al_draw_soft_triangle - Allegro 5 API
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))
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 the two segments may be absent if two vertices are
- v1, v2, v3 - The three vertices of the triangle
- state - A pointer to a user supplied struct, this struct
will be passed to all the pixel functions
- init - Called once per call before any drawing is done. The
three points passed to it may be altered by clipping.
- 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, each step will either be classified as a minor or a major step,
corresponding to the above values.
- 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.
- 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.