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Introduction to Shading

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Introduction

This tutorial demonstrates how Cutter can be used to construct shading networks that use Pixar's Bxdf and Pattern nodes. The tutorial has two section - Shape (steps 1 to 4), and Shading (step 1).

Shape

Step 1

Make sure the RPS and RfM installation directories have been set - figure 1.

Figure 1

Create the following directory structure. Refer to "Cutter: Setting Up" for information about installing Cutter.

    HOME_DIR
            |_/archives/
            |          |_ geo/
            |          |_ lights/
            |          |_ materials/
            |_/cutter
            |_/frames
            |_/ribs
            |_/shader_src
            |_/shaders
            |_/textures  <<-- converted .tex files
            |_/tiffs     <<-- source images for texture maps

Step 2 - Preparing the Rib Archives

Save bar.rib and jack.rib archives in the archives/geo directory.

    HOME_DIR
            |_/archives/
                      |_geo/
                           |_ bar.rib
                           |_ jack.rib

Step 3 - Preparing a Scene for Modeling

Generate a rib using the Beauty Pass menu - figure 2.

Figure 2

Save the file as jack_scene.rib in the ribs directory.

    HOME_DIR
            |_/ribs/
                   |_ jack_scene.rib

Edit the jack_scene.rib and replace the Translate and Sphere statements on lines 48 and 49 with the following Scale and ReadArchive statements.

    AttributeBegin
        Scale 3 3 3
        ReadArchive "geo/jack.rib"
    AttributeEnd

Render jack_scene.rib (figure 3) using the keyboard shortcut Alt+e, Control+e or Apple+e.

Figure 3

Step 4 - Improving the Lighting

Save the 3lights.rib archive the archives/lights directory.

    HOME_DIR
            |_/archives
                      |_/geo
                      |_/lights/
                              |_ 3lights.rib

Lines 28 to 41 should be replaced with the following ReadArchive statement.

    ReadArchive "lights/3lights.rib"

Figure 4

Shading

Step 1 - Applying a Material to the "floor"

It is easier to do look-development if the shading network that defines a material is specified in rib archive. For example, save an empty rib archive named ThinFilm.rib in the archives/materials directory.

    HOME_DIR
            |_/archives
                      |_/geo
                      |_/lights
                      |_/materials/
                              |_ ThinFilm.rib

Open the archive document and choose PxrSurface from the Plugins->Materials menu.

Figure 5

Cutter will insert a Bxdf rib statement into the document. Do the same again but choose Plugins->PxrPatterns->PxrThinFilm. Parameters that will not be edited can be deleted. The shading network is shown below.

Pattern "PxrThinFilm" "PxrThinFilm1"
        # params have been omitted...
        # "PxrThinFilm2:resultRGB"   uses->|color|vector|normal|point| 
        # "PxrThinFilm2:resultR"     uses->|float| 
        # "PxrThinFilm2:resultG"     uses->|float| 
        # "PxrThinFilm2:resultB"     uses->|float| 
        
Bxdf "PxrSurface" "PxrSurface1"
        "reference color diffuseColor" ["PxrThinFilm1:resultRGB"] # <-- connection
        # remaining params have been omitted...

Cutter indicates the outputs of a Pattern within the comments. Notice the diffuseColor parameter,

    "color diffuseColor" [0.18 0.18 0.18]

has been edited so that it receives color values from the output (resultRGB) of the PxrThinFilm "node".

    "reference color diffuseColor" ["PxrThinFilm1:resultRGB"]

Add the following ReadArchive immediately before the Polygon statement.

    ReadArchive "materials/ThinFilm.rib"

A similar procedure can be followed for the chromium "look" for the jack - Chrome.rib. For example,

Bxdf "PxrSurface" "PxrSurface2"
    "color specularFaceColor" [1 1 1]

The final render is shown next.

Figure 6