How to calculate the view factor when threr is an obstruction

Hello, I am a student of architecture studying about architectural environmental engineering.

I am running Radiance 5.2 from a Windows computer using Linux, And I am currently trying to calculate the view factor by ray tracing.

First, I was able to calculate the view factor between faces using the following command

  1. oconv 1019_question_front.rad > geo.oct
  2. rcontrib -h -w -I -ad 10000 -lw 0.0001 -m material_wood geo.oct <1019_question_pts.txt

Next, when there is an objection (ex. a box) between 2 faces for which I want to calculate the view factor, I tried the following command, but an error occurred and the view factor could not be calculated.

Pattern A

  1. oconv 1019_question_front.rad > geo1.oct
  2. oconv 1019_question_objection.rad > geo2.oct
  3. rcontrib -h -w -I -ad 10000 -lw 0.0001 -m material_wood geo1.oct -m material_wood geo2.oct <1019_question_pts.txt

Pattern B

  1. oconv 1019_question_front.rad > geo1.oct
  2. oconv 1019_question_objection.rad > geo2.oct
  3. rcontrib -h -w -I -ad 10000 -lw 0.0001 -m material_wood geo1.oct geo2.oct <1019_question_pts.txt

I would like to know how to calculate the view factor when there is an objection between faces.

Thank you in advance.

I think you might be getting that error because you are using two octrees as inputs to rcontrib. Try this instead.

oconv 1019_question_front.rad 1019_question_objection.rad > geocombined.oct
rcontrib -h -w -I -ad 10000 -lw 0.0001 -m material_wood geocombined.oct <1019_question_pts.txt

Regards,
Sarith

1 Like

Thanks for your reply.

I have tried that commands. As a result, the Radiance worked well.
However, this gives me the view factor due to rays hitting both the surface and the cube.
What I want to achieve is to get the view factor excluding the rays hitting the cube.
In other words, the cube is an obstacle, an object that should be excluded from the view factor.
(When doing Raytrace, I want to exclude rays that pass through the cube then hit the surface)

What would be the command in this case?

It worked, but I am thinking that the value will be smaller than when there is only the surface.

Best Regards,
bonobon00

The cube should have a different material than the surface that you are calculating the view factor for. The -m material_wood flag in your command specifies that the view factor should be calculated for all the surfaces that share this material.

Regards,
Sarith

2 Likes

Thanks for the reply.

I was able to calculate the view factor between the faces excluding the box when I used different m- information for the face and the box!

Thank you for your instruction,
bonobon00