Particle FX for DAZ|STUDIO

The Set Color Gradient Operator

The Set Color Gradient sets up a mapping between a particle's parameter such as age, speed, mass or temperature and the texture mapping of the particle's shape.

As the particle ages, slows down, etc, this Operator will change the UV mapping of the particle's shape changing the shape's appearance in the scene

The Mapped Attribute Parameter selects the parameter to be used in mapping.

The Min and Max set the Minimum and Maximum range of the parameter to be mapped.

Number of Steps, sets the behavior of the color gradient by telling how the texture will be binned.

The Mapping Range tells how much the mapping will be randomized for each particle.

If the Offset Randomized Each Frame is "off" then each particle is assigned a randomized offset on its first run through the system. Otherwise it will receive a new randomized offset each frame.

If you are not familiar with texture mapping please read the "What are Texture Maps?" section of the DAZ|Studio Manual.

To see how the Set Color Gradient works, this texture is applied to a number of square sprites.

Now, when the Number of Steps is set to zero, the texture is applied normally to all the particle shapes.

Setting the Number of Steps to 1, the texture mapping of the shape will be changed.

The Age of the particle, 0.4 as an example, is mapped into the range of 0 to 1, as set by the Min and Max parameters of the Set Color Gradient Operator, which in turn is used to set the new UV coordinates of the particle's shape.

The net effect is that instead of the shape using the whole texture, it will take on the color of a specific point in the texture, as shown here.

If the Number of Steps is greater than 1, the effect is as if texture was divided into equally spaced pieces, each piece corresponding to one of the Steps.

Looking to this example, which has eight Steps, the texture applied to each particle shape is a piece of the full texture.

Internally, the UV coordinates of the shape are remapped from the lower left corner being 0 ,0 to 0.375 , 0 and the upper right corner from 1,1 to 0.5, 1.

If the particle's attribute is less than Min it is treated as if it were equal to Min.

If the particle's attribute is greater than Max it is treated as if it were equal to Max.

The gradient mapping applies to all textures being applied to the particle's shape.

Taking an opacity map with eight circular cutouts......

.... the shape of the sprite can be controlled

The color textures and any other maps such as opacity must be matched to the Number of Steps setting.

A typical use of the gradient is to set the Mapped Attribute to "Age" so that as the particles get older they change color. This is very commonly used for fire and smoke type effects.

A color spray that shows this can be made using the texture and opacity maps.

The gradient mapping affects ALL maps applied to the particle shape. This can be a useful tool to generate many different sprites in the same effect. Using this opacity map...

An effect full of many different shaped sprites can be made. Note that the opacity map shape and the color are synchronized.

Depending on the properties of the effect being built, the color gradient mapping may appear too regular or result in obvious color striations. To prevent that, the color gradient mapping can be randomized using the Mapping Range and Offset Randomized Each Frame parameters of the Set Color Gradient.

The Mapping Range gives a range, in percentage of the total mapping range from Min to Max, that the mapping of the particle's attribute can be randomized or offset.

Looking at the running example, if the Mapping Range is 10%, then the particle's mapping could be shifted one step in either direction.

This randomized offset can be computed once the first time the particle is handled by the Set Color Gradient operator or every time frame when the particle's mapping is updated.

If Offset Randomized Each Frame is set to "On" then the offset is set each frame when the particle's mapping is updated. This setting is best used in very dynamic and chaotic effects where the motion of a single particle is not readily tracked. This setting will make the particle's shape change appearance every frame of an animation.

If Offset Randomized Each Frame is set to "Off" then the offset is computed once when the particle first goes through the Set Color Gradient operator and the particle keeps the offset for the rest of its life. This setting is best used when the initial mapping needs to be randomized but the particle flow should be smoother. In a fire type gradient going from white to yellow to orange to red, a particle might start out in either as either white or yellow but then would progress through orange and red as it aged.

In this picture, the left hand size flame had Offset Randomized Each Frame to "On" while the right hand side flame is "Off".

Notice that the left hand flame is showing all the colors of the gradient throughout the flame.

The right hand flame shows a smoother hot to dark progression.

Generally, the Number Of Steps parameter should be left as it is set by the effect Pose, unless you are manually changing the texture maps being used.

Changing the Min and Max values will shift the mapping over the whole effect. Making Min very low will force the mappings to the right of the texture, while increasing Max will shift them left. Increasing both Max and Min will shrink the mapping towards the center of the texture.

As shown above, changing the mapping offsets can also have a big effect. Generally, increasing the Mapping Range will make the effect appear more chaotic or turbulent while leaving it at zero or decreasing it from a set value will result in a smoother flow. A good starting value for Mapping Range is around 10% with the Offset Randomized Each Frame set to "Off". This will give a natural appearing randomness to the effect.

If the Operator has a child Randomizer, its settings will determine the randomization of the offset.