LWF/Benchmark

[womble]

After running a quick scene benchmark from http://www.vrayelite.com/benchmarks.php I've been wondering about LWF. Now I don't think that the benchmark scene used here is set up for LWF, so when I render it using my gamma settings, I get a much brighter but more 'washed out' render. I know this is quite symptomatic of using LWF (more detail in darker areas but less saturation) but is there anything i should be doing in my scene to achieve a more 'correct' value? For example, should the vraycolor material be used in this scene to color correct the desaturated greens and oranges while still maintaining the increase in detail in the shadows?

 

I 'think' that I have my machine set up correctly, although I do seem to get very washed out images from vray (that I then correct in post production) but maybe there is just one setting somewhere thats set incorrectly. I'm trying to use LWF, so i'm assuming that has something to do with the problem.

 

So here's the three images.

 

1st) Benchmark scene rendered by someone else

2nd) My 3dsmax 9 gamma settings.

3rd) My render

 

Cheers,

[rivoli]

that's to be expected, if a scene is not set up to be rendered linearly, then it will look totally washed out. when working with gamma correction it's important to keep in mind that diffuse colours must be adjusted accordingly. a 128 grey won't look at all like what we're used to consider mid grey once you apply an inverse gamma curve, as I read once on the chaos forum: "just make it darker".

this way light will also bounce around less, giving much more contrasted results (instead of that typical evenly lit 2,2 gamma look), and shorter render times.

[Tommy L]

LWF is an 'autonomous' approach. It cannot be applied to another scenario.

[Stephen Thomas]

LWF is an 'autonomous' approach. It cannot be applied to another scenario.

Technically, though you can convert a scene as well to work with LWF. I actually work with Gary, so we've been taking a look at this.

 

Here is the scene rendered on my machine, the first shows the original file with max's gamma correction turned off. Render time was 1m29s. The second image shows the same scene with all colour swatches and the light intensity compensated for with a .454 multiplier. Render time is now down to 1m8s.

 

The colours and light level in the second image are equivalent to the original, although the light intensity is more even and realistic in the LWF image, compared to the hot spots and dark shadows of the original.

 

Obviously with higher render settings or a more complex scene the 23% saving in render time shown here would be much more valuable.

[kippu]

good going ...i never tested it but it feels weirdly going back to non LWf / gamma correction ...nice test again

[Crazy Homeless Guy]

a 128 grey won't look at all like what we're used to consider mid grey once you apply an inverse gamma curve, as I read once on the chaos forum: "just make it darker".

 

instead of just making it darker, why not go ahead and apply the inverse gamma curve with a .454 adjustment?

[Crazy Homeless Guy]

as a whole i find this interesting. it is one thing to tell people there rednerings will be faster if the work in LWF, it is another to have an example.

[shaneis]

Quick question, but wouldn't a global gamma setting (0.454) affect the procedural colours as well? It's my understanding that procedurals are already correct hence it's only the 8-bit colours/ files that need correcting. Therefore correcting 8-bit files and applying a gamma correction to the camera should provide correct results. Please note that I'm using Maya/ mentalRay, I understand that this could be different in VRay but I'm very interested in LWF and 32-bit imagery in general.

[Stephen Thomas]

Quick question, but wouldn't a global gamma setting (0.454) affect the procedural colours as well? It's my understanding that procedurals are already correct hence it's only the 8-bit colours/ files that need correcting. Therefore correcting 8-bit files and applying a gamma correction to the camera should provide correct results. Please note that I'm using Maya/ mentalRay, I understand that this could be different in VRay but I'm very interested in LWF and 32-bit imagery in general.

Yes, applying a 2.2 gamma in max preferences and ticking 'affect colour selectors' will make colours lighter. That is why I compensated by making the colour swatches in the material editor their 1/2.2 equivalent so they matched the original colours in the render.

 

The theory is that by having the colour swatch darker and applying a 2.2 gamma to it at the end, the material reflects less light and therefore less GI to calculate = quicker render times.

[shaneis]

Excellent, understood and thanks for the tip.

[aaronrumple]

I ballance the color in one of several ways.

 

1. I'll use a100x100 px image of the correct sRGB in PS and let it be imported with the same gamma correction as all other maps. This has worked well when getting color swatches from the commercial paint web sites (like Sherwin-Williams). I find light, high chroma colors the most difficult to match up with paint chips.

 

2. Set the color the use ctrl+n to pull up the calculator and multiply by .4545 for each of the RGB values. This works very well, but you don't have a good visual reference in the editor of the final result. Also I can put together a 100x100 px map in about he same time as I can make the RGB conversion. And I get the bonus of having a named clor set that matches the paint chip color I can use on other projects.

 

3. Use the Vray Color Map and set the RGB and apply the correct gamma. I think this gives you a lot more control for fine tuning colors as it uses a floating point number ather than just RGB. Now if I could just get better paint chip numbers for floating point RGB.

[Stephen Thomas]

3. Use the Vray Color Map and set the RGB and apply the correct gamma. I think this gives you a lot more control for fine tuning colors as it uses a floating point number ather than just RGB. Now if I could just get better paint chip numbers for floating point RGB.

That's basically what I did here too, used the vray colour map in a spare material slot as a colour calculator.

 

Set gamma in the vray colour map to none, paste in swatch colour from material, set gamma to 0.454 then copy back out to the original material.

 

This is only really necessary here because I was trying to match colours in a scene that wasn't set up for gamma correction. Generally when adopting a linear workflow approach you would be adjusting your colours by eye to what looks good in the render anyway. You just have to be aware that your mid point is now around 50 and not 128.

 

The vray colour map is a good option if you have a specific RGB colour to match though.

[Tyorl]

If u use ColorCorrect plugin, then u could easily match your color, because there is a compensation Gamma value. Just use CC set your color to 128-grey and set gamma to 2,2 if you are working in LWF

[rivoli]

instead of just making it darker, why not go ahead and apply the inverse gamma curve with a .454 adjustment?

 

I remember that reading that post over at the chaos forum made me laugh (in a positive way). it kind of summed up what one needs to do when going linear in a very practical way: "just make it darker".

anyway, jokes aside, you can use a vray colour map and apply a 2,2 gamma correction to your mats, or you can make diffuse, reflection colours and maps darker by a given value as in lele's method. I guess you can even tone down your gi as other users have suggested. at the end of the day it comes down to what works best for you, I guess one can even live with a washed out output and do any colour adjustment in post.

[jbrckovic]

Does anybody knows how to get correct results with max frame buffer?