Crashes and render failures

 I've been unable to render any Geoscatter-based scenes that use TrueSKY 3. I get the following error all the time:

what is an ERROR Illegal address in CUDA queue copy_from_device (integrator_intersect_shadow integrator_queued_shadow_paths_array)

The AI search tells us is

"a technical error message primarily encountered during GPU rendering in Blender's Cycles render engine. It indicates that the graphics card encountered an invalid memory address while transferring data back from the GPU to the system memory (or within GPU memory), which usually points to a bug in the rendering calculations or an unstable system.

The (integrator_intersect_shadow integrator_queued_shadow_paths_array) portion of the message specifies the exact function within the Cycles source code where the error occurred, often related to ray tracing and shadow path calculations."

Potential Causes and Solutions

The error can stem from scene-specific issues, software configuration, or hardware instability. Common fixes include:

Scene Issues (Ray Calculations):
Limit ray travel: The error often happens if a ray of light "travels to infinity" outside the scene boundaries, causing numerical instability or invalid memory indexing.

A common workaround is to place the entire scene inside a large bounding box (like a cube) to contain all light paths.

Check complex shaders/geometry: Specific elements, such as volumes, complex materials (like Principled BSDF with Adaptive Subdivision), or the Vector Displacement node causing NaN (Not a Number) values, can trigger this crash.

Simplify the scene: The issue might be related to running out of GPU memory (VRAM), which can manifest as an "illegal address" error rather than a clear "out of memory" message.

Try reducing texture resolutions or simplifying geometry.

Software and Driver Configuration:Update/Reinstall Drivers:

Ensure you have the latest stable NVIDIA Studio Drivers installed. A clean installation of the drivers after completely uninstalling the old ones can resolve issues caused by corrupted installs or Windows updates.

Use OptiX instead of CUDA: In Blender's preferences (Edit > Preferences > System > Cycles Render Devices), try selecting OptiX instead of CUDA (or vice versa) if your GPU supports it. Using both simultaneously can cause conflicts.

Disable Open Shading Language (OSL): Turning off OSL in the Render settings has been a fix for some users experiencing this specific error.Hardware and System Stability:

Check GPU Overclocking: Any GPU overclocking (e.g., via MSI Afterburner, Dragon Centre) can make the render process unstable. Disable overclocks and run your GPU at stock speeds.

Monitor GPU usage/memory: Avoid running other GPU-intensive applications (like games or browser tabs) while rendering, as this can cause resource conflicts or run you out of memory.


There have been Python crashes too, and warnings about Maximum Number of Closures Exceeded"

The warning "WARNING Maximum number of closures exceeded: 96 > 64" in Blender's Cycles render engine indicates that a material in your scene is too complex to be compiled by the rendering kernel (usually the GPU). The number 64 is a hard-coded internal limit on the number of shader "closures" (functions or components) that a single material can use simultaneously. Your scene is attempting to use 96.

This is a common limitation when using highly complex or nested shader node groups, especially with the Principled BSDF shader or when using Open Shading Language (OSL).

The current situation is complicated by the following factors:

• Blender 5.0 is new and contains known issues to be addressed as part of the ongoing 5.0.1 patch, which should be due any day.
• I have a lot of addons installed. Maybe too many. The compatibility issues between various addons, including Geo-scatter itself, might be the cause.
  
• True-Terrain is due for a significant update, which should reduce the resource cost imposed by its complex node trees.

I tested!
Scene lit by an HDRI rocking a fairly hungry set of scatters. Solid as a rock. The same scene couldn't render when the HDRI was swapped out for TrueSKY3.

In Blender 4.5.5 TrueSky 2.x runs okay with Geo-Scatter.

This is really bad news! Geo-Scatter is my preferred scatter system because it gives you so many ways to place stuff. True-Terrain's built-in scatter system is elegant and has some nice features, but it just doesn't give you as much control. I should have a play with it.

I am tempted to do a Blender refresh and install everything from scratch when Blender 5.0.1 is released, the so-called "Phoenix Protocol". Burn it to the ground and start again.

Switching between the latest and older Blender isn't going to be as straightforward as before because Blender 5.0 changes some fundamental things, although 4.5 is at least compatible with the new file format.