Tesseract-Engine/src/Windows/RenderWindow.cpp

#include "RenderWindow.h"


#include <vector>
#include <GL/glew.h>

#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include "Components/GameObject.h"
#include "Components/mesh.h"
#include "Components/transform.h"
#include "Components/CameraComponent.h"

#include "Engine/AssetManager.h"
#include "Engine/Settings.h"
#include "Engine/InputManager.h"
#include "Engine/KeyCode.h"

#include "Rendering/Shader.h"

#include "ImGuizmo.h"
#include "gcml.h"
#include "Icons.h"
#include "imgui.h"


#define CAM_FOV 45.0f
#define CAM_NEAR_PLAIN 0.1f
#define CAM_FAR_PLAIN 2048.0f

float editorYaw = -90.0f;                 // Horizontal angle, initialized to face along negative Z-axis
float editorPitch = 0.0f;                 // Vertical angle
float editorDistance = 5.0f;              // Distance from the target
glm::vec3 editorTarget(0.0f, 0.0f, 0.0f); // The point the camera orbits around

// Configuration Parameters
const float rotationSpeed = 0.1f; // Sensitivity for mouse rotation
const float zoomSpeed = 2.0f;     // Sensitivity for zooming
const float movementSpeed = 5.0f; // Speed for panning
const float minZoom = 2.0f;       // Minimum zoom distance
const float maxZoom = 20.0f;      // Maximum zoom distance

// Managers
extern AssetManager g_AssetManager;
extern Settings g_SettingsManager;
extern InputManager g_InputManager;


// Settings
extern bool DrawBBBO;

// GameObjects
extern std::vector<std::shared_ptr<GameObject>> g_GameObjects;
extern std::shared_ptr<CameraComponent> g_RuntimeCameraObject;
extern GameObject *g_SelectedObject;

// Profilers
extern int g_GPU_Triangles_drawn_to_screen;
extern int g_GPU_Draw_Calls;

// Simple container for six planes
struct FrustumPlanes
{
    glm::vec4 planes[6]; // Each plane is (A,B,C,D)
};

// Extract 6 planes from the combined view-projection matrix
inline FrustumPlanes ExtractFrustumPlanes(const glm::mat4 &vp)
{
    FrustumPlanes frustum;

    // Left
    frustum.planes[0] = glm::vec4(
        vp[0][3] + vp[0][0],
        vp[1][3] + vp[1][0],
        vp[2][3] + vp[2][0],
        vp[3][3] + vp[3][0]);

    // Right
    frustum.planes[1] = glm::vec4(
        vp[0][3] - vp[0][0],
        vp[1][3] - vp[1][0],
        vp[2][3] - vp[2][0],
        vp[3][3] - vp[3][0]);

    // Bottom
    frustum.planes[2] = glm::vec4(
        vp[0][3] + vp[0][1],
        vp[1][3] + vp[1][1],
        vp[2][3] + vp[2][1],
        vp[3][3] + vp[3][1]);

    // Top
    frustum.planes[3] = glm::vec4(
        vp[0][3] - vp[0][1],
        vp[1][3] - vp[1][1],
        vp[2][3] - vp[2][1],
        vp[3][3] - vp[3][1]);

    // Near
    frustum.planes[4] = glm::vec4(
        vp[0][3] + vp[0][2],
        vp[1][3] + vp[1][2],
        vp[2][3] + vp[2][2],
        vp[3][3] + vp[3][2]);

    // Far
    frustum.planes[5] = glm::vec4(
        vp[0][3] - vp[0][2],
        vp[1][3] - vp[1][2],
        vp[2][3] - vp[2][2],
        vp[3][3] - vp[3][2]);

