How can I use a vrscene file to directly estimate the approximate amount of memory required? without rendering. for VRay-cpu
I don’t think so. You could start a render, look at the VFB stats, and cancel it though.
The maths to find that out is difficult: some things will depend on resolution (f.e. any dynamic tessellation, like displacement or hair), some on feature settings (f.e. motion blur and number of geometric snapshots), others on intrinsic data (f.e. the number of attributes on mesh vertices, like color and uv channels, but not limited to those.).
You’d have to parse the scene with such a fine comb that it’d take you considerable time to complete, and you still may have missed something (f.e. imagine estimating the number of displaced triangles with complex mapping and adaptive displacement…).
It’s *somewhat* doable in theory (I wrote one for a car company a million years ago. It usually underestimated. Often badly enough to be useless.), but in practice it’s much better to launch the render and save out the stats (which we didn’t have back then!).
Besides the way to do it, is there a specific issue that you’re trying to solve through memory usage estimation? There are ways around RAM usage in V-Ray.