XCEngine/engine/src/Rendering/RenderSceneUtility.cpp

#include "Rendering/RenderSceneUtility.h"

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

#include <unordered_set>

namespace XCEngine {
namespace Rendering {

RenderCameraData BuildRenderCameraData(
    const Components::CameraComponent& camera,
    uint32_t viewportWidth,
    uint32_t viewportHeight) {
    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 AppendRenderItemsForGameObject(
    Components::GameObject& gameObject,
    const Math::Vector3& cameraPosition,
    std::vector<VisibleRenderItem>& outVisibleItems) {
    if (!gameObject.IsActiveInHierarchy()) {
        return;
    }

    auto* meshFilter = gameObject.GetComponent<Components::MeshFilterComponent>();
    auto* meshRenderer = gameObject.GetComponent<Components::MeshRendererComponent>();
    if (meshFilter == nullptr ||
        meshRenderer == nullptr ||
        !meshFilter->IsEnabled() ||
        !meshRenderer->IsEnabled()) {
        return;
    }

    Resources::Mesh* mesh = meshFilter->GetMesh();
    if (mesh == nullptr || !mesh->IsValid()) {
        return;
    }

    const Math::Matrix4x4 localToWorld = gameObject.GetTransform()->GetLocalToWorldMatrix();
    const Math::Vector3 worldPosition = localToWorld.GetTranslation();
    const float cameraDistanceSq = (worldPosition - cameraPosition).SqrMagnitude();
    const Containers::Array<Resources::MeshSection>& sections = mesh->GetSections();

    if (!sections.Empty()) {
        for (size_t sectionIndex = 0; sectionIndex < sections.Size(); ++sectionIndex) {
            const Resources::MeshSection& section = sections[sectionIndex];

            VisibleRenderItem visibleItem = {};
            visibleItem.gameObject = &gameObject;
            visibleItem.meshFilter = meshFilter;
            visibleItem.meshRenderer = meshRenderer;
            visibleItem.mesh = mesh;
            visibleItem.materialIndex = section.materialID;
            visibleItem.sectionIndex = static_cast<Core::uint32>(sectionIndex);
            visibleItem.hasSection = true;
            visibleItem.material = ResolveMaterial(meshRenderer, mesh, section.materialID);
            visibleItem.renderQueue = ResolveMaterialRenderQueue(visibleItem.material);
            visibleItem.cameraDistanceSq = cameraDistanceSq;
            visibleItem.localToWorld = localToWorld;
            outVisibleItems.push_back(visibleItem);
        }
        return;
    }

    VisibleRenderItem visibleItem = {};
    visibleItem.gameObject = &gameObject;
    visibleItem.meshFilter = meshFilter;
    visibleItem.meshRenderer = meshRenderer;
    visibleItem.mesh = mesh;
    visibleItem.materialIndex = 0;
    visibleItem.sectionIndex = 0;
    visibleItem.hasSection = false;
    visibleItem.material = ResolveMaterial(meshRenderer, mesh, 0);
    visibleItem.renderQueue = ResolveMaterialRenderQueue(visibleItem.material);
    visibleItem.cameraDistanceSq = cameraDistanceSq;
    visibleItem.localToWorld = localToWorld;
    outVisibleItems.push_back(visibleItem);
}

std::vector<VisibleRenderItem> CollectRenderItemsForEntityIds(
    const Components::Scene& scene,
    const std::vector<uint64_t>& entityIds,
    const Math::Vector3& cameraPosition) {
    std::vector<VisibleRenderItem> visibleItems;
    std::unordered_set<uint64_t> visitedEntityIds;
    visitedEntityIds.reserve(entityIds.size());

    for (uint64_t entityId : entityIds) {
        if (entityId == 0 || !visitedEntityIds.insert(entityId).second) {
            continue;
        }

        Components::GameObject* gameObject = scene.FindByID(entityId);
        if (gameObject == nullptr) {
            continue;
        }

        AppendRenderItemsForGameObject(*gameObject, cameraPosition, visibleItems);
    }

    return visibleItems;
}

} // namespace Rendering
} // namespace XCEngine