A Yafray renderelő program honlapján találtuk az alábbi leírást, mely sokféle témát érintve elsősorban a Blender-felhasználóknak szeretne segíteni. 

Világítás:

Pontszerű fényforrás

• If neither Ray Shado nor Buf.shadow are activated.
• If Ray Shado is activated.
• If Buf.shadow is activated.

If neither Ray Shado nor Buf.shadow are activated, YafRay will translate it into a pointlight block.

If Ray Shado is activated, YafRay will actually translate it into a spherelight. The spherelight, when used with photons, should now work better since it now samples from the sphere surface only, so using it with an emmiting object (sphere) at the same position works better, similar to the method used for arealight. Radius button controls sphere light size.


Example of Yafray spherelight used with a emitting sphere:


If Buf.shadow is activated, YafRay will actually translate it into a softlight. Although parameters are similar to the Blender settings, for YafRay both the bias parameter and the shadowbuffersize can be lower than equivalent Blender settings. Remember that 6 shadowmaps are created in this case, so can use quite a bit of memory with large buffer settings.

Glória, fényudvar

Point lights now have a simple glow option, a simple way to make lights visible. The basic effect looks like light in fog.

• 'glow_intensity' controls the intensity and size of the glow, generally very low values (usually less than 0.01) are enough, since it also depends on the light intensity itself.

• 'glow_offset' affects the central highlight of the glow, the higher this is set, the less 'peaked' the glow will be, untill it almost fades out and only a faint foggy effect around the lightsource is left.

• 'glow_type' can be set to two types, though they can look similar, type two is best, but also a bit slower. First type is a simplified own hack, the second type is based on an idea described by Han-Wen Nienhuys in RTNews7v3 (also used in MegaPov).

NOTE: just like spotlight halo's, glow is not visible against the background, there must be another object behind it. The simplest solution is to use a large black shadeless plane behind your scene.

Example of glow option usage. 'Concep 17' by TjGk:

Globális megvilágítás, dómfény

IRRADIANCE CACHE

When Irrandiance Cache is activated, we are in fact using Full Global Illumination (pathlight) but in 'occlusion' mode.

In XML language, pathlight has a new 'mode' parameter, which can be set to 'occlusion', in which case instead of full Global illumination it will sample occlusion only.

<light type="pathlight" name="path_LT" power="3.000000" mode="occlusion"
cache="on" use_QMC="on" threshold="1.000000" cache_size="0.033333" 
shadow_threshold="0.950000" grid="82" search="35" 
ignore_bumpnormals="off" samples="2048" > </light>

The main advantage is the possibility of using an irrandiace cache. An irradiance cache speeds up the time of rendering Global Illumination renders by rendering a pre-pass to determine the best areas of an image to sample. On a large flat surface, for example, it can be assumed that the diffuse lighting will be fairly even so you would need less samples. Wheras in a corner, the lighting will change more drastically, requiring more samples. The irradiance cache tells the final GI render the best places to sample.

Example of irradiance cache:

USE BLENDER AO SETTINGS (maxdistance)

A Blender AO sample is equal to 32 Yafray samples, so 16 Blender AO samples (maximum) is equal to 512 Yafray samples. Notice that Yafray Best Quality is equal to 2048 samples.

Maybe the most interesting Blender AO value that Yafray will take into account will be Distance. Distance sets the length of the Oclussion rays and defines how far away other faces give the oclussion effect.

In XML language, both 'hemilight' and 'pathlight' in 'occlusion' mode have a new parameter 'maxdistance', with which the maximum distance to detect occlusion can be set. This means that like Blender's Ambient Occlusion, it can now be used in interior scenes as well.

This is an example about how Blender AO settings are translated into a Patlight block. Blender AO samples=5 and Blender AO Distance=10. Notice samples and maxdistance tags:

<light type="pathlight" name="path_LT" power="3.000000" mode="occlusion"
   cache="on" use_QMC="on" threshold="1.000000" cache_size="0.033333"
   shadow_threshold="0.100000" grid="82" search="35"
   ignore_bumpnormals="off"
   samples="160" maxdistance="10.000000" >
</light>

BUMPNORMALS (SkyDome and Full GI)

As a temporary fix there is a button 'NoBump', but this also has the side effect that in areas of total indirect light (or when used with SkyDome cache) no bumpmapping will be visible. It is therefor best used with some direct light as well. For SkyDome with cache, and strong bumpmapping it might actually not make much difference, since for low distance values you can usually get away with low sample values as well.