    // Normalize planes (optional but recommended)
    for (int i = 0; i < 6; i++)
    {
        float length = glm::length(glm::vec3(
            frustum.planes[i].x,
            frustum.planes[i].y,
            frustum.planes[i].z));
        if (length > 0.0f)
        {
            frustum.planes[i] /= length;
        }
    }

    return frustum;
}

inline bool IsBoxInFrustum(const glm::vec3 &bmin,
                           const glm::vec3 &bmax,
                           const FrustumPlanes &frustum)
{
    // Build the 8 corners in world space
    // (We assume bmin/bmax are already in world space.)
    std::array<glm::vec3, 8> corners = {
        glm::vec3(bmin.x, bmin.y, bmin.z),
        glm::vec3(bmin.x, bmin.y, bmax.z),
        glm::vec3(bmin.x, bmax.y, bmin.z),
        glm::vec3(bmin.x, bmax.y, bmax.z),
        glm::vec3(bmax.x, bmin.y, bmin.z),
        glm::vec3(bmax.x, bmin.y, bmax.z),
        glm::vec3(bmax.x, bmax.y, bmin.z),
        glm::vec3(bmax.x, bmax.y, bmax.z)};

    // For each plane, check if all corners are behind it.
    // If yes => box is completely outside.
    for (int p = 0; p < 6; p++)
    {
        const glm::vec4 &plane = frustum.planes[p];
        int outCount = 0;

        for (const auto &corner : corners)
        {
            // Plane eq: A*x + B*y + C*z + D
            float distance = plane.x * corner.x +
                             plane.y * corner.y +
                             plane.z * corner.z +
                             plane.w;

            if (distance < 0.0f)
                outCount++;
        }

        // If all corners are 'behind' the plane, box is outside
        if (outCount == 8)
            return false;
    }
    // Otherwise, it's at least partially inside
    return true;
}

bool PlayPauseButton(const char *label, bool *isPlaying, ImVec2 Size)
{
    // Define button size

    // Begin the button
    if (ImGui::Button(label, Size))
    {
        // Toggle the state
        *isPlaying = !(*isPlaying);
        return true; // Indicate that the state was toggled
    }

    // Add tooltip
    if (ImGui::IsItemHovered())
    {
        ImGui::SetTooltip(*isPlaying ? "Pause (Space)" : "Play (Space)");
    }

    // Get the current window's draw list
    ImDrawList *draw_list = ImGui::GetWindowDrawList();

    // Get the position of the button
    ImVec2 button_pos = ImGui::GetItemRectMin();
    ImVec2 button_size = ImGui::GetItemRectSize();
    ImVec2 center = ImVec2(button_pos.x + button_size.x * 0.5f, button_pos.y + button_size.y * 0.5f);

    // Define icon size
    float icon_size = 0.4f * Size.x;
    float half_icon_size = icon_size / 2.0f;

    // Define colors
    ImU32 icon_color = ImGui::GetColorU32(ImGuiCol_Text);

    if (*isPlaying)
    {
        // Draw Pause Icon (two vertical bars)
        float bar_width = 4.0f;
        float spacing = 0.1f * Size.x;

        // Left bar
        ImVec2 left_bar_p1 = ImVec2(center.x - spacing - bar_width, center.y - half_icon_size);
        ImVec2 left_bar_p2 = ImVec2(center.x - spacing, center.y + half_icon_size);
        draw_list->AddRectFilled(left_bar_p1, left_bar_p2, icon_color, 2.0f);

        // Right bar
        ImVec2 right_bar_p1 = ImVec2(center.x + spacing, center.y - half_icon_size);
        ImVec2 right_bar_p2 = ImVec2(center.x + spacing + bar_width, center.y + half_icon_size);
        draw_list->AddRectFilled(right_bar_p1, right_bar_p2, icon_color, 2.0f);
    }
    else
    {
        // Draw Play Icon (triangle)
        ImVec2 p1 = ImVec2(center.x - half_icon_size, center.y - half_icon_size);
        ImVec2 p2 = ImVec2(center.x - half_icon_size, center.y + half_icon_size);
        ImVec2 p3 = ImVec2(center.x + half_icon_size, center.y);
        draw_list->AddTriangleFilled(p1, p2, p3, icon_color);
    }

    return false; // No toggle occurred
}

// Enum for gizmo operations
enum GizmoOperation
{
    GIZMO_TRANSLATE,
    GIZMO_ROTATE,
    GIZMO_SCALE
};

