Rendering Tip - Use Reflective surfaces

Al Hart

It's like saying that all green objects should be green.

Now we are on the same page. The whole purpose of a rendering tip is often to point out the obvious.

Someone new to rendering is often overwhelmed by all the setting and features that can be used, so a tip, and especially a set of tips like this is designed to present some obvious ideas which may be easily overlooked.

solo

Reflection is important (an obvious point) for PR renders, however I've noticed many beginners using too much reflection as opposed to too little. How many shiny floor renders are out there? to many, even I was guilty of this in the beginning.

Now reflection is not a value or a slider amount, reflection done right needs an understanding of materials and what reflections certain materials emit.
A generic reflection slider will result in a generic render, if one wants to render PR one needs to firstly have a engine that can assign different reflection types to materials as well as an understanding of the types of reflections that real world objects have.

Al Hart

@shwetabhseth said:

About adding reflections to all materials-It increases render times immensely, and i would also like to add that every object we see, rather than having normal reflection, which we generally enable in rendering engines, instead has Specular reflections which is harder to understand and work with in rendering engines i believe.

I think i would go through your thread and add some qualitative information to it.

Yes, I am often tempted to turn on reflection for everything (especially for things like space ships - see the Lego Model Thread), but it does increase rendering times.

I think, in our rendering tip we could have mentioned specular reflection, (or highlighting) versus normal reflection. In many ways that was what we wanted to say in the first place. That adding some highlighting or specular reflection to wood and other non-obvious surfaces, when combined with certain lighting conditions can enhance a rendering.

Sometimes you can specify a reflection mode which shows specular reflection or highlights, but not standard reflection, as in the glossy teapot example.

kwistenbiebel

Nah, didn't offend me.
Actually it's a smart marketing strategy.

What if your project hasn't got reflective materials?
Do you think you can't make a realistic render in that case?
I tend to disagree.
Besides, using too much reflectivity kills realism as well.

Not sure if this really is valuable 'tutorial' material.

kwistenbiebel

It seems that you are forgetting other parameters as well. Glossiness, for instance.
In your example render, most 'reflective' objects all have the same (none) glossiness, which looks unnatural.
Maybe you can make another thread "Rendering Tip - Use Glossiness".
What about specularity? Caustics? Fresnel effect? etc.. man, you have some work to do.
I doubt however that you will post any render tip about a feature that your render product does not support.

Al Hart

@kwistenbiebel said:

It seems that you are forgetting other parameters as well. Glossiness, for instance.
In your example render, most 'reflective' objects seem all have the same (none) glossiness, which looks unnatural.
Maybe you can make another thread "Rendering Tip - Use Glossiness".
What about specularity? Caustics? Fresnel effect? etc.. man, you have some work to do.
I doubt however that you will post any render tip about a feature that your render product does not support.

In a "coincidence", I added the glossy example before I read your posting. based on shwetabhseth's comment.

I suspect your were joking when you suggested a rendering tip for each type of reflection. But I think we will probably do just that. We have a reflection page which mentions all these things at once, but that approach is ofter overwhelming. I weekly tip which mentions, say Fresnel reflection, would be just perfect. It lets the reader think about one thing at a time and will give him/her ideas for the next rendering project.

Both on SCF and on some other forums I have invited people to suggest ideas for rendering tips. The one that comes to mind in biased vs un-biased. (For the life of me I cannot understand the difference or meaning of biased vs non-biased).

Here is an explanation which was sent to me:

@unknownuser said:

It's funny-- "un-biased" has become the new buzz-word that nobody understands-- used to be "Global Illumination". This type of rendering is much slower. It will have appeal to those customers looking for the highest quality possible who are willing to wait (often days) for rendering results.

It didn't help me much.

If you or some-one else wants to send me some material, (e.g. a biased and un-biased rendering of the same scene and some pointers about when to use biased vs un-biased rendering), I will be glad to turn it into a tip.

Al Hart

@solo said:

How many shiny floor renders are out there? to many, even I was guilty of this in the beginning.

When we wrote the Lightscape rendering interface for Giza (Office Furniture), that was all we did. We have a room with some ceiling lights and a shiny floor. The user placed the office furniture in the room (with no other shiny surfaces) and created a rendering.

For that industry at that time (more than 10 years ago), it was a great, easy solution.

