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FAQ
General Questions
Q01: Why do my textures not work?
A: You may have chosen an unsupported image format. YafRay only supports a limited set of texture formats, which are Targa (.tga), Jpeg (.jpg), Radiance (.hdr/.pic) and OpenEXR (.exr).
Take into account that Blender packed textures without a valid path in your hard disk won't work as well, and that you will need to unpack the Blender file first.
Making your own compilations, you should compile with all libraries in place! OpenEXR and Jpeg require additional libraries, as all other non-trivial formats would too.
Q02: Why does blender crash when using the yafray plugin from my own yafray build?
A: Apparently, your blender and YafRay builds were not done with the same compiler(-version). The reason why this doesn't work is that there is no one-and-only C++ ABI (yet) like there is for C, hence different compilers and sometimes even different versions of the same compiler (e.g. gcc 3.3 and gcc >=3.4) are
not binary compatible. So either find out what compiler was used for blender and use a compatible one, or compile both yourself with the same compiler.
Q03: In Blender, why does the Photonlight type not work?
The Photon light source or photons lamp button is not to be confused with any light source. It does not cast any shadow or direct light, it is only used in Caustics calculations and requires being placed or directed where you need the caustic calculation. Photon lamp shoots photons in an area, the photons are used by Yafray as the specialized ray elements only to calculate the caustics on passing through the objects like glass or mirrors, which have the property of reflecting or refracting light. Basically the placement of Photon lamp is to allow the user to optimize the rendering. Caustics is one of the most computation intensive jobs in Ray tracing.
Q04: Layer option for lights doesn't work in Yafray? I missing some options I have to adjust?
No, you're not missing anything, not a bug either, yafray simply does not support the 'layer' option because of its more physical-oriented lighting model.
Q05: I've just downloaded and installed Yafray for Windows (xp). But when I try to run it from Blender it says that it can't find the MSVCR71.dll. What shall I do?
MSVCR71.dll is a runtime library from microsoft MSVC7.1 (who would've guessed...) that comes amongst others with the .NET Runtime. However, you don't really need to download the whole NET runtime, do a google search and download only the dll you need. Place it in system32 folder and everything will run fine.
Q06: What do the "#" mean in Yafray's terminal window?
A '#' means 10 image area blocks of 64x64 have been rendered. Therefore, an image of 640x640 pixels would take 10 "#" to render.
In the Render pass, a dot means that it cannot use the cache and has to take new samples. This will only happen with AA enabled.
Q07: When I try to render it goes throug the parsing text and then when it gets the 'Loading plugin' it just sits there forever and nothing happens.
Be sure you don't have installed several YafRay versions and that you have got installed only the latest one.
Q08: I've heard that YafRay uses its own XML file. How to save XML from Blender. Where is it located? Can I edit XML?
To save a XML file,
XML button in YafRay Render panel must be enabled. In a standard instalation, XML files are saved in a folder called
YBtest, inside the YafRay instalation folder. This file is always given the same name,
YBtest.xml, so you must be aware that a new rendering process could overwrite the previous file located in that folder.
You can tell Blender where to save XML files in:
Window Type > User preferences > File Paths > YFexport
You can edit YafRay XML files with a text editor.
Q09: How is YafRay used as stand-alone?
YafRay, as stand-alone, shall be used in a text terminal, also known as MS-DOS Window by Windows users. Input
yafray in the YafRay executable folder (or the equivalent in your O.S.) and the usage options will be shown.
Besides, depending on your OS, you can create a direct acces to YafRay executable anywhere, in the desktop for instace. Drag and drop XML files onto the direct acces. TGA output will be automatically produced at the same place than the XML file is.
Q10: WTH? YafRay outputs a black image !?
First, you must be sure that YafRay is installed. I'm not kidding, many Blender users asume that YafRay can be used straigh away after a Blender install.
Second, you must pay attention to what the Blender terminal is telling you.
If the terminal windows shows that the rendering process is abrupty interrupted, that could be a problem with the version installed, as explained in
Q02 and
Q07.
