Radiance-general Digest, Vol 142, Issue 5

radiance-general
1

Hi group,
I have put the octree info and the picture for my rendering at http://phaugaard.blogspot.dk/2015/12/two-clipping-boxes.html Both clipping boxes are quite big and cut off one side and the top respectively. The only thing that is removed in the pictere is where the two clipping boxes intersect.
I am not familiar with the second option mentioned in the paper (used to "peek into" a space while preserving the geometry for the traced rays).
How does the second option work?
Once again thank you for your help.

Best regards
Per Haugaard

···

Den 21:01 torsdag den 3. december 2015 skrev "[email protected]" <[email protected]>:

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Today's Topics:

1. Using two clipping boxes in visualization of lighting
distribution (Per Haugaard)
2. Re: Using two clipping boxes in visualization of lighting
distribution (Guglielmetti, Robert)

----------------------------------------------------------------------

Message: 1
Date: Thu, 3 Dec 2015 14:34:32 +0000 (UTC)
From: Per Haugaard <[email protected]>
To: Radiance General Discussion <[email protected]>
Subject: [Radiance-general] Using two clipping boxes in visualization
of lighting distribution
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="utf-8"

Dear group,
I would like to use?two clipping boxes to "cut off" the top and side in my model to better visualize lighting distribution in my design.I have tried to include two clipping boxes in a clipping box octree:
oconv objects/BOX_top.rad objects/BOX_PL2-3.rad > octrees/Clipping_box.oct

I then use vwrays for illustration:
vwrays -fd -vf views/View_perspective.vf -x 1000 -y 1000 | rtrace -w -h -fd -opd octrees/Clipping_box.oct | rtrace -w -ab 1 -fdc `vwrays -d -vf views/View_perspective.vf -x 1000 -y 1000` octrees/office.oct > images/office.pic

My problem is that the only things that seem to be "cut off" is the intersecting part of the two boxes.
Is there a way to work with two clipping boxes to "cut off" the top and side in a model for better visualization of the lighting distribution?
Any input is much appreciated.

Best regards
Per Haugaard
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Message: 2
Date: Thu, 3 Dec 2015 14:49:18 +0000
From: "Guglielmetti, Robert" <[email protected]>
To: Per Haugaard <[email protected]>, Radiance general discussion
<[email protected]>
Subject: Re: [Radiance-general] Using two clipping boxes in
visualization of lighting distribution
Message-ID: <D285A323.200E6%[email protected]>
Content-Type: text/plain; charset="us-ascii"

That looks a lot like the technique John M. details here (http://radsite.lbl.gov/radiance/refer/Notes/jm_technote_02.pdf), but it seems like you're using the first technique (used to mask arbitrarily shaped, adjacent obstructions) and really want the second one (used to "peek into" a space while preserving the geometry for the traced rays. Could you post images of the result, as well as images of each octree you're using?

On 12/3/15, 7:34 AM, "Per Haugaard" <[email protected]<mailto:[email protected]>> wrote:

Dear group,

I would like to use two clipping boxes to "cut off" the top and side in my model to better visualize lighting distribution in my design.
I have tried to include two clipping boxes in a clipping box octree:

oconv objects/BOX_top.rad objects/BOX_PL2-3.rad > octrees/Clipping_box.oct

I then use vwrays for illustration:

vwrays -fd -vf views/View_perspective.vf -x 1000 -y 1000 | rtrace -w -h -fd -opd octrees/Clipping_box.oct | rtrace -w -ab 1 -fdc `vwrays -d -vf views/View_perspective.vf -x 1000 -y 1000` octrees/office.oct > images/office.pic

My problem is that the only things that seem to be "cut off" is the intersecting part of the two boxes.

Is there a way to work with two clipping boxes to "cut off" the top and side in a model for better visualization of the lighting distribution?

Any input is much appreciated.

Best regards

Per Haugaard

------------------------------

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End of Radiance-general Digest, Vol 142, Issue 5
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2

Hi Per,

You should try using a single box, setting it up so that the sides visible from your viewpoint are just inside the wall and ceiling of your space. That way, your rays will start in the appropriate place. Your rays are probably starting outside your space with your current box placements.

Cheers,
-Greg

···

From: Per Haugaard <[email protected]>
Subject: Re: [Radiance-general] Radiance-general Digest, Vol 142, Issue 5
Date: December 4, 2015 8:38:21 AM GMT+01:00

Hi group,

I have put the octree info and the picture for my rendering at Div: Two clipping boxes Both clipping boxes are quite big and cut off one side and the top respectively. The only thing that is removed in the pictere is where the two clipping boxes intersect.

I am not familiar with the second option mentioned in the paper (used to "peek into" a space while preserving the geometry for the traced rays).

How does the second option work?

Once again thank you for your help.

Best regards

Per Haugaard

3

Per

Basically your command traces rays from the view point (inside the box) to
the surface of the box. Where it intersects with the polygon it creates a
new ray to render everything on the other side of the box with rtrace.

When you use boxes as cut-away shapes for this technique you have to think
from "inside the box". I assume that your clipping boxes are very large,
both enclose the view point and the top and front of the building
respectively. In this case you would see from the inside viewpoint the
following surfaces (top to bottom in an imaginary image):

a) The inside of the box cutting away the front of the building (green
below)
b) The eave of the building (blue below)
c) The bottom of the box cutting away the top of the building (red below)

A bit of ascii art to confuse things:

···

+--------------------------------+
   > > top cutting box
+-------------------------+ |

> * viewpoint | |
> > >
> > >
> > >
> > >
> > >
> > b |
> b b |
> b | b |
+------------------b-----------b-+
                    b | b
                    b | b
                    b | b
                        >

+-------------------------+
  front cutting box

Your command will use the first ray intersection with the boxes to generate
the cutting edges: the green and red lines. Everything _behind_ these
cutting planes will be rendered. Therefore the only thing you cut out of
the image is the eave of the building.

To create the effect you want with your current command create a single box
that encloses the building core (the part you want to see). Think of it
more of a "gift wrap" than a "clipping box": It encloses the parts you
want, not the part you don't want.

Hth,
Thomas

4

Hi Greg and Thomas,
The obvious solution blinded me :)Thank you very much for your input.

Best regards
Per Haugaard

···

Den 14:16 fredag den 4. december 2015 skrev Greg Ward <[email protected]>:

Hi Per,
You should try using a single box, setting it up so that the sides visible from your viewpoint are just inside the wall and ceiling of your space. That way, your rays will start in the appropriate place. Your rays are probably starting outside your space with your current box placements.
Cheers,-Greg

From: Per Haugaard <[email protected]>Subject: Re: [Radiance-general] Radiance-general Digest, Vol 142, Issue 5Date: December 4, 2015 8:38:21 AM GMT+01:00

Hi group,
I have put the octree info and the picture for my rendering at http://phaugaard.blogspot.dk/2015/12/two-clipping-boxes.html Both clipping boxes are quite big and cut off one side and the top respectively. The only thing that is removed in the pictere is where the two clipping boxes intersect.
I am not familiar with the second option mentioned in the paper (used to "peek into" a space while preserving the geometry for the traced rays).
How does the second option work?
Once again thank you for your help.

Best regards
Per Haugaard