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POopenGL: What is the order of transformations using glm?
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copied!<p>I loaded an object from a .obj file. I am trying to apply a <code>glm::rotate, glm::translate, glm::scale</code> to it.</p> <p>The movement (translation and rotation) is made using keyboard input like this;</p> <pre><code>// speed is 10 // angle starts at 0 if (keys[UP]) { movex += speed * sin(angle); movez += speed * cos(angle); } if (keys[DOWN]) { movex -= speed * sin(angle); movez -= speed * cos(angle); } if (keys[RIGHT]) { angle -= PI / 180; } if (keys[LEFT]) { angle += PI / 180; } </code></pre> <p>and then, the transformations:</p> <pre><code>// use shader glUseProgram(gl_program_shader); // send the uniform matrices to the shader glUniformMatrix4fv(glGetUniformLocation(gl_program_shader, "model_matrix"), 1, false, glm::value_ptr(model_matrix)); glUniformMatrix4fv(glGetUniformLocation(gl_program_shader, "view_matrix"), 1, false, glm::value_ptr(view_matrix)); glUniformMatrix4fv(glGetUniformLocation(gl_program_shader, "projection_matrix"), 1, false, glm::value_ptr(projection_matrix)); glm::mat4 rotate = glm::rotate(model_matrix, angle, glm::vec3(0, 1, 0)); glm::mat4 translate = glm::translate(model_matrix, glm::vec3(RADIUS + movex, 0, -RADIUS + movez)); glm::mat4 scale = glm::scale(model_matrix, glm::vec3(20.0, 20.0, 20.0)); glUniformMatrix4fv(glGetUniformLocation(gl_program_shader, "model_matrix"), 1, false, glm::value_ptr(translate * scale * rotate)); glBindVertexArray(ironMan->vao); glDrawElements(GL_TRIANGLES, ironMan->num_indices, GL_UNSIGNED_INT, 0); </code></pre> <p>If I don't use KEY_RIGHT / KEY_LEFT, it works as expected (which means that it translates the object forward and backward). If I use them, it rotates around it's own center, but when I press KEY_UP / KEY_DOWN, it translates ... well, not as expected. </p> <p>I've put on the notifyKeyPressed() function a case to print out the movex, movey and angle value and it seems that the angle is not the one that it should: </p> <ul> <li>when the IronMan is with it's back at me, angle = 0 - this is the start point; </li> <li>when the IronMan is with his face on the right, the angle should be around -PI / 2 (-1.57), but it is around -80/-90.</li> </ul> <p>I thought this was because of the <code>glm::scale</code>, but I changed the values and nothing changed.</p> <p>Any idea why is the angle acting like this?</p>

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