Normal baking in cycles is painfully slow

Question

I'm trying to bake the normal map of a saddle.

PC ( AMD Ryzen 3 1200 Quad Core processor, 8GB RAM and a NVIDIA Geforce GTX 1050Ti)

My previous pc which had worse specs, was able to bake normal maps like these within minutes, now it takes a whole night for a single 4k normal to bake, even the 500x500 take 2-3 hours to finish... I have no idea what I am doing wrong, here is the file:

https://drive.google.com/open?id=1yYDFcKy2RYtkv7a1klIU7_kHvAsZzdT4

Answer 1

The file you provided uses 13GB of RAM at its peak when baking, which is obviously more than your entire system has. It is taking a long time because your system is hitting the swap HDD/SSD hard. For comparison, a Ryzen 7 with enough ram can bake the scene in 4 minutes.

You can try to lower the multires level on the highres mesh and see if that helps lower the memory usage.

Alternatively, you can use Blender Render's Bake from Multires function to directly bake the normal map.

1. Transfer the UV map from the low-poly model to the high-poly model, by select the target(hipoly), then the source(lowpoly), then Ctrl+L, and select Transfer UV.
2. Assign an empty image to the high-poly model
3. Switch to Blender Render and select the Hi-poly model (we don't need the low poly model)
4. Bake with 'Bake from Multires' turned on.

This is actually even faster than using Cycles baking, and much less setup.