How do I apply maps to a retopologized low poly model?

Question

I have a series of maps created in Substance designer. I wish to apply them to a model. I can apply the maps correctly after uv unwrapping the model.

I need to apply the displacement map directly (without using nodes) to generate a new mesh. This works great using the displace and subdivision surface modifiers, however it leaves me with a very high poly model. I plan on using this in a game, so the poly count needs to be much lower.

I figured I could retopologise the model… but here are my questions:

1. After retopology, how do I apply the other maps to the low poly model? e.g. normal, gloss, colour etc.

2. Surely there is a better way to do this if I have all the maps?

Note: I don’t want to apply the displacement map through the nodes because I want the model to contain the height information. The height information is not very complicated either, it’s mainly a bunch of shapes with gradients (not heaps of little details, as that’s what the normal map contains).

Answer 1

First, you need to do the retopology to create a low-poly model and uv unwrap it. Then bake the maps from the textured high-poly model to the low-poly model. Finally, connect the baked maps to the corresponding slots of the Principled BSDF node in Blender.

Use the Displacement map in the material nodes or use it with a Displace and Subsurf modifiers on the high-poly model (as you did). Then bake the Normal map. This will transfer/fake the details on the low-poly object. (Alternatively, you could bake the depth info of the Displacement map and use the baked image as a Height/Bump map. But quality might be worse.)

Note: Gloss maps are inverted Roughness maps. Use this map with an Invert node in the Roughness slot of the Principled BSDF.

I hope this helps.