I’m opening this thread to show examples of some concepts discussed in the thread “Unbounded Floating Point Pipelines”
The idea of this thread is using freely available tools to illustrate the concepts and scene-referred workflows, so in this first post I’ll show a basic setup of Blender for quick tests. Other tools and examples will come later.
Questions are welcome.
Blender is a 3D modeling and rendering FLOSS software. It’s not designed for photography, but it has a compositor built in that can be used to illustrate features and procedures that can be relevant for photo editing as well. It uses OCIO for most of its color management.
Some caveats: Blender/Cycles uses a linear rec.709 reference internally. OCIO provides the infrastructure needed for using any reference, but some legacy code present in blender makes some assumptions based on a rec.709/sRGB output, so at the moment is not possible to use wider gamut references, although there is some ongoing work to remove that limitation.
For the same reason ACES in Blender is out of question, so don’t take the following information as a reference to the ACES workflow.
We’re going to use Blender compositor and Blender’s Colour Management (based on OCIO).
First step is switching from Blender default (legacy) renderer to Cycles. This is not strictly necessary if we’re going to edit external images, but it’s needed for rendering 3D images with a more physically plausible renderer.
Next, we’re going to find the colour management section under the “Scene” panel on the right side.
The default config has a simplistic view that is inadequate for proper scene-referred work.
The drop-down selector with the “View” label allows to switch between the views defined in the OCIO config*.
There are also looks designed for each view.
We’ll use for these tests the view “Filmic” that was designed by @anon11264400 as a replacement of the default view transform. Filmic sports desaturation and dynamic range similar to the response of a filmic cinema camera
Note that this is not the original OCIO config designed by @anon11264400 but a modification done by Blender developers. Original Filmic Blender OCIO config includes a Log view and has false colour implemented as a look). It’s available at Troy’s github page:
*) Inside Blender’s install directory, under Blender/Version/datafiles/colormanagement you can find the defaut OCIO config and luts. That’s the place to put third party or your own configs.
With Filmic Blender setup as view we can proceed to switching to the compositor:
On the top row, there’s a workspace selector. Change to compositing.
Then mark the checkbox “use nodes” so the nodal compositing is activated.
When that is done, an input node corresponding to the current “render” layer appears. It’s connected to the Composite Output Node.
We’ll add a viewer node with Add > Output > Viewer and connected to the renderlayer node (just like the existing composite node).
If we click on the image icon by the “Image” label in the lower left, we can change the input for the image viewer. We can select the “Viewer Node” as source, which means that we’ll see what the viewer node is fed with.
Nothing is showed so far, because the render layer is empty. Press F12 to render the default cube, you should see the rendered image in the viewer (if the render is done in the same window where the node tree appears, just press esc when rendering is done to go back to the node viewer).
If you click on the rendered Image, you can see the value of the pixels. On the left side, you can find the scene-values. On the right side, the “CM” values (which means the values post-view transform).
Experiment changing the view and reading the values. The scene values will remain the same, while the values on the right will depend on the view.
You can try the same with an external image:
Just drag and drop a scene-referred image* to the node editor area and connect it to the viewer, replacing the renderlayer node.
Experiment with the different views, with the exposure slider, etc.
*) Blender seems to have some troubles dealing with some tiff files. For the purposes of this test it is advised to use floating point EXRs.
Ok. This was a brief introduction to how to setup Blender for our tests. Get familiar with the rather unfamiliar UI and feel free to ask questions.
When you’re ready we can move forward with other examples.