diff --git a/src/GLCamera.jl b/src/GLCamera.jl
index c73a4b7..445884c 100644
--- a/src/GLCamera.jl
+++ b/src/GLCamera.jl
@@ -1,11 +1,11 @@
 abstract Camera{T}
-immutable OrthographicCamera{T} <: Camera{T}
+type OrthographicCamera{T} <: Camera{T}
 	window_size::Signal{Vector4{Int}}
 	view::Signal{Matrix4x4{T}}
 	projection::Signal{Matrix4x4{T}}
 	projectionview::Signal{Matrix4x4{T}}
 end
-immutable PerspectiveCamera{T} <: Camera{T}
+type PerspectiveCamera{T} <: Camera{T}
 	pivot::Signal{Pivot{T}}
 	window_size::Signal{Vector4{Int}}
 	nearclip::Signal{T}
@@ -315,9 +315,9 @@ function PerspectiveCamera{T <: Real}(
 	)
 	eyepositionstart 	= Vector3{T}(1,0,0)
 	origin 				= lookatvec
-
+	vup 				= Vector3{T}(0,0,1)
 	xaxis 				= eyeposition - origin
-	yaxis 				= cross(xaxis, Vector3{T}(0,0,1))
+	yaxis 				= cross(xaxis, vup)
 	zaxis 				= cross(yaxis, xaxis)
 
 	translate 			= Vector3{T}(0,0,0)
diff --git a/src/GLMatrixMath.jl b/src/GLMatrixMath.jl
index 7d5b942..444f586 100644
--- a/src/GLMatrixMath.jl
+++ b/src/GLMatrixMath.jl
@@ -12,7 +12,6 @@ function scalematrix{T}(scale::Vector3{T})
     result[1,1] = scale[1]
     result[2,2] = scale[2]
     result[3,3] = scale[3]
-
     return Matrix4x4(result)
 end
 
@@ -89,10 +88,9 @@ end
          View frustum matrix (4x4).
 =#
 function frustum{T}(left::T, right::T, bottom::T, top::T, znear::T, zfar::T)
-    @assert right != left
-    @assert bottom != top
-    @assert znear != zfar
-
+    @assert right  != left "right is equal to left: $right"
+    @assert bottom != top  "bottom is equal to top: $bottom"
+    @assert znear  != zfar "znear is equal to zfar: $znear"
     M = zeros(T, 4, 4)
     M[1, 1] = +2.0 * znear / (right - left)
     M[3, 1] = (right + left) / (right - left)
diff --git a/src/GLRender.jl b/src/GLRender.jl
index cb64e63..084f7a5 100644
--- a/src/GLRender.jl
+++ b/src/GLRender.jl
@@ -1,25 +1,94 @@
+#==
+   Make debugging interface flexible (hopefully the compile step will remove
+   dead code when not optimizing. Higher level values mean more intrusive
+   (may render app unusable  if too much output is generated)
+       Level (ORed bit values)
+             1 : add traceback for constructors and related
+             4 : print uniforms
+             8 : print vertices
+            16 : reserved for GLTypes.GLVertexArray
+            32 : reserved for postRenderFunctions
+==#
+debugFlagOn = isdefined(:GLRenderDebugLevel)
+debugLevel  = debugFlagOn ? GLRenderDebugLevel : 0
 
+#==  Set the debug parameters; if this function is not used, GLRenderDebugLevel
+     must be set at time of package loading.
+==#
+function setDebugLevels(flagOn::Bool,level::Int)
+    global debugFlagOn
+    global debugLevel
+    debugFlagOn = flagOn
+    debugLevel  = flagOn ? level : 0
+end
+
+function debugRenderUnif(program,renderobject)
+       debugLevel & 4 == 0 && return
+       id = program.id
+       println("In debugRenderUnif program.id=$id")
+       for (key,value) in program.uniformloc
+           if haskey(renderobject.uniforms, key)
+               tv=typeof(value)
+               tu=typeof(renderobject.uniforms[key])
+               println("\t$key corresponds to value with type=$tv")
+               println("\t   and renderobject.uniform[$key] with type=$tu")
+           else
+               println("\t key $key not found in  renderobject")
+           end
+       end
+end
+
+function debugRenderVertex(va::GLVertexArray,  mode::GLenum=GL_TRIANGLES)
+       debugLevel & 8 == 0 && return
+       ln  = va.length
+       iln = va.indexlength
+       id =  va.id
+       println("In debugVertex mode=$mode, \tGLVertexArray.id=$id,\tlength=$ln,\tindexlength=$iln")
+end
+
+
+function debugPostRenderFn(fn,args...)
+    debugLevel & 32 == 0 && return
+    fntyp = typeof(fn)
+    
+    println("In debugPostRenderFn\t$fntyp\t$fn" )
+    println("   args=$args")
+    println("++++ end debugPostRenderFn output ++++\n")
+end
+                
+############  end of debugging section ############
+       
 function render(list::AbstractVector)
     for elem in list
         render(elem)
     end
 end
 
+
 function render(renderobject::RenderObject, vertexarray=renderobject.vertexarray)
     for elem in renderobject.prerenderfunctions
         elem[1](elem[2]...)
     end
     program = vertexarray.program
     glUseProgram(program.id)
+
+    debugFlagOn && debugRenderUnif(program,renderobject) ## debug
+
     for (key,value) in program.uniformloc
         haskey(renderobject.uniforms, key) && gluniform(value..., renderobject.uniforms[key])
     end
     for elem in renderobject.postrenderfunctions
+
+        debugFlagOn && debugPostRenderFn(elem[1],elem[2]...) ## debug
+        # apply elem[1]
         elem[1](elem[2]...)
     end
 end
 
+
 function render(vao::GLVertexArray, mode::GLenum=GL_TRIANGLES)
+    debugFlagOn && debugRenderVertex(vao, mode)         ## debug
+
     glBindVertexArray(vao.id)
     if vao.indexlength > 0
         glDrawElements(mode, vao.indexlength, GL_UNSIGNED_INT, C_NULL)
diff --git a/src/GLTypes.jl b/src/GLTypes.jl
index e12c226..9d11bc3 100644
--- a/src/GLTypes.jl
+++ b/src/GLTypes.jl
@@ -174,8 +174,10 @@ include("GLRenderObject.jl")
 
 
 ####################################################################################
+
 # freeing
 free(x::GLProgram)      = try glDeleteProgram(x.id) end # context might not be active anymore, so it errors and doesn' need to be freed anymore
 free(x::GLBuffer)       = try glDeleteBuffers(x.id) end
 free(x::Texture)        = try glDeleteTextures(x.id) end
-free(x::GLVertexArray)  = try glDeleteVertexArrays(x.id) end
\ No newline at end of file
+free(x::GLVertexArray)  = try glDeleteVertexArrays(x.id) end
+
diff --git a/src/GLUniforms.jl b/src/GLUniforms.jl
index 8ff478b..fbfae18 100644
--- a/src/GLUniforms.jl
+++ b/src/GLUniforms.jl
@@ -44,6 +44,7 @@ macro genuniformfunctions(maxdim::Integer)
 		#########################################################################
         push!(expressions, :(toglsltype_string(x::Type{$imalias}) = $(lowercase(string("uniform ", glslalias))))) # method for shader type mapping
         push!(expressions, :(toglsltype_string(x::$imalias) 	  = $(lowercase(string("uniform ", glslalias))))) # method for shader type mapping
+
 	end
 	for n=2:maxdim, n2=2:maxdim, typ in [GLdouble, GLfloat]
 		glsldim 	= n==n2 ? "$n" : "$(n)x$(n2)"