This is because Corona AO can only work during the rendering, and using it as a mask for Corona Scatter would require it to work before the rendering is started.

If you have encountered any of the issues listed below, there is no need to report it to us.

For bugs and limitations related to volumetric FX (Phoenix FD, FumeFX, CoronaVolumeGrid, CoronaVolumeMtl): see this separate article.

Known Bugs Problems Light transport issues These issues are some of the most commonly encountered by the users, yet they are extremely hard to fix for our development team.

Such properties include, but are not limited to: Refractive materials with disabled caustics Objects which do not cast shadows Lights with emit light option disabled Sometimes black highlights or other artifacts may appear on objects with reflection glossiness level lower than 1.

Example cases: Black highlights: - Black reflection of sunlight may be visible on materials with glossiness lower than 1, if sunlight is passing through a Corona Light material with emit light option disabled: Correct result - the plane uses a Corona Light material with emit light option enabled: Incorrect result - the plane uses a Corona Light material with emit light option disabled: - Lights may produce incorrect results (for example will be visible in reflections as dark spots) if they are behind objects with cast shadows object property disabled: Correct result - the blue plane casts shadows: Incorrect result - the blue plane has cast shadows property disabled: - Reflections of lights may appear dark under specific conditions (e.g.

Correct result - the light is visible directly, in reflections, and in refractions.

Appearance of refractive materials changes when reflection glossiness other than 1 is used (even if its set to 0,999).

The workaround here is to enable caustics for the refractive material.

Transparent materials seen through global volume material (volumetric fog) may look incorrect.

Solution: increase Enviro distance value in DevelopmentExperimental Stuff rollout ( 3ds Max C4D ).

Displacement SSS only taken into account with Base Material of CoronalayeredMtl Displacement and Subsurface ScatteringVolumetric Scattering is only taken into account when used from the base material layer of CoronaLayeredMtl, otherwise, the effect will be ignored.

Material Library Undo history (moving, scaling, rotating, changing properties, etc) is cleared after dragging and dropping a material from the library onto any scene object in the viewport.

Using the undo icon or pressing CtrlZ will only undo the most recent action, which is assigning the material to the object.

This is a 3ds Max issue, and it appears in the native material editor as well.

An example report about it from 2008 can be found on the Autodesk forums.

Interactive rendering limitations Resetting the scene or closing 3ds Max during rendering (regular or interactive) may sometimes cause a crash.

This is a 3ds Max limitation, and we do our best to prevent it, however we cannot guarantee 100 stability.

Selection marquee and region selection frame may be invisible when using IR.

Velocity render element cannot be previewed in the interactive rendering VFB.

Known limitations and unfinished features 3ds Max Falloff map in ShadowLight mode is not supported: 3ds Max Lock sampling pattern option does not work when using Coronas distributed rendering.

Max MultiSub-Object material is currently not supported when nested inside Blend, Double-sided, and TopBottom materials 3ds Max Particle Motion Blur Map (Particle MBlur) is not supported.

Solution: use Coronas native motion blur with particles - it should not introduce significant speed penalty.

Geometry Motion Blur does not work for geometry with changing topology (changing number of faces, vertices, or normals).

Motion Blur does not work on objects scattered with Corona Scatter.

Corona AO (Ambient Occlusion) map cannot be used in Corona Scatter (for example as a distribution mask).

3Ds Max 2008 Materials Library