PyOpenGL 对象保持围绕原点旋转

Question

所以我只是测试一下我的引擎是如何工作的，并尝试使用以下方法简单地旋转一个对象。

rot_y = Matrix44.from_y_rotation(glfw.get_time() * 0.5)

但是...它围绕原点而不是原点旋转。

主要代码： http://hatebin.com/rtuqgeqptw

projection = pyrr.matrix44.create_perspective_projection_matrix(60.0, w_width/w_height, 0.1, 100.0)
sphere_model = matrix44.create_from_translation(Vector3([-4.0,0.0,-3.0]))
monkey_model = matrix44.create_from_translation(Vector3([0.0,0.0,-3.0]))

glUseProgram(shader)
model_loc = glGetUniformLocation(shader, "model")
view_loc = glGetUniformLocation(shader, "view")
proj_loc = glGetUniformLocation(shader, "proj")

glUniformMatrix4fv(proj_loc, 1, GL_FALSE, projection)

while not glfw.window_should_close(window):
    glfw.poll_events()
    do_movement()

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)

    view = cam.get_view_matrix()
    glUniformMatrix4fv(view_loc, 1, GL_FALSE, view)

    rot_y = Matrix44.from_y_rotation(glfw.get_time() * 0.5)

    glBindVertexArray(sphere_vao)
    glBindTexture(GL_TEXTURE_2D, sphere_tex)
    glUniformMatrix4fv(model_loc, 1, GL_FALSE, rot_y *sphere_model)
    glDrawArrays(GL_TRIANGLES, 0, len(sphere_obj.vertex_index))
    glBindVertexArray(0)

    glBindVertexArray(monkey_vao)
    glBindTexture(GL_TEXTURE_2D, monkey_tex)
    glUniformMatrix4fv(model_loc, 1, GL_FALSE, monkey_model)
    glDrawArrays(GL_TRIANGLES, 0, len(monkey_obj.vertex_index))
    glBindVertexArray(0)

    glfw.swap_buffers(window)

glfw.terminate()

我不确定问题出在哪里以及为什么它不围绕它自己的点旋转。

Answer 1

如果您希望模型围绕网格的原点旋转，则必须在模型矩阵之前应用旋转矩阵。首先旋转模型然后平移它。进一步注意，matrix44.create_from_translation 的 return 类型是 numpy.array。这意味着您必须先创建一个 Matrix44，然后才能将矩阵相乘。

交换平移矩阵和旋转矩阵来解决您的问题：

sphere_model = matrix44.create_from_translation(Vector3([-4.0,0.0,-3.0]))

rot_y = Matrix44.from_y_rotation(glfw.get_time() * 0.5)

# roation before tranasltion
model_mat = Matrix44(sphere_model) * rot_y
glUniformMatrix4fv(model_loc, 1, GL_FALSE, model_mat)

注意矩阵乘法必须从右向左读。另见 GLSL Programming/Vector and Matrix Operations

translate * rotate:

rotate * translate:

PyOpenGL 对象保持围绕原点旋转

PyOpenGL Objects keep rotating around the origin

python

opengl

pyopengl