James Shaw – Blog

Recently Ryan Lintott and I went to a VRay training seminar by the man himself Vladimir Koylazo (one of the makers of VRay) who went through a number of facets of VRay including a step by step way of breaking down your render settings into logical steps to get the best combination of quality and speed. I thought this was just too gooder process not to share so have decided to put together the following tutorial taking people through these steps he explained so VRay will hopefully become less complicated, and so you can better critique what is happening within your scenes.

The real core of this is every scene is different and has different requirements in terms of detail resolution and Global Illumination. There are many settings posted on the web (I have done a few myself) outlining suitable settings for VRay, and much debate over which setting is best. The truth is it changes from scene to scene and although there are definitely some standards you could stick to (we have reasonably successfully in the past years at Squint Opera) if you really want quality shadow detail while remaining at a quick render time, it makes sense to progress through a more analytical approach where you can critique each step of the way.

Below I will go over the most common set up of using Irradiance Map and Light Cache, which is recommended most of the time, and then baked out. Remember for animation Brute force and Light Cache is recommended, by both Vladimir and Francesco Legrenzi (wrote the very excellent resource “VRay: The Complete Guide”)

So here are the steps:

BASIC APPROACH

In order to break up your scene use the following approach:

Set a standard DMC value > Test Light Cache > Test Irradiance Map > Customise detail level in DMC

The scene I am using was made by a colleague Nic Hamilton for testing purposes and has a combination of direct/ bounce light and broad/ fine detail. It can be downloaded here. It is set up in linear space, but don’t press sRGB in the VRay frame buffer as the gamma 2.2 is already baked in within the colour mapping.

NOTES on WHOLE PROCESS

- This process is resolution dependant. These settings are quite high as it is only a 720 res image. Same visual principles apply to bigger images, but expect your values to reduce somewhat.

- Many of the settings I have used here are quite high as it is a simple scene in terms of materials and lighting. More complex lighting and materials will mean increased render times and you will have to compromise further on these render settings.

- This scene uses linear workflow. You might to visit the link here to set up so it looks like mine (ignore the EXR stuff in that tutorial).

- This might be a little complicated for beginner users; but see how you go!

SET A STANDARD DMC VALUE

Initially set the defaults of DMC as in the image below.

The highlighted value links to these 2 under the settings tab where the adaptive amount controls how adaptively the samples will apply over surfaces, i.e. 1 is fully adaptive and will place the samples as wide as it can across large surafces, and 0 will put samples very close to one another and take longer to render. Leave these as they are below:

We will come back later and set this using the colour theshold.

TEST LIGHT CACHE

Next set your primary and secondary bounces to light cache and set subdivs etc and interp samples to the following:

Where we set the subdivs fairly low, the sample size to fairly big (for this test 720 res image) and most importantly the interp samples to 1, so there is no blurring between the samples and we can explicitly see what is going on.

Hit render and you should get something like this:

So what are you looking for? This is the key! See how the samples are quite big? This means they will miss out detail, and light samples will stretch too far across surfaces, and even bleed right through walls (light leaks). So in this instance they are a bit too small. So why, you ask, don’t we set it really small and catch all the detail? Well because of noise. Try setting the sample size to 0.001 and see what it looks like. You can see how this result, even with move subdivs and blurred with the interp samples will create a noisy solution? Try 0.02 and you should get something like this:

This is a fairly good size. It’ll cover most shadow detail in a general way, apart from maybe the shadows on the rear wall, but any smaller and we might introduce more noise. Figure out the compromise.

Now let’s up the subdivs. Each time VRay sends out a “ray” from the camera it hits a surface and makes a sphere of the sample size and subdivides that sphere into a number of ray calculations; the more subdivisions the better quality the solution as it is calculating more samples. See it as also checking out it’s neighbours colouring and then using that to colour itself.

Up the subdivs in 500 increments up to 2000 and see what you get. See the difference in smoothing of the samples colours and the corresponding render times going up? Again pick where you think is good, but 2000 is pretty OK so far.

Now try changing the light cache from “screen” to “world” and change the sample size to 0.2m (keeping 200 subdivs). You should get the following result:

See how I am now getting more samples on the back wall, as it is now dividing up the samples into 0.2 metre samples. For this scene this might be a better solution as I don’t have much in the background, it’s an interior scene, and it also might bring out some shadow detail in the pool at the back of the image.

