Rebuild Photoshop

How to setup the Base Rebuild

Overview

This write up will walk you through a basic strategy for using Coat Create AOVs to rebuild a beauty render, as well as, tips for making corrections to that rebuild to produce a final image. The focus will be on preparing the image in Photoshop as an alternative to a Nuke or other compositing software workflow.

Download the zip file of .exrs and extract them to the directory of your choice.

Within Photoshop choose File> Scripts > Load files into stack...

Navigate to where the extracted files were saved with the browse button select all the files to load them.

The resulting file should look like this. A 32 bit file with the AOVs loaded as individual layers.

Convert each layer to a smart object by right clicking it's title in the layers palette and choosing "convert to smart object".

Choose Image > Mode > 16bit/Channel from the main menu bar

Choose "Don't Merge" to retain the layer structure.

Reorder the layers by dragging them up or down as needed into the following order:

HdrColor PtZDeth PtWorldNormal PtDiffuseFilter PtReflections PtRefractions PtSelfIllumination PtGlobalIllumination PtDirectIllumination PtBackground

Hide each layer in the stack except GlobalIllumination. This will serve as the "base" of our image rebuild.

Unhide DirectIllumination and change it's blending mode to "Screen" from the layers drop down. The lighting information from this layer will be added to the base image. (In Screen blending mode the black pixels will have no effect on the underlying layer)

Repeat this process for the following layers: PtReflections, PtRefractions and PtSelfIllumination

The result should be a rebuild that is very similar to the composite image "HdrColor".

The remaining layers will be used as more or less 'utility' passes in the sense that they contain valuable information but do not contribute to the overall look of the rebuild. In this image the layers used in the rebuild are labeled green the utility passes in yellow, and the beauty layer in blue.

Making overall corrections to the rebuild

Any adjustment layers added to the layer stack above the green layers will effect everything below them equally. Add a curves adjustment layer and label it OverallContrast. Create a curve similar to the one in the screenshot to add some contrast to the rebuild.

Create an additional curves adjustment above the OverallContrast layer and label it OverallCC. This layer will be used to add a subtle color move to the image. Create a cooler over all tone by adjusting the blue and red channels as shown.

Making corrections using utility passes

Unhide the DiffuseFilter layer, and make a selection from it of the blue seats and IP elements using your preferred method. For this example color range fromt he select menu was used.

Add a Hue and Saturation adjustment layer below the OverallContrast layer created earlier. Label it BlueToRed and set the sliders to change the blue seats to a red color.

Making corrections to individual layers with in the rebuild.

Similarily it is possible to create corrections to individual layers within in the rebuild. In this example the intensity of the window reflections will be adjusted. Create a selection of the windshield opening, for this example the magic wand was used with a tolerance of 5 sampling the bright pixels from the Refraction pass.

Add a curves adjustment layer above the Reflections layer and link it to the reflection layer by Alt-clicking the divider between the two layers. The adjustment layer will now have a down arrow indicating that it is linked.

The pixels of the reflection layer can now be brightened as shown here to increase the appearance of the reflections, without affecting the pixels below

Simiarliy the pixels of the reflection layer can be darkened to reduce the appearance of the glass reflections without affecting the pixels below.

Any number of corrections can be made by repeating these steps. Here a selection has been made from the DiffuseFilter pass of the dark material of the steering wheel as well as the foot well carpets. A curves adjustment layer has been added and linked to the Reflections layer to reduce the contrast of the areas selected.

The Zdepth layer contains data regarding the distance of objects from the lens of the render camera. It can be used to add a simulated depth of field to flat image. The Zdepth layer in our working 16bit file now has the same contrast as seen in the 32bit smart object.

Double click the icon for the Zdepth layer and another window will open, this is the zdepth pass in the original 32 bit colorspace. Add an exposure adjustment layer to boost the contrast of the lightest and darkest pixels. close that file and choose save when prompted. The Zdepth layer in our working 16bit file now has the same contrast as seen in the 32bit smart object.

In the 16bit working file open the channels palette and duplicate the blue channel to a new channel by dragging it down to the + icon at the bottom of the palette. Rename it to Zdepth.

Create a merged composite layer of your working layers by clicking on the OverallCC layer and then pressing Ctrl+A to select all, Then Ctrl+Shift+C to Copy Merged. (this can also be found in the Edit menu in the main toolbar). Then press Ctrl+V and a new layer of the merged image should appear above the active layer in the layer stack. Rename it Lens Blur

With the LensBlur layer as the active layer, choose Filter > Blur > Lens Blur from the main menu bar.

When the Lens Blur filter window opens, set the source to the Zdepth channel that you saved in the previous steps. Activate the Set Focal Point option and click on the Z in the center of the steering wheel. The steering wheel will now be in focus and the objects that are farther behind it will be blurred according to the zdepth channel that was created. Darker objects in the Zdepth channel will be blurred less, brighter objects will be blurred more. You can toggle the filter on and off with the preview button to make any necessary adjustments.

Press OK and the lens blur will be applied to the active layer, the lens blur window will also close.

PtWorldSpaceNormal is a layer that is not commonly used in photoshop but can be used to relight images in programs like Nuke.

Conclusion

Ideally this article provided some clarity on how to use AOV passes from Coat in Photoshop to create a basic rebuild, and give the reader some insights for manipulating that rebuild. Hopefully this walk through has left the reader with an understanding of how these images can be used together to create a final image to their liking.