Kelsidavis-WoWee/src/rendering/camera.cpp

#include "rendering/camera.hpp"
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/constants.hpp>

namespace wowee {
namespace rendering {

Camera::Camera() {
    updateViewMatrix();
    updateProjectionMatrix();
}

void Camera::updateViewMatrix() {
    glm::vec3 front = getForward();
    // Use Z-up for WoW coordinate system
    viewMatrix = glm::lookAt(position, position + front, glm::vec3(0.0f, 0.0f, 1.0f));
}

void Camera::updateProjectionMatrix() {
    projectionMatrix = glm::perspective(glm::radians(fov), aspectRatio, nearPlane, farPlane);
    // Vulkan clip-space has Y pointing down; flip the projection's Y axis.
    projectionMatrix[1][1] *= -1.0f;
}

glm::vec3 Camera::getForward() const {
    // WoW coordinate system: X/Y horizontal, Z vertical
    glm::vec3 front;
    front.x = cos(glm::radians(yaw)) * cos(glm::radians(pitch));
    front.y = sin(glm::radians(yaw)) * cos(glm::radians(pitch));
    front.z = sin(glm::radians(pitch));
    return glm::normalize(front);
}

glm::vec3 Camera::getRight() const {
    // Use Z-up for WoW coordinate system
    return glm::normalize(glm::cross(getForward(), glm::vec3(0.0f, 0.0f, 1.0f)));
}

glm::vec3 Camera::getUp() const {
    return glm::normalize(glm::cross(getRight(), getForward()));
}

Ray Camera::screenToWorldRay(float screenX, float screenY, float screenW, float screenH) const {
    float ndcX = (2.0f * screenX / screenW) - 1.0f;
    // Vulkan Y-flip is baked into projectionMatrix, so NDC Y maps directly:
    // screen top (y=0) → NDC -1, screen bottom (y=H) → NDC +1
    float ndcY = (2.0f * screenY / screenH) - 1.0f;

    glm::mat4 invVP = glm::inverse(projectionMatrix * viewMatrix);

    // Vulkan / GLM_FORCE_DEPTH_ZERO_TO_ONE: NDC z ∈ [0, 1]
    glm::vec4 nearPt = invVP * glm::vec4(ndcX, ndcY, 0.0f, 1.0f);
    glm::vec4 farPt  = invVP * glm::vec4(ndcX, ndcY, 1.0f, 1.0f);
    nearPt /= nearPt.w;
    farPt  /= farPt.w;

    return { glm::vec3(nearPt), glm::normalize(glm::vec3(farPt - nearPt)) };
}

} // namespace rendering
} // namespace wowee