What available render elements are there?



Tutorial: Setting up and compositing CESSENTIAL render elements


 


  • Two render elements are always present: Beauty and Alpha.

  • Optional elements can be added either via the 3ds Max Render Setup > Render Elements tab, or SCN file (Corona Standalone).

  • Some render elements differ in the standalone and 3ds Max versions of Corona. This article primarily describes the 3ds Max render elements. There is a separate description of the standalone elements.

  • Use render elements wisely, because each one currently increases the RAM usage for rendering. Enabling denoising for each render element additionally increases RAM usage.

  • Some shading-derived render elements will not render when using the “Render only elements” function.


Basic beauty decomposition


These 7 elements represent the standard (but not the only possible) way to compose final image from elements in Corona Renderer: you need to render all elements starting with CESSENTIAL and compose them using the “add” operation in linear color space (i.e. before adding gamma). All of them are only computed when using regular rendering; they will output black when using “Render only elements” mode.


NameDescription
CESSENTIAL_DirectAll diffusely bounced direct illumination (light that bounced exactly once in the scene before hitting camera)
CESSENTIAL_IndirectAll diffusely bounced indirect illumination (light that bounced at least twice in the scene before hitting camera).
CESSENTIAL_ReflectAll light specularly reflected into the camera (both direct and indirect). Includes imperfect and perfectly glossy (mirror) reflections.
CESSENTIAL_RefractAll light refracted into camera (both direct and indirect). Includes imperfect and perfectly glossy (e.g. glass) refractions
CESSENTIAL_TranslucencyAll translucency lighting (both direct and indirect).
CESSENTIAL_EmissionAll light that is emitted directly into the camera, with no bounces (i.e. directly visible lights sources/scene environment)
CESSENTIAL_VolumetricsIt contains the scattering in volumetric media (useful for example for separating clouds and fog)




Geometry render elements


Render elements containing additional geometry information. They can be used for masking, DOF/motion blur simulation, denoising, or visual debugging of the scene.


name Description 
CGeometry_NormalsDotProductOutputs the angle between the surface normal and ray direction (similarly to the Falloff map). White indicates surface directly facing the view; surfaces facing away from the view (grazing angles) are black. This quickly shows how does the scene look without shading.
CGeometry_NormalsGeometryOutputs the surface normal vectors as color values (with transformation RGB = (XYZ+[1,1,1])/2. Uses normals directly calculated from the geometry, with no bump mapping/smoothing groups.
CGeometry_NormalsShadingOutputs the surface normal vectors as color values (with transformation RGB = (XYZ+[1,1,1])/2. Uses the final shading normals from the lighting calculation, which include the effects of bump mapping and smoothing groups.
CGeometry_UvwCoordsOutputs the surface mapping coordinates for selected channel. This can be used to check for mapping discontinuities and objects lacking mapping.
CGeometry_WorldPositionOutputs the surface world position XYZ vector directly as an RGB color.
CGeometry_ZDepthOutputs the z-buffer channel, with adjustable min (white) and max (black) depths.
CGeometry_VelocityStores velocity information of scene objects. Object's motion is mapped into RGB colors. Useful for adding motion blur in post production without the need for re-rendering.




Masking render elements


These render elements are used primarily for masking individual scene elements for postprocessing. They are all rendered even when using “Render elements only” function.


NameDescription
CMasking_IDAssigns a random color to each pixel using one of the available modes. The most important ones are: Primitive ID: each primitive (typically triangle) in a mesh has different color, Material ID: each assigned material has different color, and Instance ID: each scene object has different color.
CMasking_MaskCreates a custom set of rules for including/excluding each object from the mask. The available conditions are material gbuffer ID, object gbuffer ID, and direct object selections
CMasking_WireColorAssigns colors to pixels based on object's 3ds Max wire color (the default color which is assigned to newly created objects). This can be used to generate masks, for example to select specific objects in post production. 




Shading render elements


Various shading-related elements. Some of the require full rendering (not “Render only elements” mode), as indicated in the second column.


Name
 Requires shading 
Description
CShading_BeautyYesAn additional Beauty element, which can be added multiple times to get different versions of the final image:
  • With and without denoising
  • With and without bloom
  • With and without glare
CShading_AlbedoNoShows the albedo (total reflectivity of the surface - the fraction of energy that is reflected in any way from the surface) of the scene surfaces. Scenes with too high albedo can cause problems - washed-out look and excessive render times. This element can be used to quickly spot and fix problems - typically if your walls/floors/ceilings are shown in red, lowering their brightness will speed up rendering. Note: red does not automatically mean bad. Only problem is red on large, diffuse areas, like walls. For more detailed guide, see:What is albedo? How to use it?
CShading_AlphaYesDuplicates the built-in alpha channel, so it can be saved to a separate location.
CShading_ComponentsYesThis versatile render element allows selecting custom subset of lighting components. It can add diffuse, reflect, refract, and translucency lighting, in both direct and indirect (GI) variants. The basic decomposition elements can be recreated using this element (see: this illustration), or it can be used for finer division (e.g. separating reflect direct and indirect lighting).
CShading_RawComponentYesThis shows one component (diffuse, reflect, refract, …) color divided by the corresponding CShading_SourceColor (input texture) value. This results in a “raw” lighting, not containing the surface color/texture.
CShading_ShadowsYesShows the shadows (energy subtracted from the image due to shadow ray occlusion). This is the complement to the beauty element, showing white where there are black shadows. If this element is linearly added to the beauty pass, it negates the visible shadows. Note that currently the shadows from environment lighting are always shown, resulting in a washed-out element in typical interior renders.
CShading_SourceColorNoThe input color of a selected component (diffuse, reflect, refract, …). This is the value read from the texture, clamped to obey energy conservation laws.
CTexmapNoAllows evaluation of an arbitrary texmap on all scene surfaces/environment. For example the AO element can be easily created by adding CoronaAO texmap into this element's map slot.

CShading_BloomGlareYesThis element contains only the Corona's bloom and glare effect (against a black background). It can be used to compose and adjust bloom and glare in post production.
CShading_CausticsYesShows only reflective and refractive caustics coming from the fast caustics solver. It can be used to compose and adjust caustics in post production.
CShading_LightMixYesThis render element is required to show the interactive LightMix in the VFB. It is possible to add multiple elements of this type, however currently (Corona Renderer 4) each one of them will show exactly the same LightMix setup.
CShading_LightSelectYesThis render element is required to show scene lights as adjustable items of the interactive LightMix. It stores information about the specific light(s) included in this element's settings. Saving a LightSelect element will always save the light intensity and color as it is defined in the scene itself, without the LightMix adjustments.




Additional info render elements


These elements can be used to obtain additional information about the rendered image, which is sometimes useful, for example for diagnosing issues.


Name
Description
CInfo_NetworkRenderDebuggingThis element prints the name of the render node it is being rendered on during distributed rendering. It is sometimes useful for debugging (e.g. you can use it to find out which render node produces incorrect results).
CInfo_RenderStampContains only the render stamp. This is useful if you wish to render the Beauty pass without the render stamp, and have access to the statistics printed in the stamp separately.

CInfo_SamplingFocus


Shows how samples are distributed in the image during rendering. Brighter areas mean more samples. Darker areas mean less samples. This element is available only if adaptivity is enabled (it is enabled by default). It updates each time adaptivity is re-calculated (by default every 5 passes).