Clipping Regions Vs Select Render Borders In Blender: What'S The Difference And When To Use Each

Defining Clipping Regions vs Select Render Borders

Clipping regions and select render borders are two techniques in Blender that allow controlling the visible and rendered areas of a scene. Understanding the difference between the two is key to using them effectively.

Clipping regions set an area in 3D space to clip away geometry, limiting the visible contents of the scene. They function by culling and hiding geometry outside the defined region. This allows isolating specific objects or areas of interest from complex scenes. Clipping regions impact what is visible in the 3D viewport when working in Blender.

In contrast, select render borders set an area in the 2D space of the final render output. They limit what part of the full render is actually computed and saved. Select render borders crop the rendered image result, not the scene contents. This can save render time by only processing the required portion of the output image.

Table of Contents

When to Use Clipping Regions

Clipping regions are most useful when you need to isolate or focus on specific objects or parts of a complex scene. Hiding distracting or obstructing geometry lets you work more efficiently. Some common uses cases include:

Focusing on a single object or localized area
Isolating small details from large scenes
Peering inside nested sub-assemblies
Removing distracting background clutter

For example, you might set a clipping region when modeling a component that will mounted inside a larger assembly. Cutting away the enclosure lets you access the area you need while modeling, making it much easier to visualize and work.

Example Code to Set a Clipping Region

Here is a simple Python script to set a clipping region bounded by two opposing corners:

import bpy
from mathutils import Vector

# Set clip start location 
clip_start = Vector((0, 0, 0)) 

# Set clip end location
clip_end = Vector((1, 1, 1))

# Set clipping region  
bpy.context.space_data.clip_start = clip_start  
bpy.context.space_data.clip_end = clip_end

The key parameters here are the clip_start and clip_end vectors, which define any diagonal opposite corners of the region you want to clip to. Everything outside these points will be hidden from the viewport.

When to Use Select Render Borders

Select render borders are most useful when you only need to produce a cropped section of the final rendered image, not modify the actual scene contents. Reasons to use them include:

Cropping render output for efficiency
Isolating areas for closer inspection
Focusing attention on key parts of render
Excluding peripheral content

For example, you might set a select render border when producing a detail shot of a component within a larger product render. By only computing the required portion, you can save time and resources instead of rendering the full image.

Example Code to Set Select Render Border

Here is Python script to set a select render border to one quarter of the frame:

import bpy 

# Set render border to left half of render    
bpy.context.scene.render.use_border = True
bpy.context.scene.render.border_min_x = 0.0  
bpy.context.scene.render.border_min_y = 0.0
bpy.context.scene.render.border_max_x = 0.5
bpy.context.scene.render.border_max_y = 1.0

The key parameters are setting use_border to True to enable the crop border, then settings percentages for the minimum and maximum X and Y bounds. This would crop the render horizontally into two halves.

Achieving Similar Effects

Clipping regions and select render borders can sometimes achieve visually similar effects for isolating areas of interest. However, it is better to use the technique that most directly matches your specific goal and workflow.

One case where they can complement each other is using clipping temporarily while modeling complex components, then switching to select render borders later for efficient animation previews or final renders. The clipping assists with construction, select borders with output.

Pros and Cons of Each Approach

Clipping Regions:

Pros:

Limits visible geometry in 3D viewport
Makes space for working inside assemblies
Focuses attention by hiding clutter

Cons:

Can’t exclude objects from final render
Impacts scene contents not just output
Changing visible geometry can cause confusion

Select Render Borders:

Pros:

Crops rendered output directly
Saves compute resources
Does not disrupt scene contents

Cons:

Requires re-rendering to adjust border
Doesn’t help simplify viewport in modeling
Only impacts final render not workflow

In summary, clipping regions aid workflow by controlling visibility while modeling, select borders enhance rendering by cropping output image frames.

Deciding Which to Use

When choosing between clipping and select render borders, consider your end goal and where you are in the production pipeline:

Modeling – Use clipping regions to isolate components
Texturing/materials – Use either as needed
Animation – Use either to focus shots
Rendering – Primarily use select render borders

Also factor if you need to simplify interactive geometry in the 3D viewport, or crop final render output. As a rule of thumb for efficiency:

Clipping assists modeling, select borders assist rendering

Particularly for animation and rendering, selective use of crop borders can hugely improve computation times for previews, playblasts, and final frame generation.

Optimization Tips

To further optimize using clipping and select borders:

Narrow clipping regions to just areas of interest
Combine both clipping and select borders where appropriate
Animating borders? Render last frame first
Add border modifiers to Python automation scripts

Taking time to set precise borders pays off exponentially in
computation savings down the line. Tighter borders equals faster
results.

Clipping Regions Vs Select Render Borders In Blender: What’S The Difference And When To Use Each