trans, pmap and head-ache...

radiance-general
1

Hi,

I am completely stuck with my attempt to get some rather generic diffusor into my scene. I have a room which is lid by a light pipe, and to simulate this I use radiance 3.7 with the pmap extension. Everything works rather fine. Now I wanted to put some diffusing body under that light pipe, and I chosed the trans material to do so. The material definition I used should result in a simple diffuse transmitting box:

void trans genericDiffusor
0
7 1 1 1 0 0 .5 0

And I applied this to a box:

!genbox genericDiffusor Diffusor60x60 .3 .3 .01 | xform -t -.3 -.3 0

The opening is .6x.6m and centred at the origin, so that my diffusor covers only part of it. I want to see the effect of the material... And the effect is - somewhat unexpected. The "diffusor"-box appears black in my rendering. So is there anything completely wrong in my scene? Is there anything I got wrong about trans and surface normals, is it the combination of trans and pmap?

CU Lars.

2

I have used this before for a lightpipe diffuser using PMAP, the figures
were just best guess coupled to a visual trial and error process.

void trans transdisc
0
0
7 0.8 0.8 0.8 0 0.01 0.8 0.8

transdisc ring transdisc1
0
0
8
      0 0 3000
  0 0 -1
  0 266.5

I hope that is of some help.

Andrew

···

__________________________
Andrew Bissell
B.Eng(Hons) C.Eng MSLL MCIBSE MIET
Associate Lighting Designer
Cundall Light4
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-----Original Message-----
From: radiance-general-bounces@radiance-online.org
[mailto:radiance-general-bounces@radiance-online.org] On Behalf Of Lars
O. Grobe
Sent: 04 February 2009 10:51
To: Radiance general discussion
Subject: [Radiance-general] trans, pmap and head-ache...

Hi,

I am completely stuck with my attempt to get some rather generic
diffusor into my scene. I have a room which is lid by a light pipe, and
to simulate this I use radiance 3.7 with the pmap extension. Everything
works rather fine. Now I wanted to put some diffusing body under that
light pipe, and I chosed the trans material to do so. The material
definition I used should result in a simple diffuse transmitting box:

void trans genericDiffusor
0
0
7 1 1 1 0 0 .5 0

And I applied this to a box:

!genbox genericDiffusor Diffusor60x60 .3 .3 .01 | xform -t -.3 -.3 0

The opening is .6x.6m and centred at the origin, so that my diffusor
covers only part of it. I want to see the effect of the material... And
the effect is - somewhat unexpected. The "diffusor"-box appears black in

my rendering. So is there anything completely wrong in my scene? Is
there anything I got wrong about trans and surface normals, is it the
combination of trans and pmap?

CU Lars.

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3

Hi Andrew,

thank you for the example, but this also appears black in my scene.

Lars.

Bissell, Andrew wrote:

···

I have used this before for a lightpipe diffuser using PMAP, the figures
were just best guess coupled to a visual trial and error process.

void trans transdisc
0
7 0.8 0.8 0.8 0 0.01 0.8 0.8

4

Sorry... this was complete nonsense, I had the modifier overwritten by one of my xform-transformations, so it never was trans!

Please forger my posting, sorry for this, just found it.

Lars.