If the rendering process is finished, and you were expecting a lighting that otherwise would work in Blender, then It can be related to the differences between Blender and Yafray regarding lighting, as explained in the next question.
Q11: Why does YafRay renders images darker than Blender?
YafRay and Blender use completely different lighting models. Despite the fact that Yafray is well integrated in Blender, YafRay doesn't always mimic Blender behaviour, mainly if YafRay developers consider that a YafRay raytracing approach is more correct than which is used in Blender.
That's particularly true with Arealights for instance.
Apart from more power for lighting, YafRay developers have always recommended the use of Gamma Correction & Exposure settings, which can help to overcome this problem as well.
In real life,
exposure is a combination between two camera settings: how long the shutter stays open and how big the aperture of the camera "pupil" is. In photography, this combination can produce some effects apart from the change in lighting.
In YafRay,
exposure is a non-linear tone mapping setting (it is in fact a curve). The first advice is to set an
exposure value before lighting up the scene, like photographers do with their cameras. This exposure value should be related to the characteristics of the scene. The higher the amount of light, the lower the exposure.
When it is 0, exposure is bypassed. Values between 0.5 and 4 can be used for a well lit indoor for instance. Use higher values for darker indoors and for objects in typical night. Use lower values for outdoors and for objects in full sunlight. YafRay
Exposure setting is based in this paper:
http://freespace.virgin.net/hugo.elias/graphics/x_posure.htm
Gamma correction used in small quantities can help as well, between
1 and
1.5. Higher values will render textures and colours washed out and it is only advisable for the
Linear Workflow case.
Q12: What is a PhotonMap?
Why we need a photon map?
Traditional GI methods (ambient occlusion, path tracing, radiosity) are not optimised for all kind of indirect ilumination, or can't compute some of them at all. That's why different GI solutions provide differents results, and why people are all the time seeking for new GI algorithms. When you change from
Skydome (ambient occlusion) to
Full GI (path tracing), you are in fact using a different
GI algorithms.
For instance, when lighting calculations are made with rays shot from the camera (path tracing), it is difficult for them to eventually find the light sources, using only probabilistic algorithms for bouncing, mainly if light sources are small.
That's why
photon mapping was invented. In this technique, rays are shot from light sources and bounce around using probabilistic algorithms too. But this time it does not matter whether they reach the camera or not, only matters the lighting calculation. The result is a
photon map, which is 'read' by a traditional
path tracing solution, but this time the
path light rays bounce just one time, just to 'see' the
photon map. That's why the
photon mapping tecnique is faster and can provide accurate results in less time.
What is a Photon map?
Photon Mapping technique is a GI algorithm that can compute caustics, indirect illumination and color bleeding. It shoots rays (photons) from the light sources and not from the camera like other algorithms do, like path tracing.
OK, smart guy. That's something that more or less everyone knows. But what is really a photon?
A photon is a ray shot from a light source, that carries a fraction of the light source energy. Photons bounce and interact, but everytime a photon strikes a surface, information about that 'hit' is stored (intersection point, direction, energy, etc.) in a special data structure called
photon map. There are in fact two classification of photons (and two photon maps in fact), one for caustics and another for 'normal' photons (
Depth and
Cdepth).
Yah, but if true we would need trillions of photons for filling the whole scene, would'nt we?
True, but instead of that, we use just a few hundred thousands. The correct appereance of a surface in a given point is estimated by examining photons in the neighborhood (
Radius and
MixCount). That is why we need less photons than in real life.
In fact, Photon Mapping is a two-pass technique. The first pass consists in producing the photonmap, the second is a path tracing pass from the camera, where the information from the photon map is smoothed by an Irrandiance Cache. Caustics photons are directly read in this second pass and not smoothed.
You can see the photonmap aspect when
tune photons button is enabled.
Q13:How should I configure Photons settings?
In this case, and depending on your computer, there coud be different combinations of settings that can work for a given scene, so this time we've gathered some tips about how photon settings work:
- When photons are used, noise is more likely to appear when light sources are small and powerful, such as small emitting objects, small windows and HDRI with light concetrated in small areas.
