The enhanced 2-phase method and the imageless method

Dear Radiance experts,

I am using aBSDF type materials on Rhino and HB-Radiance to simulate the effects of the CFS on indoor light environments.

Now, I have two problems:

  1. I noticed that an enhanced 2-phase method used to calculate the annual daylight in HB-Radiance. The recipe is described as " This recipe uses an enhanced 2-phase method for daylight simulation which accurately models direct sun by tracing rays from each sensor to the solar position at each hour of the calculation."
    The enhanced 2-phase method can be used to simulate the model applied aBSDF type materials? I would like to know more about the enhanced 2-phase method and is there any reference or information about it?

  2. Similarly, the imageless method can be used to simulate the model applied aBSDF type materials? I found an article by Nathaniel L. Jones @Nathaniel_Jones about the imageless method (The Imageless Method for Spatial and Annual Glare Analysis · nljones/Accelerad Wiki · GitHub), but this article on calculating annual DGP using BSDFs does not seem to be updated.

Thank you for your time and patience!


Hi Xuran,

I can’t comment on the first part of your question. As to the second part, the imageless glare method is assumes that all glare sources are viewed directly, so it wouldn’t be appropriate to use it with light-redirecting surfaces. Thus there is no support for aBSDF materials.

Dear Xuran,

Sorry for the delayed response, I attempted to reply by email but the post never went through, which I just now noticed. A first clarification: There is a distinction between the simulation method (how light is accounted for between source and sensor) and whether the simulation results in illuminance sensor values or view specified images. I believe what honeybee is describing is a sensor-based simulation.

The enhanced 2-phase method can be performed to generate either sensor values (cosine weighted illuminance) or images (with any view projection). Sarith Subramaniam put together a tutorial (found here: which includes enhanced 2-phase (called 2-phase DDS). The example scripts include a sensor based example. For an image based version, I modified these scripts (combined with the 5-phase example) for this paper: You can find the scene files and run scripts here: reference radiance model and result data for an office building near LAX | Zenodo (see This method will work with an aBSDF material, assuming aBSDF is appropriate for the cases you are modeling, which other would need to comment on.

If discomfort glare is one of the effects you are looking at, which I am guessing you are since you mentioned the imageless method, I would also take a look at this paper (A Critical Comparison of Annual Glare Simulation Methods), where we compared a range of approaches to calculate DGP under a wide range of conditions (not an aBSDF specifically, but I would expect similar results to the trans and rollershade materials).

good luck,


1 Like

Hi @Nathaniel_Jones

Thanks for your reply. It was very helpful. In addition, I am studying your paper about imageless glare method.

Again, really appreciate your help!

Best wishes,

Hi Stephen,

Thanks for your response. Your response contains a wealth of information that is worth a weekend of study.

Your kind assistance on this is very much appreciated!

Best wishes,