Simulating LED lighting...

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Permalink Reply by Render Plus on October 8, 2011 at 6:16am

Here is the image you attached:

 

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Permalink Reply by Render Plus on October 8, 2011 at 6:33am

The use of the brightness control is not "cheating". IRender nXt automatically adjusts the brightness of the rendered image, much like a modern camera. The effect of this that if you light a scene with just one light, then whether it is 1 watt or 100 watts, the scene will appear the same. Wattage is only meaningful relative to other light sources.

If you want images which are darker, then you will have to use the brightness control to adjust them as desired.

We no longer allow a choice between Lumens and Watts, all lights are specified in Watts. I will go into the documentation and change it to refer only to Watts.

 

 

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Permalink Reply by Randy S on October 9, 2011 at 3:49am

OK, if that's the case, then it makes sense why all my pics look more or less the same. But it also makes little sense to specify a wattage which is really only a relative to other lights. Does this mean I can solve this issue by sticking a great big light (say 1000 watts) somewhere way out of the scope of view? And hence my 1 watt light might render the way I want it?

 

It is a shame that you guys are removing lumens as a way to specify brightness. Watts is pretty old school and extremely subject to prejidice as your documentation points out - 5 watts of LED light is vastly different then 5 watts of incandescent light.

Anywho, moving on, am I supposed to be able to set my ambient light to none and turn off my artificial lighting? when I turn both off I get a rendering error (don't recall what it says but can tell ya if it helps, something like "rendering stopped..."). It doesn't crash as I originally posted. But seems logical to me that both should be able to be turned off.

 

cheers,

-randall

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Permalink Reply by Render Plus on October 9, 2011 at 7:05am

We dropped Lumens as an input, because it was making it too difficult to maintain the software. Every dialog which dealt with lighting had to have a radio box for Watts/Lumens and it was causing us more problems than it was worth. I know this isn't a good answer. But for now, you should look up the Lumens af the item you are placing, and divide it by 17 to convert it to Watts. Even thought this is not the correct wattage for many light types.

If you turn off artificial lighting, then you would need to have light from the sun or sky. There has to be light from somewhere. Currently if you have no artificial lights, no sun and no sky, we put a light at the camera. This is supposed to get rid of the "Rendering stopped" error you see. If you get an eror again, save the model and send it to us and we will try to get rid of the error itself. However, the only way we can do so is to add a light somewhere.

This thread is a little "apologetic" on our part. But our goal is to make it easy for a SketchUp user to get a good rendering with as little effort as possible, while still allowing much better renderings for people who spend some time making settings and changing the scene a bit to get betere renderings. In a model like yours, for example, where the SketchUp view is inside of a closed room with no windows, we add some artificial lights if the user doesn't have any because otherwise people trying out the software the first time would just see a black screen every time they tried ot render an interior.

We sugget you leave ambient light on. And artificial lights should only be turned off when you are rendering an exterior scene and don't want to process any lights except sun and sky. The example for this would be a model which had lots of lights inside, which weren't going to effect an exterior rendering.

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Permalink Reply by Randy S on October 9, 2011 at 8:19am

Hi,

 

Thanx for the info - no need to apoligise. As an application developer myself I can understand and appreciate the shortcuts we take so we can maintain our sanity :)

 

My SKP file is 10mb. Do you want it broken out in two msgs (a zip broken into parts)? Regarding your comment about lights and the fact that you have to have something - well I do have some, 3 actually. So if I am reading what you are saying correctly, it shouldn't need to add a camera type light since I already provide lighting. In other words - are we looking at a bug?

 

As for the ease-of-use for basic sketchup/ntx users, your template setting should/would do the trick, assuming they control the artificial lighting and ambient lighting we are referring to.

 

So, getting back to a question you didn't answer - can I trick the system by adding a very strong light that is out of scope - say 100m from my actual model? Or is the rendering engine smart enough to know that light is irrelivant and hence goes back to what you initially said - where it is attempting to normalise lighting (eg a singe 1 watt bulb is a bright as a single 100w bulb)?

