Skyligt Portals & Linear Workflow

[Jock]

Hi there,

 

I've worked with vray now for a few years and i am fairly confident with the software, though i dont use linear workflow. I've tried to in the past a number of times and never been happy with the result. What always seems to happen is that the textures are way too washed out and basically look nothing like the actual jpeg that i used.

 

I'm going to give it one more try and wondered if you could point me to what may be regarded as the best tutorial out there at the moment. I have found several on google but there seems to be subtle differences between them and hoped someone could recommend the best one.

 

The other issue is skylight portals. Up to now i light my interior scenes by using either a vray sun and physical camera or a direct light and std camera, in both cases i also put vray lights up at the openings. I recived some course documents from a course my company paid for a little while ago and just getting round to looking at it. Now in his examples he uses skylight portals rather than default vraylights but for the life of me i cant work them out. No matter what i do, the skylight portals do nothing, they produce no light and it makes no difference to the scene whether i delete them or not. Can anyone shed some light on how they are meant to be used.

[Jock]

Ok ive went ahead and tried out one tutorial while i wait for a response but ive ran into the same old problem i come across every time.

 

I load in a wood texture and the thing looks horrible and washed out, nothing like the actual texture.

 

Now according to the aversis, to correct this, you set the input gamme to 2.2 in the preference settings or you change it manually on the options for the map.

 

I already have the setting at 2.2, and it makes no difference and in fact the only thing that makes a difference is to do it manually. So does this mean i have to manually change the setting for every single map i use in my scenes? Seems like a bit of hassle I could do without but then i've no idea why the first setting does nothing, and certainly not what it says it should on the tutorial.

[david.s]

Hi Stewart

In Vray you set up Linear workflow differently. Leave the 3dsmax Gamma settings at their default of 1.0.

In the vray exposure settings set the gamma output to 2.2.

Make sure you use the vray frame buffer when rendering, as the max frame buffer does not display the 2.2 gamma setting by default.

Plus the vray frame buffer manages memory better. This should solve your gamma problems.

When you use the skyportals, are you using vray portals? The default skyportals in max are for mental ray.

[Jock]

Its vraylights i'm using but they have the tickbox so you can opt to turn them into skylight portals, and when you do so it greys out a lot of the options, though as mentioned whenever i do it, the light seems to become redi=undant as it seems to emit no light. On top of that one of the options thats greyed out is the intensity so its not like you can turn it up.

 

By vray exposure settings so you mean the gamma section in the colour mapping area? I have that set to 2.2 but i also have the max preferences set to 2.2 also. So i should change the max one back to 1?

[david.s]

That is correct regarding the colour mapping section. And yes, you should set the max gamma preferences back to 1.0 (incl bitmap gammas). But as mentioned, you will need to use the vray frame buffer and not the default max frame buffer.

The skyportals only focus illumination from the sunlight/daylight so are dependant on the sunlight/daylight settings you use. I would personally not use the portal setting but use a default vray rectangle light set to invisible. More control this way over light intensity and colour.

[Jock]

Yeah thats how i've always used the lights in the past, i'll just go back to using them how i used to.

 

I always use the vrayframe buffer so that shouldnt be a problem.

 

Thanks for the help.

[Tommy L]

The whole idea of LWF is to give you predictable results for image inputs such as jpgs and to correct the gamma curve so your mid-tones are correct. Non-LWF tends to polarise the values (midtones are under exposed).

The main concept under-pinning LWF is EXPOSURE. If you do not have a fairly comprehensive grasp of the way the image created is controlled by exposure values, LWF becomes a little hazy. The reason I think you do not understand Vray exposure is that the skylight portals in your scene are not effective. This is due to the exposure of your scene being incorrect. If the exposure is correct then the skylights portals just create windows to the Vray sky in your scene which generates light.

Here's a good place to get started:

Vray Phys Cam (default settings)

Vray sun/sky (default settings)

Max's gamma enabled input 2.2 / output 1 (effect bitmaps ticked)

Vray Color Mapping: Exponential, gamma set to 2.2, LW ticked

 

When test rendering to check exposure, turn off geometry. Just render the sky. When the sky is a nice pale blue, you are in the right ballpark. To adjust exposure, JUST CHANGE THE PHYSICAL CAMERA PARAMETERS. You are now using one example of LWF.