Reflection Guidelines

Reflections in a studio setting

A user was having problems with reflections with studio lighting, se we created some examples for him:

The tree like reflections you see in your surfaces are from our default studio lighting. This lighting model filters the sky through a forest which creates a nice shading effect. However, for smppth, reflective surfaces you can see too much of the trees

Here is a similar model I rendered with the studio lighting:

Original rendering


There are a few ways you can change this. Here I changed to default lighting to exterior sun, then turned off the sun so that all you gete is lighting from the sky

Automatic Sky

No sun.png


GLossy Reflection

Here I left the forest on, but changed the materials to be glossy - which smooths out the highlights.



Blurry Reflection

Here I left the forest on, but set the sharpness of the materials down to 0.20 so that the reflections would be smoothed out. For this blurry reflection effect you need to use more rendering passes


Here is the result after 22 passes


Here is the result after 100 passes


Bright sun and Highlighting

This is a model where the bright sun shining on the floor was making highlight in the cabinets which were too intense.


Although the highlights are too intense, the image may be fairly realistic.
(Bright sun can produce a lot of glare - especially here in Colorado in the Winter)

  1. This is the Walnut-medium gloss nXt .ArMaterial. If we were to use the low gloss version from the library, there would be less highlighting of the light on the cabinet.
  2. The sun is reflecting from the floor. If we made the floor less reflective, then less sun would reflect from it.
  3. The sun may be too bright and it is shining directly onto the floor. We could lower the intensity of the sun.
  4. The ambient light is set to the default of medium, if we were to raise the ambient light to high, it may cause less reflection from the sun.
  5. You could set the reflective bounces to 1 rather tha 3. This might eliminate the bounces from the floor to the cabinet.
  6. You could set the cabinet to be glossy.

For this next image I:

  1. Use the low gloss material
  2. Made the floor 25% rather than 50% refelctive
  3. Lowered the intensity of the sun. (Sin, sky and cloudiness all at .33)
  4. Set ambient light to High

Here is the result after 20 passes:


The problem with trying 4 ideas at once, is that you are not sure which one worked best. The result of all 4 changes may be a bit too subdued.

This next image was created with all the original settings, except for the use of the low gloss material.


Here is the effect, with the original settings, of making the material use glossy reflection whic spreads out the highlighting.


Reflection Settings

Reflection Settings are used by nXt when it calculates reflections. The default settings are the best choice for most materials. However there are times when another choice might offer better performance, converge faster, or produce fewer artifacts in the process.

Many of the settings deal specifically with how artificial light sources are reflected in a material. There are two fundamental algorithms used by nXt to calculate these reflections. The first is a “ray casting” algorithm and the second is a “highlight” algorithm. These two algorithms are mathematically equivalent and will eventually produce identical results.

Reflection Settings used in IRender nXt are:

  • Balanced. (default) This is the default shader and is the correct choice for most situations. nXt automatically balances the two algorithms based on the Sharpness of the reflection.
  • Glossy. This shader increases the blurriness of the reflection and prevents ray-casting entirely. No object or light reflections are calculated. Use this shader to increase performance and prevent artifacts for materials with very blurry reflections. Some reflective subtlety may be lost.
  • No Light Source Reflections. This shader excludes ray-casted reflections of light sources. This is sometimes useful in preventing “speckle” artifacts if your material is blurry and your scene contains small, bright, light sources.
  • Monte Carlo. Only raycasting is used to calculate reflections of light sources. The raycasting occurs in an initially very noisy way, and gradually converges to the correct solution. It is most useful when the surface is not too blurry. Both convergence and frame rate may slow when using this option.

See also: Blurry Reflection

Percentage reflection

A user sent me a model in which he couldn't see any reflection in the swimming pool. He had clouds turned on and was also using a water material.

I discovered that you need to set reflection higher on a surface which has a material.

Here is an image of reflection with just colored water.


(The reflection is 0%, 10%, 20%, ..., 90% as you move from left to right)

As you can see the reflection becomes visible at about 40%

I then added the SketchUp "sparkling water" material to the water. You can see that you need higher reflection settings to see the reflection of the fence in the water.


Now the reflection is visible at 50%, but not really what you would expect until you get to 60% or 70%

So: Plan to set reflection higher on textured surfaces.

See also