- When light sources are small, you need more sampling which means more GI Quality.
- Photons give information to the render pass about where the light is coming from. Put photon emitters (area/sphere/point/spotlights) in every light source such as emitting objects and windows. See 'Lighting with Yafray' tutorial for more info on this technique:
http://wiki.yafray.org/bin/view.pl/UserDoc/YafRayLighting
- 'Count' defines the number of photons to shot. While a relatively high number of photons means more precision, less noise, clearer caustics, more natural color bleeding and softer shadows, it means as well more time for render, since there are more photons to look for during the render pass. A few hundred thousands will be enough for a good photon map in almost every situation.
- Area/sphere/point/spotlights work as photon emitters when Ful GI is enabled. Therefore, light samples don't affect the render quality. See question Q34.
- Always leave Arealight and spherelight energy setting at 1 when using photons GI. Control light intensity with 'EmitPwr' in the GI panel. On the other hand, power of the other photons emitters types (point light, spotlight) can be controlled with the Energy slider and in fact the Emitpwr value does not affect them.
- GI power should only be tweaked as last option, too large values break any physical concept, lowering should rarely be necessary unless your materials are way too bright.
- You can also use lower photoncounts by increasing the radius a bit without getting a worse quality. Even 'low'' GI sampling setings can still get you good quality renders with higher radius (a bit like blur for photonlights) and less photons.
- Arealights and spherelights, should always have the same energie value as the emitting object (backgrounds and objects with 'Emit'). For example, if your background has color=(0.2, 0.2, 0.6), then set your arealights, that are set in windows or whatever, to the same value. If you have a lightsource, like a little plane, with full emiter (1) and white color, you can set your arealight to 1. That's more realistic, because an object can't reflext more light than it gets from its environment.
- Sometimes, light leaks are due to non-solid objects, like single-face walls.
- With higher Photons Count and more bounces (Depth) we'll get less noise but it means more render time.
- Larger Radius can help to reduce noise as well. Disadvantages of large radius are less sharpness and detail, problems of over-averaging and less contrast.
Q14: Can I use photon mappping for outdoor scenes?
The problem of outdoors scenes is that many photons can be lost for the photon map calculation. If your background is not actually seen or you can get by with just a plain color, you can encircle your scene with a hemisphere to avoid lost useless photons. Remember that each photon carries a fraction of the light source energy, so you may need more photons than usual in case of several light sources (sunlight, skylight, etc.)
Q15: What's an Irradiance 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. Whereas 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.
Q16: How should I configure cache settings?
The available settings for cache mode are:
- ShadQu: Shadow quality, irradiance samples are increased when close to other objects by following this value. The higher, the more samples will be taken near a shadowing object. The default value 0.9 is good enough for most scenes.
- Prec: Pixel precision. At least one irradiance sample is taken each X pixels of distance. You can imagine a grid of samples (X spaced), that would be the irradiance sample distribution if we had just a plane. A value of 10 is good for high res images (1024x768). At lower resolutions sometimes a lower prec value (8) helps to improve the quality of the image.
- Refinement: YafRay has the ability of refining the shadows once a first result is taken (after the first render pass). This is a threshold value. If we set it to 0.2, light steps of more than 0.2 (intensity) are refined (antialiased) taking more irradiance samples. It's quite similar to the common pixel selective anti-alias but applied to light values all over the scene.
Q17: Can I get YAFRAY to render wireframe?
Yes you can, but using some kind of workaround, since Blender "Wire" button is not currently supported. For example, you can UV-texture an object with alpha version of the UV layout ifself.
Q18: Why do glass and reflections sometimes appear black in YafRay?
If you have several interposed transparent objects, you need more
raydepth to see through all of them. The same happens with reflections that are difficult to reach from the camera angle or if there are many reflective objects in the scene. Increase
raydepth until all black areas have disappeared.
Q19: Where can I find YafRay examples?
