MODELLING CONCEPTS

 

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The direction a normal is pointing tells blender which is the front and back of a face. Lighting will render incorrectly and the manifold properties of a mesh can be broken if the normals are not pointing in the correct direction. Blender provides easy and reliable tools to manage face normals.

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There is an option to use custom normals across a mesh using split normals but this is considered bad practice. It is often used (mostly incorrectly) in hard surface modelling with booleans and beveling to hide mistakes across the topology. The resulting models are not portable between softwares, deformation and animation become unreliable and unpredictable and shaders will not behave consistently between models.

 

Similar tricks using "data transfers" can also be used to fake shading and hide errors but these are all considered to be bad practice and I will not be covering them in any tutorials.

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In professional modelling, the normals should not deviate from their original calculated position.

 

All normals should point directly out of the face from which they originate. Detail is very often added by using normal maps to fake detail when modelled geometry would be wasteful (as it can be for game models). But these normal maps are there to create detail on top of objects modelled with good topology. they are not used to disguise mistakes in modelling resulting from simplistic modelling techniques such as booleans and bevels. Normals are commonly manipulated during the texturing phase of a model's creation. Not during the modelling phase. 

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Any process which smooths, averages or manipulates normals on a mesh will mean that the model will not be accepted in a professional environment.

 

Blender provides many opportunities to manipulate normals and these are often employed in polygonal modelling to disguise topology errors. Using these techniques is universally avoided in professional modelling as it reduces the portability of a model below the accepted conventions accepted throughout the industry.

 

Normal maps must be provided to migrate between the various softwares involved in any production and as these are resolution dependant, they are not considered a future proof solution.

 

Older versions of software remain in the production pipeline for decades and will often be unable to interpret unusual normal calculations.

 

Many bespoke pieces of software are used and the code scripts and geometry manipulators in lots of 2D and 3D software will not be able to use them.

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The exporters and importers of the various object formats in 3D are wildly different across almost every piece of software. Blander, maya, max, houdini, unreal, unity, substance and every other software you may want to use will have serious, unfixable problems when normals have been tampered with using edge splits and weighted normals. Just don't do it!

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The biggest 3D software library and model distribution service - TurboSquid - will not certify any model for their professional model catalogue unless the normals remain at their calculated averages. This is because studios will not buy or use them.

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Unfortunately Normal manipulation to fix shading problems has become a common practice among learning blender users and this is keeping a lot of modellers at a hobbyist level.

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