glm rotate usage in Opengl

Question

I am rendering a cone  and I would like to rotate it  90 degrees anti-clockwise  so that the pointy end faces west  I am using OpenGL 3    Here is my code in my Cone cpp so far     PROJECTION     glm  mat4 Projection   glm  perspective 45 0f  1 0f  0 1f  100 0f          VIEW     glm  mat4 View   glm  mat4 1        View   glm  translate View  glm  vec3 2 0f 4 0f  -25 0f           MODEL     glm  mat4 Model   glm  mat4 1 0         Scale by factor 0 5     Model   glm  scale glm  mat4 1 0f  glm  vec3 0 5f         glm  mat4 MVP   Projection   View   Model      glUniformMatrix4fv glGetUniformLocation shaderprogram spaceship   MVP matrix    1  GL FALSE  glm  value ptr MVP         glClearColor 0 0  0 0  0 0  1 0        glDrawArrays GL LINE STRIP  start cone  end cone      Not all of the code is shown   Can somebody guide me through the rotation  I do have to multiply the View matrix right   with  glm rotate  function

User · Answer

I noticed that you can also get errors if you don't specify the angles correctly, even when using glm::rotate(Model, angle_in_degrees, glm::vec3(x, y, z)) you still might run into problems. The fix I found for this was specifying the type as glm::rotate(Model, (glm::mediump_float)90, glm::vec3(x, y, z)) instead of just saying glm::rotate(Model, 90, glm::vec3(x, y, z))

Or just write the second argument, the angle in radians (previously in degrees), as a float with no cast needed such as in:

glm::mat4 rotationMatrix = glm::rotate(glm::mat4(1.0f), 3.14f, glm::vec3(1.0));

You can add glm::radians() if you want to keep using degrees. And add the includes:

#include "glm/glm.hpp"
#include "glm/gtc/matrix_transform.hpp"

User · Answer

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       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   note  earlier versions accepted angles in degrees  This is deprecated since 0 9 6  Model   glm  rotate Model  angle in degrees  glm  vec3 x  y  z       where x  y  z is axis of rotation  e g  0 1 0

User · Answer

GLM has good example of rotation   http   glm g-truc net code html  glm  mat4 Projection   glm  perspective 45 0f  4 0f   3 0f  0 1f  100 f   glm  mat4 ViewTranslate   glm  translate      glm  mat4 1 0f       glm  vec3 0 0f  0 0f  -Translate     glm  mat4 ViewRotateX   glm  rotate      ViewTranslate      Rotate y      glm  vec3 -1 0f  0 0f  0 0f     glm  mat4 View   glm  rotate      ViewRotateX      Rotate x      glm  vec3 0 0f  1 0f  0 0f     glm  mat4 Model   glm  scale      glm  mat4 1 0f       glm  vec3 0 5f     glm  mat4 MVP   Projection   View   Model  glUniformMatrix4fv LocationMVP  1  GL FALSE  glm  value ptr MVP

[c++] glm rotate usage in Opengl

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