C++ glm Opengl转换和旋转glm::vec4 4与glm::mat4

Question

因此，我正试图为我的批处理渲染系统翻译CPU上的顶点。我试过复制glsl，但它根本不起作用。(模型没有出现)

glm::vec4 off = glm::vec4(0, 0, 0, 1);

off = Util::createTransform(offset, glm::vec3(0, 45, 0)) * off; //translated the vertex by the offset(supplied by the function) and rotates by 45 degrees on the Y axis

for (int i = 0; i < Tvertex.size(); i++) {
    Tvertex[i] *= glm::vec3(off.x, off.y, off.z); //I think its here I might have messed up?
}

下面是"Util::createTransform“函数：

glm::mat4 Util::createTransform(glm::vec3 pos, glm::vec3 rot) {
    glm::mat4 trans = glm::mat4(1.0);
    trans = glm::rotate(trans, glm::radians(rot.x), glm::vec3(1, 0, 0));
    trans = glm::rotate(trans, glm::radians(rot.y), glm::vec3(0, 1, 0));
    trans = glm::rotate(trans, glm::radians(rot.z), glm::vec3(0, 0, 1));
    trans = glm::translate(trans, pos);
    return trans;
}

我在哪里搞砸了？

Answer 1

Util::createTransform()返回一个glm::mat4，而您只需获取该矩阵的最右边列并将其存储在一个glm::vec4中。

您正在尝试创建一个转换矩阵，它表示旋转和平移的组合。此操作不能由单个vec4表示。您可以单独进行转换，然后简单地将相同的向量添加到所有顶点，以转换偏移量。但是，对于轮转--或者除了翻译之外的其他转换--您将需要完整的矩阵。

由于glm使用旧的“固定函数”GL所使用的相同约定，所以您必须使用矩阵*向量乘法命令将转换矩阵应用到顶点。所以您的代码应该如下所示：

glm::mat4 off = Util::createTransform(offset, glm::vec3(0, 45, 0)) * off; //translated the vertex by the offset(supplied by the function) and rotates by 45 degrees on the Y axis

for (int i = 0; i < Tvertex.size(); i++) {
    Tvertex[i] = off * Tvertex[i];
}

Answer 2

这个怎么样：

// I think its here I might have messed up?
Tvertex[i] *= glm::vec3(off.x, off.y, off.z); 

// I think that might be what you wanted:
Tvertex[i] += glm::vec3(off.x, off.y, off.z);