The Online POV-Ray Tutorial

Finish Reference

The topics covered in this section are the following Here's the basic test scene used to render the examples. For comparison, this one uses only the default finishes.

All images in this page are links to the scene file that generated them.

Ambient

Them ambient finish controls how much of the color of a surface comes from ambient lighting. Its parameter is a float value in the range 0.0 to 1.0 (typically). Ambient light is light in a scene that comes from no specific source. It's used to adequately model light that bounces off of objects. This light cannot be efficiently modelled by raytracing due to the "backward" nature of tracing rays. POV-Ray cheats by instead just mixing in a little bit of white to every pigment. The ambient value of an object controls how much white is mixed in. The default value is 0.1. A value of 0.0 means that objects that are not directly lighted will be completely black. Low values mean that objects which are not directly lit will retain some of their color. Higher values can make an object appear to glow (although it will not actually emit any light). The images below show basically how ambient lighting works. The first is the default, the second is rendered with ambient 0.6.

For more information about declaring finishes, see the finish section.

Brilliance

Brilliance modifies the behavior of diffuse lighting. Brilliance takes a float parameter which modifies how diffuse light bounces off an object. The default value is 1.0. The way diffuse lighting works is by calculating the angle between the surface and the incoming light ray. The flatter this angle is, the less the surface is illuminated. Higher brilliance values make the light illuminate less at flat angles. This can make the object appear more polished or metallic. Values that are less than one cause the light to illuminate more at low angles, giving the surface a somewhat softer and less smooth feel. The first image below was rendered with the default, the second with brillance 5, and the third with brilliance 0.2.

For more information about declaring finishes, see the finish section.

Crand

Crand can be used to simulate very rough surfaces like concrete and sand which have grainy surfaces. Crand works by randomly darkening pixels of the object to create a grainy shadow effect. Crand takes a float parameter from 0.0 to 1.0. The default is 0.0. Usually you shouldn't need more than very low values (such as 0.1). Higher values result in your objects turning into random pixel messes. Crand has some interesting features which can make it somewhat intractable, though. First off, because it's applied to pixels and not to objects, it looks the same on large objects as on small. It also changes when you change the resolution of the image. Finally, crand is one of the few completely random features in POV-Ray, which means that you should not use crand in animations, unless you want your objects to look like static. Anyway, the first image is again the default, while the second has crand 0.1 thrown in.

For more information about declaring finishes, see the finish section.

Diffuse

The diffuse lighting model is the main way objects are lit. By default most of the coloring of an object comes from diffuse lighting. Diffuse light is basically light that comes from a light source and diffuses in all directions. It illuminates objects by striking them directly. Any object which does not have a direct, unblocked line to a light source will not be lit by diffuse lighting and will have to be lit by other models (ambient, for example). Light that directly lights a surface does so as a function of the angle at which it hits the surface. A surface which has the light source directly overhead will appear brighter than a surface which is lit from a very low angle. This angle effect can be modified to some extent by the brilliance keyword. The diffuse keyword takes a float parameter which expresses how much of an object's color comes from direct (diffuse) lighting. The value can range from 0.0 (no light from light sources) to 1.0 (very well lit). The default value is 0.6. Here are a few sample images for your viewing (and understanding) pleasure. The first is the default, the second has diffuse 0.3, and the third has diffuse 0.9.

For more information on declaring finishes, see the finish section which, conveniently, is next.

Finish

The finish statement is used to define how objects interact with light. Specifying a finish for an object allows you to make the object mirrored, appear polished, appear to glow, or any number of other things (if you're wondering, the above effects can be created through use of reflection, phong or specular, and ambient, respectively). But moving along, the general format for a finish declaration goes something like this 

finish {
   ambient ambient lighting
   brilliance brilliance
   crand crand amount
   diffuse diffuse lighting
   ior index of refraction
   metallic
   phong phong highlighting
   phong_size phong size
   reflection reflected light
   refraction refract toggle
   roughness roughness
   specular specular highlighting
}

All of the parameters for the finish specifiers are float values (except for metallic which takes no parameter). The individual sections have more specific information about each type of finish. But here are some general things to keep in mind.

Finishes can be declared like just about anything else. All the of the example finish images were rendered using delcared finishes. As finishes aren't based on absolute locations, transforming them doesn't make sense.

Ior

This value controls the index of refraction for transparent objects which refract. See refraction.

Metallic

The metallic keyword is a modifier for the phong and specular highlights. It basically means that the highlight on an object should be modified by the object's surface color, and not just determined solely from the color of the light source. Metallic takes no parameter; either it's there or it's not. This keyword will have no effect if there isn't either phong or specular highlighting on an object. See either of those topics for information on highlights. The following sample images will almost undoubtedly explain this better than I have. The first was rendered with phong highlighting without metallic, and the second is with metallic.

For more information on declaring finishes, see the finish section.

