> For the complete documentation index, see [llms.txt](https://docs.betterbuilding.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.betterbuilding.io/user-guide/workflows/daylight/simulation.md).

# Simulation

{% hint style="info" %}
We recommend defaulting to 'High' for all project deliverables when modelling daylight. 'Low' can be used to get fast results during early design stages or to check design changes, but should always be avoided for reporting final results.
{% endhint %}

<figure><img src="/files/t4B7TG0uRACZD93y92C0" alt=""><figcaption></figcaption></figure>

The table below presents various radiance parameters used in daylight modelling, categorising them from "Low" to "High".

These parameters define different levels of accuracy and quality in the simulation, with corresponding settings for ambient parameters. The higher the quality, the more precise the modelling, but it may require more computational resources. This categorisation helps select the appropriate settings based on the project's requirements, balancing accuracy, quality, and computational efficiency.

| Radiance Code           | Description                                                                    | -ab | -aa  | -ar  | -ad  | -as  |
| ----------------------- | ------------------------------------------------------------------------------ | --- | ---- | ---- | ---- | ---- |
| Low                     | Fast, but not recommended for project work                                     | 1   | 0.3  | 128  | 256  | 128  |
| Standard                | Lowest usable quality - but will underestimate illuminance                     | 3   | 0.25 | 256  | 512  | 256  |
| Good (no interpolation) |                                                                                | 4   | 0.00 | 512  | 1024 | 512  |
| Good                    | Default setting for balanced accuracy and simulation speed                     | 4   | 0.22 | 512  | 1024 | 512  |
| Accurate                | Best setting for highest practical accuracy                                    | 5   | 0.20 | 512  | 2048 | 1024 |
| High                    | Use when highest quality is required and a long wait for results is acceptable | 7   | 0.18 | 1024 | 4096 | 204  |

In addition to the above, Direct Daylight Settings can also be for Daylight Factor simulations.&#x20;

| Direct Daylight Setting         | Objective                                                                                                                                                  | Default |
| ------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| Direct Sampling (ds)            | Direct lighting contributions are directly sampled to improve accuracy in rendering or simulation.                                                         | 0.05    |
| Direct Thresholding (dt)        | Applies a threshold to direct lighting contributions, ignoring values below a certain level to optimize computation.                                       | 0.15    |
| Direct Certainty (dc)           | Prioritises direct lighting calculations based on their certainty or reliability, enhancing simulation accuracy.                                           | 0.75    |
| Direct Presampling Density (dp) | Adjusts the density of pre-sampled direct lighting data, balancing accuracy and computational efficiency.                                                  | 512     |
| Grouped Ambient Cache           | Applies to Daylight Factor simulations. Controls whether rtrace simulations are grouped by Zone (enabled) or combined into a single simulation (disabled). | Enabled |


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