When we introduced SketchUp to one of the users, he immediately went after the reflective floor again - without using a renderer - by mirroring all the furniture and walls below the floor, and making the floor partially transparent.

A shiny floor still goes a long way.

This is the furniture image, rendered entirely in SketchUp with floor reflection.
(Courtesy Steve Ulstad - ProjectMatrix)

solo

Luckily she is not wearing a skirt.

Rich O Brien

Or if it's a 'He' we're even luckier it's not a Kilt

Al Hart

@solo said:

Luckily she is not wearing a skirt.

But I think it is an impressive rendering for a new user who is trying to find a way to get reflection without having to use an external rendering engine.

Actually, there is a similar trick where you put the camera below the floor, grab an image, and merge the image into the floor texture. This could easily be done with a ruby (are you listening Chris F. ?)

kwistenbiebel

Reflection, glossiness, fresnel ,to show what each parameter does.

Reflection and glossiness probably speak for themselves.
'Fresnel effect'= the fact that the amount of reflectance you see on a surface depends on the viewing angle.

(values are Vray )

materials with a very high IOR(index of refraction), such as metals:

For unbiased render engines like Maxwell, other specific variables like 'roughness','ND' etc.. are used.

Gaieus

@solo said:

...Luckily she is not wearing a skirt.

OK, joking aside. Indeed in reality, every material reflets light (otherwise we could not see them obviously). As was pointed out above, there are several parameters that need to be taken into account. Most important is how it reflects light (that's governed by the IOR value - i.e. it will be a sharp, pointy reflection with higher values or more dispersed with lower ones) and the shininess (i.e. the amount of this reflection).

Now here is an example below where there is the outside with the physical sun shining direct sunshine (the direction is shown by the red arrow from the door) and the indirect kind of lighting "shone" by the physical sky (this is practically coming from every direction but of course, "pinholed" by the openings).

It is very interesting to see how a rather flat brick texture still reflects direct and indirect light as well and causes different, multiple reflections say on the left, when the light from the door first hits one column which then reflecting (but with low IOR, also dispersing) this sunshine and lighting the other column (that's what we can see on the left) as well as the wall all around.

The more indirect sky light is lighting everything more subtly but gives an overall "global illumination" to the scene and only reflects when our eye is directly exposed to the reflections caused and directed by the IOR (these are marked with blue).

The whole mixture of these bouncing photons will eventually give the "photorealistic" feel of a render (this particular one of course does not claim to be a real PR render - not to speak about the still untextured walls and window frames).

Obviously a "newbie mistake" is to overdo shininess (and I am still in this newbie phase of course) but reflection is not (necessarily) about visible shininess but about such multiple, bouncing reflections.

And please, everybody excuse me now for this post as I am really inexperienced at rendering.

Al Hart

@gaieus said:

And please, everybody excuse me now for this post as I am really inexperienced at rendering.

Good - if watching us all argue about this tip gets you to try some more renderings than we have had at least one positive effect.

You might appreciate this next weeks tip: Use 2 pt perspective for better vertical alignment

(Unless, of course, the columns are actually placed at an angle. You do not seem to have the camera pointing up or down)

Al Hart

@kwistenbiebel said:

And the tip for the week after that:Tip Of the Week after next week

.

@unknownuser said:

Shamelessly Effective Self-Promotion by Debbie Allen

When a friend of mine, Larry James, first stated, “I’m a shameless self-promoter,” I laughed. Then I thought for a moment, and I realized that I’m a shameless self-promoter, too. I had never thought of my marketing approach as being shameless before. I would have described myself more like the Energizer Bunny. I just keep on marketing and marketing and doing whatever it takes to make it happen. I had never thought of this as shameful, unless it’s shameful to believe in something so much that you want to tell everyone you meet. I call it good marketing!

Thanks,

Maybe I can learn something from this.

kwistenbiebel

@al hart said:

You might appreciate this next weeks tip: Use 2 pt perspective for better vertical alignment

And the tip for the week after that:Tip Of the Week after Next Week.

.

kwistenbiebel

sorry, couldn't resist

sepo

Gaieus

@al hart said:

You might appreciate this next weeks tip: 2 pt perspective for better vertical alignment...

No, they are not at all placed in angle - here is a "real ortho" (parallel projection) view...

I am (of course) not happy with some of the procedural textures yet...