Particle Billboard

Particle Billboard

Shader Type: Particle (texture)

Output: Color (RGB) value

Renders particles as a 2D surface (a billboard) upon which you can create many different effects.

Name

The shader’s name. Enter any name you like, or leave the default.

Rendering Properties

Geometry

Shape	The outline shape of the billboards: • Square is a square shape that is circumscribed by the particle’s radius. • Rectangular is the same as Square except that its aspect ratio is the same as the sprite that’s applied to the particle. • Circular is a circle shape with the same radius as the particle.
Surface Normal Type	The calculated normal for lighting calculations: Billboard or Spherical.
Face Direction	Direction that the billboard faces: • Camera: the billboard faces the camera. • Incoming ray: billboard faces the camera unless there are reflections. If so, the billboard tries to orient itself so that it faces the reflected/refracted ray as well. • Camera and Lights: the billboard faces the camera unless shadows are being cast. If so, the billboard faces each shadow casting light. This ensures that the billboard’s Shape doesn’t appear flat, giving the illusion that it is three-dimensional. • Use Rotation: billboard uses the particle’s Orientation values set in the Particle Emission property editor.
Rotation Follow Velocity	Particle billboard rotates in the direction of the velocity. This is disabled if the billboard Face Direction is set to Use Rotation.
Texture Coordinates	Controls which texture coordinates are generated for the particle. • Planar is a straight planar UV mapping with origin in the lower-left corner. • Particle’s Local Space is the hit point in the particle’s own local space. • Cloud’s Local Space is a hit point in the local space of the particle cloud. • World Space is the hit point in the world coordinate space.

Effects

Burn	Adds the particle’s RGB values together when particles overlap in space (sometimes called color burn or additivity). This lets you create bright spots of colors and glows where many particles are on top of each other.
Self-Shadowing Factor	Shadows cast by the particles onto themselves are attenuated by this factor.

Shading Properties

Apply Shading

Applies a simple shading model to the particles. If not selected, only shadows are calculated, and the particles are still visible even if no lights are applied to the cloud.

Ambient

Type	The way in which the ambient color is calculated: % of Base Color (particle type color), Use Ambient Color (the values of the Color sliders below), or None.
Color	When you select Use Ambient Color as the Type, this is the surface’s underlying ambient color, which gets modified by the scene’s ambience. To get luminescent particles, use a high value for this parameter.
% of Base	When you select % of Base Color as the Type, this is the percentage of the particle type’s color (the base color) to use as the ambient color. To “blast” the base color, enter values higher than 100%.

Specular

Type	The way in which the specular color is calculated: % of Base Color (particle type color), Use Specular Color (the values of the Color sliders below), or None.
Color	When you select Use Specular Color as the Type, this is the color of the surface specular highlight.
% of Base	When you select % of Base Color as the Type, this is the percentage of particle type (base) color to use as the specular color.
Shininess	Shininess of the specular highlight. Lower values result in a larger highlight.

Global Illumination

Irradiance

Irradiance determines how much color the particle type receives from other surfaces during final gathering.

Type	The way in which the irradiance modifier color is calculated: % of Base Color (particle type color), Use Irradiance Color (the values of the Color sliders below), or None.
Color	When you select Use Irradiance Color as the Type, this is the color received by the particles.
% of Base	When you select % of Base Color as the Type, this is the percentage of the color received from the particle type.

Radiance

Radiance determines how much color the particle type transmits onto other surfaces.

Type	The way in which the radiance modifier color is calculated: % of Base Color (particle type color), Use Radiance Color (the values of the Color sliders below), or None.
Color	When you select Use Radiance Color as the Type, this is the color transmitted by the particles.
% of Base	When you select % of Base Color as the Type, the color that is transmitted is this percentage of the particle type’s color.

Make Connections

Connects different shaders to this one.

Connect To

Sprite	Connects the sprite shader to this one.
Shape	Connects the shape shader to this one.
Color Gradient on age	Connects the particle color gradient shader to this one. The gradient shader works on the particle’s age % by default.

Making Transparent Particles

There are three basic ways in which you can create transparent particles with the Billboard shader:

• On the Particle Type > Color page, set the Alpha value for the level of transparency you want. Then on the Shading Properties page in the Billboard shader, set the Ambient - Type to Use % of Base Color and set the % of Base to 100% or more to see the effect better.

• Plug the Particle Color shader into the Color input of the Billboard shader to override the particle type color. In the Particle Color shader property editor, select Override Particles - Alpha and set the New Color - Alpha value to the level of transparency you want.

• Plug the Particle Gradient shader into the Color input of the Billboard shader to override the particle type color. In the Particle Gradient shader property editor, select Alpha and set the alpha value and the gradient control to the level of transparency you want.

As well, you can plug the Raytracing > Transparency or Opaque shaders into the Color input of the Billboard shader and set their values to an appropriate level of transparency.

Autodesk Softimage v.7.5