Section Cuts

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giannis
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Fri Jul 17, 2015 2:50 pm

Dear friends,

a feature asked many times, with primary usage for architectural visualization, is the section cut support. The idea of section cuts is that, without breaking your current model, you can define certain shapes (usually planes) cutting away the geometry and giving the possibility to take a "look inside".

In Thea Render context, section cuts are defined as planes that cut part of the scene. The cuts are defined per camera and they are making the geometry outside them, invisible to the camera. This means that the geometry is not actually removed but it is still there, contributing to the reflections, secondary bounces, etc.

Here is a render by Juan Felipe (jc4d) utilizing a vertical section cut. This gives us the possibility to see inside the house. The lighting within the house is the same as if the section cut was missing; so it is possible to evaluate the lighting conditions in that space, which is not possible otherwise (for example, by actually removing the geometry before handling the scene to the renderer).
SectionCut_JuanFelipe.jpg
Note that currently, section cuts can only be setup through the integrations (Thea for Cinema4D/Rhino/SketchUp, 3dsMax pending) and not through the Studio (Studio renders them without issue but there is no interface to add or change them).

Best wishes
Science may limit knowledge but should never limit imagination - Bertrand Russell
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gwengosch
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Fri Jul 17, 2015 4:20 pm

I love it!
Gwenael Gosch
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niki
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Fri Jul 17, 2015 5:02 pm

it keeps getting better and better.. glad i purchased thea render.
Thanks again for this new tech Giannis
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rogerpenna
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Fri Jul 17, 2015 9:10 pm

I guess this was simple to implement, considering there was already a camera section cut (section cut perpendicular to camera view)? Just needed to do the same but as if seen from another camera :)

Maybe this could be a workaround the Studio implementation? Use a camera to regulate where you want the section camera, then click on that camera and "transform it" on a section cut camera... other cameras will now view the model with the section camera created by the section cut camera...?
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Javadevil
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Sat Jul 18, 2015 2:44 am

Looks good,
Looks like some of the cuts are filled with black but the main wall is hollow.
Is it possible to have all cuts filled ?
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Frederik
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Sat Jul 18, 2015 5:50 am

rogerpenna wrote:I guess this was simple to implement...
Far from...
If it had been a simple task then you would have seen it long time ago... ;)
In addition you need to remember that such features needs to be coded with all the render engines available in Thea Render...

Perhaps it's worth mentioning that although Section Cuts work great, there's no setup mechanism for section cuts nor any indication of the sections cuts in Thea Studio...
The section cuts is primary thought for with the plugins (i.e. Thea4SU, Thea4Rhino etc...)
Cheers
Kim Frederik

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Frederik
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Sat Jul 18, 2015 5:59 am

Javadevil wrote:Looks like some of the cuts are filled with black but the main wall is hollow.
Is it possible to have all cuts filled ?
Section cuts are not filled...
Unless you make a fill yourself in your modeling application where the section cut is placed, they will make the cut into a hollow space, however, they will appear black as there's no light inside...
If you make a hole in the wall or insert light in the walls, light will travel through and they will be visible...

Not to users of SketchUp:
Please note that although section cuts will appear exactly where you've placed them in SU, they won't make a "real" cut like section cuts do it in SU...

I will post a few images to explain better in a moment...
Cheers
Kim Frederik

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giannis
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Sat Jul 18, 2015 7:20 am

Frederik wrote:
rogerpenna wrote:I guess this was simple to implement...
Far from...
If it had been a simple task then you would have seen it long time ago... ;)
In addition you need to remember that such features needs to be coded with all the render engines available in Thea Render...

Perhaps it's worth mentioning that although Section Cuts work great, there's no setup mechanism for section cuts nor any indication of the sections cuts in Thea Studio...
The section cuts is primary thought for with the plugins (i.e. Thea4SU, Thea4Rhino etc...)
It was somewhere in the middle. Not as easy as z-clipping, which is very clearly defined. It proved though indeed easier to code for the engines than I expected. :)
Science may limit knowledge but should never limit imagination - Bertrand Russell
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giannis
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Sat Jul 18, 2015 7:25 am

Frederik wrote: I will post a few images to explain better in a moment...
I think it would be good to have some explanatory images.

There is a difference between how SketchUp renders section cuts compared to Thea. SketchUp actually removes the geometry beyond the cut plane and does not take that into account during rendering at all. Thea on the other hand, still carries that geometry beyond the cut plane but makes it invisible to the camera.

The practical difference of the above, is that for a house that is cut in SketchUp you will see the sun & sky now lighting the inside whereas in Thea, the sun & sky will not pass the wall but will be coming through the same entries (windows) that was coming before.

To be honest, the Thea implementation is easier to do for a ray tracer but it is also the one that you cannot achieve otherwise (the SketchUp variation can be generically achieved by actually removing the geometry beyond the cut plane before passing that to the renderer -> this is for example, how it is done in ArchiCAD).

Best wishes
Science may limit knowledge but should never limit imagination - Bertrand Russell
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Rombout
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Sat Jul 18, 2015 8:16 am

Killer features!
Last edited by Rombout on Sat Jul 18, 2015 9:15 pm, edited 1 time in total.
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