Let's see how to bake a Normal Map to transfer the details from a High Poly model to a Low Poly object.
Video Transcript
Hello everyone! A few days ago, I published the final episode of a short introductory series on photogrammetry using Blender, Substance Painter, and Meshroom. In one of the last episodes, I showed how to bake a Normal Map in Substance Painter to transfer the details from a High Poly object to its Low Poly version. In this video tutorial, I'll show you how to do the same thing in Blender.
In a new Blender project, I've imported both the High Poly object and the Low Poly object, keeping them in the same position and orientation.
I select the Low Poly object and, in Edit Mode, I scale it up slightly so that it fully encloses the High Poly version. For more complex shapes, you could also use the Shrinkwrap modifier set to Outside.
The Low Poly object already has its own UV unwrap, which is where the Normal Map we're about to create will be applied. This UV map can be very different from the one on the High Poly geometry, this isn't a problem.
At this point, we need to select the Low Poly object and assign it a Material, if it doesn't already have one. Then, in the Shader Editor, we add a new Image Texture node to that Material, leaving it unconnected for now.
Click New in the Image Texture node to define a new image with your desired name and resolution settings. In my case, I'm calling the image Baked Normal Map and setting the resolution to 2048 by 2048. I'm also disabling the Alpha checkbox, since a transparency channel isn't needed for a Normal Map.
Keep this node selected, because the baking information will be saved directly to this image. That means it's crucial for this node to be active and part of the Low Poly object's material.
To bake, switch to Object Mode, select both the High Poly and the Low Poly objects, making sure that the Low Poly is the active object in the selection.
Now go to the Render tab in the Properties editor, ensure that the render engine is set to Cycles, and scroll down to find the Bake section.
In this section, change the Bake Type to Normal and, further down, enable the Selected to Active option. This tells Blender to bake from the High Poly object, which is part of the selection, to the Low Poly object, which is not only selected but also active.
Click Bake and wait for the process to complete. If you notice artifacts or if details don't transfer well, try increasing the Extrusion value under the Selected to Active section and bake again until you get a good result. When the bake is finished, Blender will let you know that the generated image is still inside the project and hasn't been saved to disk yet.
To save the image to disk, go to the Image menu in the Image Editor. This step is important not just to have a backup copy, but also because it allows you to change the Color Space of the node and avoid errors when applying the texture.
To properly use this image as the Normal Map for the Low Poly object's material, first set its Color Space to Non Color Data. Then add a Normal Map node and connect the image to this new node, which will interpret it correctly as a Normal Map. Finally, connect the output of the Normal Map node to the Normal input of the material.
On screen, I'm showing you a rendering preview of the model, which currently uses the default Base Color and the newly created Normal Map. I've changed the background lighting from an originally a flat color to an HDRI environment texture, to give the object different lighting and highlight its details. As you can see, these details come from the Normal Map itself, and you can adjust their intensity via the Strength parameter of the node.
