From BlenderWiki

Jump to: navigation, search

Introduction

Lighting is a very important topic in rendering, standing equal to modeling, materials and textures. The most accurately modeled and textured scene will yield poor results without a proper lighting scheme, while a simple model can become very realistic if skillfully lit. Lighting, sadly, is often overlooked by the inexperienced artist who commonly believes that, since real world scenes are often lit by a single light (a lamp, the sun, etc.) a single light will also do in computer graphics. This is false because in the real world even if a single light source is present, the light shed by such a source bounces off objects and is re-irradiated all over the scene, making shadows soft and shadowed regions not pitch black, but partially lit.

Viewing Restrictions

The colour of an object and the lighting of your scene is affected by:

  • Your ability to see different colours (partial colour blindness is common).
  • The medium in which you are viewing the image (e.g. an LCD panel versus printed glossy paper).
  • The quality of the image (e.g. a JPEG at 0.4 compression versus 1.0).
  • The environment in which you are viewing the image (e.g. a CRT monitor with glare versus in a dark room, or in a sunshiny blue room).
  • Your brain’s perception of the colour and intensity relative to those objects around it and the world background colour.

So, the exact same image viewed by Person A on monitor B in room C may look very different to Person D viewing a printout E of the image while on the subway F.

Global Influences

In Blender, the things under your control that affect lighting are:

  • The colour of the world ambient light.
  • The use of Ambient Occlusion as a way to cast that ambient light onto the object.
  • The degree to which the ambient light colours the material of the object.
  • The use of Radiosity, where the colour of one object radiates onto another.
  • The render engine used (Blender Internal versus Yafray).
  • The lamps in your scene.

The physics of light bouncing around in the real-world is simulated by Ambient Occlusion (a world setting), buffer shadows (which approximate shadows being cast by objects), ray tracing (which traces the path of photons from a light source). Also, within Blender you can use the Radiosity engine. Ray tracing, ambient occlusion, and radiosity are computer-intensive processes. Blender can perform much faster rendering with its internal scan line renderer, which is a very good scan line renderer indeed. This kind of rendering engine is much faster since it does not try to simulate the real behaviour of light, assuming many simplifying hypotheses.

Lighting Settings

Only after the above global influences do you get into adding on light from lamps in your scene. The main things under your control are the:

  • Type of light used (Sun, Spot, Lamp, Hemi, etc).
  • Colour of the light.
  • Position of the light and its direction.
  • Settings for each of those lights, including energy and falloff.

Then you are back to how that material’s shader reacts to the light.

This chapter attempts to address the above, including how lights can work together in rigs to light your scene. In this chapter we will analyze the different type of lights in Blender and their behaviour, we will analyze their strong and weak points. We also describe many lighting rigs, including the ever-popular three point light method.

Lighting in the Workflow

In this User Manual we have placed Lighting before Materials; you should set up your lighting before assigning materials to your meshes. Since the material shaders react to light, without proper lighting, the material shaders will not look right, and you will end up fighting the shader, when it is really the bad lighting that is causing you grief. All of the example images in this section do not use any material setting at all on the ball, cube or background.

Over-riding Materials to reset lighting

If you have started down the road of assigning materials, and are just now fiddling with the lighting, we suggest that you create a default, generic grey material; no VCol, no TexFace, no Shadeless, just plain old middle grey with an RGB of (0.80.80.8). If you click the auto-namer button, it should fill in “Grey”.

Mat field highlighted in yellow.

Next go to Scene context (F10) of the Buttons window, and find the Render sub-context. In the Render Layers panel, enter “Grey” into the Mat field. If the name sticks, you know you entered it correctly. This will override any materials you may have set, and render everything with this flat boring colour. Using this material, you can now go about adjusting the lighting. Just empty this field to get back to your original materials.