[GEM-dev] model bug: ignores normals in obj file

[Claude Heiland-Allen]

Hi,

I was frustratedly trying to get smooth shading to work.  Eventually I
discovered a bug in [model].  It seems on initialisation it forcibly
sets the smooth property (to 0.5, if unset, to a value in [0..1] if
set), which results in a call to glmVertexNormals(), which *overwrites*
the normals read from the .obj file with some calculated from
vertex/face positions.  They can then not be recovered or used.  My
quick hack is below, I didn't test it much.  It might break expected
behaviour for other models that don't specify normals.

Before and after patching modelOBJ.cpp to avoid forcing "smooth":

http://mathr.co.uk/misc/2013-03-26_urchin_torus.png
http://mathr.co.uk/misc/2013-03-26_urchin_torus_smooth.png


Claude


diff --git a/plugins/modelOBJ/modelOBJ.cpp b/plugins/modelOBJ/modelOBJ.cpp
index 4ff9d9e..be79716 100644
--- a/plugins/modelOBJ/modelOBJ.cpp
+++ b/plugins/modelOBJ/modelOBJ.cpp
@@ -63,11 +63,13 @@ bool modelOBJ :: open(const std::string&name, const
gem::Pro

   glmFacetNormals (m_model);

+/*
   gem::Properties props=requestprops;
   if(gem::Properties::UNSET==requestprops.type("smooth")) {
     props.set("smooth", 0.5);
   }
   setProperties(props);
+*/

   glmTexture(m_model, m_textype, 1,1);
   m_rebuild=true;



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