client: render: gl_studio_init: added proper handling of null normals…

… in studiomodels

client/render/gl_studio_init.cpp

@@ -1249,6 +1249,19 @@ void CStudioModelRenderer :: SetupSubmodelVerts( const mstudiomodel_t *pSubModel
 				m_arrayxvert[m_nNumArrayVerts].vertex = pstudioverts[ptricmds[0]];
 				m_arrayxvert[m_nNumArrayVerts].normal = pstudionorms[ptricmds[1]];
 
+				// replace null normals with random ones, because null normals causes NaNs in vertex shader
+				// after normalizing. therefore we should avoid null normals in studiomodels
+				// TODO: warn about null normals in studiomodel on loading stage
+				if (m_arrayxvert[m_nNumArrayVerts].normal.Length() < 0.1f) 
+				{
+					vec3_t randomDirection = vec3_t(
+						RANDOM_FLOAT(-1.0f, 1.0f), 
+						RANDOM_FLOAT(-1.0f, 1.0f), 
+						RANDOM_FLOAT(-1.0f, 1.0f)
+					);
+					m_arrayxvert[m_nNumArrayVerts].normal = randomDirection.Normalize();
+				}
+
 				if( m_iTBNState == TBNSTATE_GENERATE || use_fan_sequence )
 				{
 					// transformed vertices to build TBN