| 1. Establish Orientation | North reference | True north = 0°; east = 90°; south = 180°; west = 270° | Azimuth is measured clockwise from true north | Rotate the building or sun system so façade exposure matches the site survey |
| 2. Define Location | Latitude and longitude | Latitude controls seasonal solar height; longitude supports local solar-time conversion | Solar position depends on geographic coordinates and date | Enter the project coordinates before selecting sun direction or shadow studies |
| 3. Select Date | Solar declination | Approximately +23.44° at the June solstice, 0° near the equinoxes, and −23.44° at the December solstice | Earth’s axial tilt produces the annual change in solar declination | Use the actual visualization date when evaluating overhangs, glazing, and façade shadows |
| 4. Set Solar Time | Hour angle | H = 15° × (solar time − 12); 15° equals one hour of apparent solar time | The sun moves approximately 15° in azimuthal hour angle per hour | Convert clock time to solar time before positioning the sun |
| 5. Calculate Solar Height | Solar altitude angle | sin(α) = sin(φ)sin(δ) + cos(φ)cos(δ)cos(H) | α is the angle between the sun and the horizontal plane | Use altitude to control shadow length and the amount of direct light on vertical surfaces |
| 6. Calculate Solar Direction | Solar azimuth angle | At local solar noon, the sun is due south in the Northern Hemisphere and due north in the Southern Hemisphere | Solar noon is determined by the sun’s highest daily altitude, not necessarily 12:00 on the clock | Aim the direct-light vector toward the correct true-north azimuth |
| 7. Validate a Sample Position | Latitude 40° N at equinox, local solar noon | Solar altitude ≈ 50°; solar azimuth ≈ 180° | At the equinox, declination is approximately 0°, so altitude ≈ 90° − latitude | Use this as a basic scene check for a north-aware sun setup |
| 8. Compare Seasonal Angles | Latitude 40° N at solar noon | June solstice ≈ 73.44° altitude; December solstice ≈ 26.56° altitude | Values use declinations of approximately +23.44° and −23.44° | Test roof projections and façade shading under both high-sun and low-sun conditions |
| 9. Choose Sky Distribution | CIE standard sky type | Use a clear-sky distribution for strong directional sunlight or an overcast distribution for diffuse illumination | CIE standard skies describe how luminance is distributed across the sky vault | Match the sky type to the intended weather condition and visual purpose |
| 10. Define Sky Luminance | Zenith-to-horizon brightness gradient | Clear skies are generally brighter near the sun and horizon; overcast skies are brightest near the zenith | CIE sky models use angular luminance distributions rather than a uniform background | Avoid a flat environment light when realistic façade gradients are required |
| 11. Set Ground Reflectance | Diffuse ground albedo | Typical modeling assumptions: dark asphalt ≈ 0.05–0.15; vegetation ≈ 0.15–0.25; light concrete ≈ 0.40–0.60 | Albedo is the fraction of incident radiation reflected by a surface | Use ground reflectance to control bounce light under eaves and around lower façades |
| 12. Configure Direct Sunlight | Sun disc and shadow softness | The sun’s apparent angular diameter is approximately 0.53° | A finite solar disc produces physically plausible penumbra rather than an infinitely sharp light source | Use a physically sized sun disc and adjust only for artistic presentation when necessary |
| 13. Set Atmospheric Clarity | Aerosol or turbidity condition | Lower turbidity gives clearer, higher-contrast sunlight; higher turbidity increases haze and warm scattering | Atmospheric particles reduce contrast and redistribute direct solar energy | Coordinate haze, sun intensity, and sky brightness so they describe the same weather condition |
| 14. Check Façade Exposure | Incidence angle | Direct irradiance on a plane varies approximately with cos(θ), where θ is the angle between the sun direction and the surface normal | Lambert’s cosine law describes projected direct illumination on diffuse surfaces | Confirm that south-, east-, west-, and north-facing façades receive the expected relative light |
| 15. Final Quality Control | Scene verification checklist | Confirm true north, coordinates, date, solar time, altitude, azimuth, sky type, ground albedo, and shadow direction | A rendering is geographically consistent only when orientation, solar geometry, and sky distribution agree | Render a shadow pass and a clay pass before final materials and color grading |