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Lunatite

18.04.2024, 08:17

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Protal light 2

Protal light 2
Description:	Having contemplated Horo's "Ignored" image which has interesting similarities to this idea I am toying with, I have decided to experiment with reflection lighting. Top Left. Lit with a single radial. However, a lot of the "light" evidient is reflected from Horo's Jeeprobe hdr. The hdr background had an unexpected bonus for me in terms of lighting. While it appeared white, mostly at all levels of intensity (as a background) turning the intensity up did increase the ammount of light reflected from this background. The practical upshot of this was that I could light the scene entirely with the hdr background (if I'd have wanted) even if only a small view of the hdr background were admitted through a window. A standard bryce sky could not have achieved this effect, because it could never be bright enough. So that was something. I did add a radial light to put in a nice sharp shadow from the boxes. But like I said, it wasn't needed to light the scene, the scene could have been lit completely with reflection. To make the reflection less obvious I used premium effect blurry reflections at 256 rpp and a ray depth of just 3 (to reduce render time which was only a couple of hours). The material for the room and cubes was standard grey with 35 reflection, 100 metallicy (to help it express it's colour) and speculative halo of 224 (this controls the level of blur). Top right. I wanted to be sure, having got what I felt was a reasonable effect from the blurred reflection lighting of the hdr background, that material colour and bump could be expressed and also that it was compatable with soft shadows. So the materials were revised to have some blue in (hence the need for the metallicy setting earlier - even though it would not have had much impact on the grey which blue the blue is then transferred to the reflection and if most of the lighting is reflection then that is key to seeing the colour of the material since metallicy transfers diffuse colour to reflection.) Oh, and gave the radial light 15 soft shadows and switched soft shadows on in premium effect. Again, the render time was not too hideous at about three hours. Bottom Left. As top left set up. But soft shadows set in premium. 0.1 HDRI effect on IBL since the intensity was set very high any more and the scene would be flooded. Render time six hours with just a quality of 16. So a little too time consuming for not very much in terms of extra lighting. Bottom Right. A control scene for this experiment. Default grey material used all around. Shadow intenstiy set to 60. 5 white light sources (one for each wall and one over the ceiling), a bluish source in the window and a orangy one over the camera. All set to 100 shadow softness. At standard AA this scene took about 4 minutes (10 times that for premium at 256rpp). So really, dispite thinking I'd been clever by using the HDR as a background to light my scene via reflection, there does not appear to be much to be gained over using standard lighitng approaches which are considerably easier to set up. That being said there may be advantages to be gained from the reflection approach when rendering more complex geometries.
Added by:	davidbrinnen
Keywords:	davidbrinnen, bryce6.1, IBL, hdr, Horo, Jeeprobe, experiment
Date:	10.28.2007 10:19
Hits:	3395
Downloads:	82
Rating:	0.00 (0 Vote(s))
File size:	172.8 KB

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Horo
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Join Date: 05.26.2004
Comments: 4721

From a lighting/shadow point of view, top left and bottom right are the most pleasing. Render times cannot be compared here, because top left has the gaps in the tiles smoothed while bottom right has not. As you say, a more "cluttered" scene would be needed to establish whether the hdri or the 5 radials version is more appropriate.

The more lights you need to light the scene, the more render time increases. I'm currently experimenting with "Ignored" with a different setup and 24 lights. The render time will go from 6 hours (1 light) to 10 days (24 lights) if I use premium 64 rays as I did for Ignored (which I won't).

So there might be a complexity of a scene where the hdri/reflection option turns out to render faster and is easier to set up.

However, your tests are priceless. They show that there is not just one method for every case.

10.28.2007 10:47

rashadcarter1
Admin

Join Date: 06.04.2006
Comments: 2610

Ohh, nice tests David! Around and around we go. More than once this idea of using reflection as a shadow correction method has been considered. I knew that the reflections were really leveling up Horo's "Ignored."

As we all know there is the old B-solutions chapter on using material reflections and blurred reflections premium AA to create very realistic indirect lighting very similar to radiosity or GI in more powerful programs. The reflection really spells out the model contours by basically making every visible object in the scene into a light source. The render times can be outrageous though, just for the premium effects alone but also because of the reflections themselves. I'm not sure if the reflection approach will work well for complex scenes, at least not my version of complex that can get out of hand. Alot of reflection is alot of color calculation. Tina Gazcon waited 6 days for her scene due to the reflections alone. In your bathroom scene where you did a radiosity simulation, the results were fine, but I think the best approach would have been reflections blurred, with as few real light sources as possible to allow us to trace out the bouncing. Blurred reflections are the bryce equivalent to bouncing light.

From what I see there are a couple of things to keep in mind. First, is how to get hdri light into an indoor scene. One way is to disable the shadow casting abilities of the walls and floors only to allow the all of the outside hdri light to enter the room and illuminate the objects within it. We would never notice that the walls did not cast shadows iof the viewer were indeed inside of the room. We could also lower shadow intensity to around 60%, this allows a decent amount of light in while still giving the benefit of shadows.

Next to consider is the indirect lighting within the room itself. This is where the reflection values make a huge difference.

This theory of reflection in complex scenes has already been tested by me. In Livin' Large every material surface in the scene from the sofa cushions to wood tables and wood floors and walls all have reflection. The only surfaces that don't have reflection are the brick walls and the plant leaves, but that's all. It took many days to render, but I'm happy with the resulting interaction between the lighting and the other elements.

One can also use bumpmapping to force some blurring, I believe Horo did this with the door of Ignored. This saves us the trouble of premium effects in some cases.

10.28.2007 16:05

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