Lightning questions

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stinger
Licensed Customer
Posts: 26
Joined: Mon Feb 27, 2012 1:30 pm

Hi all!!
I have been doing some lightning test and I have 2 questions:

1- I have read in older posts that currently the use of HDRI + Daylight is not possible, and HDRI to cast shadows neither. Will in the future this be posible?
2- When I use Daylight + Directlighting in Ambient Occlusion mode, I always get blue colored floor planes. Am I doing anything wrong? Any idea how to fix it? (see the image below)

Thank you!
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blue colored floor.jpg
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t_3
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Joined: Tue Jul 05, 2011 5:37 pm

stinger wrote:Hi all!!
I have been doing some lightning test and I have 2 questions:

1- I have read in older posts that currently the use of HDRI + Daylight is not possible, and HDRI to cast shadows neither. Will in the future this be posible?
2- When I use Daylight + Directlighting in Ambient Occlusion mode, I always get blue colored floor planes. Am I doing anything wrong? Any idea how to fix it? (see the image below)

Thank you!
you see blued shadows, because the sun environment also includes a blue sky ;) and thus shadows are tinted by ambient sky light. hdri definitely cast shadows; but as it is ambient light, coming from everywhere, it's shadows are pretty different from what a sun (which is a directional light source) will cast. you might combine hdri lighting with a sun-like (big & far away) emitter, but if this really helps, depends on what you want to achieve...
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cornel
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Can´t see any lightnings in your scene. I suggest adding them in post. :mrgreen:
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Refracty
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I think there is no way to work with the direct lighting kernel in ambient mode without having a blue shadow tint when using daylight even indoors.
You would have to switch the mode to DL diffuse or change the kernel to PT or PMC or use an HDR instead.
stinger
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Joined: Mon Feb 27, 2012 1:30 pm

Thank you guys for your answers!
The reason of this is my laptop's GPU (see how many cuda cores has the 9600m GT :oops: ) and the render times I get with Diffuse, PT and PMC, that I'm not going to tell you because I don't want to afraid you GTX users! :lol:
a.boeglin
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Joined: Wed Dec 15, 2010 7:36 pm

The reason why you get this blue tones is an incorrect white balance. I mean it could be correct for artistic reasons, but your materials that are supposed to appear white appear blue. The skylight temperature is around 6500K, which is pretty bluewish already. The direct sunlight though is way warmer, this explains why your direct light areas are quite white. By using a daylight white balance you would offset your blue and get it back to white. But it would also make your direct light areas warmer, therefore going more yellow/orange. Light temperatures is all about compromises and balance, but thats what makes it interesting. Another solution would be to use an hdri that you desaturate, and use a white area light as a sun light, but all your colors will look a bit off and flat ( a greyish day for example ), colors will miss saturation. The only problem for now, is that octane doesn't handle color balance yet. You can only access a few film presets which are pretty old school and have a lack of control. The best way for now is to render a 32 bits picture and fix it in post production by adjusting the levels for example.
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Refracty
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It would be useful to have a slider to tone down the blue level of the shadows for the direct lighting kernel.
a.boeglin
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Or simply a camera white balance setting, it would make more sense.
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Refracty
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But the white balance slider would also affect the direct warm sun color so I don't think this will be enough.
I think the problem is not simply the blue shadow. The problem is the blue shadow in an indoor scene (with no or little windows). Outdoors a blueish shadow is mostly wanted.
a.boeglin
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Well, if the problem is the blue shadow then you'd better drag a white color in the environnement instead of use the sky system. The white balance would react physically and therefore bring true results. There is no photo with this light setup that would bring white shadows and white direct light. Photography is about the compromise between cold tones and warm tones. If one wants to do abstract, using physical tools such as the sky system isn't the best go imo.
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