org.jogamp.glg2d.impl

Class SimpleOrTesselatingVisitor

java.lang.Object

org.jogamp.glg2d.impl.SimplePathVisitor

org.jogamp.glg2d.impl.SimpleOrTesselatingVisitor

All Implemented Interfaces:

PathVisitor

public class SimpleOrTesselatingVisitor
extends SimplePathVisitor

Tesselating is expensive. This is a simple workaround to check if we can just draw the simple, convex polygon without tesselating. At each corner, we have to check the sign of the z-component of the cross-product. If it's the same all the way around, we know that every turn went the same direction. That ensures it's convex. That's necessary, but not sufficient since we might still have self-intersections. For that, we check that the total curvature along the path is 2π. That ensures it's simple.

This checks every corner and if it has the same sign and total curvature is 2π, we know the polygon is convex. Once we get to the end, we draw it. If it's not convex, then we fall back to tesselating it.

There are many places where we could fail being a simple convex polygon and then have to fail over to the tesselator. As soon as we fail over we need to catch the tesselator up to the current position and then use the tesselator from then on. For that reason, this class is a little messy.

Field Summary

Fields inherited from class org.jogamp.glg2d.impl.SimplePathVisitor

CURVE_STEPS

Constructor Summary

Constructors

Constructor and Description
SimpleOrTesselatingVisitor(PathVisitor simpleVisitor, PathVisitor tesselatorVisitor)

Method Summary

Methods

Modifier and Type	Method and Description
void	beginPoly(int windingRule) Starts the polygon or polyline.
void	closeLine() Specifies that the preceding subpath should be closed by appending a line segment back to the point corresponding to the most recent call to #moveTo(float[]).
void	endPoly() Signifies that the polygon or polyline has ended.
void	lineTo(float[] vertex) Specifies the end point of a line to be drawn from the most recently specified point.
void	moveTo(float[] vertex) Specifies the starting location for a new subpath.
void	setGLContext(GL context) Sets the GL context to be used for the next drawing session.
void	setStroke(BasicStroke stroke) Sets the stroke to be used when drawing a path.

Methods inherited from class org.jogamp.glg2d.impl.SimplePathVisitor

cubicTo, getNumCurveSteps, quadTo, setNumCurveSteps

Methods inherited from class java.lang.Object

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

Constructor Detail

SimpleOrTesselatingVisitor

public SimpleOrTesselatingVisitor(PathVisitor simpleVisitor,
                          PathVisitor tesselatorVisitor)

Method Detail

setGLContext

public void setGLContext(GL context)

Description copied from interface: PathVisitor

Sets the GL context to be used for the next drawing session.

Parameters:

context - The GL context

setStroke

public void setStroke(BasicStroke stroke)

Description copied from interface: PathVisitor

Sets the stroke to be used when drawing a path. It's not needed for visitors that fill.

beginPoly

public void beginPoly(int windingRule)

Description copied from interface: PathVisitor

Starts the polygon or polyline.

Parameters:

windingRule - The winding rule for the polygon.

moveTo

public void moveTo(float[] vertex)

Description copied from interface: PathVisitor

Specifies the starting location for a new subpath.

Parameters:

vertex - An array where the first two values are the x,y coordinates of the start of the subpath.

lineTo

public void lineTo(float[] vertex)

Description copied from interface: PathVisitor

Specifies the end point of a line to be drawn from the most recently specified point.

Parameters:

vertex - An array where the first two values are the x,y coordinates of the next point in the subpath.

closeLine

public void closeLine()

Description copied from interface: PathVisitor

Specifies that the preceding subpath should be closed by appending a line segment back to the point corresponding to the most recent call to #moveTo(float[]).

endPoly

public void endPoly()

Description copied from interface: PathVisitor

Signifies that the polygon or polyline has ended. All cleanup should occur and there will be no more calls for this shape.