Yafray KÖD.

<render camera_name="MAINCAM"
   raydepth="5" gamma="1.500000" exposure="0.000000"
   AA_passes="4" AA_minsamples="4"
   AA_pixelwidth="1.500000" AA_threshold="0.050000"
   background_name="world_background"
 >
   <fog_density value="0.1" />
   <fog_color r="0.85" g="0.85" b="0.95" />
   <outfile value="c:\Documents and Settings\Alvaro\Escritorio\YBtest.tga" />
</render>

Árnyalás, anyagok

Tükröződések

Again, same as Blender 'rayMir' sets the amount of reflection. Next button 'frsOfs' however controls fresnel offset, meaning that when this is set to 1, you will get no fresnel effect and when set to 5, reflection is totally determined by fresnel, which is important for forrealistic glass/metals/etc.

What is Fresnel?: http://www.hash.com/am2004/Rendering/Fresnel%20Term/Fresnel%20Term.htm

IOR is self-explanatory, same as Blender. When you have 'Ray Transp' enabled, the blender 'filter' button will appear next to the IOR button. This has the same effect as in Blender.

More information about filtering: http://www.blender3d.org/cms/Transparent_Filtering.514.0.html

Absorption Dispersion

      <dispersion_power value="0.800000" />
      <dispersion_samples value="30" />
      <dispersion_jitter value="off" />

If you want scattering on the ground on your scene a photonlight is needed (no photonlight used here)

Absorption is, in short, when a material absorps a certain wavelength of light, letting others pass/reflect. For example, an object that absorbs blue, green and yellow light will appear red when viewed under white light. To get the effect change these variables in you XML scenefile:

      <absorption r="0.000000" g="5.000000" b="7.000000" />

These setting are also available through Blenders interface like so:


Dispersion

• Pwr: Dispersion power, more means more presision - 0=no dispersion
• Samples: Using too little samples will result in objects of a single color, or at least not representing the objects true color. For realistic materials, 25 maximum should be more than enough.
• Jitter: Enables jittering of wavelengths - adds noise.

• DS: Absorpsion distance scale

A much more technical description can be found in the changelog for Yafray 0.0.8: http://projects.blender.org/viewcvs/viewcvs.cgi/yafray/src/shaders/blendershader.cc?cvsroot=yafray

Texture modulation and blending modes

All blending modes are supported as well.

Diffuse and Specular modes

In any case, in practice those differences might not be too noticable at all.

Image texture

<shader type="image" name="IMrembrandt-03.jpg" >
   <attributes>
      <filename value="F:\2006\rembrandt-03.jpg" />
      <interpolate value="none" />
   </attributes>
</shader>

More info about interpolation:
http://www.dpreview.com/learn/?/key=interpolation

HDRI as texture

Utilizing this can make objects illuminate a scene.

Both HDR and OpenEXR images can be applied as normal textures in Blender (and in the XML scenefile):

<shader type="image" name="IMStageEnvLatLong.exr" >
   <attributes>
      <filename value="../StageEnvLatLong.exr" />
      <interpolate value="bilinear" />
   </attributes>
</shader>

Sphere textured with an HDRI-probe.

Sphere textured with an EXR-image:

HDRI as background

Besides, 'Hori' must now be enabled for probes to work.

In YafRay XML language, though still supported for backwards compatability, backgrounds of type 'HDRI' can now completely be replaced by the 'image' type background (see XML in HDRI Prefiltering below). The image background now has the exact same functionality, including the 'exposure_adjust', which replaces the 'power' parameter (still supported but deprecated).

The 'mapping' parameter now also includes 'angular' though it is just another name for 'probe' mapping.

Exposure control is now a floating point value so anything in between 0 1 and 2 will work too.

