XCEngine/engine/src/Rendering/Extraction/RenderSceneUtility.cpp

#include "Rendering/Extraction/RenderSceneUtility.h"

#include "Components/CameraComponent.h"
#include "Components/GaussianSplatRendererComponent.h"
#include "Components/GameObject.h"
#include "Components/LightComponent.h"
#include "Components/MeshFilterComponent.h"
#include "Components/MeshRendererComponent.h"
#include "Components/TransformComponent.h"
#include "Components/VolumeRendererComponent.h"
#include "Rendering/Materials/RenderMaterialResolve.h"
#include "Scene/Scene.h"

#include <unordered_set>

namespace XCEngine {
namespace Rendering {

namespace {

RenderObjectId BuildRenderObjectIdOrInvalid(const Components::GameObject& gameObject) {
    RenderObjectId renderObjectId = kInvalidRenderObjectId;
    TryConvertRuntimeObjectIdToRenderObjectId(gameObject.GetID(), renderObjectId);
    return renderObjectId;
}

} // namespace

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.worldRight = camera.transform().GetRight();
    cameraData.worldUp = camera.transform().GetUp();
    cameraData.worldForward = camera.transform().GetForward();
    cameraData.clearColor = camera.GetClearColor();
    cameraData.perspectiveProjection =
        camera.GetProjectionType() == Components::CameraProjectionType::Perspective;
    cameraData.verticalFovRadians = camera.GetFieldOfView() * Math::DEG_TO_RAD;
    cameraData.orthographicSize = camera.GetOrthographicSize();
    cameraData.nearClipPlane = camera.GetNearClipPlane();
    cameraData.farClipPlane = camera.GetFarClipPlane();

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

    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 RenderObjectId renderObjectId = BuildRenderObjectIdOrInvalid(gameObject);
    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.renderObjectId = renderObjectId;
            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.renderObjectId = renderObjectId;
    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);
}

void AppendVisibleVolumesForGameObject(
    Components::GameObject& gameObject,
    const Math::Vector3& cameraPosition,
    std::vector<VisibleVolumeItem>& outVisibleVolumes) {
    if (!gameObject.IsActiveInHierarchy()) {
        return;
    }

    auto* volumeRenderer = gameObject.GetComponent<Components::VolumeRendererComponent>();
    if (volumeRenderer == nullptr || !volumeRenderer->IsEnabled()) {
        return;
    }

    Resources::VolumeField* volumeField = volumeRenderer->GetVolumeField();
    Resources::Material* material = volumeRenderer->GetMaterial();
    if (volumeField == nullptr ||
        !volumeField->IsValid() ||
        material == nullptr) {
        return;
    }

    const Math::Matrix4x4 localToWorld = gameObject.GetTransform()->GetLocalToWorldMatrix();
    const Math::Vector3 worldPosition = localToWorld.GetTranslation();

    VisibleVolumeItem visibleVolume = {};
    visibleVolume.gameObject = &gameObject;
    visibleVolume.volumeRenderer = volumeRenderer;
    visibleVolume.volumeField = volumeField;
    visibleVolume.material = material;
    visibleVolume.renderQueue = ResolveMaterialRenderQueue(material);
    visibleVolume.cameraDistanceSq = (worldPosition - cameraPosition).SqrMagnitude();
    visibleVolume.localToWorld = localToWorld;
    outVisibleVolumes.push_back(visibleVolume);
}

void AppendVisibleGaussianSplatsForGameObject(
    Components::GameObject& gameObject,
    const Math::Vector3& cameraPosition,
    std::vector<VisibleGaussianSplatItem>& outVisibleGaussianSplats) {
    if (!gameObject.IsActiveInHierarchy()) {
        return;
    }

    auto* gaussianSplatRenderer = gameObject.GetComponent<Components::GaussianSplatRendererComponent>();
    if (gaussianSplatRenderer == nullptr || !gaussianSplatRenderer->IsEnabled()) {
        return;
    }

    Resources::GaussianSplat* gaussianSplat = gaussianSplatRenderer->GetGaussianSplat();
    Resources::Material* material = gaussianSplatRenderer->GetMaterial();
    if (gaussianSplat == nullptr ||
        !gaussianSplat->IsValid() ||
        material == nullptr) {
        return;
    }

    const Math::Matrix4x4 localToWorld = gameObject.GetTransform()->GetLocalToWorldMatrix();
    const Math::Vector3 worldPosition = localToWorld.GetTranslation();

