physical sky Question

[Ryan_Chiong]

how can i acheive a purple night sky? i tweaked everything but no go.

/Ryan

[voltron7]

Did you try the physical camera white point? LeLe has a thread somewhere that mentions this, I think....

[Ryan_Chiong]

i was trying to search for that thread but i couldnt find.

[jacksc02]

ryan, you will be better off using an hdri or just a coloured environment map

[Ryan_Chiong]

hi jacks. that was my last option. but i solved the problem. A tint of green to the white balance does the trick.

thanks voltron for the tip.



/Ryan

[Ryan_Chiong]

too bad. its affecting the light colors aswell.

[jacksc02]

go for the environment light or HDRI option

[voltron7]

sorry to hear it. Is doing the sky in post an option for this one?

[Ryan_Chiong]

actually i need the purple sky mainly not for the background but for the ambient lighting. im using physical cam but i need to increase intesity of HDRI beyond normal, say 100 from the normal 1 intensity.

[studioDIM]

Ryan, in the tutorial thread on the physcam there's a simple math method to discover what the correct multiplier for an hdri is dependent on exposure of the physcam.
It is correct that the hdri multiplier should be so high, as the average hdri intensity for the brightest spots rarely exceeds a value of 10 float, whereas a sun at midday is about 385 float.
You could , in any case, use a standard camera, and render a 360 hdri of the sun and sky alone, do a white balance of it in post, and then assign it to a dome (assigning it to the bg would likely miss the sun hotspot), that can then be calculated with the irmap to speed up things and get more than one bounce from it.

Hope it helps.

Lele

[Ryan_Chiong]

Hi Lele,

Its not usual for me to use HDRI for illuminating a big scene. but where do i actually put the HDRI map? diffuse, vraylight material, self illumination??

/Ryan

[studioDIM]

Standard HDRI workflow allows you to put it in a number of places: generally most hdris don't have the huge range the format allows, so a background slot, or any of the override slots in the vray environment, under the render panel will do.
However, a sun+sky rendered hdri will have a huge range and contrast ratio.
Hence, in the case, you will need importance sampling (a technique that analyses the HDRI to find bright spots and passes these informations on to the GI engine), and that can only be done through a dome light, at present.
So, in the case, you'll have to put the hdri into the texture slot of the dome light.

Here's why:
http://www.chaosgroup.com/forum/phpB...=153359#153359

Hope i clarified it for you a bit.

Lele

[Ryan_Chiong]

Thanks for patiently explaining this.
very much appreciated

/Ryan

[Ryan_Chiong]

Where is the dome cam? and whats the .255 method?

[studioDIM]

dome LIGHT
Create a vray light, set it to dome, at the bottom there's a map slot: put the hdri in there.
With a standard camera you can turn on the sperical camera to render 360 panormas in the camer section of the vray render panel.

For anything concerning the .255 method (and most importantly the ideas behind it, don't stop by the label )watch the video tutorial (and read the thread) in the tips and tricks section...

Lele