What's wrong with my LuxRender?

Leo Chen

I use Luxus to bridge to LuxRender.
The image come out has something wrong!

1. The Skin Tone is very granny.

2. Some texture's color is very wrong.

SimonJM

It might just need a 'bit more' time to de-speckle and clean up the image. How glossy are the surfaces in front of the figure? What sort (type and numbers) of lighting are you using?

mjc1016

Also, if the textures were 'autoconverted' they may not actually set up optimally.

SpottedKitty

mjc1016 said:

Also, if the textures were 'autoconverted' they may not actually set up optimally.

Yes, this is one of the major things to watch for in using LuxRender, mainly the Specular value does not play nice with the normal range LuxRender is expecting; normal values are very, very low, and the conversion process does not change the parameter value. For auto-converting, anything over a grayscale value of 50 or so will be literally unnaturally shiny, and many materials turn out to have a Specular of full white, 255. This works in 3Delight, but in LuxRender it causes textures to appear washed-out and faded.

There's a similar problem with Bump and Displacement. D|S measures in centimetres, LuxRender uses metres... again, using the same numbers in the parameters. Also, Displacement is an extra parameter in LuxRender, it doesn't get auto-converted, you must set this up manually for each material that uses it.

Jaderail

As Noted before The Speckles WILL clear up the LONGER the render runs. In LUX it is Total number of passes that clears up the images not TIME.

EDIT: And EACH render will need a DIFFERENT total of Passes before HIGH quality is reached. There is no default in LUX as it depends on how each Scene is set up.

Leo Chen

Thank you all.

Because I am still a very new user, especially Luxus+LuxRender, I am afraid I just can not understand these stuff now.
But thank you anyway.

Leo Chen

SimonJM said:

It might just need a 'bit more' time to de-speckle and clean up the image. How glossy are the surfaces in front of the figure? What sort (type and numbers) of lighting are you using?

I use only default setting...
The blue color of the pant just be totally gone, how come?

Leo Chen

Jaderail said:

As Noted before The Speckles WILL clear up the LONGER the render runs. In LUX it is Total number of passes that clears up the images not TIME.

EDIT: And EACH render will need a DIFFERENT total of Passes before HIGH quality is reached. There is no default in LUX as it depends on how each Scene is set up.

Thank you,Jaderail.

I have run LuxRender for a day without any setting changed, the skin is still very granny.

Since I do not know anything about "pass", I did not set "pass" yet.

Jaderail

You Do not SET the PASSES that is on the LUX Console and shows the number of times that LUX has run as SPK/Hr or something. I stopped using LUX because it takes TOO long to get good renders. I need fast output for my type of work. I hope you keep at LUX and get good at it.

Herald of Fire

What Jaderail is trying to explain is that Luxrender works very differently to biased render engines like 3Delight. Instead of examining each portion of the screen and working out which pixels go where (highly simplified version of what happens, but it's easier to understand) Luxrender actually captures the LIGHT reflected off the surfaces in your scene, much like a real-world camera would.

What this means is that the exposure for any given pixel in the image may vary because the light rays are calculated individually, and some light rays may have been refracted from other sources giving odd colours in places you didn't expect. Over time, these light rays converge to form an image much like how film captures a photograph.

The surfaces in your scene, therefore, have a HUGE impact on the render as a whole and not just its own appearance. If a surface is too shiny, it will reflect a lot of light and those light rays will be calculated a lot longer before they are 'destroyed' by the render engine. When you consider the hundreds of thousand light rays bouncing around a scene, this is usually something you want to minimize in order to get a good render.

In your example, it looks as though the diffuse for the shorts may have been considerably lowered. Ideally you may want to change the reflectivity of the hair to add a little slight sheen. The automatic conversion only works so well, so for trouble materials like those you'll want to manually alter the settings by applying a glossy material to the surface and using the 'Copy Studio Parameters' option.

Set the diffuse to white [255,255,255] and the specular no higher than [32,32,32]. Even that is quite shiny, so play around with the settings until you find one which works for you. Because specular reflections are calculated in a very realistic way, things don't need to have a high specular colour to have a sheen. In fact a very high specular value means that it will have a physically impossible index of refraction (IOR) meaning your surfaces will look very odd and often overexposed.

I'll be the first to admit though, Luxrender IS an advanced engine and it won't be something you'll master overnight. You need to abandon the way you normally think about a 3D scene and start thinking more about real-world physics. The tricks you use in 3Delight will rarely work in Luxrender, and because surfaces act in a physically realistic way, you need to be careful how every surface in your scene interacts with the light reflected from others. That means a lot more consideration has to go into the surface materials to get the best look overall.

I'm still learning myself, but keep at it because you can gets some absolutely beautiful work out of the engine with a little time and dedication.

Leo Chen

Thank you, HeraldOfFire and Jaderail.