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Merge branch 'ettoretorti-master'

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vurtun 2017-08-12 17:57:17 +02:00
commit b73e3c755c
1 changed files with 33 additions and 4 deletions
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nuklear.h
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@ -8586,11 +8586,40 @@ nk_draw_list_path_arc_to(struct nk_draw_list *list, struct nk_vec2 center,
NK_ASSERT(list);
if (!list) return;
if (radius == 0.0f) return;
for (i = 0; i <= segments; ++i) {
const float a = a_min + ((float)i / ((float)segments) * (a_max - a_min));
const float x = center.x + (float)NK_COS(a) * radius;
const float y = center.y + (float)NK_SIN(a) * radius;
/* This algorithm for arc drawing relies on these two trigonometric identities[1]:
sin(a + b) = sin(a) * cos(b) + cos(a) * sin(b)
cos(a + b) = cos(a) * cos(b) - sin(a) * sin(b)
Two coordinates (x, y) of a point on a circle centered on
the origin can be written in polar form as:
x = r * cos(a)
y = r * sin(a)
where r is the radius of the circle,
a is the angle between (x, y) and the origin.
This allows us to rotate the coordinates around the
origin by an angle b using the following transformation:
x' = r * cos(a + b) = x * cos(b) - y * sin(b)
y' = r * sin(a + b) = y * cos(b) + x * sin(b)
[1] https://en.wikipedia.org/wiki/List_of_trigonometric_identities#Angle_sum_and_difference_identities
*/
const float d_angle = (a_max - a_min) / (float)segments;
const float sin_d = (float)NK_SIN(d_angle);
const float cos_d = (float)NK_COS(d_angle);
float cx = (float)NK_COS(a_min) * radius;
float cy = (float)NK_SIN(a_min) * radius;
for(i = 0; i <= segments; ++i) {
const float x = center.x + cx;
const float y = center.y + cy;
nk_draw_list_path_line_to(list, nk_vec2(x, y));
const float new_cx = cx * cos_d - cy * sin_d;
const float new_cy = cy * cos_d + cx * sin_d;
cx = new_cx;
cy = new_cy;
}
}