3d_modeling:blender:baking_a_normal_map [Instructions]

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====== Baking a normal map ======

The file size of a 3D scan can be large. It can be reduced by removing surface details and faking them instead. A normal map is similar to a texture map, but instead of being rendered in color, it is interpreted by the render engine as surface details that catch the light or cast shadows. 

===== Reduce file size =====
  * Import the 3D file, scale, orient and set origin as needed. After scaling, apply scale (shortcut: ''ctrl + a > Scale'').
  * Perform a [[3d_modeling:blender:clean_up_occipital_3d_scan|general 3D scan cleanup]] if necessary.
  * Save the blender project as the high-resolution version. For example: scallop_hires.blend.
  * Save the same file, but name it as the lowres version. For example: scallop_lowres.blend.
  * Add the remesh modifier
    * Set the ''mode'' to ''smooth''.
    * Set the ''Octree Depth'' to ''8'' and lower the ''Scale'' until you find a good spot between preserving the general shape and vertex count. Depending on the complexity of the object you might need to experiment with a different Octree depth.
    * Apply the modifier.

{{:3d_modeling:blender:normals_01_reduce_collage_arrows.jpg|}}\\
Reducing the file size of the mesh by remeshing the object.

    * In edit mode, recalculate normals. ''Mesh > Normals > Recalculate Outside'' (shortcut: shift + n).

===== UV wrapping =====

A normal map is essentially an image texture wrapped around a 3D model. Images are flat, so we need to define how we will flatten the 3D object in order to create a reference where the texture will go. Look at the model and find lines where we can cut the model in order to flatten it without too much distortion.

  * Since the shell is a simple shape, I can make a single cut that separates both halves of the shell. If you have a more complex shape, more cuts can be made.\\Hint: select the shortest path between vertices with ''ctrl + left mouse button''.
  * Mark the current selection as a seam. ''Edge > Mark Seam'' (shortcut: ''ctrl + e'')

{{:3d_modeling:blender:normals_02_uv_mark_seam_collage_arrows.jpg|}}\\
Marking the current selection as a seam.

  * Select all vertices
  * Unwrap. ''UV > Unwrap'' (shortcut: ''u'')
  * Go to the ''UV Editing'' workspace to see how the unwrap turned out.

{{:3d_modeling:blender:normals_02_uv_unwrap_arrows.jpg|}}\\
Unwrapping the object in the UV editing workspace.

===== Baking normals =====