Solar Radiation

Solar Radiation reports how much solar power reaches your geometry at a single instant. For each sensor it computes direct, diffuse, and total irradiance in W/m², and paints the total across your geometry as a colored sensor field.

What it Computes

From each sensor, the study casts one ray at the sun and a cosine-weighted set of rays over the sky hemisphere, keeping only the energy that arrives unobstructed.

Component	Meaning
Direct	Beam irradiance from the sun — DNI · cos θ, zeroed when context occludes the sun ray or the sun is below the horizon.
Diffuse	Sky irradiance over the hemisphere the sensor can actually see.
Total	Direct + diffuse — the instantaneous solar load, in W/m².

Sensor orientation is meant to be handled by excluding hemisphere samples that point below the horizon — those look at ground, not sky. The closed form is Liu–Jordan's sky-view factor (1 + cos β)/2: a roof should read DHI, a vertical facade DHI / 2.

The Sky Model

The sky is isotropic: the diffuse-horizontal irradiance you enter becomes one uniform sky radiance (L₀ = DHI / π), integrated over each sensor's unobstructed view. Fast, robust, and a faithful baseline for comparative work.

Assumptions

Fixed by the v1 physics. They decide what a number means, so they travel inside every export — a #-prefixed header block in CSV, an assumptions object in JSON — rather than living only on this page.

Assumption	Value
Sky model	isotropic
Ground reflection	not modelled
Ground albedo	0 — the ground is black
Accumulation	instantaneous — never summed over a period
Units	W/m2
Sun azimuth reference	deg from model +Y, cw — model space, not geographic north

Each export also carries that run's own inputs: DNI, DHI, sun altitude, sun azimuth, and the hemisphere sample count. Two consequences worth stating plainly:

• No reflected component appears in the results. Ground reflection isn't modelled, so the term is left out rather than shipped as a column of zeros that reads like a measurement.
• A value that couldn't be computed is not zero. It serializes as null and displays as an em-dash — missing data and a fully shaded sensor are different facts.

Use Cases

• Facade studies — see where solar load concentrates, to inform shading, glazing ratios, and materials.
• PV siting — rank roof and facade areas by instantaneous total. A ranking at the one sun position you chose; sizing a real array is separate work for a tool that simulates a whole period.
• Energy-aware massing — compare options early, balancing solar gain against overheating risk.

How to Run

Type WrenglerRadiation in the Rhino command line and answer the prompts in order; each is pre-filled, so Enter accepts the shown value.

1. Shading / obstacle geometry — the context that shades your sensors. Enter to skip for open sky.
2. Sensor surface(s) — the surfaces the sensor grid is built on. At least one required.
3. Sun position — altitude in degrees above the horizon, then azimuth in degrees from the model's +Y axis, clockwise. This is a model-space angle; the document north angle is deliberately not applied.
4. Sky inputs — DNI and DHI, both in W/m².
5. Grid spacing — in model units. Finer spacing means more sensors and a longer run.

The command reports the sensor count, the backend used, and min / mean / max total to the command line, and paints the total as a blue→red ramp. Direct and diffuse are computed per sensor and exported, but not separately displayed in the viewport today.

Related

• Geometry Grouping — reusable named scopes.
• Services overview — how every service shares one engine.