[Radiance-general] two sided surface

[Greg Ward]

Hi Nick,

Thomas is probably right about rendering times, but for completeness,  
here is the other method for making the front side diffuse and the  
back side chrome:

void plastic diffuse_gray
0
0
5 0.5 0.5 0.5 0 0

void metal chrome
0
0
5 0.93 0.93 0.93 1 0

void mixfunc blind_mat
4 diffuse_gray chrome if(Rdot,1,0) .
0
0

# ... etc.

Hope this helps.
-Greg

> From: Thomas Bleicher <tbleicher at googlemail.com>
> Date: April 22, 2010 6:21:49 AM JST
>
> Nick.
>
> In Radiance geometry and material definition go hand in hand. You
> could try evaluating the surface normal to chose the correct material
> in a custom expression but that would increase your render time
> significantly.
>
> As an alternative you could use the same geometry with a small
> z-offset. If you have all the blinds in a separate *.rad file use the
> -m option of xform to give them a new modifier:
>
> !xform -m grey_mat blinds.rad
> !xform -m chrome -t 0 0 -0.001 blinds.rad
>
> That will offset the blinds by 0.001 units down and use the material
> 'chrome' for this 'side'.
>
> Regards,
> Thomas
>
> On Wed, Apr 21, 2010 at 5:16 PM, Nick Hubof <nhubof at gmail.com> wrote:
>> I am modeling a large amount of physical blinds in an office scene.  
>> I am
>> replicating a Warema blind that has an opaque surface (grey) on the  
>> convex
>> side and a chrome surface (93% reflective) on the concave side. To  
>> minimize
>> the amount of geometry I was hoping there is an easy way to apply two
>> materials to the curved plane instead of adding a thickness and  
>> more than
>> double the geometry.
>>
>> I have searched the knowledge database and could not find what I  
>> was looking
>> for. I hope there is an easy way to do this.
>>
>> For instance the surface normal is the chrome material and the  
>> opposite side
>> is the opaque material.
>>
>> Thank you in advance.
>>
>> Nick