Hello everyone,

I'm using Diva to calculate annual glare. The following warning and errors appear as the simulation runs, but at the end, I get the results. I wanted to know if my results are accurate since I have these errors. Thanks!

Warning: Sun altitude below zero at time step 1 9 7.50 printing error sky

Rpict: fatal – (C:\Diva\temp\file name\gen_dgp_sky.oct): bad object count; octree stale?

Rpict: 0 rays, 0.00% after 0.000 hours

Error reading line 511

Notice: low brightness scene. Dgp below 0.2! dgp might underestimate glare sources

Views: 46

Reply to This

Replies to This Discussion

Hi Maryam,

I've been away from the forum for a long time, and I apologize that no one answered your question. So my answer my no longer be useful to you...

Anyways, as long as that error doesn't appear at every timestep, then you are fine. Basically gen_dgp_profile uses some tricks to save time, and when the sun is below the horizon, this breaks. Luckily before sunrise, glare is not an issue in most cases. The low brightness scene warnings are also expected and can be safely ignored.

Best,

Alstan

Hi Alstan,

Thank you for your response. Actually, it is still useful for me!

Well, this error does not happen at every timestep, but at many of them. So according to what you said I guess my results must be OK.

I also have two more questions, and I would appreciate it if you could give me the answer:

The first one is about the annual glare output file (the .dgp file). It looks like the start time of the day for calculating glare in this file is 0.5, and I think that it corresponds to 12:30 am. Is that correct? I was wondering if there is also a way to shift this time to half an hour earlier so the start time would be 12:00 am?

My other question is about the annual illuminance calculations. I wanted to know if there is a way to generate an .ill file which gives the annual illuminance of only one point on the grid as opposed to all nodes of the grid? In other words is it possible to specify a point in the space and only calculate the annual illuminance for that specific point?

Thank you!

Maryam

> The first one is about the annual glare output file (the .dgp file). It looks like the start time of the day for calculating glare in this file is 0.5, and I think that it corresponds to 12:30 am. Is that correct? I was wondering if there is also a way to shift this time to half an hour earlier so the start time would be 12:00 am?

From the DIVA interface, there is not. It may be that if you edit the .wea file to use your timestep and then run Daysim's gen_dgp_profile again manually, it would work. I haven't tried it.

> My other question is about the annual illuminance calculations. I wanted to know if there is a way to generate an .ill file which gives the annual illuminance of only one point on the grid as opposed to all nodes of the grid? In other words is it possible to specify a point in the space and only calculate the annual illuminance for that specific point?

From DIVA-Grasshopper you can do this, but not from the DIVA Rhino Toolbar--see below. You need to expose the hidden "Grid from Sensors" input in the Daylighting Grid component by zooming in and clicking on the +.

Best,

Alstan

Thank you, Alstan.   

About your answer to my first question, do you mean that I can just change the timesteps manually? If so, this means that the irradiation data could remain the same and I should just change the timestep? The other thing is that the timestep in the .epw file is from 1 to 24 which is exactly what I need, but looks like Diva shifts this timestep in the generated .wea file. So I was wondering if there is any interpolation going on or I can say that for example the 0.5 timestep or the 12:30 timestep in the .wea corresponds to the 1:00 timestep in the .epw? 

Could you also explain a little bit more about how I can run the Daysim's gen_dgp_profile manually or if there is a link or file which I can learn more from there it would also be great!

Thank you so much for your help!

Maryam

I think the idea behind the shift in the timestep is that the hourly values in the EPW are simply averages, so calculating the solar position at the 30 minute mark isn't really a problem. There isn't any irradiation interpolation, just a shift in time. Its pretty safe to relate them 1-to-1 in that case.

> Could you also explain a little bit more about how I can run the Daysim's gen_dgp_profile manually or if there is a link or file which I can learn more from there it would also be great!

You would just browse to the C:\DIVA\Temp\Rhinofilename\ folder and run: C:\DIVA\DaysimBinaries\gen_dgp_profile.exe RhinoFilename.hea

Best,

Alstan

Thank you!!

Reply to Discussion

RSS

© 2017   Created by jeff niemasz.   Powered by

Badges  |  Report an Issue  |  Terms of Service