HDRI Prefiltering

<background type="image" name="world_background" exposure_adjust="0.000000" mapping="probe" >
   <filename value="/hdri/stpeters_probe.hdr" />
   <interpolate value="bilinear" />
   <prefilter value="on"/>   < !-- here! -- >
</background>

Examples of "on/off" prefiltering option:

Clipmode

<shader type="blendermapper" name="MAMaterial.002_map0">
   <attributes>
      <input value="IM060ppr.jpg" />
      ...
      <clipping value="checker" />
      <checker_mode value="odd" />
      <checker_dist value="0.000000" />
      <cropmin_x value="0.000000" />
      <cropmin_y value="0.000000" />
      <cropmax_x value="1.000000" />
      <cropmax_y value="1.000000" />
      <rot90 value="off" />
   </attributes>
</shader>

Procedurals

In XML language, besides the existing procedural shaders (marble, woods, clouds), there are aswell five new procedural shaders, which are:

• voronoi
• musgrave
• distorted_noise
• gradient
• random_noise

Furthermore, inside every procedural shader, there are at least two new parameters:

• noise_type which controls the noise type, as in Blender.
• shape which controls the kind of wave to produce bands, as in Blender

In the noise_type field you can input the following noisetypes:

"blender", "stdperlin", "newperlin", "voronio_crackle", 
"voronoi_f1", "voronoi_f2", "voronoi_f3", "voronoi_f4", 
"voronoi_f2f1" and "cellnoise"

Shape can now be set to "sin", "saw", and "tri" as in the Blender settings.

Inside the XML file, the order of several shader blocks in order to produce, for instance, a procedural marble material would be:

• First the Procedural shader, where noise_type and shape are defined, apart from other procedural parameters.

<shader type="marble" name="example_procedural" > 
<noise_type value="blender" /> 
<shape value="saw" /> 
... 

• Second, the Blender mapper shader, where the texturing is defined, along with the procedural shader as input.

<shader type="blendermapper" name="example_textura"> 
<input value="example_procedural" /> 
... 

• And finally the Blender shader, where the material final aspect is defined, using the Blender mapper shader as input.

<shader type="blendershader" name="example_material" > 
<input value="example_textura" /> 
...

Kam has written an excellent YAFRay v0.0.8 Procedural Shader Reference, with lots of examples: http://www.geocities.com/kam_b_lai/tutorials/procedural/yashader_ref.htm

Ramps

• 'Result' ramp input mode is not supported at all.
• 'Energy' ramp input mode also won't generally give the same results as in Blender.
• The only ramp shader that will work properly when used with GI is the 'Normal' ramp input mode.
• When ramp is in 'energy' or 'shader' mode and using it with GI enabled, YafRay can only 'see' the underlying material color, not the ramps, which results in a mix of the ramp colors (from direct light) with the material color (from indirect light).
• All blending modes are supported.

Example of YafRay Ramps, by Jendrzych:

In XML language, Yafray Ramps are defined first by colorband shaders, one for each type of Ramps (color and specular), where color and modulators (ramp steps) are defined:

<shader type="colorband" name="MAMaterial_difframp" >
   <attributes>
   </attributes>
   <modulator value="0.000000" >
      <color r="0.000000" g="0.000000" b="0.000000" a="0.000000" />
   </modulator>
   <modulator value="1.000000" >
      <color r="0.000000" g="1.000000" b="1.000000" a="1.000000" />
   </modulator>
</shader>

<shader type="colorband" name="MAMaterial_specramp" >
   <attributes>
   </attributes>
   <modulator value="0.000000" >
      <color r="0.000000" g="0.000000" b="0.000000" a="0.000000" />
   </modulator>
   <modulator value="1.000000" >
      <color r="0.000000" g="1.000000" b="1.000000" a="1.000000" />
   </modulator>
</shader>

Finally there should be a blendershader block, where previous colorband shaders are called, respectively, in diffuse_ramp value and specular_ramp value tags. There are several ramps parameters in the blendershader block as well:

<shader type="blendershader" name="MAMaterial" >
   <attributes>
      <color r="0.800000" g="0.800000" b="0.800000" />
      <specular_color r="1.000000" g="1.000000" b="1.000000" />
      <mirror_color r="1.000000" g="1.000000" b="1.000000" />
      <diffuse_reflect value="0.800000" />
      <specular_amount value="0.500000" />
      <alpha value="1.000000" />
      <emit value="0.000000" />
      <matmodes value="traceable shadow" />
      <diffuse_brdf value="lambert" />
      <specular_brdf value="blender_cooktorr" />
      <hard value="50" />
      <diffuse_ramp value="MAMaterial_difframp" />
      <diffuse_ramp_mode value="shader" />
      <diffuse_ramp_blend value="mix" />
      <diffuse_ramp_factor value="1.000000" />
      <specular_ramp value="MAMaterial_specramp" />
      <specular_ramp_mode value="shader" />
      <specular_ramp_blend value="mix" />
      <specular_ramp_factor value="1.000000" />
   </attributes>
</shader>

Anisotropic models

Subsurface Scattering

<shader type="sss" name="w_ssstest_10">
   <attributes>
      <color r="1.0" g="1.0" b="0.0"/>
      <radius value="1.5"/>
      <samples value="100"/>
   </attributes>
</shader>

<shader type="blendershader" name="MAamarillo" >
   <attributes>
      <color r="1.000000" g="1.000000" b="0.000000" />
      <specular_color r="1.000000" g="1.000000" b="1.000000" />
      <mirror_color r="1.000000" g="1.000000" b="1.000000" />
      <diffuse_reflect value="0.800000" />
      <specular_amount value="0.500000" />
      <alpha value="1.000000" />
      <emit value="0.000000" />
      <matmodes value="traceable shadow" />
      <diffuse_brdf value="lambert" />
      <specular_brdf value="blender_cooktorr" />
      <hard value="50" />
      <environment value="w_ssstest_10" />
   </attributes>
</shader>

Finally, objects to have the SSS look will call the blendershader block in the shader_name tag:

<object name="OBCube" shadow="on"  shader_name="MAamarillo" >
   <attributes>
   </attributes>
   <mesh autosmooth="0.1" has_orco="off" >
      <points>
         <p x="12.030326" y="4.124888" z="3.882569" />
         <p ...

Conetrace block

It must be noted that this isn't an anisotropic shader, nor is it fully correct, it can however produce very good renders.

To get the effect a few steps must be taken:

1. Create your scene and apply a normal reflective material to your object just as you nomally would.

2. Export your scene to XML and open it for editing.

3. Copy/Paste the conetrace block into the XML before the reflective objects shaderblock. (this is essential) Note the name of the conetrace-block.

4. Now find your object material and enter the name of the conetrace-block as an 'environment value' (just before "/attributes")

<environment value="env" />

5. Tweak (look below for explanation) the values of the conetrace-block, save and launch 'yafray scenefile.xml'

XML example of chromeball with conetrace:

<shader type="conetrace" name="env" reflect="on" angle="7" samples="5" IOR="1">
      <attributes>
         <color r="0.5" g="0.5" b="0.5" />
      </attributes>
</shader> 

<shader type="blendershader" name="MAball" >
   <attributes>
      <color r="0.800000" g="0.800000" b="0.800000" />
      <specular_color r="1.000000" g="1.000000" b="1.000000" />
      <mirror_color r="1.000000" g="1.000000" b="1.000000" />
      <diffuse_reflect value="0.800000" />
      <specular_amount value="1.568463" />
      <alpha value="1.000000" />
      <emit value="0.000000" />
      <IOR value="1.000000" />
      <reflect value="on" />
      <reflect_amount value="1.000000" />
      <fresnel_offset value="0.937500" />
      <reflected r="1.000000" g="1.000000" b="1.000000" />
      <min_refle value="0.937500" />
      <matmodes value="traceable shadow" />
      <diffuse_brdf value="lambert" />
      <specular_brdf value="blender_cooktorr" />
      <hard value="249" />
      <environment value="env" />
      
   </attributes>
</shader>

This will render an image similar to this:

Parameters for conetrace:
reflect: 'on' will reflect the ray, 'off' will refract the ray.
angle: determines the distortion/grainyness of the reflection 0 for clear reflections.
samples: samples on the reflection. 0 for none.
IOR: index of refraction. 1 for none.
color: filtering color for incoming light.

Renderelés

Antialiasing

In the Blender GUI, this option is controlled by the 'Clamp RBG' button, in the Render panel, by default on.

