Radiance Render

The ClimateStudio Radiance Render workflow supports the creation of physically based renderings using a path tracing version of the Radiance raytracer.

Simulation Setup

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To prepare a model for rendering, work your way through the five subpanels labeled 1-5 in the figure above.

2 - Sky
4 - Luminaires (optional)

If you have not done any lighting simulations in ClimateStudio, it is recommended that you go through the Lighting Model Setup video tutorial (5 minutes). The Rhino file used in the tutorial is available for download.

Once all required inputs have been populated, click the Render Window button (6), which opens a form with a render view on the left and camera settings on the right. The render view displays renderings that are complete or in progress, so this area will remain blank until the Start button is clicked.

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Camera Setup

  • Projection: Radiance supports a series of lens types that determine how a the surrounding scene is projected onto a two-dimensional image. For more details consult the Radiance rpict manual pages. The default projection – the Rotating Fisheye – is a custom type available only in ClimateStudio. For a given camera location, it generates a 360-degree panorama, which is remapped onto an oriented 180-degree angular fisheye on the screen in real time. This allows the user to rotate the view direction without having to start a new rendering.

  • Position: Corresponds to the location of the camera in the scene.

  • Rotation and Tilt: Controls the direction the camera is facing. Rotation is measured in degrees counterclockwise from East, and Tilt in degrees above or below the horizon.

  • Width/ Height (pixels): Sets the pixel resolution of the image.

  • Lens Length (mm): Only applies to perspective projections. Sets the opening angle of the camera, which in turn determines the extent of the scene shown on the rendering.

Position and view direction may be set manually, or by using the “Pick” button, which allows setting the camera using a saved Rhino view or ClimateStudio sensor. Once the camera is set, a rendering is invoked by pressing the Start button. ClimateStudio uses a progressive path-tracing version of the Radiance raytracer. While a rendering is in progress, pixels are sampled until the user-specified number of samples has been reached, or the Stop button is pressed. Details on the simulation settings can be found by clicking the Settings button.

Simulation Results

../_images/RadianceRender.gif

Radiance renderings are high dynamic range (HDR) images. For each pixel, an HDR image contains red, green, and blue color channels similar to a traditional bitmap, plus a luminance value that determines the pixel’s absolute brightness. Because it contains absolute luminances, an HDR image can record physical lighting conditions and serve as the basis for predicting human visual comfort responses, which low-dynamic range (LDR) images cannot. Another benefit of HDR images is that exposure levels can be re-adjusted to highlight different regions of the image in post-processing.

The Image Display section contains settings responsible for converting the HDR image into the LDR representation that appears on the screen:

  • Scheme determines the type of mapping. Options include RGB and Greyscale, which mimic the response of a traditional photographic film, or Falsecolor, which maps luminance values onto a color scale.

  • Exposure and Gamma work in concert to determine the brightness of pixels under RGB or Greyscale mapping. Exposure is a scalar that adjusts the overall brightness of the displayed image, while Gamma is a parameter that describes the nonlinearity of the tone scale. A gamma of 2.2 is a reasonable default for mimicking the power responses of photographic film and the human eye.

  • Glare Pixels may be enabled to flag all pixels above a user-defined luminance (by default 2000 cd/m2) with a distinctive color.

Luminance values for individual pixels or rectangular regions may be tagged by clicking or clicking-and-dragging (respectively) over the image. For rotating fisheye projections, right clicks are used (to distinguish from rotation); otherwise, left clicks are used.

For the rotating fisheye projection, ClimateStudio calculates the daylight glare probability (DGP) for the current view and classifies it as either imperceptible, perceptible, disturbing or intolerable. Details can be found under the Annual Glare workflow.

Once the simulation has been stopped, the rendering can be saved as a ClimateStudio result file and/or exported to HDR or LDR image formats.