// Initialize with a default operation
GizmoOperation currentOperation = GIZMO_TRANSLATE;

void RenderWindow::Show(bool *GameRunning, double deltaTime)
{
    // Begin the ImGui window with an icon and label
    ImGui::Begin(ICON_FA_GAMEPAD " Editor##EditorWindow");

    ImGuizmo::BeginFrame();

    ImGuizmo::SetOrthographic(false);
    ImGuizmo::SetDrawlist();

    // Initialize OpenGL resources if not already done
    if (!m_Initialized)
    {
        InitGLResources();
        m_Initialized = true;
    }

    // Get the available size for rendering within the window
    ImVec2 size = ImGui::GetContentRegionAvail();
    int w = static_cast<int>(size.x);
    int h = static_cast<int>(size.y);

    // Check if there's space to render
    if (w > 0 && h > 0)
    {
        // Resize the FBO if the window size has changed
        if (w != m_LastWidth || h != m_LastHeight)
        {
            m_FBO.Create(w, h);
            m_LastWidth = w;
            m_LastHeight = h;
        }

        // Render the 3D scene to the FBO
        RenderSceneToFBO(GameRunning);

        // Display the rendered scene as an image in ImGui
        // Correctly cast the texture ID for OpenGL
        ImGui::Image(m_FBO.GetTextureID(), size, ImVec2(0, 0), ImVec2(1, 1));

        // Calculate button position to place it slightly right and down from the top-left of the image
        ImVec2 imagePos = ImGui::GetItemRectMin();

        // Add an offset to position the button
        ImVec2 buttonOffset(10.0f, 10.0f); // 10 pixels right and 10 pixels down
        ImVec2 buttonPos = ImVec2(imagePos.x + buttonOffset.x, imagePos.y + buttonOffset.y);

        // Set cursor position for the button
        ImGui::SetCursorScreenPos(buttonPos);

        // Dynamically calculate button size based on window size
        float buttonWidth = size.x * 0.05f; // 5% of the window width
        ImVec2 buttonSize = ImVec2(buttonWidth, buttonWidth);

        // Render the Play/Pause button with the calculated size
        PlayPauseButton("##PlayPauseButton", GameRunning, buttonSize);

        // ---------------------------------------------------
        // *** Gizmo Operation Selection UI ***
        // ---------------------------------------------------

        // ---------------------------------------------------
        // *** Integrate ImGuizmo for Manipulating Objects ***
        // ---------------------------------------------------

        // Ensure a GameObject is selected
        if (g_SelectedObject)
        {
            // Retrieve the TransformComponent from the selected object
            auto transform = g_SelectedObject->GetComponent<TransformComponent>();
            if (transform)
            {
                // Get the current transformation matrix
                glm::mat4 modelMatrix = transform->GetTransformMatrix();

                // Obtain view and projection matrices from the active camera
                glm::mat4 viewMatrix;
                glm::mat4 projectionMatrix;
                // Camera Selection and Setup Logic (e.g., within your rendering or update function)

                if (m_ActiveCamera)
                {
                    // Use the existing active camera
                    viewMatrix = m_ActiveCamera->GetViewMatrix();
                    projectionMatrix = m_ActiveCamera->GetProjectionMatrix();
                }
                else
                {
                    m_ActiveCamera = m_EditorCamera->GetComponent<CameraComponent>();

                    // 1. Mouse Input for Rotation
                    if (g_InputManager.IsMouseButtonPressed(MouseButton::RIGHT))
                    {
                        float deltaX = g_InputManager.GetMouseDeltaX();
                        float deltaY = g_InputManager.GetMouseDeltaY();

