Rendering a Cinema 4D spline with Arnold requires adding an Arnold tag to the Spline object. The tag contains Arnold specific settings, such as thickness, mode, sample rate, etc.

Arnold tag added to a Spline object

The use of SSS is not supported with point and spline primitives and is therefore not recommended.


Determines whether or not the curve will render.


Defines the rendered thickness of the curve.

Thickness 0.01 - 0.1

Thickness can be randomized per curve via the variation and distribution controls under the Thickness parameter (click on the small arrow before the label).


Thickness is increased or decreased randomly by this value, 0% means no change, 100% means change by a maximum of the original thickness (e.g. eliminate or double the size).


Random seed of the Variation.


Remaps the random variation value assigned to each curve. This way you can art direct the frequency of high-deviation thickness.

Thickness Curve

Controls thickness along the curve. The X axis represents the start and end of the curve (from 0 to 1). The Y axis is a multiplier over the base Thickness. 

Thickness Texture

It is also possible to connect a texture map or shader (e.g. Noise) to control the thickness. The shader is evaluated along the U coordinate (V=0). U=0 is the start and U=1 is the end of the spline.

Thickness modified by a Noise texture

Only C4D shaders are allowed, no Arnold shader networks can be used.



Min. Pixel Width

Export IDs

Export the index of each curve to the curve_id user parameter.

Motion Blur


Enable/disable motion blur of the spline.