I would like to model trees outside buildings in my Radiance runs. I would like to model them transmitting about 20% of light and make the canopy 40% reflective.

* Can I do this by using a translucent material?

* If so, can you point me to a tutorial?

* Will this be compatible with the 3-phase method of daylighting analysis? (I.e., daylight coefficient method with the 3-phase method and a BSDF for the window).

Thanks for any help,

Tim

Hi Tim,

You can do it with trans, and it will work with the 3-phase method. Here are some useful posts:

[Radiance-general] trans mat

[Radiance-general] trans dashboard widget

Hope this is enough to get you started!

-Greg

## ···

From: Tim Perry <[email protected]>

Date: December 5, 2011 5:34:27 PM PST

I would like to model trees outside buildings in my Radiance runs. I would like to model them transmitting about 20% of light and make the canopy 40% reflective.

Can I do this by using a translucent material?

If so, can you point me to a tutorial?

Will this be compatible with the 3-phase method of daylighting analysis? (I.e., daylight coefficient method with the 3-phase method and a BSDF for the window).

Thanks for any help,

Tim

Dear Greg,

Does the surface roughness matter if the reflected specularity (Rs) is zero?

Thanks,

Tim

PS: Is there a Radiance beginners list? I surely belong there.

PPS: Here is my full definition. I'm using pages 325-326 in Rendering With Radiance as my guide.

Diffuse reflectance (Rd = 40%)

Red: 25%Cr

Green: 70%Cg

Blue: 25%Cb

Reflected Specularity (Rs): 0

Surface Roughness (Sr): 0.0

Diffuse Transmissivity (Td) = 19%

Transmitted Specularity (Ts) = 1%

** Final Material **

void trans TransTreeMat

0

0

7 0.375 1.05 0.375 0 0 0.33333 0.05

## ···

________________________________

From: Greg Ward <[email protected]>

To: Tim Perry <[email protected]>; Radiance general discussion <[email protected]>

Sent: Monday, December 5, 2011 5:48 PM

Subject: Re: [Radiance-general] Trees

Hi Tim,

You can do it with trans, and it will work with the 3-phase method. Here are some useful posts:

[Radiance-general] trans mat

[Radiance-general] trans dashboard widget

Hope this is enough to get you started!

-Greg

From: Tim Perry <[email protected]>

Date: December 5, 2011 5:34:27 PM PST

I would like to model trees outside buildings in my Radiance runs. I would like to model them transmitting about 20% of light and make the canopy 40% reflective.

* Can I do this by using a translucent material?

* If so, can you point me to a tutorial?

* Will this be compatible with the 3-phase method of daylighting analysis? (I.e., daylight coefficient method with the 3-phase method and a BSDF for the window).

Thanks for any help,

Tim

Hi Tim,

The roughness will influence any transmitted specular component as well.

Your calculation of trans parameters is off because your Rd is not 40% using RGB of 25%, 70% and 25%. If you want 40% reflectance, you need to adjust the RGB to (0.181,0.508,0.181). I computed these based on the Y function in "ray/src/cal/cal/xyz_rgb.cal".

With these changes, I get:

void trans TransTreeMat

0

0

7 0.272 0.761 0.272 0 0 0.33333 0.05

Does this make sense?

-Greg

## ···

From: Tim Perry <[email protected]>

Date: December 6, 2011 12:31:15 PM PST

Dear Greg,

Does the surface roughness matter if the reflected specularity (Rs) is zero?

Thanks,

Tim

PS: Is there a Radiance beginners list? I surely belong there.

PPS: Here is my full definition. I'm using pages 325-326 in Rendering With Radiance as my guide.

Diffuse reflectance (Rd = 40%)

Red: 25%Cr

Green: 70%Cg

Blue: 25%Cb

Reflected Specularity (Rs): 0

Surface Roughness (Sr): 0.0

Diffuse Transmissivity (Td) = 19%

Transmitted Specularity (Ts) = 1%

** Final Material **

void trans TransTreeMat

0

0

7 0.375 1.05 0.375 0 0 0.33333 0.05

Greg,

My mistake was taking the simple average, rather than the photopic average, right? I looked right past that adjective....

Thanks for catching my error,

Tim

## ···

----- Original Message -----

From: Gregory J. Ward <[email protected]>

To: Tim Perry <[email protected]>

Cc: "[email protected]" <[email protected]>

Sent: Tuesday, December 6, 2011 5:32 PM

Subject: Re: [Radiance-general] Trees

Hi Tim,

The roughness will influence any transmitted specular component as well.

Your calculation of trans parameters is off because your Rd is not 40% using RGB of 25%, 70% and 25%. If you want 40% reflectance, you need to adjust the RGB to (0.181,0.508,0.181). I computed these based on the Y function in "ray/src/cal/cal/xyz_rgb.cal".

With these changes, I get:

void trans TransTreeMat

0

0

7 0.272 0.761 0.272 0 0 0.33333 0.05

Does this make sense?

-Greg

From: Tim Perry <[email protected]>

Date: December 6, 2011 12:31:15 PM PST

Dear Greg,

Does the surface roughness matter if the reflected specularity (Rs) is zero?

Thanks,

Tim

PS: Is there a Radiance beginners list? I surely belong there.

PPS: Here is my full definition. I'm using pages 325-326 in Rendering With Radiance as my guide.

Diffuse reflectance (Rd = 40%)

Red: 25%Cr

Green: 70%Cg

Blue: 25%Cb

Reflected Specularity (Rs): 0

Surface Roughness (Sr): 0.0

Diffuse Transmissivity (Td) = 19%

Transmitted Specularity (Ts) = 1%

** Final Material **

void trans TransTreeMat

0

0

7 0.375 1.05 0.375 0 0 0.33333 0.05