Troubleshooting and FAQ

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Known Problems


  • LW9.6+: Pressing F9 or F10 will not use most recent Kray settings. You must save scene first or map F9/F10 keys to KrayFrame/KrayAnim commands or use render buttons inside Kray options window.
  • Kray 2.0 RC1: if you get "Cannot acquire 'LW Image list...'" or "Unknown command 'ExtRendererPick'" error when pressing render frame in Kray then you are using wrong Kray.p version with your LightWave. Make sure you use latest LightWave with latest Kray.p version.
  • LW older then 9.6 : : When using "Bounding box", "Vertices" or "Wireframe" view mode in Layout wrong normal vectors are passed to Kray. Solution is to change view mode in Layout. Wrong normal vectors can cause completely black renders and many other problems. Please use "Front Face Wireframe", "Shaded solid" or "Textured" view modes in Layout. This is LW bug and it is fixed in LW 9.6.
  • LW 8.0 only : If you get Cannot access input file 'KRAY.LS' when trying to open Kray options or render, please make a copy of and place it in Programs (where LightWave's executable files are located) and Content folder. This version of LW seek for *.ls files there while loading the scene.
  • After any Kray button is pressed dialog box with Script type 'master' differs from architecture appears. To solve it you can manually add Kray to master plugins (master plugins dialog box in LW) before clicking Kray's buttons or you can install alternative buttons in Lscript.
  • When trying to open Kray Options (or other master plugins) you get Line xxxx,invalid control identifer provided to ctlrefresh(). This is Lightwave Lscript bug in versions prior to 9.6.1. Update your LightWave installation to latest version.

Surface Nodes

Due to limitations in LightWave SDK some nodes that require special render prepass will not work correctly with Kray and will render black.

Rendering Animations

Please remember to keep Passes Steps on FG tab to 1 when rendering animations. If you use 2 or more passes too each frame this will add many new samples which will eventually cause too many samples and rendering will become very slow. In future releases we hope to fix this problem.

Tips for avoiding problems


  • be sure to merge points otherwise you may get "light leaks“
  • use Unify Polygon command to eliminate double geometry. This may produce artifacts when rendering.
  • check for floating points, 2 point polygons, non-planar polys, corrupted or messed up polys, intersecting polys. If you have LWCAD a FixPolygon pass is useful too. Generally speaking, most problems in Kray are caused by messed up models or wrong geometry. Kray is good at "filtering" these but it is better to just stay clean as possible.
  • Check for UVs: remove all not used UVs, remove imported obj/3ds uvs or rebuild them.
  • In each UV, select all polygons and cut them. If some points remain in UV view, select these and use "remove Vmap from vertices", then paste polygons you cut before. UVs should be only on desired geometry.


  • delete each empty layer (i.e. image layers without a map)
  • delete non-used layers (deactivated and 0% ones)
  • In surfaces it's better to use few layers; Kray is highly compatible with Lightwave surfacing but too many layers can give problems
  • remove any shaders


  • Delete unused geometry and so on. The cleaner the scene is, the better.
  • Be sure all lights you use have inverse square falloff and lower ambient to zero. In render global, activate all raytrace tags.

Troubleshooting scenes

Although we do everything we can to track down all the bugs there is simply no way to find them all during development cycle. This is why users feedback is very important to make application more stable.

Whenever you encounter an error during Kray rendering it can be because of several different reasons.

Unexpected exception is often caused because Kray runs out of memory (if the scene is heavy). This can be resolved by lowering Octree depth from the default 20 down to 15 or even 10.

It can also be caused by bad geometry so be sure to check „tips for avoiding problems“ section in the Kray User Manual.

Artifacts like black dots on surfaces are usually caused by a specific surface setting. This can be for example gradient on a channel that Kray interprets wrong. If you get this kind of errors it's best to reset surface to default one by one until you find the surface that is causing the problem.

The same goes for sudden crashes. Try to identify surface/object that is causing it.

Reporting bugs

Bug reports are welcome. Please send all to including Your configuration (especially operating system and LW version), details about the bug and any accompanying LW or OS crash reports. If you are going to attach the scene with Your email (which is best way to report a bug that appears in particular scene) make it as simple as possible. The simpler buggy scene is, the faster bug will be fixed. Scenes will be used for debugging puposes only.

You can also use our forum for reporting bugs.