diff --git a/src/engine/engine.cc b/src/engine/engine.cc
index 4646fdf..d489f5f 100644
--- a/src/engine/engine.cc
+++ b/src/engine/engine.cc
@@ -70,12 +70,9 @@ void Engine::Run() {
   Initialize();
 
   DeltaTimer timer;
-  float accumulator = 0.0;
-  float frame_frac = 0.0f;
+  float accumulator = 0.0f;
 
   for (;;) {
-    TaskRunner::GetThreadLocalTaskRunner()->RunTasks();
-
     platform_->Update();
     if (platform_->should_exit())
       return;
@@ -83,8 +80,6 @@ void Engine::Run() {
     if (!renderer_->IsInitialzed())
       continue;
 
-    Draw(frame_frac);
-
     // Accumulate time.
     accumulator += timer.Delta();
 
@@ -94,8 +89,11 @@ void Engine::Run() {
       accumulator -= time_step_;
     };
 
+    TaskRunner::GetThreadLocalTaskRunner()->RunTasks();
+
     // Calculate frame fraction from remainder of the frame time.
-    frame_frac = accumulator / time_step_;
+    float frame_frac = accumulator / time_step_;
+    Draw(frame_frac);
   }
 }
 
diff --git a/src/engine/imgui_backend.cc b/src/engine/imgui_backend.cc
index 61260dd..5630a01 100644
--- a/src/engine/imgui_backend.cc
+++ b/src/engine/imgui_backend.cc
@@ -135,6 +135,8 @@ void ImguiBackend::Draw() {
   if (draw_data->CmdListsCount <= 0)
     return;
 
+  renderer_->SetViewport(0, 0, draw_data->DisplaySize.x, draw_data->DisplaySize.y);
+
   base::Matrix4f ortho_projection;
   ortho_projection.CreateOrthoProjection(
       draw_data->DisplayPos.x,
@@ -169,6 +171,7 @@ void ImguiBackend::Draw() {
     renderer_->DestroyGeometry(geometry_id);
   }
   renderer_->ResetScissor();
+  renderer_->ResetViewport();
 }
 
 }  // namespace eng
diff --git a/src/engine/renderer/opengl/renderer_opengl.cc b/src/engine/renderer/opengl/renderer_opengl.cc
index f7c6ca4..3c23b9a 100644
--- a/src/engine/renderer/opengl/renderer_opengl.cc
+++ b/src/engine/renderer/opengl/renderer_opengl.cc
@@ -47,7 +47,6 @@ RendererOpenGL::~RendererOpenGL() {
 void RendererOpenGL::OnWindowResized(int width, int height) {
   screen_width_ = width;
   screen_height_ = height;
-  glViewport(0, 0, screen_width_, screen_height_);
 }
 
 int RendererOpenGL::GetScreenWidth() const {
@@ -58,6 +57,14 @@ int RendererOpenGL::GetScreenHeight() const {
   return screen_height_;
 }
 
+void RendererOpenGL::SetViewport(int x, int y, int width, int height) {
+  glViewport(0, 0, width, height);
+}
+
+void RendererOpenGL::ResetViewport() {
+  glViewport(0, 0, screen_width_, screen_height_);
+}
+
 void RendererOpenGL::SetScissor(int x, int y, int width, int height) {
   glScissor(x, screen_height_ - y - height, width, height);
   glEnable(GL_SCISSOR_TEST);
@@ -436,6 +443,7 @@ void RendererOpenGL::SetUniform(uint64_t resource_id,
 }
 
 void RendererOpenGL::PrepareForDrawing() {
+  glViewport(0, 0, screen_width_, screen_height_);
   glDisable(GL_SCISSOR_TEST);
 }
 
diff --git a/src/engine/renderer/opengl/renderer_opengl.h b/src/engine/renderer/opengl/renderer_opengl.h
index 9d035f1..ce9e356 100644
--- a/src/engine/renderer/opengl/renderer_opengl.h
+++ b/src/engine/renderer/opengl/renderer_opengl.h
@@ -32,6 +32,9 @@ class RendererOpenGL final : public Renderer {
   int GetScreenWidth() const final;
   int GetScreenHeight() const final;
 
+  void SetViewport(int x, int y, int width, int height) final;
+  void ResetViewport() final;
+
   void SetScissor(int x, int y, int width, int height) final;
   void ResetScissor() final;
 
diff --git a/src/engine/renderer/renderer.h b/src/engine/renderer/renderer.h
index 37708de..93f336b 100644
--- a/src/engine/renderer/renderer.h
+++ b/src/engine/renderer/renderer.h
@@ -39,6 +39,9 @@ class Renderer {
   virtual int GetScreenWidth() const = 0;
   virtual int GetScreenHeight() const = 0;
 