Now we have this solution, save it out so we don’t have to calculate it when testing other things and save a huge amount of render time. Do this by hitting “save” and save as say LC:

Then change this to

Just remember to change it back to single frame if you change any of the light cache settings or move the camera. The only exception to this is the interp samples.

Interp samples essentially blurs this solution. So you can change this after you’ve saved out as above. Change it to about 40, or whatever looks good. Remember this does come at slight cost, the more you blur it the more you lose shadow detail. Again it’s up to you to decide.

NOTES on LIGHT CACHE

- The other thing to consider is the difference between light cache “screen” and “world”. As Vladimir said “world” is good for interior type scenes with little background detail, but is bad for massive exterior scenes as the light cache will try and sample hundreds of objects into say 0.1m (whatever you set the sample size to) in the background. This will give a noisy result and take a long time.

- Number of passes refers to the number of cores you have, and VRay will use this to send individual calculations to. Set it to the maximum number. So if you have 8 cores, then 8, or if you have hyperthreading enabled set this to 16 (like I have done). If you’re using a render farm, set it to their maximum. A simple way to tell is open task manager and click on the performance tab and see how many cpu meters you have (goto view> CPU history> one graph per CPU to see).

TEST IRRADIANCE MAP

Now change the primary to irradiance map and keep the secondary as light cache, still loading the pre-calculated map as above with 40 interp samples.

Also change the irradiance map from a preset of high initially, then to custom, and change the values like the image below. Remember set the interp samples to 1 so we can see what’s happening with the samples:

Changing the “max rate” to the same as the “min rate” lets us have a look at where the min rate is putting samples. Do a render and you should get something like this, with a blackened image with obvious white samples across the image:

Now down the max and min rates to -4 and see what happens. See how the samples move further apart? You are basically telling the irradiance map to, on areas that it can be fully adaptive, use that spacing as the minimum. Now up the max rate to -1, keeping the min rate at -4 and you should get this:

Now what are we looking for? Well now that we’ve put the max rate up, see how it’s putting samples around the areas of detail? (detail is defined by pixel contrast or threshold difference in colours) So what we want to see is it putting samples on areas of shadow/ GI detail that we want. i.e. at the bottom of chair legs, on window surrounds or perhaps grout detail on the floors.

Now try min -3 and max 0. This looks pretty good, as seen below, as I now have a good number of samples around areas I want to see shadow detail, like the bottom of the chairs, grout lines, and the samples in the open areas I’ve brought together to get a nice even spread. Look at the difference between render times as well; still acceptable at 35 seconds.

Now let’s look at what happens when we change the value “clr thresh” in the next column of numbers. This stands for colour threshhold, and tells VRay how finely to look for contrasts in colour between pixels. So at 0.1 (show as 1st image below) it will look at extremely fine/ small contrast between colours in pixels and sample up to it’s maximum rate there. You can see this is too fine, as it’s plastered the whole image with samples, and will cost us a lot of time in rendering and cause noise.

A value of 0.9 is the 2nd image. At the opposite end of the scale it is looking for high contrast of colours in pixels to put it’s samples, and is not very sensitive. You can see how it picks out major details, but detail is lost in the areas between details, or there is not very good blending between fine and course details in shadows.

Let’s stick with a value of 0.3 (default), as this is usually a good compromise, and seems to be putting the samples where we want them. Leave “nrm thresh” and “dist thresh” alone. Vladimir admitted these are kind of unnecessary levels of control.

Now turn “show samples” off, and change the “HSph subdivs” to 20. This stands for hemispherical subdivisions, and relates to (again) the rays sent out by the camera hitting and then subdividing into a number of rays off a surface. The higher the number the more rays are sent out and the higher quality the sample. So this is to do with the quality of the irradiance sample.  Hit render and we get something like this:

Now try 50:

Now try 100:

What are we looking for? Well render time vs noise. The 1st was 20 secs, 2nd 30 secs and 3rd 75 secs. The 1st will probably cause a noisy result, even if we blur (interp amount) it, so clearly this is unsuitable. At 50 the samples look like a fairly even spread of colour and there are a few blothes, but these will probably even out. 100 isn’t massively better than 50, and comes with a huge cost in render time, so somewhere around 50 looks likely.

Compromises again! You decide on render time vs quality; but now you know what to look for and how to change it.

Now save out like you did with the light cache, but name it IR:

Then change the interp samples to 20 (default). More will cost you in render time, and like light cache will blur the solution more and more and might lose you some shadow detail.

