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f-curve easing: Adjustments to Robert Penner elastic easing 

Compensate for the clamped amplitude by blending the elastic effect.

Allows for a subtle elastic effect which wasn't possible before.
This commit is contained in:
Campbell Barton 2014-04-29 05:31:50 +10:00
parent e158fbf934
commit 89b3dcaf82
2 changed files with 52 additions and 11 deletions
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2
source/blender/blenkernel/intern/fcurve.c
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@ -2083,7 +2083,7 @@ static float fcurve_eval_keyframes(FCurve *fcu, BezTriple *bezts, float evaltime
const float change = bezt->vec[1][1] - prevbezt->vec[1][1];
const float duration = bezt->vec[1][0] - prevbezt->vec[1][0];
const float time = evaltime - prevbezt->vec[1][0];
const float amplitude = prevbezt->amplitude + fabsf(change); /* see T39405 */
const float amplitude = prevbezt->amplitude;
const float period = prevbezt->period;
/* value depends on interpolation mode */

61
source/blender/blenlib/intern/easing.c
View File

@ -38,6 +38,8 @@
#include "BLI_strict_flags.h"
/* blend if (amplitude < fabsf(change) */
#define USE_ELASTIC_BLEND
float BLI_easing_back_ease_in(float time, float begin, float change, float duration, float overshoot)
{
@ -141,76 +143,115 @@ float BLI_easing_cubic_ease_in_out(float time, float begin, float change, float
return change / 2 * (time * time * time + 2) + begin;
}
#ifdef USE_ELASTIC_BLEND
/**
* When the amplitude is less then the change, we need to blend
* \a f when we're close to the crossing point (int time), else we get an ugly sharp falloff.
*/
static float elastic_blend(float time, float change, float amplitude, float period, float f)
{
if (change) {
/* Looks like a magic number,
* but this is a part of the sine curve we need to blend from */
const float t = fabsf(period) / (32 * (float)M_PI);
if (amplitude) {
f *= amplitude / fabsf(change);
}
else {
f = 0.0f;
}
if (fabsf(time) < t) {
float l = fabsf(time) / t;
f = (f * l) + (1.0f - l);
}
}
return f;
}
#endif
float BLI_easing_elastic_ease_in(float time, float begin, float change, float duration, float amplitude, float period)
{
float s;
float f = 1.0f;
if (time == 0.0f)
return begin;
if ((time /= duration) == 1.0f)
return begin + change;
time -= 1.0f;
if (!period)
period = duration * 0.3f;
if (!amplitude || amplitude < fabsf(change)) {
#ifdef USE_ELASTIC_BLEND
f = elastic_blend(time, change, amplitude, period, f);
#endif
amplitude = change;
s = period / 4;
}
else
s = period / (2 * (float)M_PI) * asinf(change / amplitude);
time -= 1.0f;
return -(amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period)) + begin;
return (-f * (amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period))) + begin;
}
float BLI_easing_elastic_ease_out(float time, float begin, float change, float duration, float amplitude, float period)
{
float s;
float f = 1.0f;
if (time == 0.0f)
return begin;
if ((time /= duration) == 1.0f)
return begin + change;
time = -time;
if (!period)
period = duration * 0.3f;
if (!amplitude || amplitude < fabsf(change)) {
#ifdef USE_ELASTIC_BLEND
f = elastic_blend(time, change, amplitude, period, f);
#endif
amplitude = change;
s = period / 4;
}
else
s = period / (2 * (float)M_PI) * asinf(change / amplitude);
time = -time;
return (amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period) + change + begin);
return (f * (amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period))) + change + begin;
}
float BLI_easing_elastic_ease_in_out(float time, float begin, float change, float duration, float amplitude, float period)
{
float s;
float f = 1.0f;
if (time == 0.0f)
return begin;
if ((time /= duration / 2) == 2.0f)
return begin + change;
time -= 1.0f;
if (!period)
period = duration * (0.3f * 1.5f);
if (!amplitude || amplitude < fabsf(change)) {
#ifdef USE_ELASTIC_BLEND
f = elastic_blend(time, change, amplitude, period, f);
#endif
amplitude = change;
s = period / 4;
}
else
s = period / (2 * (float)M_PI) * asinf(change / amplitude);
time -= 1.0f;
if (time < 0.0f) {
return -0.5f * (amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period)) + begin;
f *= -0.5f;
return (f * (amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period))) + begin;
}
else {
time = -time;
return (0.5f * amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period)) + change + begin;
f *= 0.5f;
return (f * (amplitude * powf(2, 10 * time) * sinf((time * duration - s) * (2 * (float)M_PI) / period))) + change + begin;
}
}