HDRI lighting with SSS shaders? QMC shadows

Support Materials and Textures
#1

I have been playing around with SSS shaders, and would like to try lighting them with HDR images. I’m using blender 2.45 (official release) and the blender internal renderer. I can not figure out how to light a scene using and HDRI in blender. How would I approach this? Would the SSS shader be taken into consideration?

Also do SSS shaders have to be on really low scales to avoid a wax look? It seems like I have to keep the scale in under 0.077 to get a decent affect. And this still yields a sculpey like skin effect. Not very realistic, but not bad looking.

I also heard something about a QMC shadow. What is this? If there is alternate methods of accheving a more realistic lighting setup, I would love to know them!

#2

I also heard something about a QMC shadow. What is this? If there is alternate methods of accheving a more realistic lighting setup, I would love to know them!
QMC stands for quasi-monte carlo
Monte Carlo is a type of sampling for raytracing (it is named after Monte Carlo because it it random, and so are card games and such). QMC is a different way of sampling than MC. With these sampling algorithms, you can get more realistic/refined shadows with less computation time. QMC AO and shadows are available in SVN. This allows really nice AO and fuzzy shadows.

#3

SVN? What does that mean?

#4

SVN refers to development versions of the Blender source code. Installable builds of SVN versions, with the latest features, are available at Graphicall.org (among other sites).

SSS materials will take HDRI lighting into account when calculating the effect.

A form of HDRI lighting can be done by using a sky texture as the basis for Ambient Occlussion.

#5

Ah. Haven’t messed with a working build for quite a while! So the QVC shadows is a new feature that will be in the next official version, or the current build. Would you have to use Yavray to get true HDRI effects? I’m guessing to get it a semi HDRI effect, you use sky texture option to calculate the AO?

#6

I’ve never really used Yafray, so I’m not familiar with it’s HDRI implementation (I’d guess that it’s better than BI though).

Yeah, the QMC stuff is in SVN, and will be in the next official release. Besides soft shadows, it is also used to improve the speed/quality of AO . . . so keep that in mind if you go this route for your HDRI lighting.

BTW: There are better things coming for HDRI lighting.

#7

Is that HDRI update in the current SVN build?

#8

I’m not sure . . .

If it is, I’d like to know about myself.

#9

I’ve used these new AO & shading effects and they are pretty neat. Also included is the ability to blur reflections which adds a lot of realism and options to raytraced reflections now. However, I think its a bit of a stretch to associate these with HDR imaging. Yes, they use an algorithm that cuts down on sample quantities and so speed up certain raytrace-related operations, but they have little or nothing to do with hi dynamic range image lighting, a GI technique. The AO within blender (a way to fake similar effects) is only linked in that it can be set to utilize the colors within a world texture, if present.

To investigate genuine HDR lighting, you’ll need to move on to a GI renderer like yafray or indigo (& others). Yaf, AFAIK, doesn’t yet have SSS, tho Indigo has a really sophisticated and effective function. The trade off is render time. This is the reason for most of the “faking” attempts in scanline or raytrace renderers: to same time. Software like Indigo can genuinely achieve photoreal effects, due to its attempt to realistically mimic the actual physical behavior of light - it just takes “forever”. Blender’s internal engine tries to get close via workarounds so that the artist doesn’t have to wait around for days for his frame to finish cooking. And it does so very effectively & efficiently, I might add… :slight_smile:

#10

Are you referring to the stuff mentioned on Matt Ebb’s site, or the features that have been in SVN for a while now?

#11

No… just the SVN stuff for 2.50. Pretty cool (both those and Ebb’s work)… makes the internal renderer more and more attractive.

One thing I’m interested in knowing is if it were possible to incorporate an algorithm into mapped shadows that would allow the shadow to darken as it neared its casting object. There’s currently an alpha value used by shadows (or something that allows them to not go completely black where they’re cast) that would be neat to make into a controllable gradient as the shadow got further away from the mesh which is casting it: less transparent close and progressively more transparent as it got further away. (…am I making any sense at all?)

Is there such a function already? Surely its been thot of a bazillion time before… Am I just nuts? :spin:

#12

Not that I know of. But it would be useful, probably being faster than the new soft shadow options (which are great additions).