Re: FAO Dalomar - LWF & colour bleeding
All in all, this is a very complicated question, and one that is a personal decision of how you want to work. V-Ray is setup for linear work flow with the correct RGB and LDR options. Lele’s method is very good, and something I think is very promising, however its much easier to implement and keep track of within Max (via maxscript).
All that being said, I’ll run down how I would go about Lele’s method within vfsu (in principle his method is actually fairly simple, although his explanation and logic for the method goes through a number of complex steps). I must also note, that I haven’t gone through and fully tested this workflow, that is been a little while since I’ve dealt with this, and that I am not currently using this workflow (all be it that I’m not doing that much vis work at the moment).
At the heart of Lele’s method is the brightness of the sun/sky, how materials react to that brightness, and how the physical camera exposes the materials and the sky. He argues that the sun/sky system is the basis for photometric lighting in v-ray (in max this may be argued, but in vfsu this is most certainly the case), and that one of the implications of using that system is that the physical camera must be enabled as well in order to expose this brightness.
What Lele gathers through a series of very logical, although not incredibly apparent, steps, is that the relationship of the sun/sky to the physical camera is acting correctly, but that vray materials are “miscalibrated” in a way that they do not work correctly within that system. Therefore, when we adjust the exposure of our cameras, we typically do so with the understanding that we must properly exposes our materials (which are “wrong”) as opposed to the sky (which is right).
This leads to two major issues; the darker appearance of the sky, and a physically incorrect reaction of the materials. The physically incorrect reaction of the materials can be seen in the caustics effect of the gargoyle (if you remember the video), scenes that seam to bounce around two much light, and the “gathering” of lighting in certain areas where it shouldn’t be. Essentially with material settings as they are the materials wind up “reflecting” too much of the sun’s intense light energy. This is because if we keep a very simple model of the shading/reflectance energy, then the materials do not decrease this energy, but rather, maintain that energy at levels that will overexpose standard images (this is the simple equations that lele uses as example at the start of the video).
So this leads us to a situation where we need to adjust the material model that is currently in v-ray. Lele’s solution for doing this is to essentially multiply the materials by .255 which essentially darkens all of the materials. To compensate for these “darker” materials, the exposure of the physical camera must be changed to match that (ie we have to increase the exposure some how…lele suggests iso which is a good way). Once we do this, the dark sky that we were seeing before is now at its proper/expected illumination.
AFAIK lele does not suggest this as an alternative to LWF. In fact he retains the gamma correction of all images and colors (inversely corrected) as well as gamma correcting the final image. So in vfsu that wouldn’t change (this leaves the sRGB button unnecessary).
So know that all the cards are on the table, how do we make this work in vfsu.
1. All colors must be set through the AColor map…you would set the color as you normally would, and then change the texture multiplier to .255
2. All maps must have a texture multiplier of .255… this causes a bit of an issue with linked materials. Therefore, even though it is still advised to use linked materials to generate proper mapping coordinates, you will have to add another layer ON TOP OF the linked layer with the same texture and a multiplier of .255. That will effectively “remove” the texture from the SU material.
Here are somethings that I am not sure of how they will react in vfsu.
1. Reflections - specifically filter colors. I don’t think that setting the reflection value (ie fresnel in most cases) will need to changed. I also don’t think that the .255 thing should extend to setting filter colors, since that would effectively decrease the reflections by doing that (this I’m a little more unsure of).
2. Light emitting materials - These are hard to pin down when using the physical camera any way, so I would stick with the mantra of “just set it at whatever works for the scene” (I kinda just made that up, but you get it). My advice would be to know what the exposure of the scene is before you go messing with levels and things. Since there will be more exposure you should probably notice less of a need for very high multipliers (but they will still probably be significant).
3. Refraction/Fog - I really don’t have much of an idea on this, so I’m not even going to postulate.
Keep in mind that this system requires complete adherence. It either all or nothing because that one material that doesn’t adhere has the potential to really through things off. There also isn’t an automated way to take care of all of this…its basically you going through and checking out every material, so be aware when you make them and when you modify them.
Within this system, I feel that the camera is key. Be very mindful of setting exposures correctly. Also, one of the most underrated features of the physcam IMHO is white balance. You’d be surprised what you can do/adjust with using that feature (its a very good way to adjust any color bleeding that may occur).
Your main issue was color bleeding, and I think this is something that should help that, since the preservation of that light energy will no longer be as significant as it was with “standard” materials. Your current method for decreasing color bleeding isn’t bad (I’ve used it myself a number of times), but also remember that you don’t have to go all the way to pure white to decrease the effect. Sometimes just a less saturated version of the color/material is enough to make it work. Interestingly enough I’ve seen some very significant color bleeding in real life that I would have deemed “undesireable” if I was doing a render of that situation…just an observation.
Hope this helps…I’m sure you’ll have questions and I hope you can post some results so that we can see how it works out. I think this method shows promise, its just that its implementation is kind of hard to swallow (in a number of senses).