                        editorYaw += deltaX * rotationSpeed;
                        editorPitch += deltaY * rotationSpeed;

                        // Clamp the pitch to prevent flipping
                        if (editorPitch > 89.0f)
                            editorPitch = 89.0f;
                        if (editorPitch < -89.0f)
                            editorPitch = -89.0f;
                    }

                    // 2. Scroll Input for Zooming
                    float scrollDelta = g_InputManager.GetScrollDelta();
                    editorDistance -= scrollDelta * zoomSpeed;
                    editorDistance = glm::clamp(editorDistance, minZoom, maxZoom);

                    // 3. Keyboard Input for Panning (WASD)
                    glm::vec3 forward = glm::normalize(editorTarget - m_EditorCamera->GetComponent<TransformComponent>()->GetPosition());
                    glm::vec3 right = glm::normalize(glm::cross(forward, glm::vec3(0.0f, 1.0f, 0.0f)));
                    glm::vec3 up = glm::vec3(0.0f, 1.0f, 0.0f);

                    deltaTime = static_cast<float>(deltaTime);

                    if (g_InputManager.IsKeyPressed(KeyCode::W))
                        editorTarget += up.y * movementSpeed * deltaTime;
                    if (g_InputManager.IsKeyPressed(KeyCode::S))
                        editorTarget -= up.y * movementSpeed * deltaTime;
                    if (g_InputManager.IsKeyPressed(KeyCode::A))
                        editorTarget -= right.x * movementSpeed * deltaTime;
                    if (g_InputManager.IsKeyPressed(KeyCode::D))
                        editorTarget += right.x * movementSpeed * deltaTime;

                    // 4. Calculate the New Camera Position
                    glm::vec3 direction;
                    direction.x = cos(glm::radians(editorYaw)) * cos(glm::radians(editorPitch));
                    direction.y = sin(glm::radians(editorPitch));
                    direction.z = sin(glm::radians(editorYaw)) * cos(glm::radians(editorPitch));
                    direction = glm::normalize(direction);

                    glm::vec3 newPosition = editorTarget - direction * editorDistance;

                    // 5. Update the Editor Camera's Transform
                    auto editorTransform = m_EditorCamera->GetComponent<TransformComponent>();
                    editorTransform->SetPosition(newPosition.x,newPosition.y,newPosition.z);
                    editorTransform->LookAt(editorTarget, up);

                    // 6. Retrieve Updated Matrices
                    viewMatrix = m_ActiveCamera->GetViewMatrix();
                    projectionMatrix = m_ActiveCamera->GetProjectionMatrix();

                    static ImGuizmo::OPERATION currentOperation = ImGuizmo::TRANSLATE;

                    if (ImGui::IsWindowFocused() && ImGui::IsWindowHovered())
                    {

                        if (ImGui::IsKeyPressed(ImGuiKey_T))
                        {
                            currentOperation = ImGuizmo::TRANSLATE;
                        }
                        if (ImGui::IsKeyPressed(ImGuiKey_R))
                        {
                            currentOperation = ImGuizmo::ROTATE;
                        }

                        if (ImGui::IsKeyPressed(ImGuiKey_S))
                        {
                            currentOperation = ImGuizmo::SCALE;
                        }
                    }

                    // Define snap settings
                    bool snap = false;      // Enable snapping if needed
                    float snapValue = 0.1f; // Snap increment

                    // Set the ImGuizmo rectangle to the window's position and size
                    ImVec2 windowPos = ImGui::GetWindowPos();
                    ImVec2 windowSize = ImGui::GetWindowSize();
                    ImGuizmo::SetRect(windowPos.x, windowPos.y, windowSize.x, windowSize.y);

