World Clutter

World Clutter node allows to scatter a set of identical objects (node references) randomly across the scene practically in one click. There is need any longer to position, scale and rotate every single object by hand and constantly mind the performance factor. World Clutter automatically places static objects in the scene with random parameters, all of which can be efficiently controlled, and renders them only around the camera. With World Clutter a mixed forest where different types of trees grow, rocky grounds, locations cluttered with debris and building waste can be created with ease.

Unlike a World Cluster, a World Clutter scatters objects procedurally and therefore even more memory-efficient. At the same time it means that scattered objects cannot be moved.

See also

Objects in one Clutter are node references that will be scattered throughout a definite area and for each of which the probability of its appearing is controlled.

The World Clutter is rendered as a 2D grid, in each cell of which a number of clutter objects are randomly placed depending on the Clutter density and probability of appearing. The cells are generated one by one starting from the nearest ones. This approach allows to control how close or far the scattered objects are from each other and at the same time reduce the rendering load when the camera moves and farther cells become visible.

Once added and scattered, the objects cannot be moved or rotated. The only way to change the scattering pattern is to change the seed.

Size X Size Y	The size of the clutter bounding box along X and Y axis. Within this area objects will be scattered with specified density. The size is measured in units.
Step for cells	Cell size in units. The number of cells in the Clutter is defined in the following way: size of the Clutter (both along X and Y) is divided by the step. The higher the number of cells (i.e. the smaller the step), the higher the load. However, to create one large cell takes longer time. When the camera moves fast enough, small cells will be created very slow, but large ones can noticeably pop into sight and cause a small rendering lag.
Density	Density specifies how many objects there are per square unit. In case there are more than one object in the Clutter, probability will be taken into account, but will not change the resulting number of all rendered objects. If the density value is too high, objects can be penetrating each other. Lower Density Higher Density
Visible distance	Within visible distance the number of objects is strictly specified by the density parameters. It means that all objects that should be present are found in place. If set to infinity (inf), Fade distance parameter will be ignored. The real radius of Clutter visibility directly depends on the object (surface) maximum visible distance and also its fade out distance. However, even in case it disappears at closer distance, further increase of the visible distance will carry performance penalty, because cell generation-related calculations are still performed. The visible distance is actually measured up to the cell: when the camera moves on the specified distance form it, the cell is generated. Without the fade distance or object maximum visible distance, objects will be rendered in noticeable squares.
Fade Distance	Across the fade distance the number of objects gradually decreases, as they disappear randomly one by one. The fade distance follows the Visible distance. If a fade distance is set, there is no clear line where the objects that are contained in the Clutter abruptly disappear. Instead, a few left smoothly blend into the background without any visual noise. For the best result, it is also recommended to combine this effect with objects fade-out.
Seed	The seed value for pseudo random number generator allows to create different patterns of automatic positioning. The seed is either be set manually or an engine provides a random value for a seed (Randomize option). Seed = 0 Seed = 64755331

To randomize the appearance of objects that compose the World Clutter, two types of values are used:

• Mean value (i.e. Scale, Offset, Rotation) defines the average value. This is the basic value that will be randomly made higher or lower.
• Spread value defines the range for possible variation of the parameter. The higher the value, the more diverse the final result will be.
  Spread value is optional: if set to 0, it will not influence the simulation process and only the mean value will be used for all objects.

After these values are specified, each parameter is calculated according to the following formula:

• Result = Mean + Random * Spread

Having objects uniformly scattered in all directions and places is naturally not very convenient. Instead of creating a number of small World Clutter nodes that cover a limited location, a big one can be used with a mask.

Image Mask	Areas across which the objects are randomly scattered and areas where there will be no objects from the list. For example, on the terrain a mask allows to scatter stones across the rocky areas, while leaving the grassy ones rock free. The mask is one-channel texture (R8). If there are more channels in the provided mask, they will be ignored. Zero color value specify the areas without Clutter objects. The higher the color value is, the more objects there are in this area and the denser they are positioned. Color value of 255 means the density is as specified in by the corresponding parameter. Masking is done for all objects that are contained in the Clutter list.
Threshold for mask	To control the strength of masking, a mask threshold is used. It checks the masked density for an area and if a threshold value is higher than the color value of the mask, objects are scattered across it. If the masked density is not enough, the places is left bare. With the minimum value of 0, the mask is applied as it is. With higher threshold value, the objects will be scattered only in areas marked by the mask as dense. Instead of sparse distribution, objects scattered here and there, they are likely to be rendered in dense isolated groups. With the maximum value of 1, there will be no objects scattered at all. Threshold = 0 Threshold = 1
Mesh Mask	A mesh-based mask can be used to place the objects. Vector masking allows not to depend the mask texture resolution and create roads, rivers, etc. with extremely high precision. A mesh for masking should be a simple planar mesh.
Inverse	The Inverse flag toggles if the objects are placed inside or outside the mesh contour.

Unless objects in the World Clutter are scattered over a completely flat and non-tilted surface, they can be automatically positioned to precisely repeat ups and downs of the relief without any effort. For that, an underlying surface should me made a parent of the World Clutter node. (If there are some nodes in the hierarchy between a terrain or mesh node and World Clutter, intersections will still be checked.)

A parent for intersection can only be a terrain or a mesh object. The mesh should be terrain-like, i.e. it should have only one surface vertically, along the Z coordinate.

Intersection	After the Intersection box is checked, objects in the World Clutter will be scattered across the surface of the parent object. It does not matter if the World Clutter is bigger than the parent object in size - the scattering area will be still be limited to parent object surfaces.
Orientation	This option allows to set a parent surface normal vector as the initial orientation for scattered objects. It means, if the surface in some place is vertical, the "up" direction for objects over will be actually pointing to the side. They can be still randomly rotated but relative the orientation of the parent normal. This parameter is enabled only if Intersection option is checked. Orienation enabled Orienation disabled
Angle	Just like in the case with grass, the scattering can take into account how steep the slope is. By the minimum value of 0, it makes no difference how flat or how tilted the surface over which the Clutter objects are scattered. The bigger the value is, the flatter the place should be for objects to be scattered over it. As the value increases, at first steep slopes are ignored and then flatter ones become bare. By the maximum value of 1, the objects can be scattered only over perfectly horizontal surface. This parameter is enabled only if Intersection option is checked. Low angle value High angle value