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Broccolilord
05-23-2011, 09:58 AM
Hey all,

I am working on creating a room as close to photo realism as i can get. I am using a linear work flow to achieve this as well. However I am having one issue with my reflections I just cannot figure out. If you look at my attached image you will see what I am about to describe. The floor reflections in the light are faint like i want them too. However, if you look in the shadow under the desk the floor is suddenly super reflective in the shadow. Any idea on what is causing this?

Tobian
05-23-2011, 11:53 AM
You would have to have the reflections set up to be properly energy conserving, or you can get that effect. Because Reflections are purely additive in LightWave, they just apply uniformly, unless you set up an energy conserving setup. It's likely the non-shadowed area of the floor is equally reflective, you just can't see it because the subtle reflections being added to the dominant floor material just make them harder to see.

Can you show us the material setup for the floor? It may be you also need to just dial back your Fresnel setting or increase the reflection blur.

Broccolilord
05-23-2011, 12:25 PM
I am actually newer to getting things to look Photoreal, so i do not know how to do an energy conserving set up. How would i go about doing that?
Right now my floor just has a bump and image map on it, with reflections set to 20 percent.

funk
05-23-2011, 03:34 PM
I am actually newer to getting things to look Photoreal, so i do not know how to do an energy conserving set up. How would i go about doing that?
Right now my floor just has a bump and image map on it, with reflections set to 20 percent.

The easiest way is to use a Delta material node. Id also suggest plugging a fresnel node into it's specular input instead of a constant value

Also, I'm not 100% sure, but I think its natural for the reflections to appear stronger in the shadow/darker areas

example:
http://www.leinsterfloors.com/images/sanding.jpg

Tobian
05-23-2011, 03:56 PM
Here's the most basic kind of energy conserving setup. use the output of a Fresnel node (maths>scalar) which is a kind of incident gradient in this sense. Invert it (using the invert node, also found in the same place). In this way the diffuse + reflection = 100 or less - so it's not reflecting more than 100 of the environment (reflection and diffuse are both kinds of reflection. Put in a value in the Fresnel somewhere between 1.3 and 1.6, or it will get too reflective (but still way less than 20% on that kind of angle.

For dielectric surfaces, such as polish, plastic, glass, glazes etc, you should be using some kind of Fresnel, so that reflection is a function of the angle of incidence, relative to the camera. Technically in this case what you are doing is making a very simplistic simulation of of a gloss coat (the floor varnish) over the diffuse reflecting material (the wood). so the diffuse reflection is being 'masked' by the specular reflection , and the fastest way to do that is just invert the Fresnel.

If you want to mix up the reflection amount a little, then it can get a bit more complex but that should do for such a floor surface. As a note, this will override any textures/values you have in your diffuse/reflection slots.

dwburman
05-23-2011, 09:37 PM
Basically, you want your diffuse and reflection values to equal 100%. If your reflection is 20% your diffuse should be set to 80%. That's just a rule of thumb, of course, so it's okay to deviate from it if you need to.

Broccolilord
05-24-2011, 09:53 AM
Thanks guys all of that is super helpful and I will definitely be utilizing these techniques in my future projects without a doubt.