                    // Render the gizmo and handle user interaction
                    projectionMatrix[1][1] *= -1.0f; // Flip Image Internaly
                    ImGuizmo::Manipulate(
                        glm::value_ptr(viewMatrix),
                        glm::value_ptr(projectionMatrix),
                        currentOperation,
                        ImGuizmo::LOCAL,
                        glm::value_ptr(modelMatrix),
                        nullptr,                    // Optional delta matrix
                        snap ? &snapValue : nullptr // Optional snap values
                    );

                    // Check if the gizmo is being used (i.e., if the user is interacting with it)
                    if (ImGuizmo::IsUsing())
                    {
                        // Update the TransformComponent with the modified matrix
                        transform->SetTransformMatrix(modelMatrix);
                    }
                }
            }
        }
    }
    else
    {
        // Display message if there's insufficient space to render the scene
        ImGui::Text("No space to render.");
    }

    // End the ImGui window
    ImGui::End();
}

void RenderWindow::InitGLResources()
{
    // ----------------------------------------------------
    // 1) Load SHADER from the asset manager
    // ----------------------------------------------------

    // throw this in here cus we dont have a constructor
    m_ActiveCamera = nullptr;

    m_EditorCamera = std::make_shared<GameObject>(-1, "EditorCamera");

    // Setup the editor camera
    m_EditorCamera->AddComponent(std::make_shared<CameraComponent>());
    m_EditorCamera->AddComponent(std::make_shared<TransformComponent>());

    {
        std::shared_ptr<Shader> shaderAsset = g_AssetManager.loadAsset<Shader>(AssetType::SHADER, "assets/shaders/UnlitMaterial");
        if (!shaderAsset)
        {
            fprintf(stderr, "[RenderWindow] Failed to load shader via AssetManager.\n");
            return;
        }
        // Cast back to your Shader class
        m_ShaderPtr = shaderAsset.get();
    }

    {
        std::shared_ptr<Shader> shaderAsset = g_AssetManager.loadAsset<Shader>(AssetType::SHADER, "assets/shaders/Line");
        if (!shaderAsset)
        {
            fprintf(stderr, "[RenderWindow] Failed to load shader via AssetManager.\n");
            return;
        }
        // Cast back to your Shader class
        m_LineShaderPtr = shaderAsset.get();
    }

    // ----------------------------------------------------
    // 3) Load TEXTURE from the asset manager
    // ----------------------------------------------------
    {
        std::shared_ptr<GLuint> texAsset = g_AssetManager.loadAsset<GLuint>(AssetType::TEXTURE, "assets/textures/wood.png");
        if (!texAsset)
        {
            fprintf(stderr, "[RenderWindow] Failed to load texture.\n");
        }
        else
        {
            // Cast from void* to GLuint
            m_TextureID = *texAsset; // Assign the GLuint value
        }
    }

    // ----------------------------------------------------
    // 4) Initialize GameObjects
    // ----------------------------------------------------
}

void CheckOpenGLError(const std::string &location)
{
    GLenum err;
    bool hasError = false;
    while ((err = glGetError()) != GL_NO_ERROR)
    {
        std::cerr << "[OpenGL Error] (" << err << ") at " << location << std::endl;
        hasError = true;
    }
    if (hasError)
    {
        // Optionally, you can throw an exception or handle the error as needed
    }
}

#include <glm/gtc/type_ptr.hpp> // For glm::value_ptr
#include <algorithm>            // Ensure <algorithm> is included
void RenderWindow::RenderSceneToFBO(bool *GameRunning)
{
    m_RotationAngle += 0.001f; // Spin per frame

    // 1) Bind the FBO and set up viewport
    m_FBO.Bind();
    glViewport(0, 0, m_LastWidth, m_LastHeight);

#if TRANSPERANCY
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
#endif

    glEnable(GL_DEPTH_TEST);

    glClearColor(0.f, 0.f, 0.f, 1.f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // 2) Check our main rendering shader
    if (!m_ShaderPtr)
    {
        DEBUG_PRINT("[RenderWindow] Shader pointer is null. Cannot render.");
        m_FBO.Unbind();
        return;
    }
    m_ShaderPtr->Use();

