partial solution to run-time environment configuration :

- add bool OsdGLDrawContext::SupportsAdaptiveTessellation() method
- modify glViewer to use that instead of #ifdefs

Note : this is not the final word on this as OSD really needs a more comprehensive
system to provide run-time information about available features to the client code.

fixes #111

examples/glViewer/viewer.cpp

@@ -351,9 +351,6 @@ linkDefaultProgram()
 static void
 initializeShapes( ) {
 
-#include <shapes/bilinear_cube.h>
-    g_defaultShapes.push_back(SimpleShape(bilinear_cube, "bilinear_cube", kBilinear));
-
 #include <shapes/catmark_cube_corner0.h>
     g_defaultShapes.push_back(SimpleShape(catmark_cube_corner0, "catmark_cube_corner0", kCatmark));
 
@@ -462,6 +459,9 @@ initializeShapes( ) {
 #endif
 
 
+#include <shapes/bilinear_cube.h>
+    g_defaultShapes.push_back(SimpleShape(bilinear_cube, "bilinear_cube", kBilinear));
+
 
 #include <shapes/loop_cube_creases0.h>
     g_defaultShapes.push_back(SimpleShape(loop_cube_creases0, "loop_cube_creases0", kLoop));
@@ -630,11 +630,7 @@ createOsdMesh( const char * shape, int level, int kernel, Scheme scheme=kCatmark
     g_scheme = scheme;
 
     // Adaptive refinement currently supported only for catmull-clark scheme
-#if defined(GL_ARB_tessellation_shader) || defined(GL_VERSION_4_0)
     bool doAdaptive = (g_adaptive!=0 and g_scheme==kCatmark);
-#else
-    bool doAdaptive = false;
-#endif
 
     OpenSubdiv::OsdMeshBitset bits;
     bits.set(OpenSubdiv::MeshAdaptive, doAdaptive);
@@ -1585,9 +1581,11 @@ callbackFreeze(bool checked, int f)
 static void
 callbackAdaptive(bool checked, int a)
 {
-    g_adaptive = checked;
+    if (OpenSubdiv::OsdGLDrawContext::SupportsAdaptiveTessellation()) {
+        g_adaptive = checked;
 
-    createOsdMesh( g_defaultShapes[g_currentShape].data, g_level, g_kernel, g_defaultShapes[ g_currentShape ].scheme );
+        createOsdMesh( g_defaultShapes[g_currentShape].data, g_level, g_kernel, g_defaultShapes[ g_currentShape ].scheme );
+    }
 }
 
 static void
@@ -1810,6 +1808,9 @@ int main(int argc, char ** argv)
 #endif
 #endif
 
+    // activate feature adaptive tessellation if OSD supports it
+    g_adaptive = OpenSubdiv::OsdGLDrawContext::SupportsAdaptiveTessellation();
+
     initGL();
     linkDefaultProgram();
 

opensubdiv/osd/glDrawContext.cpp

@@ -91,6 +91,19 @@ OsdGLDrawContext::~OsdGLDrawContext()
     glDeleteTextures(1, &fvarDataTextureBuffer);
 }
 
+bool
+OsdGLDrawContext::SupportsAdaptiveTessellation()
+{
+// Compile-time check of GL version
+#if (defined(GL_ARB_tessellation_shader) or defined(GL_VERSION_4_0)) and defined(GLEW_VERSION_4_0)
+    // Run-time check of GL version with GLEW
+    if (GLEW_VERSION_4_0) {
+        return true;
+    }
+#endif
+    return false;
+}
+
 bool
 OsdGLDrawContext::allocate(FarMesh<OsdVertex> *farMesh,
                            GLuint vbo,

opensubdiv/osd/glDrawContext.h

@@ -120,6 +120,9 @@ public:
     GLuint quadOffsetTextureBuffer;
     GLuint patchLevelTextureBuffer;
 
+    /// true if the GL version detected supports shader tessellation
+    static bool SupportsAdaptiveTessellation();
+
 private:
     bool allocate(FarMesh<OsdVertex> *farMesh,
                   GLuint vbo, int numElements,