1al_draw_soft_triangle(3)   Library Functions Manual   al_draw_soft_triangle(3)
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NAME

6       al_draw_soft_triangle
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SYNOPSIS

9              #include <allegro5/allegro_primitives.h>
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11              void al_draw_soft_triangle(
12                 ALLEGRO_VERTEX* v1, ALLEGRO_VERTEX* v2, ALLEGRO_VERTEX* v3, uintptr_t state,
13                 void (*init)(uintptr_t, ALLEGRO_VERTEX*, ALLEGRO_VERTEX*, ALLEGRO_VERTEX*),
14                 void (*first)(uintptr_t, int, int, int, int),
15                 void (*step)(uintptr_t, int),
16                 void (*draw)(uintptr_t, int, int, int))
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DESCRIPTION

19       Draws  a triangle using the software rasterizer and user supplied pixel
20       functions.  For help in understanding what these functions do, see  the
21       implementation   of  the  various  shading  routines  in  addons/primi‐
22       tives/tri_soft.c.  The triangle is drawn in two segments, from  top  to
23       bottom.  The segments are deliniated by the vertically middle vertex of
24       the triangle.  One of each segment may be absent if  two  vertices  are
25       horizontally collinear.
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27       Parameters:
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29       · v1, v2, v3 - The three vertices of the triangle
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31       · state  -  A  pointer  to  a user supplied struct, this struct will be
32         passed to all the pixel functions
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34       · init - Called once per call before any drawing is  done.   The  three
35         points passed to it may be altered by clipping.
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37       · first  -  Called  twice  per  call, once per triangle segment.  It is
38         passed 4 parameters, the first two are the coordinates of the initial
39         pixel  drawn  in  the segment.  The second two are the left minor and
40         the left major steps, respectively.  They represent the sizes of  two
41         steps  taken  by  the  rasterizer as it walks on the left side of the
42         triangle.  From then on, the each step will either be classified as a
43         minor or a major step, corresponding to the above values.
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45       · step  -  Called once per scanline.  The last parameter is set to 1 if
46         the step is a minor step, and 0 if it is a major step.
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48       · draw - Called once per scanline.  The function is  expected  to  draw
49         the scanline starting with a point specified by the first two parame‐
50         ters (corresponding to x and y values) going to the  right  until  it
51         reaches  the  value  of  the  third parameter (the x value of the end
52         point).  All coordinates are inclusive.
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SEE ALSO

55       al_draw_triangle(3)
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59Allegro reference manual                              al_draw_soft_triangle(3)