无法移动视图矩阵和方向视图矩阵同时指向

Question

当我在场景中四处移动时（不移动我的 'head'，这是我的视图矩阵指向的位置），一切正常。当我一动不动地环顾四周时，一切正常。但是当我将两者结合起来时，我的头脑（视图矩阵）开始变得疯狂。我假设问题出在我的 math/logic 上，但我就是想不通。

这是我的代码（当然是经过简化的）：

#define MOVE_DISTANCE 0.15f
#define LOOK_SENSITIVITY 0.01f

static GLFWwindow* window;

static glm::mat4 viewMatrix;
static glm::vec3 look_at;


static void mouseCallback(GLFWwindow* window, double x, double y){
  static double prev_x = 0;
  static double prev_y = 0;
  static float pitch = 0, yaw = 0;

  pitch += (y-prev_y) * LOOK_SENSITIVITY;
  yaw += (x-prev_x) * LOOK_SENSITIVITY;

  if(pitch > 89){
    pitch = 89;
  }
    if(pitch < -89){
      pitch = -89;
  }

  look_at = glm::vec3(cos(yaw)*cos(pitch), sin(pitch), sin(yaw)*cos(pitch) - 1.0f);

  prev_x = x;
  prev_y = y;
}

int main(){
  window = glfwCreateWindow(800, 600, "OpenGL", NULL, NULL); //I left the rest of the initialization out

  glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
  glfwSetCursorPosCallback(window, mouseCallback);

  look_at = glm::vec3(0.0f, 0.0f, -1.0f);
  glm::vec3 position(0.0f, 0.0f, 0.0f);

  glm::mat4 projectionMatrix = glm::perspective(45.0f, (float) 800/600, 0.1f, 100.0f); //fov, screen aspect ratio, near render distance, far render distance (z axis)
  glm::mat4 modelMatrix = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, 0.0f, -5.0f));
  viewMatrix = glm::lookAt(position, look_at, glm::vec3(0, 1, 0));


  while(!glfwWindowShouldClose(window)){
    if(glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS){
      position.z -= MOVE_DISTANCE;
      look_at.z -= MOVE_DISTANCE;
    }
    if(glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS){
      position.z += MOVE_DISTANCE;
      look_at.z += MOVE_DISTANCE;
    }
    if(glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS){
      position.x += MOVE_DISTANCE;
      look_at.x += MOVE_DISTANCE;
    }
    if(glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS){
      position.x -= MOVE_DISTANCE;
      look_at.x -= MOVE_DISTANCE;
    }
    if(glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_PRESS){ //FLy up
      position.y += MOVE_DISTANCE;
      look_at.y += MOVE_DISTANCE;
    }
    if(glfwGetKey(window, GLFW_KEY_LEFT_CONTROL) == GLFW_PRESS){ //Fly down
      position.y -= MOVE_DISTANCE;
      look_at.y -= MOVE_DISTANCE;
    }

    viewMatrix = glm::lookAt(position, look_at+position, glm::vec3(0, 1, 0));

    glClear(GL_COLOR_BUFFER_BIT);

    glDrawElements(GL_TRIANGLES, NUM_OF_INDICES, GL_UNSIGNED_BYTE, 0);

    glfwSwapBuffers(window);
    glfwPollEvents();
  }
}

每当我在移动鼠标的同时四处移动时，事情就会失控，我的头（我的视图矩阵指向的方向）开始四处晃动。我知道运动不受我所观察的方向的影响。我计划在未来的某个时候实现这一点。

有人可以帮我指出我的错误吗？

Answer 1

你的问题是无论你往哪里看，按W都会总是从你的世界中减去MOVE_DISTANCE-spaceposition.z 坐标，即使“向前”或“向后”移动并不一定意味着“沿着世界的 Z 轴移动”。

因此，您必须确定“前”（以便向前和向后移动）以及“右”（或“左”）和“上”或“下”的轴。当您希望 SPACE 和 CTRL 始终沿世界 Y 轴移动 up/down 时，后者可能不是必需的。

对于其他两个轴，当您有任意视图矩阵m（例如通过glm::lookAt构建的矩阵）时，您可以轻松提取right、up 和 forward 向量，像这样：

#include <glm/gtc/matrix_access.hpp>
...
glm::vec4 right(glm::row(m, 0));
glm::vec4 up(glm::row(m, 1));
glm::vec4 forward(-glm::row(m, 2));

就像@3Dave 在上面的评论中所说的那样，您已经知道“forward”在哪里，因为您正在自己操纵该向量并从中计算 lookat 转换，所以您可以省略它。

现在，当你想移动 left/right 时，你 subtract/add right 到你的世界 - space position 其他轴也是如此。

另一件不正确的事情是，在使用键盘键移动时，您还从 look_at direction 中添加/减去。这是错误的，因为你的 look_at 向量是 direction 并且你在计算 glm::lookAt 调用的参数时已经将它用作方向向量。

将所有这些合并到您的代码中（连同一些轻微的重构），将导致以下 while 循环：

while (!glfwWindowShouldClose(window)) {
  glm::vec3 right(glm::row(viewMatrix, 0)),
            up(glm::row(viewMatrix, 1)),
            forward(-glm::row(viewMatrix, 2));
  glm::vec3 v(0, 0, 0);
  if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
    v += forward;
  if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
    v -= forward;
  if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
    v += right;
  if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
    v -= right;
  position += v * MOVE_DISTANCE;
  viewMatrix = glm::lookAt(position, position + look_at, glm::vec3(0, 1, 0));
}

无法移动视图矩阵和方向视图矩阵同时指向

Cannot move view matrix and direction view matrix is pointing in simultaneously

c++

opengl

math

glfw

glm-math