So this is our final image. It’s got good shadow/ GI detail around the chair legs on the floor and good depth throughout. Perhaps the only thing that is noticeable is the noise from the sun on the back wall. This is to do with the light quality though (and related to size multiplier) and we can get rid of this by increasing the subdivs on the sun to 16. Give it a go.

Now we have a solution to our GI.

NOTES on IRRADIANCE MAP

- This will probably be quite a high quality result (slow to render possibly for drafts), so these would be our production settings. But now we can go back to the adaptive DMC and use the colour threshold to control our quality and render time overall in the next step.

- You can use this method in animation by incrementally saving the irradiance map and light cache to files every, say 10 frames, rather than sending out single passes (use “fly-through” for light cache and “multi-frame incremental” for irradiance map). This will eliminate flicker and save you massive amounts of render time. As long as nothing moves within the scene this is the best way.

Customise detail level in DMC

The last part of this tutorial is how to set detail levels in terms of antialiasing, and use the DMC colour threshold as a global slider for quality.

If you click back into your Adaptive DMC settings you locked it using the DMC sampler. Now you could keep this as is and adjust the noise and adaptive amount in the settings tab, but you can essentially do a similiar job with the colour threshold:

So start by unticking the box above and change the “Clr thresh” to 0.1.

Also go into your render elements and add the following VRaySampleRate so you can see what is happening with the samples while also looking at your image:

Now in the VRay frame buffer you can view either the RGB image (beauty pass) or the Sample rate by changing this. We’ll be clicking backwards and forwards in this to see the relation between the samples and the quality of the image:

So now hit render using the settings above and you should get something that looks like this:

What you’re seeing in the VRaySampleRate is where it is putting samples to do the antialiasing. The lighter the blue the more samples it is putting in place. You can see this is super quick to render, so great for telling what is happening in the image overall for a draft, but we need to up the quality.

Now try a value of 0.01 in the colour threshold:

You can see there are more samples now, and the image is fairly clean. This is pretty much the default values we had before. But to get more detail in the foreground chairs we might need more samples. Put the max subdivs up to 6 and see what happens. We get something like this:

So if we keep on turning this max subdivs up then you’ll find it won’t make much of a difference to the samples. This is because the colour threshold is capping it off at a certain value. It will get to a certain quality and decide “that’s good enough” and within the colour contrast threshold between pixels.

Change the colour threshold to 0.001 and you’ll get a result like below. We can see that now it is picking up detail across the flat surfaces, and if we had a high resolution and more complex materials you would find this would make a huge difference to render times, but it would be able to pick out this type of super fine detail. So in theory we could run the max subdivs pretty high and just use this colour threshold as like a global slider of quality that slides between the min and max values.

This comes with a WARNING though! These are VERY sensitive values. Look extremely carefully at the visible quality vs render time. If the max rate is too high it might spend too long on some extremely fine details that you’ll never see. Run this as low as you can, and then you can run your colour threshold at a lower (high quality) setting. Open up these renders and have a look at the render times. The difference between the 2 above is 12 and 46 secs! And that is with little, or no visible difference, so be sensible and er on the side of speed otherwise you’ll be waiting forever for renders.

I found with this scene that 6 for the max subdivs and 0.008 for the colour threshold was about right. All compromises considered.

As well as the original movie that we were all wowed by (found here http://vimeo.com/7809605 or here http://www.jamesshaw.co.nz/blog/?p=285 with teasers), by Jorge Seva, aka Alex Roman I found some of the making off which have some interesting shot breakdowns including compositing below and the 2nd, more interestingly, the original sourcing, modeling, texturing, lighting and finals etc on his Kahn’s Exeter short film.

Very interesting stuff. I love the comments online that he must be doing something amazing technically, and am pleased to see he likes to keep things simple. So less about the technicality of it all and more on the artistry. The approach of visualization as a photographer is one I can relate to, but one that is all to often forgotten in archviz work.

Compositing Breakdown (T&S) from Alex Roman on Vimeo.

Exeter Shot — Making Of from Alex Roman on Vimeo.

Granted this is an existing building he visualizes so easier to identify compositions that work, as these are the ones that have already been photographed by professional photographers. Often it is hard given a sketch by architects to visualize where the good compositions might lie.

