Radial Distortion

Radial distortion, with negative and positive values resulting in pincushion and barrel distortion respectively. Real-world lenses can show such distortion when using, for example, a very short focal length or a high zoom.

Radial Distortion (-1.3 to 1)

 

A 'barrel distortion' camera lens effect has been reproduced in the interior scene below, by simply increasing the Radial Distortion to 0.2 (rollover image).

Rollover image

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

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.


  • No labels