    VisibleGaussianSplatItem visibleGaussianSplat = {};
    visibleGaussianSplat.gameObject = &gameObject;
    visibleGaussianSplat.gaussianSplatRenderer = gaussianSplatRenderer;
    visibleGaussianSplat.gaussianSplat = gaussianSplat;
    visibleGaussianSplat.material = material;
    visibleGaussianSplat.renderQueue = ResolveMaterialRenderQueue(material);
    visibleGaussianSplat.cameraDistanceSq = (worldPosition - cameraPosition).SqrMagnitude();
    visibleGaussianSplat.localToWorld = localToWorld;
    outVisibleGaussianSplats.push_back(visibleGaussianSplat);
}

bool CompareVisibleRenderItemsStable(
    const VisibleRenderItem& lhs,
    const VisibleRenderItem& rhs) {
    if (lhs.renderQueue != rhs.renderQueue) {
        return lhs.renderQueue < rhs.renderQueue;
    }

    const bool isTransparentQueue = IsTransparentRenderQueue(lhs.renderQueue);
    if (lhs.cameraDistanceSq != rhs.cameraDistanceSq) {
        return isTransparentQueue
            ? lhs.cameraDistanceSq > rhs.cameraDistanceSq
            : lhs.cameraDistanceSq < rhs.cameraDistanceSq;
    }

    const Core::uint64 lhsObjectId = lhs.gameObject != nullptr ? lhs.gameObject->GetID() : 0u;
    const Core::uint64 rhsObjectId = rhs.gameObject != nullptr ? rhs.gameObject->GetID() : 0u;
    if (lhsObjectId != rhsObjectId) {
        return lhsObjectId < rhsObjectId;
    }

    if (lhs.hasSection != rhs.hasSection) {
        return lhs.hasSection && !rhs.hasSection;
    }

    if (lhs.sectionIndex != rhs.sectionIndex) {
        return lhs.sectionIndex < rhs.sectionIndex;
    }

    if (lhs.materialIndex != rhs.materialIndex) {
        return lhs.materialIndex < rhs.materialIndex;
    }

    return false;
}

bool CompareVisibleGaussianSplatsStable(
    const VisibleGaussianSplatItem& lhs,
    const VisibleGaussianSplatItem& rhs) {
    if (lhs.renderQueue != rhs.renderQueue) {
        return lhs.renderQueue < rhs.renderQueue;
    }

    const bool isTransparentQueue = IsTransparentRenderQueue(lhs.renderQueue);
    if (lhs.cameraDistanceSq != rhs.cameraDistanceSq) {
        return isTransparentQueue
            ? lhs.cameraDistanceSq > rhs.cameraDistanceSq
            : lhs.cameraDistanceSq < rhs.cameraDistanceSq;
    }

    const Core::uint64 lhsObjectId = lhs.gameObject != nullptr ? lhs.gameObject->GetID() : 0u;
    const Core::uint64 rhsObjectId = rhs.gameObject != nullptr ? rhs.gameObject->GetID() : 0u;
    if (lhsObjectId != rhsObjectId) {
        return lhsObjectId < rhsObjectId;
    }

    return false;
}

bool CompareVisibleVolumesStable(
    const VisibleVolumeItem& lhs,
    const VisibleVolumeItem& rhs) {
    if (lhs.renderQueue != rhs.renderQueue) {
        return lhs.renderQueue < rhs.renderQueue;
    }

    const bool isTransparentQueue = IsTransparentRenderQueue(lhs.renderQueue);
    if (lhs.cameraDistanceSq != rhs.cameraDistanceSq) {
        return isTransparentQueue
            ? lhs.cameraDistanceSq > rhs.cameraDistanceSq
            : lhs.cameraDistanceSq < rhs.cameraDistanceSq;
    }

    const Core::uint64 lhsObjectId = lhs.gameObject != nullptr ? lhs.gameObject->GetID() : 0u;
    const Core::uint64 rhsObjectId = rhs.gameObject != nullptr ? rhs.gameObject->GetID() : 0u;
    if (lhsObjectId != rhsObjectId) {
        return lhsObjectId < rhsObjectId;
    }

    return false;
}

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;
}

bool IsUsableLight(const Components::LightComponent* light) {
    return light != nullptr &&
           light->IsEnabled() &&
           light->GetGameObject() != nullptr &&
           light->GetGameObject()->IsActiveInHierarchy();
}

bool IsLightVisibleForCullingMask(
    const Components::LightComponent& light,
    uint32_t cullingMask) {
    if (!IsUsableLight(&light)) {
        return false;
    }

    const Components::GameObject* gameObject = light.GetGameObject();
    const uint32_t gameObjectLayerMask = 1u << gameObject->GetLayer();
    return (cullingMask & gameObjectLayerMask) != 0u;
}

Math::Vector3 BuildRenderLightDirection(
    const Components::LightComponent& light) {
    Math::Vector3 direction = light.transform().GetForward() * -1.0f;
    if (direction.SqrMagnitude() <= Math::EPSILON) {
        return Math::Vector3::Back();
    }

    return direction.Normalized();
}

Components::LightComponent* FindMainDirectionalLight(
    const Components::Scene& scene,
    uint32_t cullingMask) {
    const std::vector<Components::LightComponent*> lights =
        scene.FindObjectsOfType<Components::LightComponent>();

    Components::LightComponent* mainDirectionalLight = nullptr;
    for (Components::LightComponent* light : lights) {
        if (light == nullptr ||
            !IsLightVisibleForCullingMask(*light, cullingMask) ||
            light->GetLightType() != Components::LightType::Directional) {
            continue;
        }

        if (mainDirectionalLight == nullptr ||
            light->GetIntensity() > mainDirectionalLight->GetIntensity()) {
            mainDirectionalLight = light;
        }
    }

    return mainDirectionalLight;
}

} // namespace Rendering
} // namespace XCEngine