We have some great debates at work whether this type of work is creative given it is an existing space and it is a facsimile of what already exists, or whether creativity lies in visualizing the non-built to this level. Is it a technical exercise in bringing archviz work in line with photography? Many architectural colleagues I have shown it to fail to see the point with the comment “why wouldn’t you just go there and photograph it?”, which is a good point. The technical brilliance is lost on them.

To this end there is a really interesting aspect of CG work evolving that we will see juxtaposed over the coming years (although has run through many creative industries over many centuries). Creativity and technical brilliance working hand in hand, and splitting of some awards in this manner (Avatar and 2012 spring to mind; dubious stories, but awarded technical marvels). I’m going to sit on the fence on this one as I can see valid points for either side. Needless to say I find Alex Roman’s work inspiring on a number of fronts, which is surely a part of artistry in itself?

Many people have had problems getting the sound to work through their HDMI cable when connected into a TV after installing Windows 7. I had the same problem and looked at a multitude of sources including windows forums, Sony’s driver and support pages and found no drivers that worked. I even talked to Sony support and they advised me to downgrade to Vista again so they could troubleshoot with me. Not going to happen Sony!

Ironically, in installing a multitude of drivers I ended up un-installing the SigmaTel High Definition Audio driver and then found upon clicking on the increase sound icon in the tray Windows 7 discovered I had a driver issue problem, or audio driver missing. It then proceeded to install a default Windows 7 audio driver (High definition Audio Driver, Driver version: 6.1.7600.16385) and hey presto now through the sound settings HDMI was no longer greyed out and I was able to set it as default. Now the HDMI cable supports audio and video into the TV.

I hope this helps other people with the same frustrating problem!

For any of you out there with a Sony Viao VGN-FZ11S looking to install windows 7, it is possible and here are a few tips! All the links below will point to the Sony Europe website as this model is not available in the US apparently.

64 or 32bit?

First of all you will have the option of installing 64 or 32bit versions. Upon contacting Sony they told me this particular motherboard only supports 2GB of RAM. So you may as well install the 32bit version as there are more drivers available and with only 2GB of RAM at your disposal it kind of defeats the purpose of installing 64bit (i.e. to utilise more than 3-4GB of RAM).

Install Disc

The installation process is easy, just pop in the 32bit disc and run. I chose a custom install for a fresh install, simply because I don’t trust window’s supposed ability to keep all my old files intact from Vista. Install as usual otherwise.

NVidia Driver

This laptop comes with a Geforce NVidia 8400M GT graphics card. Basically don’t bother to go to the NVidia website as their driver for this graphics card will not work in conjunction with the Sony Viao hardware. Instead got to the Sony update and download the latest graphics driver from there. You can click on this link to go straight there…

http://support.vaio.sony.eu/computing/vaio/downloads/info/info.aspx?l=en_GB&url=VAIO/Updates/EP0000185336.exe&m=VGN-FZ11S&ip=EP0000185336.htm

Sony Viao Updates

If you also want to re-activate Sony Viao’s updater this can be found on the following link. It’s up to you whether to install this, but the Viao’s seem to have some customized stuff that might be useful.

http://support.vaio.sony.eu/computing/vaio/downloads/info/info.aspx?l=en_GB&url=VAIO/Updates/EP0000211610.exe&m=VGN-FZ11S&ip=EP0000211610.htm

For a full list of updates check the main page of this section, which also has a link to windows 7 updates specifically.

http://support.vaio.sony.eu/computing/vaio/downloads/updates/index.aspx?l=en_GB&m=VGN-FZ11S

Hope that helps. Enjoy Windows 7… anything’s got to be better than Vista!

Autodesk in their infinite wisdom have changed the “select by name” dialog box to a “new and improved” version that is incredibly frustrating to use.

If you want to change this back to the original select by name dialog box then follow the following steps:

1. Turn off hide hidden files in windows explorer (tools> folder options> view> show hidden folders)
2. Go here:
   C:\Documents and Settings\yourusername\Local Settings\Application Data\Autodesk\3dsmax\2009 – 64bit\enu\defaults\MAX\CurrentDefaults.ini
   and change:
   [Scene Explorer]
   SelectByNameUsesSceneExplorer=1
   to
   [Scene Explorer]
   SelectByNameUsesSceneExplorer=0

And now you should have the standard selection dialog box like before! Enjoy.

Here is a tutorial on how to make grass within Max, based of Peter Guthrie’s excellent example (www.peterguthrie.net/blog/2009/03/vray-grass-tutorial-part-1/), but taking it a little further and applying this idea in bulk with Max’s built in tools.

