如何在PyOpenGL上创建一个可以对鼠标移动进行“透视旋转”的摄像机？

Question

我正在创建第一人称视角的RPG，并且想在移动鼠标时在PyOpenGL中旋转相机（就像其他游戏一样，如Minecraft）。我可以使用什么功能来执行此操作？

我尝试使用gluLookAt()它，但是尽管经历了不同的来源，但我不知道它是如何工作的。我什至不知道是否能帮上忙。

import sys,pygame
from OpenGL.GL import *
from OpenGL.GLU import *
cmddown = False
#...
keypress = pygame.key.get_pressed()#Move using WASD
    if keypress[pygame.K_w]:
        glTranslatef(0,0,0.1)
    if keypress[pygame.K_s]:
        glTranslatef(0,0,-0.1)
    if keypress[pygame.K_d]:
        glTranslatef(-0.1,0,0)
    if keypress[pygame.K_a]:
        glTranslatef(0.1,0,0)
    mouse_movement = pygame.mouse.get_rel()#Get mouse event
    #This is where the "look around" should be happen
    pygame.display.flip()

Answer 1

您可以使用glRotate绕轴旋转一定量，该量由鼠标的相对移动（pygame.mouse.get_rel()）给出：

mouseMove = pygame.mouse.get_rel()
glRotatef(mouseMove[0]*0.1, 0.0, 1.0, 0.0)

但这不会令您满意，因为如果鼠标离开窗口，该解决方案将无法再使用。
您必须将pygame.mouse.set_pos()每一帧的鼠标居中在屏幕中间。通过pygame.MOUSEMOTION事件获取鼠标移动。例如：

# init mouse movement and center mouse on screen
displayCenter = [scree.get_size()[i] // 2 for i in range(2)]
mouseMove = [0, 0]
pygame.mouse.set_pos(displayCenter)

paused = False
run = True
while run:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_ESCAPE or event.key == pygame.K_RETURN:
                run = False
            if event.key == pygame.K_PAUSE or event.key == pygame.K_p:
                paused = not paused
                pygame.mouse.set_pos(displayCenter)  
        if event.type == pygame.MOUSEMOTION:
            mouseMove = [event.pos[i] - displayCenter[i] for i in range(2)]
            if not paused:
                pygame.mouse.set_pos(displayCenter)

注意，该操作类似于glRotate
并glTranslate设置一个矩阵，然后将当前矩阵乘以新矩阵。

currentMatrix = currentMatrix * newMatrix

这对于模型动画和变换是完美的，但是对于第一人称移动来说，这是错误的方式，在这种情况下，必须更改相机的位置和视角。

viewMatrix = viewTransformMatrix * viewMatrix

做这样的操作glGetFloatv(GL_MODELVIEW_MATRIX)和glMultMatrixf。在主循环之前
通过初始化视图矩阵，gluLookAt并通过将视图矩阵加载到html" target="_blank">变量（viewMatrix）glGetFloatv(GL_MODELVIEW_MATRIX)。

在每个帧的主循环中：

• 加载身份矩阵（glLoadIdentity）
• 做新的转换到视图（glRotatef，glTranslatef）
• 将当前视图矩阵乘以viewMatrix（glMultMatrixf）

• 将新的视图矩阵加载到viewMatrix下一帧

  glMatrixMode(GL_MODELVIEW)
  gluLookAt(0, -8, 0, 0, 0, 0, 0, 0, 1)
  viewMatrix = glGetFloatv(GL_MODELVIEW_MATRIX)
  glLoadIdentity()

  run = True
  while run:

  # [...]
  
  # init the view matrix
  glLoadIdentity()
  
  # apply the movment 
  if keypress[pygame.K_w]:
      glTranslatef(0,0,0.1)
  if keypress[pygame.K_s]:
      glTranslatef(0,0,-0.1)
  if keypress[pygame.K_d]:
      glTranslatef(-0.1,0,0)
  if keypress[pygame.K_a]:
      glTranslatef(0.1,0,0)
  
  # apply the roation
  glRotatef(mouseMove[0]*0.1, 0.0, 1.0, 0.0)
  
  # multiply the current matrix by the get the new view matrix and store the final vie matrix 
  glMultMatrixf(viewMatrix)
  viewMatrix = glGetFloatv(GL_MODELVIEW_MATRIX)
  

为了向上和向下查找，您必须绕x轴进行最终旋转。旋转的枢轴取决于角度。必须对角度进行求和，并且必须在视图矩阵之后应用旋转，否则运动会根据角度改变（“高度”）水平。

viewMatrix = viewTransformMatrix * viewMatrix
finlalMatrix = lookUpDownMatrix * viewMatrix