Phong

The phong keyword creates a highlight on an object that is the color of the light source. This is done by comparing the angle you're looking at a surface to the angle at which the light is striking the surface. If these angles are opposite and approximately equal, the color of the light is mixed into the color of the object. This highlight is similar to the one created with specular. Typically, phong and specular highlights are not both used on the same object. Phong takes a float parameter which expresses how bright the highlight should be. A value of 1.0 (the max) causes a complete saturation of the light's color at the center of the highlight. Lesser values cause less complete saturations. The size of the highlight can be controlled with the phong_size parameter. These images will show exatly what phong highlights look like. Note that there is no highlight on the box because none of the faces are oriented to reflect the light into the camera.
First image: no highlights, second image: phong 0.9

Note that this finish does not actually make the object relfective. For that, see the reflection keyword.

If you're wondering, this lighting model was named for the person who devised it.

For more information on declaring finishes, see the finish section.

Phong Size

The phong_size parameter is a modifier for the phong finish. It takes a float parameter (greater than zero) which defines how large the phong highlight will be. Typical values range from 1 (pretty dull) to 250 (very shiny). The default is 40. Higher values make the highlight tighter, creating a surface which looks very polished. Low values spread the highlight out a lot and make the surface appear dull. The images below were rendered with "phong_size 40" (default), "phong_size 4", and "phong_size 180", respectively. All have "phong 0.9".

Note that the phong_size parameter is ignored if there isn't a phong finish. This parameter has a similar function to the roughness parameter for specular. For more information on declaring finishes, see the finish section.

Reflection

The reflection finish gives an object a mirrored or partially mirrored surface. This object will then reflect other objects in the scene. This keyword takes a float parameter (between 0 and 1) which describes how much reflected color to mix in. A value of 0 turns off reflection for the object, a value of 1 gives the object a perfectly mirrored surface (almost). To get an absolutely perfect reflector, you also need to specify "ambient 0" and "diffuse 0" in your finish statement. This will turn off all other coloring for the object. Normally you don't need high reflection values on objects that aren't suppose to be mirrors. Even for surfaces that are glass, a reflection value of 0.1 is sufficient to make it look realistic. Another thing to keep in mind about reflecting objects is that they will take longer to render. For every ray that strikes a reflective object, another ray has to be traced to determine what the first surface reflects. This can really add up if you have a lot of reflective objects. If you start having problems with reflective surfaces being rendered as black, try modifying the max_trace_level. But anyway, here's an example of reflection. The first scene has no reflection, the second has reflection 0.3.

Note how even with this small amount of reflectance, the objects appear very reflective. Reflection tends to like quite nice with a some phong or specular thrown in.

For more information on declaring finishes, see the finish section.

Refraction

Refraction only has meaning on objects that have at least a little bit of transparency. Refraction is the bending of light rays as they pass into a more dense or less dense medium. As light does not go through opaque things, they don't refract. Without refraction, transparent objects look like colored air. The refraction keyword takes one of two parameters either 0 (disable refraction) or 1 (enable refraction). It is legal to specify in between values, but the POV-Ray authors strongly recommend against it. In their words,
Values in between will darken the refracted light in ways that do not correspond to any physical property. Many POV-Ray scenes were created with intermediate refraction values before this "bug" was discovered so the "feature" has been maintained. A more appropriate way to reduce the brightness of refracted light is to change the "filter" value in the colors specified in the pigment statement.
You should also be aware that specifying "refraction 1.0" does not make an object transparent. You need to use filter in your pigment to make an object transmit light.

Now, specifying "refraction 1.0" alone does not change the way your object looks. It will still look amazingly like colored air. This is because the default ior (index of refraction) is the same as the surrounding empty space. The index of refraction describes how much light bends when it passes into and out of an object. Ior values are positive, and typically greater than 1.0. Empty space is arbitrarily defined to have "ior 1.0" (the default in POV). You can change the ior of a refracting object with the "ior" keyword. Some examples of indices of refraction are "ior 1.000292" (air) "ior 1.33" (water), and "ior 1.5" (glass).

For the following example images, the filter value of the objects was set to 1.0. The first image has no refraction, the second has "ior 1.5", and the third has "ior 2.0".

For more information on declaring finishes, see the finish section.

Roughness

The roughness parameter controls the size of the highlight produced by the specular keyword. Typical values range from 1.0 (sand paper) to 0.0005 (polished glass). The default roughness is 0.05. High values give very a very soft, very large highlight. Small values give a very small, tight highlight. 0 is a very bad number for roughness. Roughness is to specular as phong_size is to phong. Here are some roughness examples. All use "specular 0.9". The first uses the default roughness, the second uses "roughness 0.75", the third "roughness 0.001".

For more information on declaring finishes, see the finish section.

Specular

The specular finish is similar to phong, but this one is more accurate as far as physical laws are concerned. It produces a highlight on the object where the reflection of the light source would be if the object were reflective. This keyword takes a parameter between 0.0 and 1.0 which describes how much specular highlighting to use on an object. 0.0 (default) creates no highlight, while 1.0 creates a highlight which is completely saturated to the color of the light_source. The size of the highlight can be controlled (to some extent) with the roughness parameter. Here's what specular (0.9) looks like.

For more information on declaring finishes, see the finish section.

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