[Bf-cycles] Strange behaviour with pictures

[Christian Monfort]

Hi,

I've discovered something using Cycles that I'll consider a bug unless
someone here tells me it's not (in which case I'll find it a bit
annoying):
it seems that Cycles needs to have access all the time to pictures
used in materials
if not - because the file has been removed/rename, or is not accesible
- the material is rendered all black:

How to reproduce:

0) Start from default scene
1) Switch to Cycles Render
2) Open image in UV/Image Editor (let's say /tmp/pic1.png)
3) Quick UV/Unwrap the cube
4) In node editor, add a new material to cube (you should have
"Diffuse BSDF" & "Material Output" default nodes)
5) Add an "Image texture" node, selected previously loaded image, and
connect Color pins from "Image texture" && "Diffuse BSDF" nodes:
   [ Image.Texture/Color ] <--> [ Color/Diffuse.BSDF/BSDF ] <--> [
Surface/Material.Ouput ]
5) Set Viewport shading to "Rendered" in 3D view = > All is ok,
picture on all cube faces

6) Rename picture file on disk (/tmp/pic1.png => /tmp/pic2.png)
7) All is still ok in 3D view,
8) Set view port shading to something else than "Rendered" ("Solid"
for example),
9) then back to "Rendered" => cube is all black... (But "Material" and
"Texture" shading modes are OK)

Ok, maybe that's normal as we removed the picture file...
(but isn't the picture loaded in Blender somewhere? why Material &
Texture mode ok then?)

10) Rename back picture file to /tmp/pic1.png" and repeat 8) 9)
11) => Picture on all cube faces

Let's try something else...

12) In UV/Image editor Select "Pack Image" from "Image" menu, so that
all image data is embeded in .blend
13) Check all is ok in "Rendered" mode, then repeat 6) 7) 8) 9)
14) => Cube is all black...

I may understand the 1st case (up to point 9) - but here I thought
that packing image made that Blender needed the original file no
more... and still Cycles do?

Thanks for your time
(I don't want to open a bug report until I'm 100% sure this is not a
correct behaviour...)

Christian.