Hi list, hi Greg,

I have a question concerning the BSDF "up-vector".

For e.g. a facade-mounted fenestration system the definition of the vector

is clear.

But what, if I have a BSDF defining the material properties and use this

BSDF to

simulate the BSDF of a daylighting system (i.e. curved specular lamellae)?

The comment in m_bsdf.c says that the "up-vector" together with the surface

normal

defines the local coordinate system. How exactly is that done??

Unfortunately I did

not have time yet to dig deeper into the BSDF-code to find that out...

Cheers,

David

The code is pretty simple. So long as the "up vector" is not parallel to the surface normal, it is used to orient the 0-degree azimuth position by projecting it into the plane of the surface normal at the ray intersection point. Make sense?

-Greg

## ยทยทยท

From: David Geisler-Moroder <[email protected]>

Date: May 15, 2012 12:20:15 AM PDT

Hi list, hi Greg,

I have a question concerning the BSDF "up-vector".

For e.g. a facade-mounted fenestration system the definition of the vector is clear.

But what, if I have a BSDF defining the material properties and use this BSDF to

simulate the BSDF of a daylighting system (i.e. curved specular lamellae)?

The comment in m_bsdf.c says that the "up-vector" together with the surface normal

defines the local coordinate system. How exactly is that done?? Unfortunately I did

not have time yet to dig deeper into the BSDF-code to find that out...

Cheers,

David

1 Like

Ok, perfect -- this is exactly what I hoped it to be!

Thanks for the fast response,

cheers,

David

## ยทยทยท

2012/5/15 Gregory J. Ward <[email protected]>

The code is pretty simple. So long as the "up vector" is not parallel to

the surface normal, it is used to orient the 0-degree azimuth position by

projecting it into the plane of the surface normal at the ray intersection

point. Make sense?

-Greg

> From: David Geisler-Moroder <[email protected]>

> Date: May 15, 2012 12:20:15 AM PDT

>

> Hi list, hi Greg,

>

> I have a question concerning the BSDF "up-vector".

> For e.g. a facade-mounted fenestration system the definition of the

vector is clear.

> But what, if I have a BSDF defining the material properties and use this

BSDF to

> simulate the BSDF of a daylighting system (i.e. curved specular

lamellae)?

>

> The comment in m_bsdf.c says that the "up-vector" together with the

surface normal

> defines the local coordinate system. How exactly is that done??

Unfortunately I did

> not have time yet to dig deeper into the BSDF-code to find that out...

>

> Cheers,

> David