CODEWITHSUNDEEP
openglrotationquaternionsglm-math
Hangmoon
Hangmoon

Reputation: 1

OpenGl glm local rotation

I need to rotate object in local coordinates system, like you can rotate it in 3dmax\maya etc...

My current code is:

ModelMatrix = glm::mat4(1.0f);
TransformMatrix = glm::mat4(1.0f);
ScaleMatrix = glm::mat4(1.0f);
RotateMatrix = glm::mat4(1.0f);

ScaleMatrix = glm::scale(ScaleMatrix, glm::vec3(scalex, scalez, scaley));
TransformMatrix = glm::translate(TransformMatrix, glm::vec3(x, z, y));
RotateMatrix = glm::rotate(RotateMatrix, anglex, glm::vec3(1, 0, 0));
RotateMatrix= glm::rotate(RotateMatrix, angley, glm::vec3(0, 0, 1));
RotateMatrix = glm::rotate(RotateMatrix, anglez, glm::vec3(0, 1, 0));

ModelMatrix = TransformMatrix * ScaleMatrix* RotateMatrix;
MVP = Projection * View * ModelMatrix ;

anglex,y,z - comes from keyboard.

Right now only last dimension works as local (im my example it's glm::vec3(0, 1, 0) Z axis) At this IMAGE I show what I needed(2) and what I've got(3)... If I changes "anglez" it's always works as ROLL. But anglex and angley is in the world coordinates system.

The second my attempt - use Quaternions:

quat MyQuaternion= glm::quat(cos(glm::radians(xangle / 2)), 0, sin(glm::radians(xangle / 2)), 0);
    quat MyQuaternion2 = glm::quat(cos(glm::radians(yangle/ 2)), sin(glm::radians(yangle / 2)), 0, 0);
    quat MyQuaternion3 = glm::quat(cos(glm::radians(zangle / 2)), 0,0,sin(glm::radians(zangle / 2)));
    glm::mat4 RotationMatrix = toMat4(MyQuaternion*MyQuaternion2*MyQuaternion3);

But I have the same result

Upvotes: 0

Views: 1346

Answers (1)

Nico Schertler
Nico Schertler

Reputation: 32627

You should modify the entire ModelMatrix instead of the angles. Initialize ModelMatrix to the identity matrix. Then, when you process keyboard input:

if(rotate about x-axis)
    ModelMatrix = glm::rotate(ModelMatrix, angle, glm::vec3(1, 0, 0));
if(rotate about y-axis)
    ModelMatrix = glm::rotate(ModelMatrix, angle, glm::vec3(0, 1, 0));
if(rotate about z-axis)
    ModelMatrix = glm::rotate(ModelMatrix, angle, glm::vec3(0, 0, 1));
if(any rotation happened)
    MVP = Projection * View * ModelMatrix ;

You can do this modification at any level. Either the MVP level, the ModelMatrix level (as shown here) or the RotateMatrix level.

Upvotes: 0

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