    // 3) Obtain view/projection from the active camera (or fallback)
    std::shared_ptr<CameraComponent> activeCamera = nullptr;
    glm::mat4 view, proj;

    if (*GameRunning && g_RuntimeCameraObject)
    {
        activeCamera = g_RuntimeCameraObject;
    }

    if (activeCamera)
    {
        // TODO: Add camera Movement in editor
        view = activeCamera->GetViewMatrix();
        proj = activeCamera->GetProjectionMatrix();
        m_ActiveCamera = activeCamera;
    }
    else
    {
        // Fallback if no camera
        view = glm::translate(glm::mat4(1.f), glm::vec3(0.f, 0.f, -5.f));
        float aspect = (m_LastHeight != 0) ? (float)m_LastWidth / (float)m_LastHeight : 1.0f;
        proj = glm::perspective(glm::radians(CAM_FOV), aspect, CAM_NEAR_PLAIN, CAM_FAR_PLAIN);
        m_ActiveCamera = nullptr;
    }

    // 4) Extract frustum planes for culling
    glm::mat4 vp = proj * view;
    FrustumPlanes frustum = ExtractFrustumPlanes(vp);

    // 5) Iterate over each GameObject and render
    glm::vec4 LineColor = g_SettingsManager.S_LineColor;

    for (auto &obj : g_GameObjects)
    {
        glm::mat4 model = glm::mat4(1.f);

        auto transform = obj->GetComponent<TransformComponent>();
        auto mesh = obj->GetComponent<MeshComponent>();

        if (transform && mesh)
        {
            // 5A) Build the Model matrix
            model = glm::translate(model, transform->position);
            model = glm::rotate(model, glm::radians(transform->rotation.x), glm::vec3(1.f, 0.f, 0.f));
            model = glm::rotate(model, glm::radians(transform->rotation.y), glm::vec3(0.f, 1.f, 0.f));
            model = glm::rotate(model, glm::radians(transform->rotation.z), glm::vec3(0.f, 0.f, 1.f));
            model = glm::scale(model, transform->scale);

            // 5B) For each submesh
            for (auto &submesh : mesh->submeshes)
            {
                // Check if VAO is valid
                if (submesh.vao == 0)
                {
                    DEBUG_PRINT("[RenderWindow] Warning: Submesh VAO is not initialized.");
                    continue;
                }

                // -------------------------
                // *** FRUSTUM CULLING ***
                // Transform submesh bounding box from local -> world space
                glm::vec3 worldMin(FLT_MAX), worldMax(-FLT_MAX);
                std::array<glm::vec3, 8> corners = {
                    glm::vec3(submesh.minExtents.x, submesh.minExtents.y, submesh.minExtents.z),
                    glm::vec3(submesh.minExtents.x, submesh.minExtents.y, submesh.maxExtents.z),
                    glm::vec3(submesh.minExtents.x, submesh.maxExtents.y, submesh.minExtents.z),
                    glm::vec3(submesh.minExtents.x, submesh.maxExtents.y, submesh.maxExtents.z),
                    glm::vec3(submesh.maxExtents.x, submesh.minExtents.y, submesh.minExtents.z),
                    glm::vec3(submesh.maxExtents.x, submesh.minExtents.y, submesh.maxExtents.z),
                    glm::vec3(submesh.maxExtents.x, submesh.maxExtents.y, submesh.minExtents.z),
                    glm::vec3(submesh.maxExtents.x, submesh.maxExtents.y, submesh.maxExtents.z)};

                for (auto &c : corners)
                {
                    // Transform corner by the model matrix
                    glm::vec4 worldPos = model * glm::vec4(c, 1.0f);