There is a compilation of Blender scenes ready to be rendered with YafRay. There are also Wings examples, created by
oort. You can find more information here:
http://www.yafray.org/forum/viewtopic.php?t=1009
Q20: Where can I find examples of animations made with YafRay?
You can still find some YafRay animations in the old YafRay site:
http://old.yafray.org/gallery/index.php
Q21: Is there a good free XML editor for YafRay scenes?
Some people have suggested Notepad++ as a good XML editor:
http://notepad-plus.sourceforge.net/uk/site.htm
Q22: Why don't Blender gradient-type backgrounds work in YafRay? Is there any workaround?
YafRay, as raytracer, doesn't support many bundled Blender 2D effects, like starts, gradient-type backgrounds and postpro toon edge. However, there is a workaround to produce background with gradient effects by XML editting, explained in this post:
http://www.yafray.org/forum/viewtopic.php?p=3898#3898
Q23: I can't get texture maps with alpha channels to work. Is it alphamapping supported?
Alpha mapping is actually supported. In Blender, textures with alpha channel should be mapped as usually, using the "Alpha" texture more ("Map to" panel). In the "Mirror Transp" panel, you should use 'ZTransp' for materials that have texture maps with alpha channels, with the exception that you still have to set
alpha to a low value to get any transparency effect at all in Yafray. A good way is using
Mat.preset, but remember to enable
Ztransp and to low
rayMir value.
Q24: How can I get YafRay to use distance for AO as in Blender?
The "distance" feature is currently supported. You will find more information in YafRay 0.0.8 Release Notes:
http://wiki.yafray.org/bin/view.pl/UserDoc/ReleaseNotes008#USE_BLENDER_AO_SETTINGS_maxdista
Q25: What Does YafRay stand for?
YafRay stands for Yet Another Free Raytracer. Contrarily to what people may think, this name is not that uncommon. There are in fact other raytracing projects with similar names, as YASRT (Yet Another Simple RayTracer, by Emmanuel Viale) and YAR (Yet Another Raytracer, by Ryan Holmes). In hacker jargon, the use of 'Yet Another' as a way of padding out an acronym is fairly common.
If you want to learn more about YafRay history, take a look here:
http://www.blender.org/modules/documentation/htmlI/c12235.html
Q26: Is it possible to make an object into a light source in YafRay?
To make an object into a light source, there are several options to try, such as HDRI texturing, the 'vcol_light' feaure and using an
emit material, respectively explained in:
Q27: Can YafRay render with motion Blur?
Motion Blur is not supported. You can use workarounds for non-supported features, usually by compositing techniques. You can take advantage as well of the upcoming Blender compositing nodes to combine YafRay and Blender renders.
Q28: Is it translucency supported?
YafRay doens't suppor Blender translucency setting. Besides, YafRay doens't support translucency in material shaders. There might be some workaround, as Neil Blevins explain in his page, by using for instace "self illumination to fake translucency on flat objects" (emit), gradient effects and lighting techniques:
http://www.neilblevins.com/cg_education/translucency/translucency.htm
Example of fake translucency using supported Blender "vcol_light" feature, by
Frapl:
For a real translucency effect we would need GI and a better implemented SSS shader, although you might get close using the current SSS implementation in conjunction with other techniques, as mentioned above.
Q29: I'm using YafRay to render my animated short, but when I render, I get some pretty bad flickering of shadows. Is there any way I can get rid of this flickering?
Irradiance cache selects some pixels to calculate and then interpolates them. It works fine for still but makes the shadows flicker in animations. Going "brute force" is the only way to avoid this. In other words, Cache/Photons should be discarded, although you can still use Full GI (pahtlight) and Photon Lamps to get caustic effects in animations. Futhermore, you need to crank up the GI-quality to smoothe out the shadow discrepancies.
Q30: Is there a way to get Yafray to render using an HDRI for lighting and then not display it in the background?
You should use a compositing technique, since this feature is not currently supported.
