Iray lighting suggestions and tips

Comments

• AJ2112 Posts: 1,417

  September 2016

  Truth is, lighting techniques vary with every scene, interior, exterior, materials, etc.....  I am certainly no expert, but a method I used to slowly understand lighting is, just practice using a plane and a cube, observe how light react to surface.  I would change cube materials, colors, etc...... a tedious process, but well worth the effort.   
• 3Diva Posts: 12,001

  September 2016

  I usually use an HDRI in combination with this product: http://www.daz3d.com/promo-style-catch-lights-for-iray

  I really enjoy the presets for that light set as it can warm or cool the image depending on which light set you apply to the scene. 
• AllenArt Posts: 7,175

  September 2016 edited September 2016

  I do exactly what you suggested...I use two spots (for rim and key), an emissive plane (for fill) and a very low powered hdri to keep the shadows from being too dark and to add reflections.

  Laurie

  Post edited by AllenArt on September 2016
• DustRider Posts: 2,902

  September 2016 edited September 2016

  Double post 

  Post edited by DustRider on September 2016
• DustRider Posts: 2,902

  September 2016

  I try to light things like a photographer would, or how things are lit for professional videos or movie sets (as others have already noted).

  For example, how would a videographer of an archaeology documentary in Egypt set up for an interview on site in full sun light? They would no doubt have a translucent screen between the subject and the sun to create a diffuse light source. We can do the same in Iray by creating a large distant light or mesh light at the appropriate intensity, or use the Iray sun increasing the sun disk scale and/or decreasing ground shadow intensity. they would also have a diffuse reflector or two to help illuminate the dark areas, and further reduce shadow intensity. Again, we can mimic these techniques by making out own reflectors using proper shaders (controlling the intensity of the light reflected by making the shader material more/less reflective. Or we can add one or two low intensity fill lights in the same place we would add the reflectors, the larger the light, the more diffuse the shadows (spot lights can also work well for this to highlight the area of interest and not anything else).

  Focus on how you would light the same scene in the real world, and forget all ..... well actually most of the tricks you learned for 3Delight. A low intensity HDRI designed for genearal ambient light can be substituted for the reflectors/fill lights.

  Another trick that work well if your just want to use one light is the put your scene in a cube or cylinder, primitive set the scale to a negative number large enough to contain your scene, and give it a reflective surface. This will enable you to use a single light to light the scene (unless of course you have walls). The first image was done in Carrara using this method (only with Carrara I just inverted the normals on a cylinder) and full GI/ray tracing. It is lit with only one light, and no ambient light (for true realistic lighting effects). The second image is for comparison - same setup without the cylinder to reflect light. This can easily be done in Iray as well. However, it's probably much easier to use a good low intensity HDRI if you have one.

  Single light with cylinder for ambient lighting

  

  Single light without cylinder

  
• kyoto kid Posts: 42,048

  September 2016

  ...with photometric lights, I feel like it's a lot of trial and error (which as a former lighting tech in theatre vexes me to no ends).   in 3DL I pretty much could judge how much intensity was needed even before rendering. Like stage lights the 3DL lights (as well as AoA's Advanced lights) had a set minimum and maximum setting.  One adjusted the lighting intensity by percentages to get the right mood for various scenes, just the like 3DL lights work. For different colours one just switched the "gel" (a coloured film that went in front of the light unit) not much different to changing he light colour in Daz. This is why in 3DL I found lighting to be pretty straightforward and rarely had an issue with it.

  Not so with photometric or emissive lights.  Now I need to deal with the complexities of luminous flux and temperature the first that never came up in theatrical lighting and the second was handled by which gel as used. Furthermore the scale for luminous flux seems to be open more ended, no more 40% or 60 %. On top of it  a photo metric spot is no longer just a spotlight but has different shapes now as well as something called beam exponent.  Crikey, if I had to calculate all that for the duration of a thee hour show, I'd be ready for more than a couple pints with the crew down at the pub when it was over.

  Currently I am working on some character proofs using Mec4D's ambient environment and a simple backdrop.  Adding a photometric spot at default value adds nothing to the scene (whereas 3DL lights are set to a default of 100%), so it becomes a process of pick a random value that is higher - test render, pick the next higher random value - test render, and on and on t until it looks the way it should.. When one doesn't have GPU that is capable of handling the render process, this can become a fairly drawn out operation.  

  While I was no professional photographer, I could still hold my own OK pretty well.  I generally used three different film types/ISO settings: 64 (my favourite for outdoor photography because of the rich colour saturation), 100 and 200 (I wish Iray had "film quality" settings like LuxRender does) as those were the most common film ASAs (I also on occasion did shoot at 400 and even 800 but that was for hand held high speed action and available light photography at night). The only digital photography I have ever done is with a smartphone so any discussion relating to that is lost on me.