【Vulkan入门】24-控制视角

文章目录

• 先叨叨
• 代码信息
• 具体思路
• 关键代码
• • SDL_AppEvent
  • Camera::UpdatePositon
  • Camera::UpdateFace
  • VulkanRenderer::UpdateUniformBuffer
• 运行效果

先叨叨

在实现深度测试后，已经可以实现简单的3D渲染了。为了今后能更好的观察3D效果，所以需要在渲染时动态变换视角。本篇就介绍如何动态变换视角。

代码信息

• repository: https://gitee.com/J8_series/easy-car-ui
• tag:24-MouseControl
• url: https://gitee.com/J8_series/easy-car-ui/tree/24-MouseControl

具体思路

glm::lookAt可以生成视角矩阵，因此主要思路就是在每帧渲染之前通过这个方法生成视角矩阵。
glm::lookAt的第一个参数是视角的位置，第二个参数时视角盯着的点，第三个参数是视角的正上方向量。
我们定义一个Camera类，该类有三个属m_posistion、m_face、m_up，分别代表Camera的位置、朝向、正上方。
定义了Camera类之后就可以这样使用glm::lookAt。

mvp.view = glm::lookAt(m_camera.m_posistion, m_camera.m_posistion + m_camera.m_face, m_camera.m_up);

接下来就是根据用户输入，更新m_posistion、m_face、m_up即可。

我希望向第一视角游戏一样通过 W、S、A、D 控制视角的前后左右。按住鼠标左键可以控制视角朝向， 朝向由Yaw和Pitch角定义，Yaw的值由鼠标X值变化量得到，Pitch角由鼠标Y值的变化量得到 。

关键代码

SDL_AppEvent

这个方法是SDL接受输入的方法，在这个方法里我们会Camera的状态。

SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
{
    if (event->type == SDL_EVENT_QUIT) {
        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
    }

    if (event->type == SDL_EVENT_KEY_DOWN)
    {
        if (event->key.key == SDLK_W)
        {
            VulkanRenderer::GetInstance().m_camera.m_isForward = true;
        }
        else if (event->key.key == SDLK_S)
        {
            VulkanRenderer::GetInstance().m_camera.m_isRetreated = true;
        }
        else if (event->key.key == SDLK_A)
        {
            VulkanRenderer::GetInstance().m_camera.m_isLeftwards = true;
        }
        else if (event->key.key == SDLK_D)
        {
            VulkanRenderer::GetInstance().m_camera.m_isRightwards = true;
        }
    }
    
    if (event->type == SDL_EVENT_KEY_UP)
    {
        if (event->key.key == SDLK_W)
        {
            VulkanRenderer::GetInstance().m_camera.m_isForward = false;
        }
        else if (event->key.key == SDLK_S)
        {
            VulkanRenderer::GetInstance().m_camera.m_isRetreated = false;
        }
        else if (event->key.key == SDLK_A)
        {
            VulkanRenderer::GetInstance().m_camera.m_isLeftwards = false;
        }
        else if (event->key.key == SDLK_D)
        {
            VulkanRenderer::GetInstance().m_camera.m_isRightwards = false;
        }
    }

    if (event->type == SDL_EVENT_MOUSE_BUTTON_DOWN)
    {
        if (event->button.button == SDL_BUTTON_LEFT)
        {
            isMouseLeftButtonDown = true;
            lastX = event->motion.x;
            lastY = event->motion.y;
            deltaYaw = 0;
            deltaPitch = 0;
        }
    }

    if (event->type == SDL_EVENT_MOUSE_BUTTON_UP)
    {
        if (event->button.button == SDL_BUTTON_LEFT)
        {
            isMouseLeftButtonDown = false;
            VulkanRenderer::GetInstance().m_camera.CommitFace(deltaYaw, deltaPitch);
        }
    }

    if (event->type == SDL_EVENT_MOUSE_MOTION)
    {
        if (true == isMouseLeftButtonDown)
        {
            offsetX = event->motion.x - lastX;
            offsetY = lastY - event->motion.y;

            deltaYaw = offsetX * 0.1;
            deltaPitch = offsetY * 0.1;


            VulkanRenderer::GetInstance().m_camera.UpdateFace(deltaYaw, deltaPitch);
        }
    }

    return SDL_APP_CONTINUE;  /* carry on with the program! */
}

Camera::UpdatePositon

该方法根据Camera的状态更新Camera的位置。

void Camera::UpdatePositon(float deltaSeconds)
{
    if (true == m_isForward)
    {
        m_posistion += m_face * m_speed;
    }
    if (true == m_isRetreated)
    {
        m_posistion -= m_face * m_speed;
    }
    if (true == m_isLeftwards)
    {
        m_posistion -= glm::normalize(glm::cross(m_face, m_up)) * m_speed;
    }
    if (true == m_isRightwards)
    {
        m_posistion += glm::normalize(glm::cross(m_face, m_up)) * m_speed;
    }
}

Camera::UpdateFace

该方法根据deltaYaw和deltaPitch 更新Camera的m_face

void Camera::UpdateFace(float deltaYaw, float deltaPitch)
{
    m_deltaYaw = deltaYaw;
    m_deltaPitch = deltaPitch;

    float tmpPitch = m_pitch + m_deltaPitch;

    if (tmpPitch > 89.0f)
    {
        tmpPitch = 89.0f;
    }
    if (tmpPitch < -89.0f)
    {
        tmpPitch = -89.0f;
    }

    glm::vec3  direction {};
    direction.x = cos(glm::radians(tmpPitch)) * cos(glm::radians(m_yaw + m_deltaYaw));
    direction.y = sin(glm::radians(tmpPitch));
    direction.z = cos(glm::radians(tmpPitch)) * sin(glm::radians(m_yaw + m_deltaYaw));

    m_face = glm::normalize(direction);
}

VulkanRenderer::UpdateUniformBuffer

在该方法中调用glm::lookAt更新视角矩阵

void VulkanRenderer::UpdateUniformBuffer(float deltaSeconds)
{
    static auto startTime = std::chrono::high_resolution_clock::now();

    auto currentTime = std::chrono::high_resolution_clock::now();
    float time = std::chrono::duration<float, std::chrono::seconds::period>(currentTime - startTime).count();

    m_camera.UpdatePositon(deltaSeconds);

    ModelViewProj mvp{};
    mvp.model = glm::mat4(1.0f);
    mvp.view = glm::lookAt(m_camera.m_posistion, m_camera.m_posistion + m_camera.m_face, m_camera.m_up);
    mvp.proj = glm::perspective(glm::radians(45.0f), m_width / (float) m_height, 0.1f, 10.0f);

    memcpy(m_uniformBufferMapped, &mvp, sizeof(mvp));
}

运行效果

我不会录制gif格式图片，不过现在已经可以用鼠标和键盘控制视角了