Hi,

I'm new to OpenGL and quaternions, but after doing some tutorials from opengl-tutorial, I'm trying to do the MVP with quats.

With the MVP I get the expected rotated triangle. But with quats I get a different rotation (I would link to an image, but seems I can't).

This is what I have in my C++ loop:
Code :
		// Send our transformation to the currently bound shader, 
		// in the "MVP" uniform
		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
 
		// Let's try the same Matrix in Quat
		glm::quat qModel = glm::gtx::quaternion::toQuat(MVP);
		glm::gtc::quaternion::normalize(qModel);
		glUniform4f(qModelID, qModel.x, qModel.y, qModel.z, qModel.w);

This is what I have in the shader:
Code :
// Values that stay constant for the whole mesh.
uniform mat4 MVP;
 
uniform vec4 qModel;
 
//rotate vector, taken from kri engine
vec3 qrot(vec4 q, vec3 v)	{
	return v + 2.0*cross(q.xyz, cross(q.xyz,v) + q.w*v);
}
 
 
void main(){
 
	// Output position of the vertex, in clip space : MVP * position
	//gl_Position = MVP * vec4(vertexPosition_modelspace, 1);
 
	gl_Position =  vec4(qrot(qModel, vertexPosition_modelspace),1);	
}

Like you can see, for now, I just want to converted the MVP matrix to a Quat and use it in the shader, but I'm messing something up.

Any help would be appreciated.

Many thanks.