我有一个球体和通过其原点的轴。我想将球体在其轴上上下移动。在它的起始位置没有问题,因为轴线开始平行于全局的y轴,但是当我旋转球体,因此球体轴线围绕z轴旋转时,就变得复杂了。
我的第一个想法是将轴归一化,并简单地将其作为平移矩阵的平移向量。然后将翻译矩阵与归一化的轴相乘,球体应该在轴上推一个单位。
这是我已经得到的代码。
class Object
{
public:
inline Object()
: vao(0),
positionBuffer(0),
colorBuffer(0),
indexBuffer(0),
elements(0),
vertices(0)
{}
inline ~Object() { // GL context must exist on destruction
glDeleteVertexArrays(1, &vao);
glDeleteBuffers(1, &indexBuffer);
glDeleteBuffers(1, &colorBuffer);
glDeleteBuffers(1, &positionBuffer);
}
GLuint vao; // vertex-array-object ID
GLuint positionBuffer; // ID of vertex-buffer: position
GLuint colorBuffer; // ID of vertex-buffer: color
GLuint indexBuffer; // ID of index-buffer
GLuint elements; // Number of Elements
vector<glm::vec3> vertices;
glm::vec3 mp;
glm::mat4x4 model; // model matrix
};
glm::vec3 axis = glm::normalize(glm::vec3{
sphereax.vertices[0].x - sphereax.vertices[1].x,
sphereax.vertices[0].y - sphereax.vertices[1].y,
sphereax.vertices[0].z - sphereax.vertices[1].z}
);
translateObject(earth, axis);
void translateObject(Object &obj, glm::vec3 &translation)
{
glm::mat4x4 trans_mat = glm::translate(glm::mat4(1.0f), translation);
for (int i = 0; i < obj.vertices.size(); i++)
{
obj.vertices[i] = glm::vec3(glm::vec4(obj.vertices[i], 1.0f) * trans_mat);
}
obj.mp = glm::vec3(glm::vec4(obj.mp, 1.0f) * trans_mat);
}
翻译矩阵 translateObject();
似乎是正确的,但其中一个点的乘法和变换矩阵没有任何效果。
我建议做以下工作。
glm::vec3 rotation_axis = ...; // sphere axis
float axis_rot_angle = ...; // current axis rotation angle in radians
float distance_to_center = ...; // distance from the center of the world
float world_rot_angle = ...; // current world rotation angle in radians
glm::mat4 sphere_rot = glm::rotation(glm::mat4(1.0f), axis_rot_angle, rotation_axis);
glm::mat4 sphere_trans = glm::translate(glm::mat4(1.0f), glm::vec3(distance_to_center, 0.0f, 0.0f));
glm::mat4 world_rot = glm::rotation(glm::mat4(1.0f), world_rot_angle, glm::vec3(0.0f, 0.0f, 1.0f));
glm::mat4 model_mat = world_rot * sphere_trans * sphere_rot;