XCEngine/engine/src/Rendering/RenderSceneExtractor.cpp

#include "Rendering/RenderSceneExtractor.h"

#include "Components/CameraComponent.h"
#include "Components/GameObject.h"
#include "Components/MeshFilterComponent.h"
#include "Components/MeshRendererComponent.h"
#include "Components/TransformComponent.h"
#include "Scene/Scene.h"

namespace XCEngine {
namespace Rendering {

namespace {

bool IsUsableCamera(const Components::CameraComponent* camera) {
    return camera != nullptr &&
           camera->IsEnabled() &&
           camera->GetGameObject() != nullptr &&
           camera->GetGameObject()->IsActiveInHierarchy();
}

} // namespace

RenderSceneData RenderSceneExtractor::Extract(
    const Components::Scene& scene,
    Components::CameraComponent* overrideCamera,
    uint32_t viewportWidth,
    uint32_t viewportHeight) const {
    RenderSceneData sceneData;
    sceneData.camera = SelectCamera(scene, overrideCamera);
    if (sceneData.camera == nullptr) {
        return sceneData;
    }

    sceneData.cameraData = BuildCameraData(*sceneData.camera, viewportWidth, viewportHeight);

    const std::vector<Components::GameObject*> rootGameObjects = scene.GetRootGameObjects();
    for (Components::GameObject* rootGameObject : rootGameObjects) {
        ExtractVisibleObjects(rootGameObject, sceneData.visibleObjects);
    }

    return sceneData;
}

Components::CameraComponent* RenderSceneExtractor::SelectCamera(
    const Components::Scene& scene,
    Components::CameraComponent* overrideCamera) const {
    if (IsUsableCamera(overrideCamera)) {
        return overrideCamera;
    }

    const std::vector<Components::CameraComponent*> cameras = scene.FindObjectsOfType<Components::CameraComponent>();

    Components::CameraComponent* primaryCamera = nullptr;
    for (Components::CameraComponent* camera : cameras) {
        if (!IsUsableCamera(camera)) {
            continue;
        }

        if (camera->IsPrimary()) {
            if (primaryCamera == nullptr || camera->GetDepth() > primaryCamera->GetDepth()) {
                primaryCamera = camera;
            }
        }
    }

    if (primaryCamera != nullptr) {
        return primaryCamera;
    }

    for (Components::CameraComponent* camera : cameras) {
        if (IsUsableCamera(camera)) {
            return camera;
        }
    }

    return nullptr;
}

RenderCameraData RenderSceneExtractor::BuildCameraData(
    const Components::CameraComponent& camera,
    uint32_t viewportWidth,
    uint32_t viewportHeight) const {
    RenderCameraData cameraData;
    cameraData.viewportWidth = viewportWidth;
    cameraData.viewportHeight = viewportHeight;
    cameraData.worldPosition = camera.transform().GetPosition();
    cameraData.clearColor = camera.GetClearColor();

    const Math::Matrix4x4 view = camera.transform().GetWorldToLocalMatrix();
    const float aspect = viewportHeight > 0
        ? static_cast<float>(viewportWidth) / static_cast<float>(viewportHeight)
        : 1.0f;

    Math::Matrix4x4 projection = Math::Matrix4x4::Identity();
    if (camera.GetProjectionType() == Components::CameraProjectionType::Perspective) {
        projection = Math::Matrix4x4::Perspective(
            camera.GetFieldOfView() * Math::DEG_TO_RAD,
            aspect,
            camera.GetNearClipPlane(),
            camera.GetFarClipPlane());
    } else {
        const float orthoSize = camera.GetOrthographicSize();
        projection = Math::Matrix4x4::Orthographic(
            -orthoSize * aspect,
            orthoSize * aspect,
            -orthoSize,
            orthoSize,
            camera.GetNearClipPlane(),
            camera.GetFarClipPlane());
    }

    cameraData.view = view.Transpose();
    cameraData.projection = projection.Transpose();
    cameraData.viewProjection = (projection * view).Transpose();
    return cameraData;
}

void RenderSceneExtractor::ExtractVisibleObjects(
    Components::GameObject* gameObject,
    std::vector<VisibleRenderObject>& visibleObjects) const {
    if (gameObject == nullptr || !gameObject->IsActiveInHierarchy()) {
        return;
    }

    auto* meshFilter = gameObject->GetComponent<Components::MeshFilterComponent>();
    auto* meshRenderer = gameObject->GetComponent<Components::MeshRendererComponent>();
    if (meshFilter != nullptr &&
        meshRenderer != nullptr &&
        meshFilter->IsEnabled() &&
        meshRenderer->IsEnabled()) {
        Resources::Mesh* mesh = meshFilter->GetMesh();
        if (mesh != nullptr && mesh->IsValid()) {
            VisibleRenderObject visibleObject;
            visibleObject.gameObject = gameObject;
            visibleObject.meshFilter = meshFilter;
            visibleObject.meshRenderer = meshRenderer;
            visibleObject.mesh = mesh;
            visibleObject.localToWorld = gameObject->GetTransform()->GetLocalToWorldMatrix();
            visibleObjects.push_back(visibleObject);
        }
    }

    for (Components::GameObject* child : gameObject->GetChildren()) {
        ExtractVisibleObjects(child, visibleObjects);
    }
}

} // namespace Rendering
} // namespace XCEngine