Note: 'Auto AA' is no longer enabled automatically for certain GI quality settings, we thought it best to leave it to the user to decide.

DOF (Mélységélesség)

Pressing 'limits' and switching to the 'Yafray DoF' tab shows the clipping distance of the camera and it is this line that helps you set the focal point (notice the yellow cross on the line):

Next option is 'Aperture'. The size of the aperture determines how blurred the out-of-focus objects will be. A rule of thumb is to keep it between .100 and .500.

'Random sampling' does exactly what is says.

'Bokeh' controls the shape of out of focus points when rendering with depth of field enabled. This is mostly visible on very out of focus highlights in the image. There are currently seven types to choose from:

• 'Disk1' is the default, the same as was used before.
• 'Disk2' is similar, but allows you to modify the shape further with the 'bias' parameter (see below).
• When Triangle/Square/Pentagon/Hexagon is choosen, in addition to the bias control, you can offset the rotation with the 'Rotation' parameter (in degrees).
• 'Ring', a weird ring shaped lens, no additional controls.

The 'bias' menu controls the accentuation of the shape. Three types available, uniform, center or edge, with uniform the default.

Notes on using DoF with Yafray: Enabling and using Dof in Yafray requires higher sampling rate to get a nice blurred effect. In the render-settings for Yafray, disable 'Auto AA' and increase the 'AA Samples' and 'AA Passes'. Here is a few examples to demonstrate the effects of DoF:

Much more generic information on 'DoF' and 'Bokeh' can be found on wikipedia.org

Camera modes

In XML language, there are 4 new types of camera, which are "perspective", "ortho", "spherical" and "lightprobe". Both in spherical and in lightprobe mode, view zoom is controlled by the distance between the camera and the objects to render. This is the aspect of a camera block, with the type tag set to "spherical" mode:

<camera name="MAINCAM" type="spherical" resx="480" resy="480"
   focal="1.000000" aspect_ratio="1.000000"
   dof_distance="0.000000" aperture="0.000000" use_qmc="on"
   bokeh_type="disk1" bokeh_bias="uniform" bokeh_rotation="0.000000" >
   <from x="0.000000" y="-10.000000" z="0.000000" />
   <to x="0.000000" y="-9.000000" z="0.000000" />
   <up x="0.000000" y="-10.000000" z="1.000000" />
</camera>

The output of a "spherical" YafRay camera is a 360º view:

The output of a "lightprobe" YafRay camera have the typical round look of the lightprobes you can find on the Internet:

Render output

Yafray also supports exr output. If you want it as simple as possible, then just wait for the next version of Blender, which will support exr, so you can just use F3 to save to exr, just like any other image format that blender supports. Saving an image is totally independent of YafRay. If you want to do it now, by editing the xml, that really is also not very hard at all.

<render camera_name="MAINCAM" 
   raydepth="5" gamma="1.000000" exposure="0.000000" 
   AA_passes="2" AA_minsamples="4" 
   AA_pixelwidth="1.5" AA_threshold="0.05" bias="0.001000" clamp_rgb="on" 
   background_name="world_background" 
 > 
   <outfile value="/home/eeshlo/YFexport/YBtest.tga" /> 
</render>

Now all you need to do to save to the image as an exr file is to add the 'output_type' parameter and set it to 'exr'. It is also helpful to change the extension type of the file as set in the outfile parameter, not really needed, it is still an exr file, but it might be confusing if the file still looks like a .tga file. So for the above example, change YBtest.tga to YBtest.exr. You can add the extra 'output_type' parameter in one of two ways, here is one:

<render camera_name="MAINCAM" 
   raydepth="5" gamma="1.000000" exposure="0.000000" 
   AA_passes="2" AA_minsamples="4" 
   AA_pixelwidth="1.5" AA_threshold="0.05" bias="0.001000" clamp_rgb="on" 
   background_name="world_background" 
 > 
   <output_type value="exr" /> 
   <outfile value="/home/eeshlo/YFexport/YBtest.exr" /> 
</render>

And that really is all that there is to it. Now render the xml file with 'yafray YBtest.xml' or whatever the name of your file is, and you will find the exr in the directory as set by the 'outfile' parameter. Exposure & gamma correction are both bypassed when 'hdr' or 'exr' is the output type. That's it.