hi,

i see that DIVA can do the radiation map using a cumulative method.

so can DIVA do the simulation of an irradiation map for a specific time, a specified moment?

i am now trying to make an irrdiance map on the ground arround a building at a certain time and i also have another problem, if i build the building facade model in glass type, the building will not show in the final result since

−i Boolean switch to compute irradiance rather than radiance values. This only affects the final
result, substituting a Lambertian surface and multiplying the radiance by pi. Glass and other
transparent surfaces are ignored during this stage.

how can i solve this problem and make the building show up in the result?

Many thanks,

Jiajie

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Hi, Jiajie,

It seems the cumulative irradiance can be calculated for a a specific day but only for a period larger than or equal to 4 fours, or you'll get a falsecolor.exe error message, (see image below and the demo file). I'm not sure why this is the case...

As Alstan explained previously, transparent material will disappear when generating radiation map image due to the "-i" option for rpict. If you objective is just to visualize the radiation falling on building facades and ground, you might as well just apply opaque material to your glass facade as a work-around.

Ji

Attachments:

The falsecolor.exe error message:

Hi Ji Zhang,

thank you for your reply.

actually i am trying to simulate a reflected radiance concaved from the building facade onto the surrounding ground level for a certain time in a year. therefore the building material setting like reflectivity would be important, so i am not sure whether it is proper to change the material from glass type to plastic type as i know that the reflectivity for these two types are different.

Jiajie

Ji Zhang said:

Hi, Jiajie,

It seems the cumulative irradiance can be calculated for a a specific day but only for a period larger than or equal to 4 fours, or you'll get a falsecolor.exe error message, (see image below and the demo file). I'm not sure why this is the case...

As Alstan explained previously, transparent material will disappear when generating radiation map image due to the "-i" option for rpict. If you objective is just to visualize the radiation falling on building facades and ground, you might as well just apply opaque material to your glass facade as a work-around.

Ji

Hi Ji and Jiajie,

There are many issues afoot here, and I would like to try to address them as best I can.

> so can DIVA do the simulation of an irradiation map for a specific time, a specified moment?

From the GUI of DIVA, this cannot be achieved.

> how can i solve this problem and make the building show up in the result? [So a glass building does not disappear with the -i option]

A grid-based irradiation map can be used, and then you can see the results in the Rhino viewport where the building is still visible.

> It seems the cumulative irradiance can be calculated for a a specific day but only for a period larger than or equal to 4 fours, or you'll get a falsecolor.exe error message, (see image below and the demo file). I'm not sure why this is the case...

This is because the output is in kWh/m2 values (not Wh/m2), so unless you have a value of at least 1 kWh the program generating the scale fails. Basically, the irradiation maps only really make sense across a longer time scale because of this and because the direct solar position is not well represented over a short time scale in the visualized irradiation map calculations (see the cumulative sky paper citation at the bottom of this post).

> actually i am trying to simulate a reflected radiance concaved from the building facade onto the surrounding ground level for a certain time in a year. therefore the building material setting like reflectivity would be important, so i am not sure whether it is proper to change the material from glass type to plastic type as i know that the reflectivity for these two types are different.

This gets pretty complicated, because you want to follow the specular path of the direct solar positions. The cumulative sky method smooths the sun out into sky patches, and these concentrated specular reflections will not be present. The best solution will be to use several point-in-time visualizations and a mirror material rather than a glass material so that the specular path is always followed.

See the paper by Robinson and Stone for more details on the cumulative sky method,

Robinson, Darren, and Andrew Stone. "Irradiation modelling made simple: the cumulative sky approach and its applications." PLEA Conference. 2004.
I would also strongly recommend for you to check out this paper as it may be relevant to the results you desire,
Yang, Xiaoming, Lars Grobe, and Wittkopf Stephen. "Simulation of reflected daylight from building envelopes." Proceedings of 13th International Building Performance Simulation Association (IBPSA) Conference, Chambery, France. 2013.
Best,
Alstan

Hello

Is there a way that "transparent materials" do not disappear when generating radiation images?

Thank you so much



Jiajie Zhu said:

Hi Ji Zhang,

thank you for your reply.

actually i am trying to simulate a reflected radiance concaved from the building facade onto the surrounding ground level for a certain time in a year. therefore the building material setting like reflectivity would be important, so i am not sure whether it is proper to change the material from glass type to plastic type as i know that the reflectivity for these two types are different.

Jiajie

Ji Zhang said:

Hi, Jiajie,

It seems the cumulative irradiance can be calculated for a a specific day but only for a period larger than or equal to 4 fours, or you'll get a falsecolor.exe error message, (see image below and the demo file). I'm not sure why this is the case...

As Alstan explained previously, transparent material will disappear when generating radiation map image due to the "-i" option for rpict. If you objective is just to visualize the radiation falling on building facades and ground, you might as well just apply opaque material to your glass facade as a work-around.

Ji

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