                    // Expand worldMin / worldMax
                    worldMin.x = std::min(worldMin.x, worldPos.x);
                    worldMin.y = std::min(worldMin.y, worldPos.y);
                    worldMin.z = std::min(worldMin.z, worldPos.z);

                    worldMax.x = std::max(worldMax.x, worldPos.x);
                    worldMax.y = std::max(worldMax.y, worldPos.y);
                    worldMax.z = std::max(worldMax.z, worldPos.z);
                }

                // Now test that box against frustum
                if (!IsBoxInFrustum(worldMin, worldMax, frustum))
                {
                    // The submesh is completely outside the camera's view => skip
                    continue;
                }
                // -------------------------

                // 5C) Compute MVP and pass to shader
                glm::mat4 mvp = vp * model;
                m_ShaderPtr->SetMat4("uMVP", mvp);
                m_ShaderPtr->SetMat4("uModel", model);

                // 5D) Update tri count
                g_GPU_Triangles_drawn_to_screen += static_cast<int>(submesh.indices.size() / 3);

                // 5E) Bind textures
                const int MAX_DIFFUSE = 32;
                int textureUnit = 0;
                for (auto &texture : submesh.textures)
                {
                    if (texture.type == "texture_diffuse")
                    {
                        if (textureUnit >= MAX_DIFFUSE)
                        {
                            DEBUG_PRINT("[RenderWindow] Warning: Exceeded maximum diffuse textures.");
                            break;
                        }
                        glActiveTexture(GL_TEXTURE0 + textureUnit);
                        glBindTexture(GL_TEXTURE_2D, texture.id);

                        std::string uniformName = "uTextures.texture_diffuse[" + std::to_string(textureUnit) + "]";
                        m_ShaderPtr->SetInt(uniformName, textureUnit);

                        textureUnit++;
                    }
                }
                // Assign default texture to unused slots
                for (int i = textureUnit; i < MAX_DIFFUSE; ++i)
                {
                    std::string uniformName = "uTextures.texture_diffuse[" + std::to_string(i) + "]";
                    m_ShaderPtr->SetInt(uniformName, 0);
                }
                m_ShaderPtr->SetInt("uNumDiffuseTextures", textureUnit);

                // 5F) Draw submesh (filled)
                glBindVertexArray(submesh.vao);
                glDrawElements(GL_TRIANGLES,
                               static_cast<GLsizei>(submesh.indices.size()),
                               GL_UNSIGNED_INT,
                               nullptr);
                g_GPU_Draw_Calls++;
                glBindVertexArray(0);
                glActiveTexture(GL_TEXTURE0);

                // ----------------------------------------
                // 5G) OPTIONAL: Draw a bounding box outline
                // ----------------------------------------
                if (DrawBBBO && m_LineShaderPtr && submesh.bboxVAO != 0)
                {
                    // Use a simpler line shader that doesn't rely on textures
                    m_LineShaderPtr->Use();

                    // Recompute the MVP for the bounding box (same model, same vp)
                    glm::mat4 bboxMVP = vp * model;
                    m_LineShaderPtr->SetMat4("uMVP", bboxMVP);
                    m_LineShaderPtr->SetVec4("uColor", LineColor);
                    glLineWidth(2.0f);

                    // If your line shader has a uniform color:
                    // m_LineShaderPtr->SetVec4("uColor", glm::vec4(1,1,0,1)); // e.g., yellow

                    // Draw the bounding box in wireframe lines
                    glBindVertexArray(submesh.bboxVAO);
                    // We assume submesh.bboxVertexCount is the number of line-vertices
                    glDrawArrays(GL_LINES, 0, submesh.bboxVertexCount);

                    glBindVertexArray(0);
                    glUseProgram(0);
                }
            }
        }
    }

#if TRANSPERANCY
    glDisable(GL_BLEND);
#endif
    glUseProgram(0);

    // 6) Unbind the FBO
    m_FBO.Unbind();
}