rtrace vs. rview, mirror vs. metal or BRTD

radiance-general
1

Hi, I wish you a happy New Year! Starting with a radiance-issue...lol

In my Radiance scene I replaced my "mirror" materials with "metal" (or even "BRTD"), and although rview obviously "sees" the new material, rtrace doesn't "see" anything (irradiance measurement -I). I tried to set the rview and rtrace options as similar as possible (for instance -dr, -aa, -ar, -ad, -as) but so far without success. Is there a way of getting "metal" or "BRTD" work in a similar way to "mirror" with rtrace?

My 3 scenes (field of mirrors reflecting the sun towards a central receiver, 3 times: with "mirror", "metal", and "BRTD") are available if needed (too big in a general radiance mail); and here are some of my command lines (first "cd HelFiSim"):

···

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Mirror:

rview -vp 0 0 100.5 -vd 0 3 -1.3 -u+ -dt .03 -dc .75 -ds .2 -dr 2 -dp 512 -st .15 -ab 2 -aa .15 -ar 256 -ad 1024 -as 512 -lr -10 -lw 2e-3 PS10Hel/D81H12F1x1E0Mirror/field.oct

rtrace -ab 2 -I+ -ov -h PS10Hel/D81H12F1x1E0Mirror/field.oct < PS10Hel/D81H12F1x1E0Mirror/cavcylmeshgrid1.dat | rcalc -e '$1=(0.265*$1+0.670*$2+0.065*$3);' >> PS10Hel/D81H12F1x1E0Mirror/heatfluxD81H12F1x1E0Mirrortow1.dat
(Warning: change the name of "heatfluxD81H12F1x1E0Mirrortow1.dat" otherwise it will append the results to the already existing file)

( oconv PS10Hel/D81H12F1x1E0Mirror/sun.rad PS10Hel/D81H12F1x1E0Mirror/aperture.rad PS10Hel/D81H12F1x1E0Mirror/field.rad > PS10Hel/D81H12F1x1E0Mirror/field.oct )
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Metal:

rview -vp 0 0 100.5 -vd 0 3 -1.3 -u+ -dt .03 -dc .75 -ds .2 -dr 2 -dp 512 -st .15 -ab 2 -aa .15 -ar 256 -ad 1024 -as 512 -lr -10 -lw 2e-3 PS10Hel/D81H12F1x1E0Metal/field.oct

rtrace -ab 2 -I+ -ov -h PS10Hel/D81H12F1x1E0Metal/field.oct < PS10Hel/D81H12F1x1E0Metal/cavcylmeshgrid1.dat | rcalc -e '$1=(0.265*$1+0.670*$2+0.065*$3);' >> PS10Hel/D81H12F1x1E0Metal/heatfluxD81H12F1x1E0Metaltow1.dat
(Warning: change the name of "heatfluxD81H12F1x1E0Mirrortow1.dat" otherwise it will append the results to the already existing file)

( oconv PS10Hel/D81H12F1x1E0Metal/sun.rad PS10Hel/D81H12F1x1E0Metal/aperture.rad PS10Hel/D81H12F1x1E0Metal/field.rad > PS10Hel/D81H12F1x1E0Metal/field.oct )
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BRTD:

rview -vp 0 0 100.5 -vd 0 3 -1.3 -u+ -dt .03 -dc .75 -ds .2 -dr 2 -dp 512 -st .15 -ab 2 -aa .15 -ar 256 -ad 1024 -as 512 -lr -10 -lw 2e-3 PS10Hel/D81H12F1x1E0BRTD/field.oct

rtrace -ab 2 -I+ -ov -h PS10Hel/D81H12F1x1E0BRTD/field.oct < PS10Hel/D81H12F1x1E0BRTD/cavcylmeshgrid1.dat | rcalc -e '$1=(0.265*$1+0.670*$2+0.065*$3);' >> PS10Hel/D81H12F1x1E0BRTD/heatfluxD81H12F1x1E0BRTDtow1.dat
(Warning: change the name of "heatfluxD81H12F1x1E0Mirrortow1.dat" otherwise it will append the results to the already existing file)

( oconv PS10Hel/D81H12F1x1E0BRTD/sun.rad PS10Hel/D81H12F1x1E0BRTD/aperture.rad PS10Hel/D81H12F1x1E0BRTD/field.rad > PS10Hel/D81H12F1x1E0BRTD/field.oct )
------------------------------------------

Many thanks for your help!

Best,

Germain

----------------------------------------------------------------------
Germain Augsburger

At EPFL:
Room ME A2 391
Tel.: (+41) 21 693 59 68

Physical addresses:
ch. du Carroz 5 | 17, ch. de la Ruaz
Chez Stéphane Carrupt | Chez Stéphane & Catherine Augsburger
CH-1020 Renens (Switzerland) | FR-74140 Yvoire (France) (Tel.: (+41) 21 634 61 60 | Tel.: (+33) 4 50 72 85 29
- matter of urgency) |

Internet adresses:
MSN Messenger: [email protected]
Skype pseudonym: germainaugsburger
----------------------------------------------------------------------

2

Hi Germain,

The "mirror" type allows Radiance to find a small source like the sun by creating a "virtual source" behind the mirrored surface. The same is not true for the other types you tried, which is why your -I calculation came up empty.

With many mirrors in your scene, especially if they are not perfect mirrors, you will probably need to use rtcontrib to send rays from the direction of the sun and track them onto your object, estimating the flux density by ray counting. I think I mentioned this possibility to you at the workshop. Unfortunately, I don't have a simple example to offer you showing how it's done, and it's not what I would characterize as straightforward.

Essentially, you need to create a ray flux generator corresponding to the solar beam radiation striking your mirror array. You send these rays into rtcontrib, specifying one or more materials to record ray strikes on the heliostat receiver. These get counted up and the ratio of ray strikes to rays sent tells you the transfer efficiency.

Does this make sense?

-Greg

···

From: Germain Augsburger <[email protected]>
Date: January 5, 2009 10:33:30 AM PST

Hi, I wish you a happy New Year! Starting with a radiance-issue...lol

In my Radiance scene I replaced my "mirror" materials with "metal" (or even "BRTD"), and although rview obviously "sees" the new material, rtrace doesn't "see" anything (irradiance measurement -I). I tried to set the rview and rtrace options as similar as possible (for instance -dr, -aa, -ar, -ad, -as) but so far without success. Is there a way of getting "metal" or "BRTD" work in a similar way to "mirror" with rtrace?

My 3 scenes (field of mirrors reflecting the sun towards a central receiver, 3 times: with "mirror", "metal", and "BRTD") are available if needed (too big in a general radiance mail); and here are some of my command lines (first "cd HelFiSim"):