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Comments: 5
davidbrinnen

16.04.2024, 06:23

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Compair and Contrast

Compair and Contrast
Description:	Top left. This is the benchmark, using a trick found on Bsolutions site. Utilising premium render, 256rpp, standard ray depth of 6, soft shadows and blurry reflections. The blurry reflections controlled by the setting of the speculative halo channel scatter the light and create the illusion of indirect ambient light. But material settings are very specific. Material Diffusion 100 Speculative halo colour set to max 255 (has to be entered manually, very difficult to set using colour picker) Metalicy 100 to get the diffuse colour into the reflection Reflection 50 Lighting, Horo's bluegreymoon Quality 64 (lower quality compensated for be setting soft shadows in preimum). Intensity 11 Effect 1 Shadow intensity set to 100 Render time = horrendus, over 4 hours for this simple scene. My challenge to get something approching this in terms of lighting quality but rendering in a fraction of the time. Middle left. To set the scene, so to speak, a simple hdr render using diffusion and standard render settings Material Diffusion 100 No ambient or specular Lighting, Horo's bluegreymoon Quality 1024 (standard render cannot use soft shadow trick - hence heigher setting). Intensity 5 Effect 10 Shadow intensity set to 100 Render time about four minutes. Bottom left. An experiment, although it is said that IBL does not stimulate the specular response from a material this is not entirely true, it is possible to get a respose but lots of hdr lighting is needed. As shown. Again, standard render settings used. Material Diffusion 0 Ambient 0 Specular 100 Speculative halo colour set to max 254 (has to be entered manually, very difficult to set using colour picker) Lighting, Horo's bluegreymoon Quality 1024 (standard render cannot use soft shadow trick - hence heigher setting). Intensity 34 Effect 100 Shadow intensity set to 100 Render time about four minutes. Consider the differences between the diffusion response and the specular response to the hdr. Interesting huh? Top Right. The challenge now to combine the diffusion and specular into one scene in more or less equil proportions. I don't know if that a good idea or not, but that was the challenge I set myself. Clearly I was going to need enough hdr light to get the specular so very small quantites of diffuion would have to be applied. Material Diffusion 0.2 Ambient 0 Specular 100 Speculative halo colour set to max 254 (has to be entered manually, very difficult to set using colour picker) Lighting, Horo's bluegreymoon Quality 1024 (standard render cannot use soft shadow trick - hence heigher setting). Intensity 27 (so that the specularity did not dominate the scene) Effect 100 Shadow intensity set to 100 Render time about four minutes. Middle Right. All right, now time to get devious... Forgetting about the specularity for a moment. I've made the ground plane not cast any shadows, and also the red box. Then I placed another ground plane under the ground plane and made that partially transparent, this is to simulate light reflected from the ground plane but is in actual fact, light coming from the underside of the light probe. Thankfully bluegreymoon has light aplenty under the ground. I also added a bit of ambient to the ground plane to make it glow a bit to explain it lighting what is above it (I also changed the colour to be slightly more yellow/orange, again to help "explain" the light). The red box I then construced a cut out so the walls were solid (so they would cast shadows) but the top non shadow casting (set again in the material) under the red box I placed a red transparent box to tint the light coming through the ground. I also placed a slightly less transparent box under the back wall because that was catching too much light. Another adjustment was to set the Shadow intenisty to 80, the theory behind this was that with so much light it would be impossible to have fully black shadows anywhere (unless inside a box). And that also lets the light propigate a bit more. Material Diffusion 0.4 Ambient 0 Specular 0 Lighting, Horo's bluegreymoon Quality 1024 (standard render cannot use soft shadow trick - hence heigher setting). Intensity 27 (so that the specularity did not dominate the scene) Effect 100 Render time about five minutes. Bottom Right. Essentially as the example above but with specularity thrown into the mix. For better or for worse. Material Diffusion 0.2 Ambient 0 Specular 100 Speculative halo colour set to max 254 (has to be entered manually, very difficult to set using colour picker) Lighting, Horo's bluegreymoon Quality 1024 (standard render cannot use soft shadow trick - hence heigher setting). Intensity 27 (so that the specularity did not dominate the scene) Effect 100 Shadow intensity set to 80 Render time about five minutes. Clearly this experiment was inspired by Rashads Doc1. I'm not saying that this is the way to go with lighting, just throwing around some idea's that some of you may find interesting or even illuminating... (sorry).
Added by:	davidbrinnen
Keywords:	davidbrinnen, bryce6.1, experiment, IBL, HDR, Horo, bluegreymoon
Date:	04.30.2008 21:46
Hits:	3968
Downloads:	63
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rashadcarter1
Admin