+  virtual void SetViewport(int x, int y, int width, int height) = 0;
+  virtual void ResetViewport() = 0;
+
   virtual void SetScissor(int x, int y, int width, int height) = 0;
   virtual void ResetScissor() = 0;
 
diff --git a/src/engine/renderer/vulkan/renderer_vulkan.cc b/src/engine/renderer/vulkan/renderer_vulkan.cc
index b5e2806..1a155ba 100644
--- a/src/engine/renderer/vulkan/renderer_vulkan.cc
+++ b/src/engine/renderer/vulkan/renderer_vulkan.cc
@@ -390,6 +390,30 @@ int RendererVulkan::GetScreenHeight() const {
   return context_.GetWindowHeight();
 }
 
+void RendererVulkan::SetViewport(int x, int y, int width, int height) {
+  VkViewport viewport;
+  viewport.x = 0;
+  viewport.y = (float)height;
+  viewport.width = (float)width;
+  viewport.height = -(float)height;
+  viewport.minDepth = 0;
+  viewport.maxDepth = 1.0;
+  vkCmdSetViewport(frames_[current_frame_].draw_command_buffer, 0, 1,
+                   &viewport);
+}
+
+void RendererVulkan::ResetViewport() {
+  VkViewport viewport;
+  viewport.x = 0;
+  viewport.y = (float)context_.GetWindowHeight();
+  viewport.width = (float)context_.GetWindowWidth();
+  viewport.height = -(float)context_.GetWindowHeight();
+  viewport.minDepth = 0;
+  viewport.maxDepth = 1.0;
+  vkCmdSetViewport(frames_[current_frame_].draw_command_buffer, 0, 1,
+                   &viewport);
+}
+
 void RendererVulkan::SetScissor(int x, int y, int width, int height) {
   if (x < 0)
     x = 0;
@@ -1990,8 +2014,6 @@ bool RendererVulkan::CreatePipelineLayout(
 }
 
 void RendererVulkan::DrawListBegin() {
-  VkCommandBuffer command_buffer = frames_[current_frame_].draw_command_buffer;
-
   VkRenderPassBeginInfo render_pass_begin;
   render_pass_begin.sType = VK_STRUCTURE_TYPE_RENDER_PASS_BEGIN_INFO;
   render_pass_begin.pNext = nullptr;
@@ -2010,26 +2032,11 @@ void RendererVulkan::DrawListBegin() {
   render_pass_begin.clearValueCount = clear_values.size();
   render_pass_begin.pClearValues = clear_values.data();
 
-  vkCmdBeginRenderPass(command_buffer, &render_pass_begin,
-                       VK_SUBPASS_CONTENTS_INLINE);
+  vkCmdBeginRenderPass(frames_[current_frame_].draw_command_buffer,
+                       &render_pass_begin, VK_SUBPASS_CONTENTS_INLINE);
 
-  VkViewport viewport;
-  viewport.x = 0;
-  viewport.y = (float)context_.GetWindowHeight();
-  viewport.width = (float)context_.GetWindowWidth();
-  viewport.height = -(float)context_.GetWindowHeight();
-  viewport.minDepth = 0;
-  viewport.maxDepth = 1.0;
-
-  vkCmdSetViewport(command_buffer, 0, 1, &viewport);
-
-  VkRect2D scissor;
-  scissor.offset.x = 0;
-  scissor.offset.y = 0;
-  scissor.extent.width = context_.GetWindowWidth();
-  scissor.extent.height = context_.GetWindowHeight();
-
-  vkCmdSetScissor(command_buffer, 0, 1, &scissor);
+  ResetViewport();
+  ResetScissor();
 }
 
 void RendererVulkan::DrawListEnd() {
diff --git a/src/engine/renderer/vulkan/renderer_vulkan.h b/src/engine/renderer/vulkan/renderer_vulkan.h
index 86d296f..7cfeef0 100644
--- a/src/engine/renderer/vulkan/renderer_vulkan.h
+++ b/src/engine/renderer/vulkan/renderer_vulkan.h
@@ -33,6 +33,9 @@ class RendererVulkan final : public Renderer {
   int GetScreenWidth() const final;
   int GetScreenHeight() const final;
 
+  void SetViewport(int x, int y, int width, int height) final;
+  void ResetViewport() final;
+
   void SetScissor(int x, int y, int width, int height) final;
   void ResetScissor() final;