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Blender 2.5x : Lighting/Rendering Tests - Indirect Illumination #1

What is Indirect Illumination?

To understand what Indirect Illumination means, Please take a look at the image that I clicked sometime back.

An Indirect Lighting method
  1. Modes the light that is reflected from other surfaces to the current surface.
  2. Is more comprehensive, more physically correct, and produces more realistic images. It is also more computationally expensive.
Take a look at the following examples of a scene lit with Direct Lighting and both Direct+Indirect Lighting

Direct Lighting Schematic

Image courtesy
Direct Lighting Render

Direct+Indirect Lighting Schematic

Direct+Indirect Lighting Render


What this test in Blender tries to accomplish is to demonstrate the results of a render without and with Indirect Illumination (Light hitting a surface and then bouncing and illuminating the nearby objects).

Indirect Illumination is achieved using Global Illumination algorithms (RayTracing) and/or approximations (Point Based/Irradiance caching). The technique that is available in Blender 2.56a beta is an Approximate Gather Indirect Lighting Technique

NOTE: In Blender, a mesh object can also emit light. This page does not use that feature. If you want to learn about that feature click here.

First test
Download .blend file
Second test

Download .blend file
Third test


Download .blend file

Check it yourself

Check the test renders with different values of indirect illumination falloff.

UPDATE #1: With better shaders for terrain and with environment lighting and ambient occlusion

UPDATE #2: With modified terrain topology

UPDATE #3: Renders from various parts of the day

Case Study From Sintel

Render Development Update by Brecht During Development of Sintel

Watch Sintel


Light bounces in real life. Adding indirect illumination adds more realism to your scene.

Further Reading