The basic work flow is to model a very simple grass blade, make a cluster of grass and scatter across any object. Here is a example we (www.squintopera.com)used this technique in to give you an idea of the finished effect; www.jamesshaw.co.nz/#/content/Film/Cairo.flv/

Here is a couple of base CG beauty passes to give you an idea of the raw result before any post work has been done on it;

MAKING GRASS STRANDS

As previously mentioned this is based off Peter Guthrie’s tutorial with a few variations or notes to expand on this idea.

Firstly make a plane with 1 segment across and several in the length direction. Then add a length-ways UVW mapping, taper and using an edit mesh above this with soft select on vertex warp to a shape you like or several variations you can make into a group.

MATERIALS

Collapse the stack into an edit mesh. Then rotate the 4 strands into different directions by selecting and rotating the different elements. Then randomly set 4 id’s for them. This is so you can subtly change the colour with a colour correction within you multi-sub material.

Then make a multi-sub object material with 4 vray materials.

And within each multi sub make a VRay2SidedMtl like the following. You can also use the following grass textures by clicking on them and right click and save image. There’s a black and white one that you can use as an option for the translucency channel. But you can just leave this blank if the grass is at a distance and leave it grey.

The VRay2SidedMtl really is one of the most important things to use to get the light illuminating through the blades. Otherwise your grass will tend to look very flat.

Inside this VRay2SidedMtl sits a pretty simple vray material with the above grass blade in the diffuse channel (thank you Peter Guthrie for originally making this), with reflect set to white and Fresnel checked so it doesn’t look like chrome. Then adjust the Hilight glossiness to 0.6 which will help to spread the specular light you get off the grass. Again this is another very important part to make the grass look convincing. And unlike Refl. glossiness it will not be costly in render time and look almost identical, especially at typical grass distance.

To get variation in the grass tone change the bitmap diffuse channel to “Colour Correction” with the grass blade jpeg as the map, then shift the hue and saturation as follows differently for each of the 4 material id’s.

MAKING AN AREA OF GRASS

Now you have your clump of grass you can use this to populate surface. I found using individual strands was difficult, as the scatter we will use only really does up to around 70,000 instances before becoming a bit unstable. So if you use a clump of grass then you can spread further with less. Other options of scattering grass include pFlow and vray scatter; which I’ll go over later.

So now make a plane or use splines to create a free form extruded shape, or even detach a polygon from a surface to make a start. Remember when you extrude though to extrude 0 amount and only cap one end otherwise the grass will go underground as well. Also watch with way your normals go.

To make a scatter object of grass do the following:

• Make a compound object (on the create tab) with the grass selected and choose scatter.
• Then pick the plane as the distribution object.
• Change the duplicates to 1000
• Distribute using area
• Change rotation to 360 in the Z to mix up the direction. You can just limit this to 180 or 90 to simulate wind in a particular direction depending on the way your grass clump faces.
• Change scaling to 25% for all XYZ to give some variation
• Show Mesh with 100% to see exactly what will render, and when happy with the result change this to 10% and proxy to speed up your viewport.

Now you have a grass patch. The following is an example of how you can change the grass size on the sub-object scale and even add other simple plane flowers etc to add detail (click on it to enlarge). You can even mix grasses and flowers by using the same distribution object. Simple and no money spent… apart from Max of course.

ALTERNATIVES TO SCATTER

There are other ways of distributing grass. Peter Guthrie mentions the excellent VRay Scatter (www.rendering.ru/index.php/plugins/vrayscatter/), which has the advantage of varying colours more randomly then a multi-sub will do, and also varies the scale by a greyscale bitmap. The scatter method above has no method like this for varying and blending heights. The only problem is it’s a bit buggy (as if Max isn’t!), and it costs.

You could also use PFlow. I’ve had a quick go with this, but haven’t managed to vary the scale by a bitmap yet like VRay Scatter will do, just done density by material.

You will need a group of different grasses and some type of mesh as a distribution object. And obviously create a PF source and click on Particle View to get the following image.

Here’s how you might do this…

• Birth 3000
• Add a Position object, and add distribution object and you can use a greyscale image on a standard material to drive the density of the plants. You will have to view this standard material in a shaded viewport then activate. Weird I know.
• Rotation random horizontal, divergence at 180 and tick restrict diverg. to axis Z (1.0)
• Add Shape Instance and pick the group and tick “group members”. Scale variation 50%, and if animated tick animated shape and offset the timing by random 7 frames or whatever suits your animation.

