Advanced Distant Light for DAZ Studio

Contents

An astronaut on the moon holding a US flag. Introduction Important Concepts Quick Start Quick Tips Parameter Settings Known Issues

Introduction

A DAZ Studio render of a hooded figure riding a horse through a Medieval village. The the lights in this scene used primitive hitmode for all surfaces except the horse's main, tail and coat.

The Advanced Distant for DAZ Studio adds new features to extend control over lighting for more creativity and faster rendering.

The main focus of the light's design is aimed at faster shadow calculation. In addition to optimized internal code, you have the ability to use of different shadow quality settings for different surfaces. These features work together to make soft, ray traced shadows faster then ever.

The advanced settings of the light may be a little confusing at first and some features may take a bit of trial and experience before becoming part of a fast workflow. However, the light's dials have been set to defaults which should work well and render faster in most situations right out of the box.


Important Concepts

A render of an anime style character illustrating how shadow samples can be decreased for slow rendering surfaces such as hair.

The base settings of the Advanced Distant Light are very similar to the default DAZ Studio distant light. Settings such as intensity and light color work in the same way you expect from the DS default light.

The greatest benefit of the light is in the lighting control section which allows you to selectively adjust how the light behaves when illuminating different objects or surfaces.

Selective illumination is achieved by instructing the light to look for particular settings on surfaces in the scene. For instance, the light can be told to look for any surface which has a diffuse strength of 99%. If the light finds a surface which matches that criteria it "flags" that surface as one that should be treated in a special way.

The light has a drop-down menu with several options telling the light what to do when it finds surfaces which have been flagged. The light can use lower or higher quality settings for those surfaces, completely ignore those surfaces or illuminate only those surfaces.

Have you ever rendered a scene that went very fast except for one, very slow rendering item, such as transmapped hair? The flagging feature of the Advanced Distant Light allows for faster shadow settings to be used on those troublesome surfaces.

Another common situation is when a little extra illumination is needed for just one surface, such as an additional rim light on hair. Through flagging, you can tell the Advanced Light to only illuminate the hair.


Quick Start

DAZ Studio screen capture showing the advanced distant light being loaded into a scene.

The light can be found in the content folder under Light Presets - Age of Armour - Advanced Distant Light.

Aim the light just like you would a DS default distant light. I find that viewing through the light (In the view menu) is often the easiest method to adjust the direction of the light.

By default, the light has shadows enabled. To disable shadows simply set the shadow strength to 0% or Shadow Samples to 0. The light uses an optimized ray trace function for shadows which, with the proper settings, will render much faster than the ray traced shadows of other DS lights. Mapped shadows are not available in this light.

The most important settings to keep in mind are Hitmode, Shadow Samples, Shading Rate and Max Error. These settings all work in conjunction as speed vs quality throttles.

The higher the Shadow Samples the slower the render but the smoother soft shadows will look. Shading Rate and Max Error work the same way but in the opposite direction, where lower values produce quality results and higher values will render faster.

The remaining settings allow for more advanced customization and control over the light and are explained in detail below.

Take note that the Shadow Samples in DAZ Studio's render settings have no effect on this light. This is intentional, allowing for different lights to have different shadow sample counts for greater control over quality and render speed.

Also note that a Max Ray Trace Depth of 1 or higher, in the DS render settings, is required for shadows.


Quick Tips

General


Parameter Settings

Light Group

An outdoor scene of a crew servicing a mech. Daylight simulated using 1 distant light and one ambient light.

The parameters of the Light group contain settings which are familiar to, and work much the same as, those of standard DAZ Studio Lights.

In this group you can adjust the light's color, intensity and whether it should cast specular, diffuse or both.

One parameter that may look unfamiliar is the __category text field. This setting can be largely ignored at this time. It is included for forward compatibility of future, special purpose shaders.

Shadow Group

A comparative chart of renders illustrating the effects of various shadow sample and irradiance shading rate settings. Click here for a larger image.

The parameters in the Shadow group adjust the appearance and quality of ray traced shadows.

There are several speed enhancements, such as adaptive sampling and primitive hitmode. These enhancements may not look good in all situations.

Fortunately, because of the advanced control of the light, you can selectively illuminate different objects with different shadow settings or different lights. This allows for the speed enhancements to be turned off for onlt surfaces where higher quality settings are needed yet keep the fast rendering optimizations for surfaces where the enhancements will have no negative effect.

A comparative chart of renders illustrating the effects of various shadow sample and irradiance shading rate settings.

It is important to note that shadows are calculated by shooting rays from the surface toward the light rather than the other way around. Because of this, the shadow settings for flagged surfaces will effect the shadows that those surfaces receive... not the shadows they cast.

When you use Alternate Samples settings on a surface, for instance hair, remember that the light will use lower samples only for the shadows which the hair receives or casts onto itself. The shadows which the hair casts onto other objects will use the higher Shadow Samples setting (unless those surfaces are also flagged to use the Alternate Samples setting.

That may sound counter intuitive but it is simply how RenderMan shading works. Shadows are calculated at points on the surface, comparing their positions to the light source, and casting shadow rays to see if something is blocking the path between the surface and the light.

Although it may not seem that there would be a much of an improvement for a transmapped surface to lower the samples it receives rather than lowering the samples of the shadows it casts, it does in fact, greatly reduce rendering times.

An illustration showing the basic concept of raytracing and occlusion based shadows.

Lighting Control

3d fashion portrait render using 3 lights. Each light uses different quality settings to speed up the processing.

The features available under the Lighting Control group allow you to set how the light behaves for different surfaces and objects. This is where I feel the benefits of the Advanced Distant Light really shine.

The light examines all the shaders in the scene and looks for certain settings or "flags." The light can then, at your discretion, adjust the lighting differently for the flagged surfaces.

The light can be told to use lower shadow samples for flagged surfaces, illuminate them at different strengths or even completely ignore those surfaces. It is also simple to have the light only illuminate surfaces which have been flagged. This allows for different surfaces to be illuminated by different lights for ultimate control of your lighting.


Known Issues

Very Rare Conditions - The Advanced Distant Light will see and respect the Occlusion Shading Rate and Override settings of the UberSurface shader in all cases except when Ubersurface's Occlusion Shading Rate is set to exactly 4. All other Occlusion Shading Rate settings will function properly. This was simply a limitation that had to be incorporated in order to allow for greater overall light flexibility.

Only when using volumetric atmosphere All functions of the light work well with volumes (many of the images in this user guide were rendered from my atmospheric cameras) with the exception of when the light is set to have different intensities for flagged surfaces such as using the Set Light Strength with Surface Ambient Strength feature. This is likely to cause artifacts surrounding the lower intensity surface. The issue is a difficult one to resolve due to how atmospheric volumes work. I continue to test new light and volume codes in the hopes of finding a fix.

Somewhat Common - At the time of this writing, all surface shaders will be properly illuminated by the Advanced Distant Light but flags can only be read from surfaces which use the DS Default shader, UberSurface, pwSurface, pwCatch, HumanSurface, SimpleSurface and the AoA Subsurface Shader. I'm experimenting with some DAZ Studio scripting which may allow shaders created in Shader Mixer to be updated and allow for proper flagging.

When using copy and paste - After using CTL+C and CTL+V to copy the settings from a default DS light and pasting those settings onto an Advanced Light, if the Advanced Light is then turned off, using the eye icon in the Scene tab, you may not be able to turn the light back on again. This bug is perplexing and I have not yet been able to track down the cause.


Top Introduction Important Concepts Quick Start Parameter Settings

RenderMan (R) is a registered trademark of Pixar.