Added bezier curves

1 files changed, 55 insertions, 0 deletions

diff --git a/src/helpers/BezierCurve.cpp b/src/helpers/BezierCurve.cpp
new file mode 100644
index 00000000..845992bd
--- /dev/null
+++ b/src/helpers/BezierCurve.cpp
@@ -0,0 +1,55 @@
+#include "BezierCurve.hpp"
+
+void CBezierCurve::setup(std::vector<Vector2D>* pVec) {
+    m_dPoints.clear();
+
+    m_dPoints.emplace_back(Vector2D(0,0));
+
+    for (auto& p : *pVec) {
+        m_dPoints.push_back(p);
+    }
+
+    m_dPoints.emplace_back(Vector2D(1,1));
+
+    RASSERT(m_dPoints.size() == 4, "CBezierCurve only supports cubic beziers! (points num: %i)", m_dPoints.size());
+
+    // bake 100 points for faster lookups
+    // T -> X ( / 100 )
+    for (int i = 0; i < 100; ++i) {
+        m_aPointsBaked[i] = getXForT((i + 1) / 100.f);
+    }
+}
+
+float CBezierCurve::getYForT(float t) {
+    return 3 * t * pow(1 - t, 2) * m_dPoints[1].y + 3 * pow(t, 2) * (1 - t) * m_dPoints[2].y + pow(t, 3);
+}
+
+float CBezierCurve::getXForT(float t) {
+    return 3 * t * pow(1 - t, 2) * m_dPoints[1].x + 3 * pow(t, 2) * (1 - t) * m_dPoints[2].x + pow(t, 3);
+}
+
+// Todo: this probably can be done better and faster
+float CBezierCurve::getYForPoint(float x) {
+    // binary search for the range UPDOWN X
+    float upperX = 1;
+    float lowerX = 0;
+    float mid = 0.5;
+
+    while(std::abs(upperX - lowerX) > 0.01f) {
+        if (m_aPointsBaked[((int)(mid * 100.f))] > x) {
+            upperX = mid;
+        } else {
+            lowerX = mid;
+        }
+
+        mid = (upperX + lowerX) / 2.f;
+    }
+
+    // in the name of performance i shall make a hack
+    const auto PERCINDELTA = (x - m_aPointsBaked[(int)(100.f * lowerX)]) / (m_aPointsBaked[(int)(100.f * upperX)] - m_aPointsBaked[(int)(100.f * lowerX)]);
+
+    if (std::isnan(PERCINDELTA) || std::isinf(PERCINDELTA)) // can sometimes happen for VERY small x
+        return 0.f;
+
+    return getYForT(mid + PERCINDELTA * 0.01f);
+}
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