为此，您必须汇总上下旋转矩阵并将其乘以 viewMatrix

up_down_angle = 0.0
run = True
while run:

    # [...]

    # init model view matrix
    glLoadIdentity()

    # apply the look up and down
    up_down_angle += mouseMove[1]*0.1
    glRotatef(up_down_angle, 1.0, 0.0, 0.0)

    # init the view matrix
    glPushMatrix()
    glLoadIdentity()

    # calculate new `viewMatrix` 
    # [...]

    # apply view matrix
    glPopMatrix()
    glMultMatrixf(viewMatrix)

请参见以下示例程序，该程序演示了该过程。
请注意，该程序 将鼠标保持在 窗口 的中央 ，因此您不能再“移动”鼠标。因此， 可以通过ESC或停止return应用程序。
可以 通过pause或暂停p应用程序。暂停应用程序时， 鼠标不会居中 于窗口。

import pygame
from pygame.locals import *

from OpenGL.GL import *
from OpenGL.GLU import *

import math

pygame.init()
display = (400, 300)
scree = pygame.display.set_mode(display, DOUBLEBUF | OPENGL)

glEnable(GL_DEPTH_TEST)
glEnable(GL_LIGHTING)
glShadeModel(GL_SMOOTH)
glEnable(GL_COLOR_MATERIAL)
glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE)

glEnable(GL_LIGHT0)
glLightfv(GL_LIGHT0, GL_AMBIENT, [0.5, 0.5, 0.5, 1])
glLightfv(GL_LIGHT0, GL_DIFFUSE, [1.0, 1.0, 1.0, 1])

sphere = gluNewQuadric()

glMatrixMode(GL_PROJECTION)
gluPerspective(45, (display[0]/display[1]), 0.1, 50.0)

glMatrixMode(GL_MODELVIEW)
gluLookAt(0, -8, 0, 0, 0, 0, 0, 0, 1)
viewMatrix = glGetFloatv(GL_MODELVIEW_MATRIX)
glLoadIdentity()

# init mouse movement and center mouse on screen
displayCenter = [scree.get_size()[i] // 2 for i in range(2)]
mouseMove = [0, 0]
pygame.mouse.set_pos(displayCenter)

up_down_angle = 0.0
paused = False
run = True
while run:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_ESCAPE or event.key == pygame.K_RETURN:
                run = False
            if event.key == pygame.K_PAUSE or event.key == pygame.K_p:
                paused = not paused
                pygame.mouse.set_pos(displayCenter) 
        if not paused: 
            if event.type == pygame.MOUSEMOTION:
                mouseMove = [event.pos[i] - displayCenter[i] for i in range(2)]
            pygame.mouse.set_pos(displayCenter)

    if not paused:
        # get keys
        keypress = pygame.key.get_pressed()
        #mouseMove = pygame.mouse.get_rel()

        # init model view matrix
        glLoadIdentity()

        # apply the look up and down
        up_down_angle += mouseMove[1]*0.1
        glRotatef(up_down_angle, 1.0, 0.0, 0.0)

        # init the view matrix
        glPushMatrix()
        glLoadIdentity()

        # apply the movment 
        if keypress[pygame.K_w]:
            glTranslatef(0,0,0.1)
        if keypress[pygame.K_s]:
            glTranslatef(0,0,-0.1)
        if keypress[pygame.K_d]:
            glTranslatef(-0.1,0,0)
        if keypress[pygame.K_a]:
            glTranslatef(0.1,0,0)

        # apply the left and right rotation
        glRotatef(mouseMove[0]*0.1, 0.0, 1.0, 0.0)

        # multiply the current matrix by the get the new view matrix and store the final vie matrix 
        glMultMatrixf(viewMatrix)
        viewMatrix = glGetFloatv(GL_MODELVIEW_MATRIX)

        # apply view matrix
        glPopMatrix()
        glMultMatrixf(viewMatrix)

        glLightfv(GL_LIGHT0, GL_POSITION, [1, -1, 1, 0])

        glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)

        glPushMatrix()

        glColor4f(0.5, 0.5, 0.5, 1)
        glBegin(GL_QUADS)
        glVertex3f(-10, -10, -2)
        glVertex3f(10, -10, -2)
        glVertex3f(10, 10, -2)
        glVertex3f(-10, 10, -2)
        glEnd()

        glTranslatef(-1.5, 0, 0)
        glColor4f(0.5, 0.2, 0.2, 1)
        gluSphere(sphere, 1.0, 32, 16)

        glTranslatef(3, 0, 0)
        glColor4f(0.2, 0.2, 0.5, 1)
        gluSphere(sphere, 1.0, 32, 16)

        glPopMatrix()

        pygame.display.flip()
        pygame.time.wait(10)

pygame.quit()