![]() ![]() Notice the image on the left is much less converged, Photon Guiding was set to 0.00 while the right image used the glass bounding box information as the Photon Guiding BBox and Photon Guiding set to 0.900. Below are two images, both with 32 samples. This parameter can bias the render (make it incorrect physically) if driven with high values, but for art direction purposes it can greatly improve convergence. The PxrVCM and PxrUPBP integrators also have a Photon Guiding parameter that allows artists to direct where they want to concentrate the photons in the scene. By selectively choosing which lights use Trace Light Paths, the artist can better direct where they want photons and at what intensity. Other times it may come into the path of a very bright light and suddenly there are caustics scattered all over the scene which may be a distraction. In some cases your hero object may not get enough photons as they are scattered around the scene. Tracing photons for caustics can be very expensive and difficult to art direct. Below the dome light is using Trace Light Paths. If using Trace Light Paths on the light, you should combine this with the PxrVCM or PxrUPBP integrators and selectively enable this parameter to generate photons for realistic shadows. The integrator would render a physically correct shadow now, but the PxrPathTracer doesn't generate photons by default and would make this very difficult to resolve using Allow Caustics as seen below. If you were to disable Thin Shadows on the light by selecting Trace Light Paths, and render with the PxrPathTracer, you would see a solid shadow. ![]() You can manipulate the shadow for art direction including shadow color, distance, falloff and gamma (see each light's page for examples). It also obeys the object color such as transparent red glass or maybe green emeralds, etc. This combination produces a quick and somewhat plausible image for transparent/refractive objects. Like the versions of Renderman prior to 21. Beyond the descriptions below, it's important to know that shadow softness is controlled by the size (or apparent size in an HDRI) of the light source. The type of shadowing produced in RenderMan is based on controls in the lights as well as what's available to the integrator. The below guide explains how shadowing works in RenderMan as well as types of shadowing and quality. This is pretty straight forward, but different from how other render engines and 3d packages do it so I’m gonna post a quick how to. Soft shadows from indirect lighting and shadows from objects off-screen can also be pleasing and realistic. Alternatively, right-click on the same button to open more options for assigning properties to an object, and select Apply single shadow catcher to selection. Click the Shadow Catcher button on the V-Ray toolbar while the object is still selected. ![]() Typically users render with the PxrPathTracer Integrator and the default light settings of "Thin Shadow". Blender Shadow catcher with Blender 2.8 & Cycles Evan Coates Select the object, which will become a shadow catcher. Larger light sources create softer shadows. Soft shadows from indirect lighting and shadows from objects off-screen can also be pleasing and realistic. No grading outside of White balancing, only a few lens effects (vignetting. Everything from time of day to how many lights there are can be inferred from shadows. HDRI lighting only for this first test, shadow catcher workflow, 4k rendering. Only one problem I still didn't solved - in my beauty pass of the car alone without the floor plane and environment, the environment is still visible in the windows and it should not be there.Shadows in an image convey a lot of information. If you wanna test it yourself, I attached the whole scene, images, renders and Nuke comp file into one zip in the next post. Yes, it would be nice to have a possibility to see the result of shadows in preview render immediately without need to comping it, like for example RenderMan, V-Ray etc. In Nuke I have two ways how to comp it, (1) first using the shadow material defined in Houdini and (2) second using constant or anything you want. ![]() For my floor plane alias shadows catcher I used a built-in Material Builder, tweaked the shader little bit to be close to the env asphalt. There is no need to use shadow_matte material. One ROP network, inside 3 render nodes - first for shadow pass (with extra pass direct_shadow), second for the beauty pass of the car and third just an environment background. Just using 2 takes, one for separating the shadows under the car, second for the beaty pass of my car. ![]()
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