glm::translate with local space

Question

I want to move a matrix according to it's own space (direction) and not world space.

Specifically I want to move the view matrix/the "camera".

glm::mat4x4 view = glm::lookAt(glm::vec3(1.1f, 1.3f, 1.2f),
                                   glm::vec3(0.0f, 0.0f, 0.0f),
                                   glm::vec3(0.0f, 1.0f, 0.0f));

view=glm::rotate(view, r, glm::vec3(0,1,0));
view=glm::translate(view, glm::vec3(x,y,z));

The translation is equal disregarding it's rotation, but I'd like to translate according to where the camera is facing, e.g. when the camera is facing the x axis, and I translate z, it should translate along world axis x. How can this be done?

Jherico Jherico · Accepted Answer · 2014-02-19T00:50:06

If you want to manipulate the camera position, you should store the camera position and only put it into view space when you need to.

glm::mat4 camera =  glm::inverse(glm::lookAt(
                               glm::vec3(1.1f, 1.3f, 1.2f),
                               glm::vec3(0.0f, 0.0f, 0.0f),
                               glm::vec3(0.0f, 1.0f, 0.0f)));
camera = glm::rotate(camera, r, glm::vec3(0,1,0));
camera = glm::translate(camera, glm::vec3(x,y,z));
glm::mat4 view = glm::inverse(camera);

It's also possible that doing pre-multiplcation of your view matrix is what you want, but I'm uncertain, since I try to avoid having to deal with pre vs post multiplication as if my life depended on it.

glm::mat4 view =  glm::lookAt(
                               glm::vec3(1.1f, 1.3f, 1.2f),
                               glm::vec3(0.0f, 0.0f, 0.0f),
                               glm::vec3(0.0f, 1.0f, 0.0f)));
view = glm::rotate(glm::mat4(), r, glm::vec3(0,1,0)) * view;
view = glm::translate(glm::mat4(), glm::vec3(x,y,z)) * view;

glm::translate with local space

1 Answers