3 Ways to Speed Up Rendering in Blender with View Regions

by Render Pool

March 9, 2021

If you’re in Blender’s rendered shading mode and have highly complex objects and materials in the 3D viewport, you may notice that your machine’s performance takes a bit of a dive and the visualization process is substantially slower.

The question is: If you’re only interested in rendering a specific area, how do you go about disabling all other unnecessary calculations, regarding the background or other irrelevant objects, that slow down the viewport and your workflow? This is where Blender’s View Regions tools come into play.

Blender’s View Regions Tools

Blender’s View Regions allows you to set the limit of the 3D view display in the 3D viewport. This is helpful when designing complex models and scenes, because it limits how much of an element is seen or calculated. You can choose to render a selected region within the viewport instead of all of it, which is particularly helpful when you want to quickly render a specific area to preview changes to the model or scene.

Blender comes equipped with three separate View Regions tools: Zoom, Clipping, and Render.

Zoom Region

The Zoom Region tool allows you to specify a rectangular region and zoom into it so that only the designated region can be viewed in the 3D viewport.

You can achieve this by using the Shift+B shortcut, then clicking the left mouse button and dragging the rectangle to create the zoom region. Alternatively, you can zoom out of the image using the middle mouse button.

Clipping Region

When the Clipping Region tool is applied, only what is inside the region that you have designated will be visible. Other tools such as paint, carving, sorting, and transforming photography will disregard the geometry outside the boundaries of the designated region.

The Clipping Region will not simply be a flat rectangular region, it will actually create a volume:

  • Rectangular pyramid volume (infinite length) if the view is in perspective.
  • Right-angle parallelepiped volume (unlimited length) if the view is orthographic.

You can activate the tool with Alt+B or by using the View menu and locating Clipping Region in the View Regions submenu. This will produce a crosshair cursor. Using the left mouse button, click and drag to create a rectangle, which will define the region of the space to be clipped within the 3D space. You may notice that the object in your scene is no longer visible or “clipped.” You can still use navigation tools as usual to zoom and change the angle of the scene in the viewport, but you will notice that only the inside of the Clipping Region’s designated volume is visible regarding your object. All editing tools also work as usual within the designated region.

Render Region

Finally, with the Render Region tool, you can render a specific area of the 3D view, allowing for easier editing of heavy calculations. You can achieve this by using the Ctrl+B shortcut, once again clicking and holding the left mouse button and dragging the rectangle to create the region. When setting the viewport shading mode to Rendered, it will only calculate the information inside the designated render region, which should have the effect of decreasing rendering time.

When working on a complicated scene, you can isolate geometry or complex elements and limit the calculations needed to render in the viewport. For designers with slower workstations and extremely large files, this can be very useful.

Pressing Ctrl+Alt+B, or selecting Clear Render Region in the View Regions submenu in the View menu will disable the region. This can also apply to renders through the lens of your specified camera.

Rendering your final render can also be confined to your designated region as well. In the Dimensions submenu within the Output Properties tab, you will find the Render Region and the Crop to Render Region options. Enabling the Render Region option will render the region and a transparent background. If you don’t want a transparent background, enabling the Crop to Render Region option will render only the dimensions of the region.

Animated Render Border Add-on

Render Region is a great way to maximize your computing power and focus on a specific element in a scene, and it’s great for workflows when making single still images but not so much if you’re working on an animation where an object of interest is moving around on the screen.

Ray Mairlot has created a really useful add-on that’s helpful for rendering animations in designated render borders called Animated Render Border.

The add-on claims to make the designated render region adaptive so that it updates its location and size every frame in the scene’s timeline to always track a specified object, collection of objects, or even keyframe positions, focusing your renders on just a specific part of an image in motion.

You can find this add-on available in the Blender Market.

Improve Rendering Speed with View Regions

When testing a new material or checking lighting, repeatedly rendering an entire scene just to tweak a single parameter is time-consuming and counter-productive, especially if you’re working with larger scenes or heavier geometry.

As we’ve mentioned in previous guides, using Blender’s Eevee rendering engine helps everything become quite responsive in the viewport — no noticeable slowdown, no graphical issues. However, when the need to create realistic or physically accurate renders arises, it’s usually recommended to rely on Cycles as the engine for your final rendering. While these View Region’s tools are available for both rendering engines, they are particularly effective with Cycles, since they can help provide a solution for reducing unnecessarily long rendering times during production. Happy rendering!