons are emitted from and where they are hitting. If the water in the pool is oddly illuminated as if in a spherical shape, these values should be increased.
Finally, the Caustics switch in the Global Illumination rollout of the Render settings must be enabled and the pool can be rendered: