Animation plays a crucial role in creating immersive experiences in video games, movies, and other digital media. To achieve smooth and realistic animation, non-linear animation editing is essential. Non-linear animation editing allows animators to control different aspects of an animation, such as timing, curves, and blending, to ensure the desired output. In this blog post, we will explore how to implement non-linear animation editing in C++ for animation tools.

Table of Contents

• Introduction
• Key Concepts
• Data Structures
• Interpolation Techniques
• Animation Blending
• Curve Evaluation
• Conclusion

Introduction

Non-linear animation editing provides animators with the freedom to manipulate an animation’s timeline by adding, removing, and modifying keyframes. It also allows for controlling the interpolation between keyframes, giving animators fine-grained control over motion curves.

To implement non-linear animation editing in C++, we need to understand a few key concepts and techniques.

Key Concepts

• Keyframe: A keyframe represents a specific point in time in an animation where important changes occur. Keyframes store the animation values of properties, such as position, rotation, and scale.
• Timeline: A timeline stores all the keyframes of an animation, allowing animators to visualize and edit the animation. Each timeline is associated with a specific property or bone.
• Curve: A curve defines the motion between two keyframes. It represents the interpolation between the keyframes’ values.
• Interpolation: Interpolation defines how an animation property value changes over time. Common interpolation techniques include linear interpolation, cubic interpolation, and spline interpolation.
• Blending: Blending refers to the process of smoothly combining multiple animations at different weights or percentages. It allows for seamless transitions between animations.

Data Structures

To implement non-linear animation editing, we need suitable data structures to store and manipulate the animation data. Here are some essential data structures:

• Keyframe: A keyframe structure containing information such as time, property values, and curve type.
• Timeline: A timeline structure holding a collection of keyframes for a specific property or bone.
• AnimationClip: A collection of timelines representing the different animation properties or bones.
• AnimationBlender: A utility class to handle blending between different animations.

Interpolation Techniques

Interpolation techniques determine how an animation property value changes between keyframes. Common interpolation techniques include:

• Linear Interpolation: Linear interpolation smoothly transitions between values by using a straight line.
• Cubic Interpolation: Cubic interpolation uses cubic Hermite splines to create smooth curves.
• Spline Interpolation: Spline interpolation uses spline curves to generate more complex and natural motion.

Implementing these interpolation techniques requires understanding the mathematics behind curves and how to calculate points along the curves.

Animation Blending

Animation blending allows for the seamless combination of multiple animations, enabling smooth transitions between different motions. To implement animation blending, we can use techniques like:

• Weighted Blending: Weighted blending combines animations by assigning different weights to each animation. The final animation is a weighted average of the animations based on their weights.
• Crossfading: Crossfading gradually blends between two animations by fading out the current animation and fading in the target animation. This results in a smooth transition from one animation to another.

Implementing animation blending requires interpolating between animations at different weights and properly managing the blending process.

Curve Evaluation

To evaluate a motion curve at a given time, we need to interpolate between the keyframes that surround the desired time. This can be done using the interpolation techniques mentioned earlier.

Depending on the curve type (e.g., linear, cubic, spline), the evaluation process may vary. The key is to obtain the correct interpolation function for each type of curve and calculate the intermediate values accurately.

Conclusion

Implementing non-linear animation editing in C++ for animation tools involves understanding key concepts, interpolation techniques, animation blending, and curve evaluation. By leveraging suitable data structures and algorithms, animators can have powerful tools at their disposal to create rich and dynamic animations.