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Fix calculation in clutter_cubic_bezier

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The calculation for cubic bezier curves had an extra multiplication by
3 which was causing the curve to go over 1.0 very quickly. This had
the affect of making test-animation appear to complete much before the
completed signal is emitted.
This commit is contained in:
Neil Roberts 2008-12-18 12:20:46 +00:00
parent 2bf815131a
commit 4168ed09de
1 changed files with 5 additions and 5 deletions
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10
clutter/clutter-alpha.c
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@ -1282,7 +1282,7 @@ clutter_cubic_bezier (ClutterAlpha *alpha,
* B(t) = (1 - t)^3 * P_0 * B(t) = (1 - t)^3 * P_0
* + 3t * (1 - t)^2 * P_1 * + 3t * (1 - t)^2 * P_1
* + 3t^2 * (1 - t) * P_2 * + 3t^2 * (1 - t) * P_2
* + 3t^3 * P_3 (with t included in [0, 1]) * + t^3 * P_3 (with t included in [0, 1])
* *
* the P_0 and P_3 points are set to (0, 0) and (1, 1) respectively, * the P_0 and P_3 points are set to (0, 0) and (1, 1) respectively,
* and the curve never passes through P_1 and P_2 - with these two * and the curve never passes through P_1 and P_2 - with these two
@ -1294,14 +1294,14 @@ clutter_cubic_bezier (ClutterAlpha *alpha,
* *
* B(t) = 3t * (1 - t)^2 * P_1 * B(t) = 3t * (1 - t)^2 * P_1
* + 3t^2 * (1 - t) * P_2 * + 3t^2 * (1 - t) * P_2
* + 3t^3 * P_3 (with t included in [0, 1]) * + t^3 * P_3 (with t included in [0, 1])
* *
* and, similarly, since the final point is (1, 1) we can simplify * and, similarly, since the final point is (1, 1) we can simplify
* it further to: * it further to:
* *
* B(t) = 3t * (1 - t)^2 * P_1 * B(t) = 3t * (1 - t)^2 * P_1
* + 3t^2 * (1 - t) * P_2 * + 3t^2 * (1 - t) * P_2
* + 3t^3 (with t included in [0, 1]) * + t^3 (with t included in [0, 1])
* *
* since an alpha function has only a time parameter and we have two * since an alpha function has only a time parameter and we have two
* coordinates for each point, we pass the time as the first * coordinates for each point, we pass the time as the first
@ -1314,11 +1314,11 @@ clutter_cubic_bezier (ClutterAlpha *alpha,
b_t = 3 * t * pow (1 - t, 2) * x_1 b_t = 3 * t * pow (1 - t, 2) * x_1
+ 3 * pow (t, 2) * (1 - t) * x_2 + 3 * pow (t, 2) * (1 - t) * x_2
+ 3 * pow (t, 3); + pow (t, 3);
res = 3 * b_t * pow (1 - b_t, 2) * y_1 res = 3 * b_t * pow (1 - b_t, 2) * y_1
+ 3 * pow (b_t, 2) * (1 - b_t) * y_2 + 3 * pow (b_t, 2) * (1 - b_t) * y_2
+ 3 * pow (b_t, 3); + pow (b_t, 3);
return res; return res;
} }