Hope that may help someone out there! Enjoy.

Here is a useful script that does similiar to netstumbler for identifying other wireless connections around yours. This is useful to know to look for channel conflicts, if you’re having issues with wireless network performance and speed.

Type this into a dos prompt to get a list:
netsh wlan show networks mode=bssid
(originally from this site: http://marcusoh.blogspot.com/2007/01/misc-netstumbler-in-vista.html)

 And if you want more information on slow network performance this is a good site http://networking.nitecruzr.net/2005/10/wifi-will-never-be-as-fast-as-ethernet.html

There are many ways of using a Vray physical camera, but it is sometimes confusing which settings to use especially with f stop, shutter speed and ISO and what they do. Below I have attempted to clarify what each does and some basic values for each after initially setting up a datum point for your lighting, which always helps in keeping your exposure settings fairly consistent between shots.

1. SET A DATUM POINT FOR YOUR LIGHTS

Having a datum point for lighting is always a good idea, especially when sharing files as lighting setups can then be shared from one file to another. So you could either set your HDRI for your GI environment to a multiplier of 1 (This should make the sun around 0.015 for it’s multiplier) and calibrate everything to that or our preferred method which is to set the vray sun to a multiplier of 1. We’ve found the GI spread to be more robust with the sun set to 1, and most of the Vray camera settings come close to real world figures which does help get ball park figures matching things like your background plates, if you have them.

Of course the only problem with changing the sun multiplier to 1, is it changes all your (GI & Reflection) maps to about multiplier 30, i.e. they just appear white within the material browser, and you can’t render through the viewports; only through a vray camera.

2. VRAY CAMERA SETUP

So a solution is to change your exposure through your vray camera using the following outlined settings.

First of all identify what you want to do through your Vray camera, and this will affect how to put in these values highlighted in orange above. I’ve made a table below that might help adjust these values a bit more logically depending on what you want the Vray camera to do on the right.

.

These values don’t always relate to real world camera settings of course but it helps to at least place them in these real world ranges especially with f stop ranges that in real life range from about 2.6-36 depending on your lens. Motion blur also mimics reality with 1/50 (or 50) giving a fairly decent motion blur just like you’d expect with a real camera.

Rendering times also increase with motion blur and 3D depth of field depending on the number of subdivs as highlighted in orange above. The lower number you can get away with the better for rendering times, but the blur will become more noisy.

ALTERNATIVES

There are a few notes in relation to the above, many of which depends what you do in post-production. Because motion blur and 3D depth blur increase render times, it can become more desirable to do these in post instead to save time. In these cases you would use the f stop for exposure only. The only thing I haven’t listed below is vignetting which of course can be done quite easily in post-production so can be left off for that stage.

MOTION BLUR

So the 1st option is for motion blur. Through most compositing programs, like Fusion and Nuke, they will have a 2D motion blur which is average at best although there is a great plugin called realsmart motion blur which does a great job for things like panning shots etc. But this might not work on faster moving objects within scenes, so for this you can output a separate render element called a velocity pass that can easily be used in compositing programs to blur some pixels more than others depending on the rendering element’s velocity, which it colours differently through the RGB channels.

Remember also motion blur won’t work through the usual camera settings as in the dialog below. This can only be done through motion blur on the vray camera or the options above.

3D DEPTH BLUR

Also under your render elements you can output is something called z-depth. Measure your scene’s maximum depth and put this in the max field under the render elements dialog when z-depth is selected. This will render you a black and white mask where white is foreground and black is background. You can then use this through compositing programs to blur the black bits, but not the white bits and of course varying degrees in between. Hey presto, cheap depth blur.

The only problem is extreme foreground elements where you will find it’ll blur these edges too much and you get a soft edge around these foreground objects. This is because it should be blurring what is behind the object, but obviously this won’t work because it hasn’t got this information. A solution to this is rendering extreme foreground objects separately and blurring them as a separate pass in post-production, or if you can spare the render time do it in 3D.

I hope the above helps, any questions let me know below and I’ll try and answer.

As a continuation of experiments with linear work flow and now EXR rendering output I have put together a more extended version as there are a lot of settings to get right.

