How to Set Up Caustics in D5 Render: An Interior Guide

Bright patterns created by light passing through glass or reflecting off a water surface can make the lighting in an architectural visualization feel more convincing. According to D5 Render’s official documentation, caustics must be enabled for both the relevant material and the light source to achieve this effect. Chaos’s explanation of caustics in Corona Renderer describes why caustics are challenging to calculate and how a different approach handles the process. Neither source specifies a software version; the steps below are based on the features described in the current documentation.

When are caustics useful?

Caustics are bright patterns created when light passes through or reflects off a surface and becomes concentrated on another surface. Rippling light patterns on the bottom of a pool and bright shapes cast onto a table through a glass are familiar examples. In interior visualizations, light passing through glass and creating patterns on the floor or nearby surfaces can also affect the scene’s lighting.

Chaos describes caustics as a light path in which light from a source hits a reflective or refractive surface, then reaches a diffuse surface before arriving at the camera. Because this path is difficult to calculate, some conventional approaches use shortcuts, such as limiting bright rays or ignoring glass geometry. These solutions may simplify the image in some cases, but they may not accurately represent how glass affects light.

Setting up caustics in D5 Render

1. Check the material template. According to D5 Render’s documentation, caustics are supported by the Custom, Transparent, and Water material templates. Custom supports reflective caustics, while Transparent and Water can produce both reflective and refractive caustics. If the material in your scene does not use one of these templates, the documentation does not specify caustics support for it.

2. Enable caustics on the material. Enabling the feature only on the light source is not enough; the caustics option must also be enabled for the relevant material. Changing the light settings without enabling the material does not meet the simultaneous requirement described in the documentation.

3. Enable caustics on the light source as well. D5’s documentation states that four types of light sources, along with Geo Sky and HDRI-Sun, support the effect. The documentation does not provide a step-by-step menu path or specify where the setting appears in the interface, so no particular panel path is given here.

4. Adjust intensity and softness to suit the scene. Caustics Intensity changes the brightness of the effect as a multiplier; higher values make caustics brighter. Softness has an effect when the light source radius is greater than zero. When evaluating softness, check that the light source radius meets this condition.

1. Keep in mind that the pattern can be affected by surface properties. According to D5’s documentation, changes to bump and the normal texture map in the model affect the shape of the caustics pattern. Check how the pattern looks in the scene by evaluating these properties together with the light’s intensity and softness. The source does not recommend specific values for these textures, so there is no fixed numerical recipe.

2. Monitor the number of light sources and the performance impact. D5 Render supports up to 64 light sources with caustics enabled at the same time. The documentation also notes that caustics add to render load and recommends choosing and adjusting the feature as needed. Rather than enabling it on every light, identify the sources where caustics are needed in the scene for a more controlled workflow.

Compatibility and preview limitations

There is an important compatibility limitation when using caustics with transparent materials: according to D5’s documentation, the effect is not compatible with those materials’ own UV and triplanar effects. If you use either of these effects on a transparent material, don’t assume they will work alongside caustics; check the scene’s output instead.

Caustics from sunlight may flicker slightly in the preview. D5’s documentation says this is done to reduce computational resources and that the flicker will not appear in rendered images. This means the preview should not be evaluated as if it were the final render.

Impact on architecture and archviz workflows

This feature can be useful in interior visualizations where the interaction of glass, water, or glossy surfaces with light needs to be visible. When a bright pattern cast onto a surface is important to the scene, enabling the options on both the material and the light is a key checkpoint. Also bear in mind that shortcuts that ignore glass or limit bright rays may change the appearance of caustics.

Chaos says Corona Renderer uses an approach that combines backward ray tracing with automatic photon mapping to handle caustics. According to the company, this method removes the need for manual setup required by traditional photon maps and typically limits the impact on render time to around 50 percent. This information is not about D5 Render settings; it describes the manufacturer’s approach in Corona. Therefore, the options or performance results in the two software products should not be treated as equivalent.

Common mistakes

• Enabling caustics only on the material or only on the light source; D5 requires it to be enabled on both.

• Expecting refractive caustics from the Custom template; the documentation specifies reflective support only for this template.

• Assuming Softness will take effect when the light source radius is zero.

• Assuming caustics are compatible with UV or triplanar effects on transparent materials.

• Treating flicker in the sunlight caustics preview as a final-render error, or overlooking the added render load.