anchor.diff:      type [<StructuralEquality; NoComparison>] PhysicallyBasedGeometry =
           { VertexBuffer : uint
             IndexBuffer : uint
  +          PrimitiveType : OpenGL.PrimitiveType
  +          ElementCount : int
             PhysicallyBasedVao : uint }
   
       /// Assert a lack of Gl error. Has an generic parameter to enable value pass-through.
  
positive.code:         // make physically based geometry
          { VertexBuffer = vertexBuffer
            IndexBuffer = indexBuffer
            PhysicallyBasedVao = vao }
  
      /// Draw a sprite whose indices and vertices were created by OpenGL.Gl.CreateSpriteQuad and whose uniforms and shader match those of OpenGL.CreateSpriteShader.
  
negative.code:             modelsRow3Ptr.Free ()
  
          // draw geometry
          OpenGL.Gl.DrawElementsInstanced (geometry.PrimitiveType, geometry.ElementCount, OpenGL.DrawElementsType.UnsignedInt, nativeint 0, modelsCount)
          Assert ()
  
          // teardown geometry
  