This is a step by step process how to make a production like digi-double.

I would like to deeply thank Thomas Mansencal for his help explaining the importance of the linear photos for textures, as well as the ACES pipeline and his overall technical assistance.

If you are wondering what is ACES ? The website with all the informations
https://www.colour-science.org/

Here is an alternative (and excellent) website maybe more artists oriented:
https://chrisbrejon.com/cg-cinematography/chapter-1-5-academy-color-encoding-system-aces/


Materials notes:
a – Photos were not all taken in the same time, only one after the other with the actor turning around, so photogrametry is not an option.
b – No Macbeth color checker was used during photoshoot, so color can’t be adjusted accordingly.
c – Photos are very good quality, polarized, DNG format was provided for cam datas, plus utility maps.


CONTENT

  1. Process photos for linear pipeline
    1. DNG Profile Editor
    2. Photoshop – Camera Raw
    3. Photoshop – Paint
    4. Conversion to ACES With Nuke
  2. Building the 3d scene
    1. The Camera
    2. The Model
  3. Making the textures
  4. Preparing the render scene

1 – PROCESS PHOTOS FOR LINEAR PIPELINE

For converting photos for a linear pipeline, I’ve followed the instructions from the Triple gangers website.
https://triplegangers.com/blog/cat/technology/post/linear-pipeline/

As the author explained:
The ACR tone curve is a creative tone curve whose purpose is to increase contrast and saturation on image. It is perfectly fine (and needed) for Photographers and in applications aiming direct representation on a display (Display-Referred imaging) as it provides a faithfull and pleasing output. However it should ABSOLUTELY be avoided when you create colour textures as it will inject non-linearity in the rendering system and thus bias the light transport equation.”

This is why image must have ACR tone curve removed.


1.1 – DNG Profile Editor

  • Open DNG_Profile Editor
  • Open one of your DNG image
  • Switch the Base Tone Curve from ‘Camera Raw Default‘ to ‘Linear
  • File > Export Nikon D810 profile to “C:\Users\” ” “\AppData\Roaming\Adobe\CameraRaw\CameraProfiles” > call it “Nikon D810 – Linear.dcp

1.2 – Photoshop – Camera Raw

Import your DNG photos with camera Raw

  • [A] Choose the corresponding linear profil exported from DNG Profil Editor
  • [B] Change to sRGB colorspace
  • [C] Enable the lens correction in order to remove the lens distortion and unwrap the image
  • [D] Focal lens will be useful information for later in maya
  • [E] The Macbeth color checker would give use the correct amount to set. I just guessed what would be a good value.

1.3 – Photoshop – Paint Process

The photos will then go through a manual process of removing the shadows, highlights and hairs.

  • Duplicate the “Background” layer (switch to Linear Dodge (Add) ), create a mask to reveal the layer effect and paint with a brush in shadow area.
  • Once you achieve to remove shadows, the painted area seems also slightly desatured. I would suggest to reduce the opacity by 50%, duplicate the layer (switch to Color Dodge).
  • For removing the highlights, same process (but switch to Multiply).
  • To remove the hairs, I’ve used a stamp using all layers.
  • Save your photos (tif – 16 bit int)

1.4 – Conversion to ACES With Nuke

In Nuke, convert the texture to the ACEScg colorspace.

  • Read your photos exported from Photoshop using colorspace as “Utility – sRGB – Texture“.
  • Write an output using colorspace as “ACES – ACEScg

2 – BUILDING THE 3D SCENE

2.1 The Camera

We know the camera is a Nikon D810.
We need to know what is the image sensor of the camera.
In this case 35.9 x 24.0 mm

In Maya set your cameras properly.

From the DNG photo, we know the focal length is 105 mm.

Set the Camera Aperture with the info from the camera.
Because the photo are taking as portrait. First is vertical, second is horizontal (35.9 x 24.0mm)


2.2 The Model

In Maya, place your cameras one by one and build your model accordingly.
Both cameras and model will modify as you are adjusting positions and shapes.
There is no big shortcut, this step is tedious.

I’m trying to use a similar lighting as the photos, that will help me model to understand volumes, highlights and shadows. HDRI taking during the photoshot would be ideallic. In this scene I’ve just created two areas lights.

  • At the end, export model in ‘obj’ and cameras in ‘fbx’.



3 – MAKING THE TEXTURES

In Mari, create a new project with the exported Obj.

  • Import cameras one by one.
  • Create a projector for each cameras
  • Set the input file with the correct ACES images exported from Nuke.
  • Project each image on a different layer and use a mask to reveal the best angle of the photo
  • Export the images
  • Repeat the same operation for the Albedo images provided by the photoshot package.
  • Export files

3 – PREPARING THE RENDER SCENE

Use a correct macbeth already converted to ACEScg ACEScg_ColorChecker2014.exr

In order to normalize the lookdev of all your assets, the light intensity of your scene – whether you use an HDR or spotlights – you must keep this grey value as closer as possible at 0.19


RENDER TEST