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lottie: implement skew transformation

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Added support for skew transformation by
a specified angle around a specified axis.
Applied to layers and shapes, not to repeaters.

@Issue: https://github.com/thorvg/thorvg/issues/2262
This commit is contained in:
Mira Grudzinska 2024-05-15 01:26:02 +02:00 • committed by Hermet Park
parent baaae5e416
commit dc6ddd83f5
3 changed files with 50 additions and 2 deletions
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46
src/loaders/lottie/tvgLottieBuilder.cpp
View file

@ -129,6 +129,42 @@ static void _rotationZ(Matrix* m, float degree)
}
static void _skew(Matrix* m, float angleDeg, float axisDeg)
{
auto angle = -mathDeg2Rad(angleDeg);
float tanVal = tanf(angle);
axisDeg = fmod(axisDeg, 180.0f);
if (fabsf(axisDeg) < 0.01f || fabsf(axisDeg - 180.0f) < 0.01f || fabsf(axisDeg + 180.0f) < 0.01f) {
float cosVal = cosf(mathDeg2Rad(axisDeg));
auto B = cosVal * cosVal * tanVal;
m->e12 += B * m->e11;
m->e22 += B * m->e21;
return;
} else if (fabsf(axisDeg - 90.0f) < 0.01f || fabsf(axisDeg + 90.0f) < 0.01f) {
float sinVal = -sinf(mathDeg2Rad(axisDeg));
auto C = sinVal * sinVal * tanVal;
m->e11 -= C * m->e12;
m->e21 -= C * m->e22;
return;
}
auto axis = -mathDeg2Rad(axisDeg);
float cosVal = cosf(axis);
float sinVal = sinf(axis);
auto A = sinVal * cosVal * tanVal;
auto B = cosVal * cosVal * tanVal;
auto C = sinVal * sinVal * tanVal;
auto e11 = m->e11;
auto e21 = m->e21;
m->e11 = (1.0f - A) * e11 - C * m->e12;
m->e12 = B * e11 + (1.0f + A) * m->e12;
m->e21 = (1.0f - A) * e21 - C * m->e22;
m->e22 = B * e21 + (1.0f + A) * m->e22;
}
static bool _updateTransform(LottieTransform* transform, float frameNo, bool autoOrient, Matrix& matrix, uint8_t& opacity, LottieExpressions* exps)
{
mathIdentity(&matrix);
@ -154,6 +190,16 @@ static bool _updateTransform(LottieTransform* transform, float frameNo, bool aut
_rotateX(&matrix, transform->rotationEx->x(frameNo, exps));
}
auto skewAngle = transform->skewAngle(frameNo, exps);
if (fabsf(skewAngle) > 0.01f) {
// For angles where tangent explodes, the shape degenerates into an infinitely thin line.
// This is handled by zeroing out the matrix due to finite numerical precision.
skewAngle = fmod(skewAngle, 180.0f);
if (fabsf(skewAngle - 90.0f) < 0.01f || fabsf(skewAngle + 90.0f) < 0.01f) return false;
auto skewAxis = transform->skewAxis(frameNo, exps);
_skew(&matrix, skewAngle, skewAxis);
}
auto scale = transform->scale(frameNo, exps);
mathScaleR(&matrix, scale.x * 0.01f, scale.y * 0.01f);

2
src/loaders/lottie/tvgLottieModel.h
View file

@ -338,6 +338,8 @@ struct LottieTransform : LottieObject
LottiePoint scale = Point{100.0f, 100.0f};
LottiePoint anchor = Point{0.0f, 0.0f};
LottieOpacity opacity = 255;
LottieFloat skewAngle = 0.0f;
LottieFloat skewAxis = 0.0f;
SeparateCoord* coords = nullptr; //either a position or separate coordinates
RotationEx* rotationEx = nullptr; //extension for 3d rotation

4
src/loaders/lottie/tvgLottieParser.cpp
View file

@ -585,8 +585,8 @@ LottieTransform* LottieParser::parseTransform(bool ddd)
else if (transform->rotationEx && KEY_AS("ry")) parseProperty<LottieProperty::Type::Float>(transform->rotationEx->y);
else if (transform->rotationEx && KEY_AS("rz")) parseProperty<LottieProperty::Type::Float>(transform->rotation);
else if (KEY_AS("nm")) transform->name = getStringCopy();
//else if (KEY_AS("sk")) //TODO: skew
//else if (KEY_AS("sa")) //TODO: skew axis
else if (KEY_AS("sk")) parseProperty<LottieProperty::Type::Float>(transform->skewAngle);
else if (KEY_AS("sa")) parseProperty<LottieProperty::Type::Float>(transform->skewAxis);
else skip(key);
}
transform->prepare();