Animation tools often require the ability to smoothly interpolate between keyframes to create fluid and seamless animations. This is where keyframe interpolation comes into play. In this article, we will explore how to implement keyframe interpolation using C++.

Table of Contents

• Introduction to Keyframe Interpolation
• Linear Interpolation
• Bezier Interpolation
• Spline Interpolation
• Conclusion

Introduction to Keyframe Interpolation

Keyframe interpolation is the process of calculating intermediate values between two keyframes to create smooth transitions. In animation, keyframes represent specific frames at which important changes occur. By interpolating the values between keyframes, we can create the illusion of continuous motion.

Linear Interpolation

The simplest form of keyframe interpolation is linear interpolation, also known as lerp. Linear interpolation calculates intermediate values by evenly distributing the change in values between two keyframes. It is the most straightforward and efficient interpolation method.

Here’s an example implementation of linear interpolation in C++:

template<typename T>
T lerp(const T& a, const T& b, float t) {
    return a + (b - a) * t;
}

In the above code, a and b represent the values of the keyframes, and t is a value between 0 and 1 representing the interpolation factor. The function returns the interpolated value between a and b based on the interpolation factor t.

Bezier Interpolation

Bezier interpolation allows for more control and flexibility in interpolation by using control points to define the shape of the interpolation curve. This type of interpolation is commonly used in graphic design and animation to create smooth curves.

Implementing Bezier interpolation in C++ can be a bit more complex, as it involves calculating the positions of the control points and interpolating between them using the Bezier formula. However, various libraries exist that provide ready-to-use functions for Bezier interpolation.

Spline Interpolation

Spline interpolation is a widely used method for creating smooth and natural-looking animations. It involves fitting a curve to a set of control points, allowing for more organic interpolation. Spline interpolation can be implemented using various algorithms like Catmull-Rom or B-spline.

Here’s an example code snippet for Catmull-Rom spline interpolation in C++:

glm::vec3 catmullRomInterpolation(const glm::vec3& p0, const glm::vec3& p1, const glm::vec3& p2, const glm::vec3& p3, float t) {
    float t2 = t * t;
    float t3 = t2 * t;
    float blend1 = -t3 + 2.0f * t2 - t;
    float blend2 = 3.0f * t3 - 5.0f * t2 + 2.0f;
    float blend3 = -3.0f * t3 + 4.0f * t2 + t;
    float blend4 = t3 - t2;

    glm::vec3 result = (p0 * blend1 + p1 * blend2 + p2 * blend3 + p3 * blend4) * 0.5f;

    return result;
}

In the above example, p0, p1, p2, and p3 represent the control points, and t is the interpolation factor. The function returns the interpolated value based on the Catmull-Rom spline formula.

Conclusion

Keyframe interpolation is a fundamental technique for creating smooth animations in various animation tools. In this article, we explored linear interpolation, Bezier interpolation, and spline interpolation in the context of C++ programming.

By implementing these interpolation methods, you can enhance your animation tools’ capabilities and create visually pleasing and realistic animations.

Happy animating! 🎬🚀