If you enable 'RGBA' button in the format panel, and save the image in a format that supports an alpha channel (png/ exr/tga/etc) then the background can be masked out using the alpha channel (Format panel, Render Buttons F10). Inside XML files, the key parameter is
save_alpha:
<render camera_name="MAINCAM"
raydepth="5" gamma="1.000000" exposure="0.000000"
AA_passes="0" AA_minsamples="0"
AA_pixelwidth="1.500000" AA_threshold="0.050000"
background_name="world_background"
save_alpha="on" >
<outfile value="c:\Documents and Settings\Alvaro\Escritorio\YBtest.tga" />
</render>
There are other alpha parameters that might be useful in the cases where the anti-aliasing around the objects still can show a hint of the background, setting either one of these might help to remedy that:
- alpha_premultiply - "off","on"
- alpha_maskbackground - "off","on"
They are explained here:
http://www.yafray.org/forum/viewtopic.php?t=61
Q31: I'd like to know if there's actually a way to produce soft shadows with Sunlight and to get rid of these strange looking sharp shadows?
In conjunction with a sunlamp, you can use another kind of lamp at the same position which supports soft shadows, such as sphere light or arealight.
Q32: Does the higher sample rate for YafRay lights affect the shadows?
When they work as light sources, arealight and sphereligh (sphereligh=lamps with radius) samples affects dramatically the quality of shadows, the higher the better, but the more render time as well.
Q33: What is the purpose of emitting objects used in combination with arealights/spherelights?
Area/sphere/point/spotlight (sphereligh=lamps with radius) become pure photon emitters when used with GI using photons, they don't cast light directly anymore. You have to use them with an object with emitting material at the same location to get direct light.
For and arealight, add a plane at the same location, same size, add an emitting material.
For a spherelight, add a uv or ico sphere set it to the same radius (or less) as the light source, also with emmiting material. Control light intensity of all emitting objects with the EmitPwr slider.
Inside the XML files, whether to work as light source or as photon emitter is managed by the dummy tag. OFF means light source, ON means photon emitter:
<light type="arealight" name="LAMP2" dummy="on" power="2.000000" samples="16" psamples="0" >
<a x="8.074930"...
Q34: Then, is it possible to create soft raytraced shadows with GI enabled?
You have to use an emitting object with the arealight/spherelight.
Q35: Where the YafRay XML specification is documented?
There is an (outdated) description of the xml in the old wiki:
http://www.coala.uniovi.es/wiki/index.php/YafrayDoc
(if the server wants to answer you, that is...)
Since the yafray developers announced that the scene description language will change for the new yafray, nobody is currently updating this anymore.
Q36: Where can I find a comprehensive list of YafRay current supported features?
First you should take into account that YafRay, as pure raytracer, doesn't have to support all the Blender internal features, and that there are several YafRay features that are not supported by the Blender-to-Yafray exporter, such as SSS shading, conetracing, SunSky background, etc. You can acces them only by XML editting.
YafRay generic capabilities as stand-alone raytracer:
Which is supported, related to Blender, can be found mainly at two locations. YafRay supported features (0.0.7 release) related to Blender:
YafRay 0.0.8 release notes for Blender users:
Q37: I can' get YafRay Lights to lit through window glasses? Am I missing anything? is there any workaround?
This question is a bit tricky to solve. In closed enviroments, when the only light source is a key light coming in through a glass, as in a windows, you will notice that, while indirect light can pass to the inside, direct light can't get in, no matter if we look from inside or from the outside. There are two solutions for this problem.
The first solution consist in using a photonlight to achieve such a caustic effect with it that it resembles direct light from a key light. The transparent object must have IOR=1. The photonlamp must have the same direction than the Key light. Use 'Blur' and 'Search' to blur the Photon map.
Alternatively, instead of using photons, you can bypass this problem by simply disabling the shadow casting flag of the window glass, which in xml is the object's 'shadow' flag, or if you use Blender, disable the 'traceable' button in the 'Links and Pipeline' panel of the material section.
Q38: Is it edge rendering techniques supported?
