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Portals

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Hi,

looking at the portal info it gives the example of a physical sky and panoramic backgrounds.

Doesn't the portal also concentrate GI rays from internal objects such as a glass lightbulb so when using GI you should look at setting up your objects accordingly as a portal and you can in turn reduce the number of bounces as the portal will increase the quality of the render which means the greater the number of portals the greater the increase in quality and also the quicker the render?

(waiting to hear that there is a downside here somewhere)

thanks

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As far as I am aware, having a textured object with Portal enabled in the texture settings makes that object function as if it is emitting light directly similarly to background lighting. I believe it ONLY replicates lighting from the background and not from individual light objects or glow textures, but I have not confirmed this through testing or via the rendering team.

I will do both this upcoming week, they recently granted me access to a 24 core (TWENTY-freakin-FOUR!) machine and I have been abusing it thoroughly with rendering work.

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Thanks Jim

I am struggling with portals. The Indirect Lighting time in one case went from 51 secs to 5 min 51 secs when the material was changed to portal. The material in this case was glass on an orb around an area light.

I have not tried it with background but it should not behave the way it has with my tests.

It seems that adding a portal may well need 24 cores :)

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I don't have the time to test as thoroughly as I would like today, but combining your feedback with my initial tests I think that each object with Portals enabled in its texture is effectively being counted as a new source of light. This would increase quality, but also render times as well. I will check with the rendering team directly to see if they can recommend a workflow.

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Looks like the general recommendation is that Portal should be enabled for exterior glass like doors and windows, but not for interior objects like lightbulbs, fixtures, decorative items or glassware. It will improve the quality of ANY light that strikes it, but it is intended to be used on flat, thin glass surfaces facing the exterior, so effectively; window and door glass panes.

This option however is intended to increase realism, if the render time detriment is too significant or not needed for the artistic style you are trying to achieve, it should then be disabled.

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Thanks Jim

I looked up Portals on C4D and they are available for all materials (from what I can see) and they do reduce the render time by concentrating the light source.

Maybe the help manual should be more explicit because my render time was x 6 when I used it on internal glass (room with no windows) and there was certainly no quality improvement.

When you say thin is there a recommendation?

thanks

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Agreed. I will notify the tech pubs team.

"Thin" generally meaning that the glass wouldnt be thick enough to notice any significant absorption, I would say half an inch or less. Basically any standard window glass and not something unusual like custom curved glass or glass distorted in some other way, such as antiqued or rippled.

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Thinking about this the issue I see is that making your texture a portal and then using the same texture on internal materials. Inexperienced users would quite easily make the 'window glass' a portal and then use the same glass for several other objects?

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It would be an easy thing to overlook, but unfortunately its one of those so-specific things that there isn't much other choice than to cover it specifically in the Help entry regarding Portals. However I will suggest that options like this where the user may incur severe rendering time increases come with a permanently-dismissible warning explaining the cause.

(After recently doing work on the Rendering seminar from the Summit, it became immensely clear that I could easily talk about rendering in Vectorworks for 16 straight hours.)

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After recently doing work on the Rendering seminar from the Summit, it became immensely clear that I could easily talk about rendering in Vectorworks for 16 straight hours

Sadly I would be happy to listen :(

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Haha well you're going to get a solid two hours or so regardless! I may also integrate more of that into the next revisions of the Renderworks guide as well, whenever that comes up on my list.

Glad you enjoy my ramblings!

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Does anyone have any side-by-side examples of a time when the Portal setting was employed to improve the rendering? Just starting to play around with it, and there isn't much explanation in the Help files. Would love to understand it better.

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I'm not sure it will improve the time of the rendering so much as it will improve the rendering quality. Portals direct the GI algorithm to shoot more samples through them (as in the case of windows) so that you aren't wasting samples on areas that don't matter (the solid exteriors of the wall).  But I would think that the same amount of samples are being shot regardless. 

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