How to do...

Dondec

Hi everyone.  I am a reasonably competent Carrara user giving DS 4.9 IRay a first try.  There are a couple things  I hope exist in DS but can’t seem to find:

1.       How to shade or lighten dark skin:  In Carrara if a figure comes in too dark or red for my scene lighting, I can go into the figure’s Shader and Add, Subtract or Multiply another color to the base color.  Is there a way to do that in DS Iray?  I’ve already played around with all the IRay Top Coats and Emissive settings with marginal results.  I'm thinking about going into Photoshop to adjust the base figure skin mats?  Seems extreme.

2.        Is it possible to create render-layers and object masks in DS: In Carrara I can, in a single batch render, create multiple Photoshop layers for such things as: Base render, Diffuse only, Specular only, GI lighting, Reflections only etc.  Incredibly useful for post  work.  I don't think those are available in IRay, but the most important of these is Carrara’s Photoshop “Index” Channel, an Alpha Channel like B/W layer you can use with PS’s Wand tool to select (and create a clipping mask for) any individual figure, object or article of clothing.   Anything like that in DS?

3.       Batch Render: is there any way to queue up several Iray jobs and let them run, one after the other, overnight?

Thanks in advance

-          Don

Steven-V

1. Skin color is very complex in Iray. They've also done some things in the latest iteration that makes many skins seem to look darker if you take all the defaults from a 4.8 or earlier figure.  There are many ways to tweak this.  One option is to use the scatter/transmit settings, under Base/Diffuse...  Play with Translucency Weight, Translucency Color, and SSS reflectance tint.  Additionally you can turn scatter and transmit off and make it just scatter... this loses some skin realism and translucency but definitely lightens it up, especially with G2 figures converted from DS to Iray shaders.

2. I used to do render layers using 3DeLight, but Iray is unbiased lighting so it CANNOT do specular only, diffuse only, reflections only... unbiased lighting is designed to mimic as closely as possible the real world's physics, and it is not physically possible in the real world to turn off the reflection of an object when you make a photograph, or to have only specular lighting.  There is no such thing in the real world, so there is generally no such thing in Iray.  So the old tricks from biased rendering like having one light source produce shadows and one not produce them, you just cannot do in Iray with turning stuff on and off. All ights act as they physically would in the real world, and you must get used to that. You are doing the equivalent of real-world photography and lighting in Iray and the quicker you get next to that idea, the more easily you will adjust. Now you can certainly still do layers but the idea of setting up lighting schemes for each thing - diffuse, reflective, shadows, etc -- is just not something you want or need for Iray.  You should be able to set lights up so you do a single render and it looks good.

3. I have no idea if you can batch render with Iray but because of (2) above, there should be little need to do this for a single shot, since you don't need to make multiple renders of the same scene in most cases with Iray. Set all your lights up the right way and you should be able to do it all in one render.

Now, for 2 and 3, I am NOT saying you will never need to render something several times or do any postwork with Iray. Of course you will. But it will be more in the manner of how you would do it with a photographic camera. You do not take shots with a camera using diffuse film, specular film, reflectance film, and shadow film and then composite them all in photoshop. You take shots with different exposures or lighting conditions (that have ALL those elements - diffuse, spec, etc) and then composite those.

With Iray, you're better off setting up your lighting and playing with individual lights and tone maps, rather than playing with diffuse, specular, type of shadow, shadow intensity, etc -- since you can't control those things anyway, at least not with the UI. You control them with real-world physics. So if you want weaker shadows coming from your spotloight, you have to put a light back thee to illuminate that section of the shot correctly and weaken/cancel out the shadow... rather than turning the shadows off for that light.

Dondec

Thx Steven-V, I certainly appreciate the time spend and expertise in your answer.

So the Shader Mixer stuff I see tuts about on YouTube are 3Delight things I guess.  I can't hack a skin shader in there for IRay.  Ok, I'll try those other strategies you mentioned.

The loss of the various render layers is understandable, given your explanation.  I guess the biggest loss to me then is the rendered Index Channel, the one that allows you to select a single object from a picture using the PS Wand tool.  Of course this can be done a great deal more slowly by hand.  I'm starting to understand there are trade-offs when you go with IRay.

Your example about softening a shadow using an extra spotlight really hammers home the change in thinking required.

   - Don 

SpottedKitty

Dondec said:

Your example about softening a shadow using an extra spotlight really hammers home the change in thinking required.

Another option is right there in the light controls — with one of your lights selected, go to the Parameters tab and click on "Light". In the middle of the parameters that appear is a "Light Geometry" setting, with size controls. This lets you change the light from a point source to a shape, which will automatically soften any shadows cast by that light.

One unobvious gotcha to keep in mind; the "Intensity" control at the top should be ignored if you're using Iray, instead use the "Luminous Flux" to set the amount of light, and a combination of "Color" and "Temperature" to set the light's colour.

Dondec

Great tips SpottedKitty.  TY

   - Don

prixat

Iray has 'Canvasses' for the render layers function.

MaxHancock

And you can change the spread (soften) the edge of a shadow by changing the size of the light sphere.  

 

 

 

Dondec

Prixat dropped a hint about using "canvasses".  Searching the forun I found this link to SnowSultan's Tutorial about them.  They seem to be, though haven't tried, a method to manually ID (name) objects and render just those, with Alpha.  SnowSultan showed an example where a plane was used to cast a shadow, without the plane actually being rendered.  Interesting.  Not exactly the 2D postwork masking trick I was hoping for, but its something.  Here's the link to the tut

http://dazstudio-iray.deviantart.com/art/Iray-Canvas-Tutorial-565641976

   - Don

 

Dondec

Thanks MaxHancock.  Another great tip.

    - Don

Steven-V

Just another comment... other than Distant lights, most Iray lights, like real world lights, weaken over distance using physical rules. So a spotlight put 3' from the subject will give much more illumnation than one put 9' away, etc.  In addition to things being different by changing the size/shape of the light.

I also recommend you experiment with HDRI. Iray can produce some veyr pretty results with HDRI maps.