 

thanx,

-randall

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Permalink Reply by Render Plus on October 9, 2011 at 8:44am

If you want to send us a large file, use the Upload tab at the top of the page. Be sure to include a comment so we can remember what the file is for. Our emails can easily handle 20MB files.

 

There is not way to "trick" the renderer into making a dim scene. The AutoExpoure will pretty much take over. That said, however, if you turn on Lighting Channels, then when you load the Lighting Channels wizard during rendering, you can lock The exposure control, which turns off auto-exposure while you adjust the lighting channel. This "lock" setting is remembered when re-rendering from the Render Window, but is not currently saved or restored when re-rendering from SketchUp.

 

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Permalink Reply by Randy S on October 9, 2011 at 10:44am

Um, my Lighting Channels dialog doesn't have a "lock" option:

 

I'm running version KI30. The above dlg is from "Set Lighting Channel" button off the Lights tab of the Setup Options dlg.

 

-randall

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Permalink Reply by Roy Hirshkowitz on October 9, 2011 at 11:02am

Randall-- just to clarify Al's responses a bit.

"Watts" mean electrical power of an incandescent source.  As mentioned before, 17 watts per lumen is used as a conversion factor.  A 100 watt source yields a 1700 lumen source internally, approximately the power of a naked 100 watt incandescent bulb.

Our relative tone mapping works very well for most circumstances.  It does not simulate the effects of low light levels (mesopic and scotopic vision) which begin around 1 cd/m^2-- although I am experimenting with some new tone operators that do.  We consciously made the decision to not do this, at least not by default, since the data provided by the users is often not accurate (uncalibrated HDRi, for example.)

The only way to simulate low light levels with the current tone op is to use the Brightness control.  "Cheating" is not recommended.  Using the Lock switch is pretty much equivalent to using the Brightness prop, with a lot less control of the effect.

 

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Permalink Reply by Render Plus on October 9, 2011 at 11:04am

Make sure you are loading the one from the Render Dialog, and not the one from SketchUp.

Randy S said:

Um, my Lighting Channels dialog doesn't have a "lock" option:

 

I'm running version KI30. The above dlg is from "Set Lighting Channel" button off the Lights tab of the Setup Options dlg.

 

-randall

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Permalink Reply by Roy Hirshkowitz on October 9, 2011 at 11:06am

I should mention, in addition, that using the Path Tracer will probably give you more accurate results.  The ambient setting is a crude approximation of light that is not calculated by the Packet Tracer.  The Path Tracer ignores this setting.

Also, you can always measure the light levels (luminance) in your model by exporting the result to an nXt Image.  The data will be "correct" regardless of tone mapping.

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Permalink Reply by Render Plus on October 9, 2011 at 12:49pm

 

If you get an eror again, save the model and send it to us and we will try to get rid of the error itself. However, the only way we can do so is to add a light somewhere.

 

I was able to turn off both ambient light and artificial lights in your model, and did not get a crash (Simply a black rendering). However we do not recommend that you do this. I considered adding a check for it, but it is relatively difficult to check for the absence of all lighting sources - including sun, sky, HDRI skies, materials with self glow, lights, etc.

For now, I can't find anything to fix.

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Permalink Reply by Render Plus on October 9, 2011 at 12:53pm

Thank you for your additions to this thread Roy.

Is there any way do do what this client wanted from the start - to see how the room would "actually" look with lighting of a defined intensity - in terms of brightness. Of course, to do this correctly, you would also have to have precisely the proper color, material, and reflection properties on every surface in the room. And also, perhaps, know about the retinal properties of the observers eye, etc.

Roy Hirshkowitz said:

I should mention, in addition, that using the Path Tracer will probably give you more accurate results.  The ambient setting is a crude approximation of light that is not calculated by the Packet Tracer.  The Path Tracer ignores this setting.

Also, you can always measure the light levels (luminance) in your model by exporting the result to an nXt Image.  The data will be "correct" regardless of tone mapping.

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