How do you rotate a vector by 90 degrees?
Rotating a vector 90 degrees is particularily simple. (x, y) rotated 90 degrees around (0, 0) is (-y, x) . If you want to rotate clockwise, you simply do it the other way around, getting (y, -x) .
What is glMatrixMode in OpenGL?
glMatrixMode sets the current matrix mode. mode can assume one of four values: Applies subsequent matrix operations to the modelview matrix stack. GL_PROJECTION. Applies subsequent matrix operations to the projection matrix stack.
What does glm :: translate do?
glm::translate function, together with a translation vector. It returns our translation matrix. Then we multiply our vector by the transformation matrix and output the result.
How do you find the directional angle of a vector?
Apply the equation theta = tan–1(y/x) to find the angle: tan–1(1.0/–1.0) = –45 degrees. However, note that the angle must really be between 90 degrees and 180 degrees because the first vector component is negative and the second is positive.
How do you make a vector go the opposite direction?
A negative sign will reverse the direction of a vector and make it a negative vector. Vectors are only negative with respect to another vector. For example, if a vector PQ points from left to right, then the vector QP will point from right to left.
How to rotate a vector by a given direction in OpenGL?
To rotate your vec you can write vec = glm::vec3 (rotationMat * glm::vec4 (vec, 1.0)); Note: Because you have a 4×4 matrix you need a vec4 to multiply it with the matrix. Generally it is a good idea always to use vec4 when working with OpenGL because vectors in smaller dimension will be converted to homogeneous vertex coordinates anyway.
How to get vector at 90 degrees from provided vector?
One is your “provided vector” and the other is a vector perpendicular to the plane you want to rotate 90 degrees over. This will return a vector that is perpendicular (at 90 degrees) to both normals (unit vectors). some_vector must not point in the same direction nor can be opposite to provided_vector.
How do you convert degrees to radians in GLM?
Note that to convert from degrees to radians, use glm::radians(degrees) That takes the Model matrix and applies rotation on top of all the operations that are already in there. The other functions translate and scale do the same. That way it’s possible to combine many transformations in a single matrix.
Do you need to multiply the model matrix in GLM?
You need to multiply your Model matrix. Because that is where model position, scaling and rotation should be (that’s why it’s called the model matrix). All you need to do is (see here) Model = glm::rotate(Model, angle_in_radians, glm::vec3(x, y, z)); // where x, y, z is axis of rotation (e.g. 0 1 0)