bokehKernel(withSize:)
Creates and returns a texture, based on the camera’s aperture blade count, to be used in rendering out-of-focus highlights in a scene.
Declaration
func bokehKernel(withSize size: vector_int2) -> MDLTextureParameters
- size:
The pixel dimensions of the texture to create.
Return Value
A new bokeh kernel texture.
Discussion
The shape of a real-world camera’s aperture is determined by the number of overlapping blades that form an adjustable iris, whose center opening light passes through between the lens and the imaging surface (film or sensor). This shape affects that of out-of-focus highlights, commonly called bokeh, that appear in images seen by the camera. The aesthetic quality of a lens’ bokeh is one of the characteristics that drives the choice of a lens for a particular scene. To specify the blade count for a camera, use the apertureBladeCount property. Then, use this method to create a texture image for use in rendering bokeh highlights.
A renderer typically uses this texture to simulate lens effects in one of two ways:
As the kernel for a convolution filter over the entire rendered image. This option provides a realistic, but computationally expensive blur effect for out-of-focus areas.
As a sprite texture placed at the locations of point highlights in the rendered scene. This option can produce a facsimile of realistic bokeh effects at a lower cost to rendering performance.