Difference between revisions of "Smoothing Groups"

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= Smoothing Groups =
 
= Smoothing Groups =
3ds Max uses ''Smoothing Groups'' to create hard/soft edges between smooth-shaded polygons, by "breaking" vertex normals along the edges between polygons with different Smoothing Group assignments.
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3ds Max uses ''Smoothing Groups'' to create hard/soft edges between polygons, by splitting/combining [[VertexNormal|vertex normals]]. When neighboring polygons do not share the same Smoothing Group, this creates a hard edge between them.
  
Each vertex in a mesh has at least one ''vertex normal''. Vertex normals are used to control the direction a triangle will be lit from; if the normal is facing the light the triangle will be fully lit, if facing away from the light the triangle won't be lit. When two triangles have different vertex normals along their shared edge, this creates a shading seam, called a ''hard edge'' in most modeling tools. 3ds Max uses ''Smoothing Groups'' to create hard/soft edges, while Maya uses ''Harden Edge'' and ''Soften Edge'' to do the same thing. These tools create hard and soft edges by splitting and combining the vertex normals.  
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Maya uses ''Harden Edge'' and ''Soften Edge'' to do the same thing.  
  
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== UV Shells ==
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To reduce shading errors with tangent-space [[NormalMap|normal maps]], it is best to split the UVs everywhere there are hard edges on the model.
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However, hard edges are not needed for every UV edge. There can be more UV edges than there are hard edges, in fact more UV seams are often necessary to reduce texture warping.
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Hard edges need to be separated in UV space, to allow the [[Normal_Map_Technical_Details#Tangent_Basis|tangent basis]] to twist around appropriately. This creates less extreme gradients in the normal map (which reduces shading errors when using a [[Normal_Map_Technical_Details#Synched_Workflow|non-synched]] renderer), and reduces errors introduced by [[LevelOfDetail|LOD]]s.
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* [http://www.polycount.com/forum/showthread.php?t=107196 You're making me hard. Making sense of hard edges, uvs, normal maps and vertex counts] Polycount Forum thread
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== Smoothing Tools ==
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* [http://www.matthewlichy.com/turboTools.html turboTools] for 3ds Max includes a tool to convert UV shell borders into hard edges.
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* [http://renderhjs.net/textools/ TexTools]  for 3ds Max includes a tool to convert hard edges into UV shell borders. The author also wrote a script to convert UV shell borders into hard edges, see [http://www.polycount.com/forum/showpost.php?p=1105439&postcount=7 3dsmax UVW seams to Smoothing Groups?] Polycount Forum thread.
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* [http://www.scriptspot.com/3ds-max/scripts/edgesmooth EdgeSmooth] for 3ds Max is a tool to convert selected edges into hard edges, acting much like Maya's workflow. However the resulting mesh creates shading errors in some game engines.
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* [http://www.polytools3d.com/polyunwrapper/ PolyUnwrapper] ($) for 3ds Max includes a tool to convert UV shell borders into hard edges.
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== Tutorials ==
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[[image:smoothing_groups.jpg|left|frame|Smoothing Groups tutorial for 3ds max by [http://poopinmymouth.com Ben "poopinmymouth" Mathis].]]<br clear="all" />
  
 
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[[Category:Glossary]] [[Category:TextureTechnique]]
 
[[Category:Glossary]] [[Category:TextureTechnique]]

Latest revision as of 16:20, 1 June 2015

Smoothing Groups

3ds Max uses Smoothing Groups to create hard/soft edges between polygons, by splitting/combining vertex normals. When neighboring polygons do not share the same Smoothing Group, this creates a hard edge between them.

Maya uses Harden Edge and Soften Edge to do the same thing.


UV Shells

To reduce shading errors with tangent-space normal maps, it is best to split the UVs everywhere there are hard edges on the model.

However, hard edges are not needed for every UV edge. There can be more UV edges than there are hard edges, in fact more UV seams are often necessary to reduce texture warping.

Hard edges need to be separated in UV space, to allow the tangent basis to twist around appropriately. This creates less extreme gradients in the normal map (which reduces shading errors when using a non-synched renderer), and reduces errors introduced by LODs.

Smoothing Tools

  • turboTools for 3ds Max includes a tool to convert UV shell borders into hard edges.
  • TexTools for 3ds Max includes a tool to convert hard edges into UV shell borders. The author also wrote a script to convert UV shell borders into hard edges, see 3dsmax UVW seams to Smoothing Groups? Polycount Forum thread.
  • EdgeSmooth for 3ds Max is a tool to convert selected edges into hard edges, acting much like Maya's workflow. However the resulting mesh creates shading errors in some game engines.
  • PolyUnwrapper ($) for 3ds Max includes a tool to convert UV shell borders into hard edges.

Tutorials

Smoothing Groups tutorial for 3ds max by Ben "poopinmymouth" Mathis.


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