Blendshapes are a commonly used technique in animation tools that allow the deformation of a character’s face to create various facial expressions and emotions. In this blog post, we will explore how to implement blendshapes in C++ for animation tools.
Table of Contents
Introduction to Blendshapes
Blendshapes, also known as morph targets, are a way to manipulate and blend different vertex positions of a 3D model to create various facial expressions. Each blendshape represents a different facial expression, such as a smile, frown, or raised eyebrows. By interpolating the values of the blendshapes, we can smoothly transition between different facial expressions.
Animation tools, such as 3D modeling software or game engines, use blendshapes to give characters more life-like and expressive facial animations. These tools allow animators to control the weights of each blendshape, determine the degree of deformation, and create complex facial animations.
Implementing Blendshapes in C++
To implement blendshapes in C++, we first need to understand the basic concept of storing and manipulating vertex positions. Typically, the vertex positions of a 3D model are stored in a vertex buffer, often represented as an array of structures. Each structure contains the X, Y, and Z coordinates of a vertex.
To create blendshapes, we need to store the base mesh, which represents the neutral expression of the character, and the blendshape targets, which represent different facial expressions. Each blendshape target is also represented as an array of structures, containing the modified vertex positions for that particular expression.
Here is an example code snippet that demonstrates the implementation of blendshapes in C++:
struct Vertex
{
float x, y, z;
};
struct Mesh
{
std::vector<Vertex> vertices;
};
struct Blendshape
{
std::string name;
std::vector<Vertex> vertices;
float weight;
};
void ComputeDeformedVertices(const Mesh& baseMesh, const std::vector<Blendshape>& blendshapes, std::vector<Vertex>& deformedVertices, float blendWeight)
{
deformedVertices = baseMesh.vertices;
for (const auto& blendshape : blendshapes)
{
for (size_t i = 0; i < deformedVertices.size(); i++)
{
deformedVertices[i].x += blendshape.vertices[i].x * blendshape.weight * blendWeight;
deformedVertices[i].y += blendshape.vertices[i].y * blendshape.weight * blendWeight;
deformedVertices[i].z += blendshape.vertices[i].z * blendshape.weight * blendWeight;
}
}
}
In the above code, we define the Vertex struct to store the X, Y, and Z coordinates of a vertex. The Mesh struct represents the base mesh, and the Blendshape struct represents each blendshape target, along with its weight. The ComputeDeformedVertices function takes the base mesh, blendshapes, blend weight, and outputs the deformed vertices.
The function calculates the deformed vertices by adding the weighted delta values of each blendshape to the base mesh vertices. The amount of deformation is determined by the blend weight.
Conclusion
Blendshapes are a powerful technique used in animation tools to create expressive facial animations. Understanding and implementing blendshapes in C++ allows developers to build their animation tools with the ability to manipulate and blend facial expressions seamlessly. By providing animators with control over blend weights, they can create realistic and lifelike character animations.
By incorporating blendshapes into your animation tools, you can enhance the overall quality and attractiveness of your animations. Start experimenting with blendshapes in C++ to unlock a whole new level of facial animations in your projects.
References:
#animation #blendshapes