feat: add camera viewport rect render areas

engine/src/Rendering/SceneRenderer.cpp

@@ -5,6 +5,7 @@
 #include "Scene/Scene.h"
 
 #include <algorithm>
+#include <cmath>
 
 namespace XCEngine {
 namespace Rendering {
@@ -40,6 +41,20 @@ RenderClearFlags ResolveClearFlags(const Components::CameraComponent& camera, si
     }
 }
 
+Math::RectInt ResolveCameraRenderArea(
+    const Components::CameraComponent& camera,
+    const RenderSurface& surface) {
+    const Math::Rect viewportRect = camera.GetViewportRect();
+    const float surfaceWidth = static_cast<float>(surface.GetWidth());
+    const float surfaceHeight = static_cast<float>(surface.GetHeight());
+
+    const int32_t left = static_cast<int32_t>(std::floor(viewportRect.x * surfaceWidth));
+    const int32_t top = static_cast<int32_t>(std::floor(viewportRect.y * surfaceHeight));
+    const int32_t right = static_cast<int32_t>(std::ceil((viewportRect.x + viewportRect.width) * surfaceWidth));
+    const int32_t bottom = static_cast<int32_t>(std::ceil((viewportRect.y + viewportRect.height) * surfaceHeight));
+    return Math::RectInt(left, top, right - left, bottom - top);
+}
+
 } // namespace
 
 SceneRenderer::SceneRenderer() = default;
@@ -101,9 +116,13 @@ std::vector<CameraRenderRequest> SceneRenderer::BuildRenderRequests(
         request.camera = camera;
         request.context = context;
         request.surface = surface;
+        request.surface.SetRenderArea(ResolveCameraRenderArea(*camera, surface));
         request.cameraDepth = camera->GetDepth();
         request.clearFlags = ResolveClearFlags(*camera, cameraIndex);
-        requests.push_back(request);
+        if (request.surface.GetRenderAreaWidth() > 0 &&
+            request.surface.GetRenderAreaHeight() > 0) {
+            requests.push_back(request);
+        }
     }
 
     return requests;