Cameras

Native perspective and orthographic (Left, Right, Front, Back, Top, Bottom projection) Cinema 4D cameras are supported by C4DtoA. The supported settings of a Camera object are:

  • Focal Length
  • Field of View
  • Film Offset
  • Focus Distance / Focus Object
  • Near / Far Clipping

 

To adjust the settings for an Arnold camera node, you need to add an Arnold Tag to the camera object. To do this, you must right click the Camera and select C4DtoA Tags > Arnold Parameters:

Common Camera Attributes

The following parameters are common for each camera type. For specific type of parameters, please see the specific camera pages.

Exposure

Simulates the effect of camera exposure (in a non-physical way). Increasing this parameter by a value of one gives you one stop up (doubles the brightness). 

Filtermap

Weights the camera sample by a scalar amount defined by the shader linked to the filtermap. This shader will use as an input, u,v coordinates in image-space coords [0,1) and x,y in pixel coordinates. This allows you to darken certain regions of the image, perfect to simulate vignetting effects.

There is an optimization in place where if the filter returns pure black then the camera ray is not fired. This can help in cases such as when rendering with the fisheye camera where, depending on its autocrop setting, parts of the frame trace no rays at all.

Circular ramp mapped to the camera's 'filtermap' to create a vignette effect

Rolling Shutter

Rolling Shutter is used to simulate the type of rolling shutter effect seen in footage shot with digital cameras that use CMOS-based sensors such as Blackmagics, Alexas, REDs, and even iPhones. This method is implemented by rolling (moving) the shutter across the camera area instead of the entire image area all at the same time. 

Without rolling shutter (rollover image).

With rolling shutter (rollover image).

 

The Rolling Shutter direction specifies the direction that the rolling shutter takes place. The default is 'off'' and can be set to 'top' (top to bottom being the most common scanning direction), 'bottom', 'left' or 'right'. 

 

Interesting effects can be achieved when combining motion blur 'length' with rolling shutter:

Motion blur 'length' from 0 to 2

A video tutorial about Rolling Shutter can be found here.

Rolling Shutter Duration

With this parameter, it is possible to control the duration of exposure of the scanlines in a rolling shutter camera. Valid values for this parameter are in the 0 to 1 range, where a value of 0 gives you an instantaneous exposure of each scanline (the default value and the rolling shutter's previous behavior), and a value of 1 exposes every scanline for the entirety of the camera's shutter interval (the same result that a camera without rolling shutter would give).


Enable DOF

Enables depth of field effects.

Focus Distance

The Focus distance attribute is on the standard C4D camera parameters (Object tab).

This is the distance at which objects appear in perfect focus, for a non-zero aperture value. 

Aperture

Aperture Size

The radius of the aperture in world units. The smaller the aperture, the sharper the images (shallower depth of field). In the limit, a size of zero produces no depth of field blurring. 


Aperture Blades

A number of blades (or polygon sides) of the polygonal aperture. 0 is considered a circle aperture

Aperture Blade Curvature

The curvature of the polygonal aperture sides. A value of 0 means hard straight sides. Increasing this value results in progressively more curved edges, all the way to 1.0 which produces a perfect disk. Negative values produce a "pinched" or star-shaped aperture.

Aperture Rotation

Rotates the aperture by the specified number of degrees. 


 

Aperture Aspect Ratio

Values bigger than one produce an elongated defocusing effect, reminiscent of an anamorphic lens, while a value less than one will squash it.

 

UV Remap

This parameter takes a 2D displacement image and uses it to distort the rendered output of the camera's lens. The left image below has been rendered using a colored ramp connected to the UV Remap attribute. In the right image, the same ramp texture has been distorted in a 2d image post processing software package.

When using uv_remap you should use the image shader's 'image.swrap clamp' and 'image.twrap clamp' attributes to minimize edge effects due to filtering.

Shutter

 

Custom Shutter Size

By default, the shutter size defined in the Arnold Render settings are used. This option allows you to setup a smaller shutter size within the global range.

Shutter Start/ End

The shutter range of the camera can be made smaller than the motion blur range exported from the scene by changing the Shutter Start and Shutter End parameters. The value is frame relative which means 0 stands for the frame start and 1 is for the frame end.

The camera Shutter Start and End should be set to the same value when rendering out a Motion Vector AOV.

Shutter Type

The filtering applied to time samples. By default, this is a box filter, with all time samples having the same weight. A triangle (or "tent") filter is also available which produces smoother trails.

Arnold supports custom shutter shapes with the shutter curve camera parameter. You can define as many points as required. Coordinates increase from 0 (corresponding to the shutter_start) to 1 (corresponding to the shutter_end). Values in the vertical axis must be non-negative, and it is not recommended to enter values above 1. The values are linearly interpolated between each point. In the examples below, you can see the effect different curve shapes have on the motion blur trail of a sphere that has been key-framed moving from left to right.

Various custom camera shutter curve shapes

 

Custom camera types

You can define custom Arnold camera types via the Arnold tag of a Camera object. Enable Custom type and select the Camera type on the Camera tab of the tag. In this case, the native C4D Camera Projection type will not be used. 

 

 

Arnold provides the following built-in camera types:

 

The perspective or standard camera is the most common. Both the perspective and fish-eye cameras provide depth of field and model the effect of altering the camera aperture. The orthographic, cylindrical and spherical camera types enable certain non-perspective views to be created but do not attempt to model any real-world lens effects (they are normally used for creating environment maps).

Third-party cameras

Developers can extend Arnold with custom camera implementations. To install a third-party camera, you must point the ARNOLD_PLUGIN_PATH environment variable to the folder where the camera plugin binary is located, or just simply copy the binary to the C4DtoA/shaders folder. The camera can then be selected in the Custom camera type combo box like any other built-in camera.

 

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