Blender Documentation Volume II - Reference Guide: Last modified March 29 2004 S68
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# Shading Context

The Shading context is among the most complex, exhibiting 5 Sub-contextes and several Panels. Many of these panels are Condesed into a single Panel with Tabs in the default Blender settings.

## Lamp Sub-Context

The settings in these Sub-context visualise the Lamp DataBlock. The Lamp Buttons are only displayed if the active Object is a Lamp.

### `Preview` Panel

***FIG HERE***

As for all these Sub-contextes, except radiosity, the first Panel contains a preview square window.

Right of the Window a column of four Toggle Buttons allows to select the Lamp Type:

#### Lamp

The standard lamp, a point light source.

#### Spot

The lamp is restricted to a conical space. The 3DWindow shows the form of the spotlight with a broken line.

#### Sun

The light shines from a constant direction; the distance has no effect. The position of the Lamp Object is thus unimportant, except for the rotation.

#### Hemi

Like Sun, but now light is shed in the form of half a sphere, a hemisphere. This method is also called directional ambient. It can be used to suggest cloudy daylight.

### `Lamp` Panel

***FIG HERE***

The top button row presents:

#### Lamp Menu

Choose another Lamp Block from the list provided.

#### LA:

Shows the current Lamp name. SHIFT-LMB to edit it into a new and unique name.

#### Users

If the Lamp Block is used by more than one Object, this button shows the total number of Objects. Press the button to make the Lamp "Single User". This duplicates the Lamp Block.

#### Dist

For the lamp types `Lamp` and `Spot`, the distance affects the intensity of the light. The standard formula is used for this:

D = "Dist" button, r = distance to the lamp. Light intensity = D/(D + r).

This is an inverse linear progression. With the option `Quad`, this can be changed.

Left button column presents:

#### Quad

The distance from the lamp is in inverse quadratic proportion to the intensity of the light. An inverse linear progression is standard (see the buttons `Dist`, `Quad1` and `Quad2`).

#### Sphere

The lamp only sheds light within a spherical area around the lamp. The radius of the sphere is determined by the `Dist` button.

#### Layer

Only Objects in the same layer(s) as the Lamp Object are illuminated. This enables you to use selective lighting, to give objects an extra accent or to restrict the effects of the lamp to a particular space. It also allows to you keep rendering times under control.

#### Negative

A lamp casts 'negative' light.

#### No Diffuse

The lamp does not interact with the "Diffuse" shader of the objects.

#### No Specular

The lamp does not interact with the "Specular" shader of the object.

Right button column presents:

#### Energy

The intensity of the light. The standard settings in Blender assume that a minimum of two lamps are used.

#### R, G, B

The red, green and blue components of the light.

#### Quad1, Quad2

The light intensity formula of a Quad Lamp is: Light intensity = D / (D + (quad1 * r) + (quad2 * r * r)) D = `Dist` button. r = distance to the lamp. The values of quad1 and quad2 at 1.0 produces the strongest quadratic progression. The values of quad1 and quad2 at 0.0 creates a special Quad lamp that is insensitive to distance.

### `Spot` Panel

***FIG HERE***

In the case of a Spot Lamp a full separate Panel is needed for additional settings. The left column contains:

#### Shadows

The lamp can produce shadows. Shadow calculations are only possible with the Spot lamps. The render option `Shadows` must also be turned ON in the DisplayButtons to enable Shadows at a global level.

#### OnlyShadow

For spot lamps (with `Shadow` ON), only the shadow is rendered. Light calculations are not performed and where there are shadows, the value of `Energy` is reduced.

#### Square

Spotlamps can have square Spotbundles with this option. For a better control over shadows and for slide projector effects.

#### Halo

The lamp has a halo. This only works with Spot lamps. The intensity of the halo is calculated using a conic section. With the option `Halo step:` it also uses the shadow buffer (volumetric rendering). The scope of the spot halo is determined by the value of `Dist`.

The right column contains:

#### SpotSi

The angle of the beam measured in degrees. Use for shadow lamp beams of less than 160 degrees.

#### SpotBl

The softness of the spot edge.

#### HaloInt

The intensity of the spot halo. The scope of the spot halo is determined by `Dist`.

#### Shadow Buffer

Blender uses a shadow buffer algorithm. From the spotlight, a picture is rendered for which the distance from the spotlight is saved for each pixel. The shadow buffers are compressed, a buffer of 1024x1024 pixels requires, on average, only 1.5 Mb of memory.

This method works quite quickly, but must be adjusted carefully. There are two possible side effects:

- Aliasing. The shadow edge has a block-like progression. Make the spot beam smaller, enlarge the buffer or increase the number of `Samples` in the buffer.

- Biasing. Faces that are in full light show banding with a block-like pattern. Set the `Bias` as high as possible and reduce the distance between `ClipSta` and `ClipEnd`.

#### ClipSta, ClipEnd

Seen from the spot lamp: everything closer than `ClipSta` always has light; everything farther away than `ClipEnd` always has shadow. Within these limits, shadows are calculated. The smaller the shadow area, the clearer the distinction the lamp buffer can make between small distances, and the fewer side effects you will have. It is particularly important to set the value of `ClipSta` as high as possible.

#### Samples

The shadow buffer is 'sampled'; within a square area a test is made for shadow 3*3, 4*4 or 5*5 times. This reduces the aliasing.

#### Halo step

A value other than zero in the button `Halo step` causes the use of the shadow detection (volumetric rendering) for Halos. Low values cause better results and longer rendering times. A value of eight works fine in most cases.

#### Bias

The bias used for sampling the shadow buffer.

#### Soft

The size of the sample area. A large `Soft` value produces broader shadow edges.

### `Texture and Input` Panel

***FIG HERE***

This texture panel, and the following are a simplified version of the Material texture panels.

Left column contains:

#### Texture Channels

A Lamp has six channels with which Textures can be linked. Each channel has its own mapping, i.e. the manner in which the texture works on the lamp. The settings are in the buttons described below and in the `Map To` Panel.

Right column contains:

#### Texture Data Block

##### Texture Menu

Select an existing Texture from the list provided, or create a new Texture Block.

##### TE:

The name of the Texture block. The name can be changed with this button.

##### Clear

The link to the Texture is erased.

##### Users

If the Texture Block has multiple users, this button shows the total number of users. Press the button to make the Texture "Single User". Then an exact copy is made.

##### Auto Name

Blender assigns a name to the Texture.

#### Texture Mapping Input

Each Texture has a 3D coordinate (the texture coordinate) as input. The starting point is always the global coordinate of the 3D point that is seen in the pixel to be rendered. A lamp has three options for this.

##### Glob

The global coordinate is passed on to the texture.

##### View

The view vector of the lamp; the vector of the global coordinate to the lamp, is passed on to the texture. If the lamp is a Spot, the view vector is normalised to the dimension of the spot beam, allowing use of a Spot to project a 'slide'.

##### Object

An Object is used as source of co-ordinates. The Object name must be entered in the Text Butt