YafRay Edge Toon is explained in the 008 Release notes, although it doesn't work the same as in Blender and it works better with spherical shapes and organic modelling:
http://wiki.yafray.org/bin/view.pl/UserDoc/ReleaseNotes008#Toon_Edge
You can still achieve a toon edge more akin to Blender by compositing techniques, as explained by
tone 3D in this post:
http://www.yafray.org/forum/viewtopic.php?p=3155#3155
Q39: How Can I blur YafRay refractions and reflections?
Yafray does both refraction and reflection blur, and it is not just total random sampling but just general stratified sampling.It only is possible with XML editing. About this subject, there is a superb explanation by eehslo in this post:
http://www.yafray.org/forum/viewtopic.php?p=1634#1634
Q40: Are Blender Particles supported?
YafRay does support duplivert objects using particles though, with which you could try to emulate blender particles by parenting billboard planes with some alpha texture. Though this currently doesn't work all that well because of the somewhat unstable alpha mapping in yafray which doesn't always work.
Static particles for hair/fur do work without problems though.
Installation
GNU/Linux
Windows
Mac OSX
Compilation
GNU/Linux
Cleaning your system
First you should make sure YafRay is not installed through your Linux distribution package system, otherwise it could make a little mess if you have several versions installed.
Preparing the system
First of all, you need the
gcc C++ compiler and the
scons scripts. They can be installed through the packaging system of every major Linux distribution.
Having the 'gcc' command does
not suffice, you need
g++, make sure that 'g++ -v' prints you the compiler version!
YafRay's dependencies (libraries that need being installed in order to be able to compile the source code) are:
libc, libgcc, libstdc++,
libjpeg,
libopenexr,
zlib
Note that libc, libgcc and libstdc++ are libraries that should come as dependencies with gcc/g++.
Search your package system for them and also install the
-dev (or
-devel) version (
-dev/-devel are the packages for developers)
Next, we will create a directory for storing the source files. i.e:
$ mkdir yafray-cvs
Now, enter into the new directory
$ cd yafray-cvs
Getting the files
The command to access CVS (Concurrent Versions System) system to get the YafRay files is:
$ cvs -z3 -d:pserver:anonymous@cvs.blender.org:/cvsroot/yafray co yafray
(It is easier having this line in a small shell script, this way you will not need to remember all every time you want to dowload the latest version)
Compiling the source code
And now, we will compile the source code:
$ scons arch=i686
This command will compile the code in an optimized way for computers using a Pentium Pro processor or better. Since YafRay does a lot of calculations, it is highly recommended to do any optimization. If you don't have any of these systems, you should search for the parameters to do an optimized compilation for your computer (another possible parameters are
pentium4 and
athlon-xp. You can see full list
Here). Another In case you don't find it, you could always use scons without the arch parameter to compile the code.
Installing the files
After scons says that everyting is ok, we will install the files into their proper directories (You will need superuser access to do this)
# scons install
WARNING If you used some kind of parameter on scons compilation (i.e
scons arch=i386) you must
repeat it here. Followin the example above, right command for instalation is:
#scons arch=i686 install
In other case, scons will re-compile all stuff without optimizations before start to install it.
Testing the system
At last, we just need to test it (render your best cube
)
In case it doesn't find a file, I would suggest the use of the commands "locate" & "which" to know where is the system searching for the files and see where are really installed. Make your symlinks or correct it any other way.
The problem of those "lost" files is due the default directory intalation, which is done under
/usr/local. It means that executable files will be in
/usr/local/bin and that should be in the enviroment variable
PATH in order to be able to find it.It is the same thing for Yafray's libraries, which are installed under
/usr/local/lib. If our system is unable to find them there, it will need a proper configuration so it can be found. This is often done by adding
/usr/local/lib/ to the file
/etc/ld.so.conf and running (as superuser) the command
ldconfig.
It is possible that there appear some files called
.sconsign under the Yafray library's folder. When it comes to register the libraries (shaders, lights, ...), YafRay will find those files and it will warn us that those are not libraries. It is not something to worry about since they are ignored, but in case you want to get rid of the messages, we could delete those files.
Misc.
Next time we want to update the program to the latest cvs code, just start from point 3 ("Getting the files") and follow the same steps
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