This short tutorial will cover how to use the Set Parameter, Collection, and Disable operators to change the lights and self-shadowing of some teapots and alter the shading of the sphere. The scene contains two lights casting shadows on three teapots and a sphere with a simple Utility shader assigned to it.

The scene file can be downloaded here.

• Start by creating an Arnold ROP in Output.

Collection

We will use the Collection operator to reference a selection. This can be used to avoid writing a selection multiple times (optional in this case).

• Create a Collection operator containing two teapots. Under Selection add the following (we will apply a Set Parameter that will only affect these two teapots):

/obj/teapots_operators_FBX/Teapot001* or /obj/teapots_operators_FBX/Teapot002*

_{Teapot Collection}

Set Parameter (Disable Self Shadows on the Teapots)

• Create a Set Parameter. Create the following expression:

self_shadows=false

#the_teapots

Disable Light

We can turn off one of the lights by using the Disable operator.

• Create a Disable operator and under Selection enter for the following Arnold light:

/obj/arnold_light1*

_{ArnoldLight001 disabled}

Set Parameter: Sphere Utility Shader

Now we will change the Overlay Mode for the spheres Utility shader.

• Assign a Utility shader to the sphere and rename it to the_utility.
• Create another Set Parameter and under Expression enter the following:

overlay_mode="wire"

• Under Selection enter the following:

/shop/the_utility/the_utility

_{Utility shader altered with Set Parameter}

_{Final Operator Graph output}