LB_IncidentRadiation - int mtx output

AbrahamYezioro · December 25, 2022, 7:16pm

Hi,
Checking the values of the int_mtx output of the IncidentRadiation component i get that for each sensor i get 290 values instead of the expected 145 (as Tragenza number of patches), like this:

.

The hint of the output says:

Each sub-list of the matrix (aka. branch of the Data Tree) represents one of the points used for analysis. The length of each sub-list matches the number of sky patches in the input sky matrix (145 for the default Tregenza sky and 577 for the high_density Reinhart sky).

This is not a critical question but will be nice to understand if i’m missing something or there is a bug in the output.

Thanks,
-A.

charlie.brooker · December 25, 2022, 8:37pm

Hi @AbrahamYezioro,

I’m fairly sure that the first 145 is for the sky and the second 145 is for the “ground” (a reflection of the sky with a modifier of 0.2)

I haven’t checked it though!

AbrahamYezioro · December 26, 2022, 3:59am

Hi @charlie.brooker ,
Thanks for answering. I don’t believe the second results relates to ground. At least, for some sample results, they all look the same. I’m wondering …
-A.

charlie.brooker · December 26, 2022, 12:32pm

Hey @AbrahamYezioro

My python isn’t the best, but from what I can tell all_vecs is a list 290 long made up of sky and ground vectors.

int_mtx is then generated from int_mtx_init taking all_vecs as an input, so I assume the length of int_mtx should be based on the sky and ground vectors.

Here’s a snippet from

github.com

ladybug-tools/ladybug-grasshopper/blob/master/ladybug_grasshopper/src/LB Incident Radiation.py

# Ladybug: A Plugin for Environmental Analysis (GPL)
# This file is part of Ladybug.
#
# Copyright (c) 2022, Ladybug Tools.
# You should have received a copy of the GNU Affero General Public License
# along with Ladybug; If not, see <http://www.gnu.org/licenses/>.
# 
# @license AGPL-3.0-or-later <https://spdx.org/licenses/AGPL-3.0-or-later>

"""
Calculate the incident radiation on geometry using a sky matrix from the "Cumulative
Sky Matrix" component.
_
Such studies of incident radiation can be used to apprxomiate the energy that can
be collected from photovoltaic or solar thermal systems. They are also useful
for evaluating the impact of a building's orientation on both energy use and the
size/cost of cooling systems. For studies of photovoltaic potential or building
energy use impact, a sky matrix from EPW radiation should be used. For studies
of cooling system size/cost, a sky matrix derived from the STAT file's clear sky
radiation should be used.

This file has been truncated. show original


for vec in lb_vecs)
    all_vecs = [from_vector3d(vec) for vec in lb_vecs + lb_grnd_vecs]

    # intersect the rays with the mesh
    normals = [from_vector3d(vec) for vec in study_mesh.face_normals]
    int_matrix_init, angles = intersect_mesh_rays(
        shade_mesh, points, all_vecs, normals, cpu_count=workers)

    # compute the results
    results = []
    int_matrix = []
    for int_vals, angles in zip(int_matrix_init, angles):
        pt_rel = [ival * math.cos(ang) for ival, ang in zip(int_vals, angles)]
        int_matrix.append(pt_rel)

From

AbrahamYezioro · December 26, 2022, 4:49pm

Hi @charlie.brooker ,
You are right. Checked the code and the sun vectors are duplicated and their direction reversed. I’m assuming here that some diffused radiation is included in the calculation (the one from the ground).

What confused me at the beginning is the hint explanation of int_max output. I believe it is not correct.

Thanks for looking into it. Good eye.

-A.

charlie.brooker · December 26, 2022, 6:31pm

Happy to help - agree that the description would benefit from some tweaking