Default material

[Ros. Riha]

Roy says:

"The default material is ~0.7 grayscale, which is about 50% matte reflective surface. No specularity.  No-- don't use specular reflection on the walls unless you want specular reflection on the walls (glossy paint, etc.)"

 

Couple of questions:

1. Would it be possible to allow editing the default material?
2. Is 50% matte reflectivity accurate for interior applications? At the beginning of a project I would like to simulate lighting conditions, so I would like to know, how would indirect light lit my interior - are characteristics of the default material suitable to be used as a substitute for regular white wall paint?

[Roy Hirshkowitz]

No editing of the default material.  It's low for walls and high for floors but generally good overall.  If you want more accurate estimates you need to use different defaults for ceilings, walls and floors.  At the bottom of this page are some industry standard values.

 

You need to take the square root of the reflectance to arrive at an nXt color-- for example 0.5 (50%) gives you about 0.7,0.7,0.7 for a color (multiply by 255 to get 180).  0.2 gives you  .447 or 114.

[Ros. Riha]

Please, find attached samples of default materials for floor/walls/ceiling, created using data, mentioned by Roy above ... results on applications with indirect lighting (see atttached clipping plane test on individual family house) are encouraging - pathtracer seems to be 15-20% faster compared with the use of default material only.

I still do not know if we have them defaults right (especially how much reflective intensity should be used).

 

For the future, we would like to have proper white/gray defaults for:

1. Interior walls
   1. White paint, smooth
   2. White paint, rough
   3. Exposed concrete/stone
   4. Wallpaper
   5. Tiles
2. Ceiling
   1. White paint
   2. Tiles
3. Floor - interior
   1. Wood - highly reflective
   2. Wood - matte
   3. Tiles - reflective
   4. Tiles - glossy
   5. Vinyl
   6. Carpet
4. Furniture
   1. Reflective
   2. Glossy
   3. Metal
   4. Leather
   5. Canvas
5. Exterior
   1. Pavement
   2. Asphalt
   3. Tiles
   4. Grass
6. ....

maybe some of these are not necessary, maybe some are missing... 25 defaults seems too much to me anyway, but still: either using layers on vanilla AutoCAD or styles on AutoCAD Architecture it is quite easy to create more realistic setup for white renderings even with this many materials...

would you be willing to help creating such defaults?

 

[Roy Hirshkowitz]

Not for a while....

[Ros. Riha]

Sorry Roy, this request was ment rather to others than you - I would like to see you adding new functions and improving existing ones rather than doing such mundane stuff as creating multiple default materials :-)

I hope we will be able to put this together ourselves... only some sort of guidance from you at the beginning would be helpful - for example: how much reflective intensity should be used to achieve realistic effect? Do you happen to know where to find relevant data?

[Roy Hirshkowitz]

There are lots of design analysis sources out there.  These guys, for example, list a few approximations for surface reflectance.  When you do this, remember, do not add any Highlight or Bump maps.  Use pure, gray-scale, matte surfaces only.  Remember, in nXt, to take the square root of the value suggested to represent your reflectance and multiply by 255 to get your color intensity.  For example 80% reflectance means sqrt(0.8) * 255 or approximately 228.

 

Don't make too much of this stuff. It's for estimation purposes only and these materials make a lot of assumptions.  Getting too specific with your "default" materials is generally not worth it.

[Ros. Riha]

I am still not getting it, sorry: you say "matte" surface - but in the real life almost every material reflects its surroundings, so there should be the Reflective Intensity to set to something other than zero, should it not?

[Roy Hirshkowitz]

"Default" materials are meant to be approximate solutions only for the sake of quick lighting analysis.  Once you start adding glossy or specular reflection to the mix you might as well design the entire material.

[Ros. Riha]

Based on the experience of our studio, I cannot agree.

• For an architect, ultimate goals of the rendering are two:
  • To present the project to the client.
  • To make sure that you are following the correct path.
• While presenting the project to the client, you often find yourself to be asked to prematurely present certain outcomes of your activity - IOW, the client wants to see what are you working on while you are not quite sure what it is.
  • You need to show some renderings at the stage, where you do not even know what shape are rooms going to have, so you do not want to start messing with materials - it is too early to start to do so.
  • Thus, you would like to show something, that outlines what you are working on, and clearly shows that it is just a sketch - at the same time it should look presentable. We use white+glass renders to achieve this effect - check the attached.
• During the design process itself, you often need to check whether your ideas are working, if the spaces you contemplate would create the feeling you want them to...
  • So you make preliminary renderings for your use only - you do not want them to take long, so you do not want to use complex materials with textures, bumps etc. ... 
  • While working on the overall concept, you also do not want to be distracted by all these texture/color effects, these can always be added later
  • You just want to feel the space - so you want to have as accurate information regarding the lighting as possible.

All in all:

1. In the real life, object reflect the environment even if they are considered matte.
2. Bringing up colors, textures and bumps to a rendering takes it into much higher level than bringing up just real life proper reflection values.
3. After this longish text, my question stays very simple: how much reflection to add to shiny floor, regular white paint etc.?

 

[Roy Hirshkowitz]

Much, much too long a post-- if you want me to read them keep them much shorter.

 

You're unlikely to find any guidelines out there.  Lighting designers generally ignore this stuff because it quickly gets very complicated.  I can make up some numbers for you which would be reasonable-- but so can you.

[Chas / Aug Posekany]

I'd just add about a .4 material glow to everything.

(just kidding)