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al_draw_soft_triangle(3)                              al_draw_soft_triangle(3)

NAME
       al_draw_soft_triangle - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro_primitives.h>

              void al_draw_soft_triangle(
                 ALLEGRO_VERTEX* v1, ALLEGRO_VERTEX* v2, ALLEGRO_VERTEX* v3, uintptr_t state,
                 void (*init)(uintptr_t, ALLEGRO_VERTEX*, ALLEGRO_VERTEX*, ALLEGRO_VERTEX*),
                 void (*first)(uintptr_t, int, int, int, int),
                 void (*step)(uintptr_t, int),
                 void (*draw)(uintptr_t, int, int, int))

DESCRIPTION
       Draws a triangle using the software rasterizer and user supplied pixel
       functions.  For help in understanding what these functions do, see the
       implementation of the various shading routines in
       addons/primitives/tri_soft.c.  The triangle is drawn in two segments,
       from top to bottom.  The segments are deliniated by the vertically
       middle vertex of the triangle.  One of each segment may be absent if
       two vertices are horizontally collinear.

       Parameters:

       o v1, v2, v3 - The three vertices of the triangle

       o state - A pointer to a user supplied struct, this struct will be
         passed to all the pixel functions

       o init - Called once per call before any drawing is done.  The three
         points passed to it may be altered by clipping.

       o first - Called twice per call, once per triangle segment.  It is
         passed 4 parameters, the first two are the coordinates of the initial
         pixel drawn in the segment.  The second two are the left minor and
         the left major steps, respectively.  They represent the sizes of two
         steps taken by the rasterizer as it walks on the left side of the
         triangle.  From then on, the each step will either be classified as a
         minor or a major step, corresponding to the above values.

       o step - Called once per scanline.  The last parameter is set to 1 if
         the step is a minor step, and 0 if it is a major step.

       o draw - Called once per scanline.  The function is expected to draw
         the scanline starting with a point specified by the first two
         parameters (corresponding to x and y values) going to the right until
         it reaches the value of the third parameter (the x value of the end
         point).  All coordinates are inclusive.

SEE ALSO
       al_draw_triangle(3)

Allegro reference manual                              al_draw_soft_triangle(3)