Join Date: 06.04.2006
Comments: 2610

Amazing! First it is incredible to know that specularity indeed can be stimulated when there is enough IBL light. I really think the way Bryce handles the reflection/ specularity optic is very interesting. Surely, the Bsolutions diffuse blurred reflections works the best but as you note render times are insane. I think it is important to note that all of these examples are lit IBL which is the skylight equivalent in Carrara. The skylight is an important part of a GI simulation and it is providing all of your shadows. One of the drawbacks to using reflection alone is that reflection does not cast shadows as real light sources do so the IBL was essential to this experiment. The Bsolutions reflections work so well that often IBL or skylgiht is not necessary because the reflection picks up the sky of the environment very well.

The ground plane issue is a sensitive one. In general I am finding that I like deep shadows so I have been accelerating my shadows to 100%. To solve for the underground light I have been using radial or spotlights that do not cast shadows. Similar to the awful skydome effect but from underneath and much much dimmer. Because it is a low spotlight it only catches model faces at flat angles. This allows me to maintain full shadow depth through out the scenario while also solving the light for model undersides.

Incredible test and surely there will be alot to say about it. I just want to note my often saying that Carrara is faster that Bryce as a final render engine. As you found here to mimic indirect light you needed very high settings in Bryce and it took many hours just to generate an image a few pixels wide. Doc1 rendered so fast I do not even remember how long it took, minutes, not even close to one hour.

05.01.2008 00:43

davidbrinnen
Admin

Join Date: 01.03.2004
Comments: 2224

It would have been nice if we could have had as much control over the IBL lighting as we have over say, materials. Even if we did not know now exactly what could be a useful thing to change, we would eventually work something out. For example, how about if we could control the level of sepcular response caused by the IBL in the sky lab. Not out of the question. Useful? I don't know. I just like to be able to change things and try thing and see what happens.

Yes, I too like the deep shadows, you will not have any argument with me there. However, going back to your Doc1 example, there are few if any deep shadows to be seen, so I was looking for a way that would propagate a little extra light around the scene without resorting to too much ambient. I also like your spotlight idea, my only objection is that that is going to create an unnatural shadow region, since all of bryce's lights, dispite what they may say on their description, essentally behave as point light sources so the spot would only simulate one bounce from a surface so a bank would be needed for better simulation - increasing render time. Details I know, but here we are picking things appart to hopefully put them back better.

Carrara is faster but... In the few scenes I've done, to get the level of quality and realism I've wanted, in the end, after turning on the appropriate effects and ramping up the detail, the renders have still taken an appreciable time. Also, though this is more a criticism of the interface, I miss the plop render and the multi pass render which helps me visualise the scene without going to the trouble of a full render. Carrara's block by block approach is not helpful if you need to see the bottom right hand block and it's snap shot option is no snap shot when you have to wait five minutes for it to calculate the light map. Also, Doc1 needs to be rendered without the black spotches and timed, as things is, I know you would not be happy with it as a final render. Of course the Bsolutions method is slow, no doubt about it, it's more a curiosity than a practical approach since it is very difficult to control the final appearance of the materials involved and by force, introduces a lot of noise into the render, even at maximum rays per pixel. But hopefully all add to our understanding of the render engine and helps us find ways to bend it to our will.

05.01.2008 07:50

rashadcarter1
Admin

Join Date: 06.04.2006
Comments: 2610

Amen. I could not agree more. You make very good points.

05.01.2008 09:00

Horo
Admin

Join Date: 05.26.2004
Comments: 4721

Since David was kind enough to send me a puzzle with high specularity, wide coloured halos on a simple sphere and only IBL light, I could figure out a few things. Yes, yes - he proved me wrong that the specularity control is of no effect when IBL light is used exclusively. Brian Wagner, the principal developper of Bryce IBL, would be surprised by David's findings as well.

As David says, this only works with high IBL light settings. In fact, it only works with low contrast HDRI's, HDRI's that are very good in generating ambient but lack a prominent light source, e.g. the sun or other bright lights in a room. Only than the light sources are strong enough to create specularity blobs on a surface. Those blobs come from the lights created by the median-cut alg. This has nothing to do with reflection, because the reflection would show the over-saturated HDRI, not the light dots it is made of.

Actually, I think this is a bug in IBL, but a nice one. The actual lights generated should never be visible. At least, it gives away a few things how IBL is implemented in Bryce and for me, this is thrilling news.

Those experiments are very interesting, indeed. I couldn't think of any use for this except for a special effect. But David proves here that it could be put to good use and saving a lot of render time.

05.01.2008 12:46

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