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

Question

所以我想为我的批处理渲染系统翻译CPU上的顶点。我试图复制glsl，但它不起作用。 （该模型没有显示出来）

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? 
} 

这里是 “的Util :: createTransform” 功能：

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; 
} 

那么，在哪里我搞砸了？

Answer 1

Util::createTransform()返回glm::mat4，而你只需要的是矩阵的最右列，并将其存储在一个glm::vec4。

您正试图创建一个表示旋转和平移组成的变换矩阵。此操作不能由单个vec4表示。您可以单独使用翻译，然后只需将相同的矢量添加到所有顶点以转换偏移即可。但是，随着旋转 - 或除翻译之外的其他转换 - 您将需要完整的矩阵。

由于glm使用与旧的“固定功能”GL相同的约定，所以必须使用Matrix *向量乘法顺序将转换矩阵应用于顶点。所以你的代码应该是这样的：

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

如何：

// 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);