Contour Output Shaders

Contour output shaders are called after the regular image has been computed.

Contours Only

The contour output shader contour_only generates a contour image with a given background color in the color frame buffer, discarding the rendered color image.

contour_only

    "contour_only" (
        color           "background",
        boolean         "glow",
        boolean         "maxcomp")

background: is the background color (default black).
glow: if set to on, makes all contours become darker and more transparent near their edges, creating a glow effect.
maxcomp: if set to on, specifies that when a contour is over another contour, the maximum of the two colors (in each color band) should be used. If maxcomp is not specified (or set off), normal alpha compositing is used.

Composited Contours

This contour output shader generates a contour image composited over the rendered color image.

contour_composite

    "contour_composite" (
        boolean         "glow",
        boolean         "maxcomp")

glow: if set to on, makes all contours become darker and more transparent near their edges, creating a glow effect.
maxcomp: if set to on, specifies that when a contour is over another contour, the maximum of the two colors (in each color band) should be used. If maxcomp is not specified (or set off), normal alpha compositing is used.

PostScript Contours

The contour output shader contour_ps creates PostScript code with black contours. The PostScript code can be written to a file with a separate output statement that specifies the file type ps. This shader does not touch the rendered color frame buffer.

contour_ps

    "contour_ps" (
        integer         "paper_size",
        scalar          "paper_scale",
        scalar          "paper_transform_b",
        scalar          "paper_transform_d",
        boolean         "title",
        boolean         "landscape",
        vector          "ink_stroke_dir",
        scalar          "ink_min_frac",
        string          "file_name"
    )

paper_size

is an integer, with 0 indicating "letter" size, 1 indicating "executive", 2 indicating "legal", 3-6 indicating "a3", "a4", "a5", "a6", 7-9 indicating "b4", "b5", "b6", and 10 indicating "11x17".

paper_scale

scales the PostScript output. The default is 1.

paper_transform_b paper_transform_d

transform the Postscript coordinates according to the matrix

(	1	b	)
	0	d

where b and d are the parameters paper_transform_b and paper_transform_d. This allows compensation of printers that print with a slight skew.

title

if set to on, determines whether a title (consisting of file name and frame number) and a frame around the image are written.

landscape

if set to on, makes the output be in landscape mode rather than portrait mode.

ink_stroke_dir

if set no a non-zero vector, makes the thickness of each contour line segment depend on its orientation; this gives an ink pen look. The contour lines are widest in the stroke direction.

ink_min_frac

specifies how thin the "ink look" contour lines should be (relative to the maximum thickness) in directions perpendicular to ink_stroke_dir.

file_name

specifies the name of the PostScript file that the contours are written to.

For example, to get a PostScript file in A4 paper size with full scale, use the following statements in the camera definition:

     output "contour,rgba" "contour_ps" (
        "paper_size"         4,
        "paper_scale"        1.0,
        "paper_transform_b"  0.0,
        "paper_transform_d"  1.0,
        "title"              on,
        "landscape"          on,
        "file_name"          "contourimage.ps"
     )