So I'm trying to translate vertices on the CPU for my batch rendering system. And I've tried to replicate glsl but it simply doesn't work. (The model doesn't show up)
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?
}
And here is the "Util::createTransform" function:
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;
}
So, where did I screw up?
Util::createTransform() returns a glm::mat4, while you just take the rightmost column of that matrix and store it in a glm::vec4.
You are trying to create a transform matrix which represents the composition of a rotation and a translation. This operation cannot be represented by a single vec4. You could do that for a translation alone, and then would simply add the same vector to all of your vertices to translate the offset around. However, with rotations - or other transformations besides translations - you will need the full matrix.
Since glm uses the same conventions the old "fixed function" GL used, you have to use the Matrix * Vector multiplication order to apply a transformation matrix to your vertices. So your code should look like this:
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];
}