I have collected the settings below without much explanation as there are plenty of explanations on the web that will do a better job than I. The purpose of this is to get you up to speed quickly with both with settings we’ve found work fairly well.

Bear in mind your renders may appear less contrasty than usual due to the more efficient spread of light within the scene. Don’t worry about this as it will give you increased flexibility in post-production (Photoshop, Fusion, Shake, After Effects etc) to adjust with S curves or contrast adjustment.

SETUP OF LINEAR WORK FLOW

Firstly calibrate your screen with Gamma 2.2 and 6500K.

In 3DSmax click on Customize> Preferences and click on the Gamma and LUT tab. Change the following to 2.2:

Then under render scene dialog under the vray tab>colour mapping change the following:

LINEAR PREVIEW AND EXR

You must then use the built in vray frame buffer rather than the standard render window to view the results otherwise you will not see the product of using linear work flow.

Again go to the render scenes dialog box and open the frame buffer tab. Tick use built in frame buffer and render to raw image file.

If you browse it will automatically put in a vrimg extension; change this manually to exr, otherwise you have to batch process them; which is silly when you can change it here.

Any render elements you have selected will now be contained within this EXR file, you do not need to output seperate render channels (except if you want tga copies).

So from now on you do not need to use the standard “save as” under the common tab, just work through the vray frame buffer tab to save files.

Please watch out however that if you send off a network render or continue after doing test renders you must uncheck the “render to vray raw…” otherwise it will overwrite this without giving you any warning.

VIEWING EXR FORMAT

If you output exr files with multiple render elements such as lighting shadow, GI zdepth etc you will be able to open them in programs like Shake and Fusion just fine. They are also 32bit images so will contain huge range that allows you to adjust exposure etc on the fly. Incredibly flexible!

Photoshop and After Effects however you will need ProEXR (www.fnordware.com/ProEXR/). The standard openEXR format in Photoshop will not bring the passes in correctly so will have to rename this to .BACKUP or something Photoshop will not understand so the proEXR plugin is used instead. See image below:

The location and extensions are shown below: There are also a number of shortcuts that will arrange the layers differently and cut alpha channels in certain ways as found in the ProEXR manual (www.fnordware.com/ProEXR/ProEXR_Manual.pdf)

So in understanding this linear workflow for Max and VRay I borrowed a scene off Nic Hamilton and set about finding what the differences are. If you follow the previous posts instructions found here www.gijsdezwart.nl/tutorials.php they will give the basic setup overview.

Essentally you…

- calibrate your screen to 2.2gamma 6500K
- set the preferences>Gamma and LUT tab in max to enable Gamma correction and under diaply check “Gamma” putting in 2.2 and under Bitmap files input Gamma also to 2.2.
- In the render dialog> vray tab> colour mapping tab, change the gamma also to 2.2.

So here’s some results with a standard setup 1.0 gamma and the above turned on to 2.2 gamma or linear workflow enabled. The vray camera is set to expose both exactly the same, i.e. no settings altered.

Standard workflow 1.0 Gamma external sunlight

Linear Workflow 2.2 Gamma external sunlight

So this started me thinking, well can’t I just use the levels in Photoshop to brighten the standard image and not worry about this linear workflow? I got the following result:

Standard workflow 1.0 Gamma external sunlight with levels in Photoshop

Notice the blotchiness of the GI (global illumination)? Then look at the highlights, see how they’re now blooming out to past white? And compared with the LWF example there seems to be a lot less range in the tones through the shadows, or the lights do not seem to push as far as in standard.

Now you could crank all the lights up to compensate but the problem with doing that is the highlights will just become more washed out. I always did wonder why when inserting an interior light I would get a massive pop of light on the geometry around the light itself but then get minimal spread out from that. This LWF seems to fix that.

So here are some more tests with interior lights and no external source (sun)

Standard workflow 1.0 Gamma interior lights

Linear Workflow 2.2 Gamma interior lights

When boosted in Photoshop this has the same effect as the sunlight model.

So I hope that spreads some light on it, so to speak. I like the result personally, and might work with this linear work flow in the future to achieve more tonal range out of the shadows and GI. There seems to be a lot of banter and conflicting information on the Chaos forums etc, but little people outputting simple tests.

The only thing that is a bit annoying is your material slots will appear brighter. And I’m sure there are some other things, but that’s for future posts. I am by no means an expert having played with this for half a day, so visit the Chaos forums if you need more info www.chaosgroup.com/forums/vbulletin/