Mike Raiford schrieb:
> The following is a minimal scene to reproduce this. It requires a 
> perfect storm of using a micronormal, blurring, and a high amount of 
> dispersion samples to cause POV-Ray to run away with allocating memory.

The memory consumption is alarming even without the dispersion, rising 
as high as 1.6 GB for a 800x600 render on 8 threads.

The reason appears to be a humongous amount of crackle cache data: The 
crackle pattern is only semi-procedural, requiring random values to be 
computed and cached for subsequent queries, with a fixed amount of data 
per unit-cube in crackle pattern coordinate space. Using crackle for 
micronormals is therefore a bad idea: Scaled smaller than the density of 
actual ray-object-intersections computed, it will eventually lead to a 
separate crackle cache entry being created for each and every 
intersection. Memory consumption will then grow with every additional 
ray being traced, which is fatal with e.g. focal blur or dispersion that 
create a huge amount of rays per pixel.

With bumps instead of crackle, memory requirements stay virtually at 
idle level. Given that you can't make out the crackle structure at such 
a scale anyway, that's the way to go. If you need a different 
distribution of "slope probabilities" than the standard bumps pattern 
(e.g. to simulate a basically polished surface with comparatively sparse 
microsopic scratches), you may want to try bumps with a slope_map.

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