org.scijava.java3d.utils.geometry

Class NormalGenerator

java.lang.Object

org.scijava.java3d.utils.geometry.NormalGenerator

public class NormalGenerator
extends Object

The NormalGenerator utility will calculate and fill in the normals of a GeometryInfo object. The calculated normals are estimated based on an analysis of the indexed coordinate information. If your data isn't indexed, index lists will be created.

If two (or more) triangles in the model share the same coordinate index then the normal generator will attempt to generate one normal for the vertex, resulting in a "smooth" looking surface. If two coordinates don't have the same index then they will have two separate normals, even if they have the same position. This will result in a "crease" in your object. If you suspect that your data isn't properly indexed, call GeometryInfo.recomputeIndexes().

Of course, sometimes your model *has* a crease in it. That's what creaseAngle is. If two triangles' normals differ by more than creaseAngle, then the vertex will get two separate normals, creating a discontinuous crease in the model. This is perfect for the edge of a table or the corner of a cube, for instance.

Constructor Summary

Constructors

Constructor and Description
NormalGenerator() Constructor.
NormalGenerator(double radians) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
void	generateNormals(GeometryInfo gi) Generate normals for the GeometryInfo object.
double	getCreaseAngle() Returns the current value of the crease angle, in radians.
void	setCreaseAngle(double radians) Set the crease angle.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NormalGenerator

public NormalGenerator(double radians)

Constructor. Construct a NormalGenerator object with creaseAngle set to the given value.

NormalGenerator

public NormalGenerator()

Constructor. Construct a NormalGenerator object with creaseAngle set to 44 degrees (0.767944871 radians).

Method Detail

generateNormals

public void generateNormals(GeometryInfo gi)

Generate normals for the GeometryInfo object. If the GeometryInfo object didn't previously contain indexed data, indexes are made by collapsing identical positions into a single index. Any normal information previously contained in the GeometryInfo object is lost. Strips and Fans are converted into individual triangles for Normal generation, but are stitched back together if GeometryInfo.getGeometryArray() (or getIndexedGeometryArray()) is called without stripifying first.

setCreaseAngle

public void setCreaseAngle(double radians)

Set the crease angle. If two triangles' normals differ by more than creaseAngle, then the vertex will get two separate normals, creating a discontinuous crease in the model. This is perfect for the edge of a table or the corner of a cube, for instance. Clamped to 0 <= creaseAngle <= PI. Optimizations are made for creaseAngle == 0 (facet normals) and creaseAngle == PI (smooth shading).

getCreaseAngle

public double getCreaseAngle()

Returns the current value of the crease angle, in radians.