I’m conducting a series of daylight simulation with honeybee and the sun is scripted using azimuth and altitude angles. For some pairs of azimuth-altitude angles, I can see hdr image being created. But for some, I don’t. Does anyone know why the hdr image of the sky isn’t being created? I get an error: Bad Radiance picture.
In the image below the azimuth angle is 189 degrees. I’m assuming +y axis is 0 (N) and hence 189 degrees will be around -y (S), correct? Why is the image not being created?
Anyone know why HDR image for the sky is not being created? Wondering if @mikkel or @mostapha can help me out here. Below is the gh file. SkyError.gh (607.8 KB)
The azimuth that I added in your custom component follows the Radiance convention where azimuth is measured in degrees west of south. I noticed that the honeybee-radiance sky object throws an error in some cases, so I changed the code a little bit – see the attachment.
In any case 0 is south, 90 is west, 180 is north, 270 is east. You can also use a negative value, e.g., -90 which is east.
Maybe it is related to this excerpt from the gendaylit manual. Perhaps this combination of values is not possible according to the model in gendaylit. I am not able to give any guidance on the epsilon and delta values – you might have better luck on the Radiance forum.
The atmospheric conditions are modelled with the Perez et al. parametrization (see Solar Energy Vol. 44, No 5, pp. 271-289, 1990), which is dependent on the values for the direct-normal and the diffuse-horizontal irradiances. The three parameters are epsilon, delta and the solar zenith angle. “Epsilon variations express the transition from a totally overcast sky (epsilon=1) to a low turbidity clear sky (epsilon>6); delta variations reflect the opacity/thickness of the clouds”. Delta can vary from 0.05 representing a dark sky to 0.5 for a very bright sky. Not every combination of epsilon, delta and solar zenith angle is possible.
I see. I will ask on the Radiance forum. Thank you! Quick follow up to the question on orientation:
I wanted to compare between the GH contour plot and the corresponding shadow image created from Rhino sun (also using azimuth altitude in Rhino). Since Rhino sun considers 0=North, I wanted to keep it consistent. So I had added the below python script and connected it to your previous sky component. This should make 0=North, right? Because, this way, the contour plots and Rhino shadows match, as follows:
But as you noticed, sometimes the combination of values don’t create a sky model. And yet, Rhino can cast shadows. I’m assuming Rhino sun is simply a directional light that is directing light from a certain azimuth/altitude location?
