CODEWITHSUNDEEP
openglgraphicspointsglm-math
Schnigges
Schnigges

Reputation: 1326

Displace cube into origin with OpenGL

I'm drawing a bunch of points inside a 64x64x64 cube and can't figure out how to displace the origin so that rotations are done around the center of the cube. My vertex data is stored inside a 1D array, going from {(0,0,0), (0,0,1), ..., (63, 63, 63)}.

This is my current code to setup the matrices each frame:

// Set ProjectionMatrix
projectionMatrix = glm::perspective(90.0f, (GLfloat)width / (GLfloat) height,0.1f, 1000.f);
glUniformMatrix4fv(location_projectionMatrix, 1, GL_FALSE, glm::value_ptr(projectionMatrix));

// Set ModelViewMatrix
glm::mat4 identity = glm::mat4(1.0);
glm::mat4 viewTranslate = glm::translate(identity, glm::vec3(0.0f, 0.0f, -translate_z));
glm::mat4 viewRotateX   = glm::rotate(viewTranslate, rotate_x, glm::vec3(1.0f, 0.0f, 0.0f));
glm::mat4 viewRotateY   = glm::rotate(viewRotateX, rotate_y, glm::vec3(0.0f, 1.0f, 0.0f));
modelViewMatrix = viewRotateY;
glUniformMatrix4fv(location_modelViewMatrix, 1, GL_FALSE, glm::value_ptr(modelViewMatrix));

I tried to just translate the cube by -32 into the x and y direction, but without success.

Upvotes: 0

Views: 314

Answers (1)

Michael IV
Michael IV

Reputation: 11436

Matrix operations are non commutative .It means that doing translation first and then rotation is not the same as doing rotation and then translation.Usually the order is :scale-> rotation -> translation. So try this instead:

glm::mat4 viewRotateX   = glm::rotate(identity, rotate_x, glm::vec3(1.0f, 0.0f, 0.0f));
glm::mat4 viewRotateY   = glm::rotate(viewRotateX, rotate_y, glm::vec3(0.0f, 1.0f, 0.0f));
glm::mat4 viewTranslate = glm::translate(viewRotateY   , glm::vec3(0.0f, 0.0f, -translate_z));

Upvotes: 2

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