1 .\" RCSid "$Id: pdfblur.1,v 1.7 2008/11/10 19:08:17 greg Exp $"

     2 .TH PDFBLUR 1 1/24/96 RADIANCE

     3 .SH NAME

     4 pdfblur - generate views for depth-of-field blurring

     5 .SH SYNOPSIS

     6 .B pdfblur

     7 .B aperture

     8 .B nsamp

     9 .B viewfile

    10 .SH DESCRIPTION

    11 .I Pdfblur

    12 takes the given

    13 .I viewfile

    14 and computes

    15 .I nsamp

    16 views based on an aperture diameter of

    17 .I aperture

    18 (in world coordinate units) and a focal distance equal to the length of the

    19 .I \-vd

    20 view direction vector.

    21 When rendered and averaged together, these views will result in

    22 a picture with the specified depth of field.

    23 Either

    24 .I pinterp(1)

    25 or

    26 .I rpict(1)

    27 may be called to do the actual work.

    28 (The given

    29 .I viewfile

    30 must also be passed on the command line to the chosen renderer, since

    31 .I pdfblur

    32 provides supplemental view specifications only.)\0

    33 .PP

    34 For

    35 .I pinterp,

    36 feed the output of

    37 .I pdfblur

    38 to the standard input of

    39 .I pinterp

    40 and apply the

    41 .I \-B

    42 option to blur views together.

    43 In most cases, a single picture with z-buffer is all that is required

    44 to get a satisfactory result, though the perfectionist may wish to

    45 apply three pictures arranged in a triangle about the aperature, or

    46 alternatively apply the

    47 .I \-ff

    48 option together with the

    49 .I \-fr

    50 option of

    51 .I pinterp.

    52 (The latter may actually work out to be faster, since rendering

    53 three views takes three times as long as a single view, and the

    54 .I \-fr

    55 option will end up recomputing relatively few pixels by

    56 comparison.)\0

    57 .PP

    58 To use

    59 .I pdfblur

    60 with

    61 .I rpict,

    62 apply the

    63 .I \-S

    64 option to indicate a rendering sequence, and set the

    65 .I \-o

    66 option with a formatted file name to save multiple output

    67 pictures.

    68 When all the renderings are finished, combine them with the

    69 .I pcomb(1)

    70 program, using appropriate scalefactors to achieve an average.

    71 Note that using

    72 .I rpict

    73 is MUCH more expensive than using

    74 .I pinterp,

    75 and it is only recommended if the scene and application

    76 absolutely demand it (e.g. there is prominent refraction that

    77 must be modeled accurately).

    78 .PP

    79 For both

    80 .I pinterp

    81 and

    82 .I rpict,

    83 the computation time will be proportional to the number of views from

    84 .I pdfblur.

    85 We have found a

    86 .I nsamp

    87 setting somewhere between 5 and 10 to be adequate for most images.

    88 Relatively larger values are appropriate for larger aperatures.

    89 .PP

    90 The

    91 .I \-pd

    92 option of

    93 .I rpict

    94 may be used instead or in combination with or instead of

    95 .I pdfblur

    96 to blur depth-of-field.

    97 If used in combination,

    98 it is best to set the

    99 .I \-pd

   100 option to the overall

   101 .I aperture

   102 divided by

   103 .I nsamp

   104 to minimize ghosting in the output.

   105 .PP

   106 To simulate a particular camera's aperture, divide the focal length of

   107 the lens by the f-number, then convert to the corresponding

   108 world coordinate units.

   109 For example, if you wish to simulate a 50mm lens at f/2.0 in

   110 a scene modeled in meters, then you divide 50mm by 2.0 to get 25mm,

   111 which corresponds to an effective aperture of 0.025 meters.

   112 .SH EXAMPLES

   113 To use

   114 .I pinterp

   115 to simulate an aperture of 0.5 inches on a lens focused at a

   116 distance of 57 inches:

   117 .IP "" .2i

   118 rpict \-vf myview \-x 640 \-y 480 \-z orig.zbf scene.oct > orig.hdr

   119 .br

   120 pdfblur 0.5 57 8 orig.hdr | pinterp \-B \-vf orig.hdr \-x 640 \-y 480

   121 orig.hdr orig.zbf > blurry.hdr

   122 .PP

   123 To use

   124 .I rpict

   125 exclusively to do the same:

   126 .IP "" .2i

   127 pdfblur .5 57 5 myview | rpict \-S 1 \-vf myview \-x 640 \-y 480

   128 \-o view%d.hdr scene.oct

   129 .br

   130 pcomb \-s .2 view1.hdr \-s .2 view2.hdr \-s .2 view3.hdr \-s .2

   131 view4.hdr \-s .2 view5.hdr > blurry.hdr

   132 .SH AUTHOR

   133 Greg Ward

   134 .SH BUGS

   135 This program really only works with perspective views.

   136 .SH "SEE ALSO"

   137 pcomb(1), pinterp(1), pmblur(1), pmdblur(1), rcalc(1), rpict(1), vwright(1)