Assigning children to hgtransform object

Create an hgtransform graphics object

h = hgtransform h = hgtransform('PropertyName',PropertyValue. )

Description

h = hgtransform creates an hgtransform object and returns its handle.

h = hgtransform(' PropertyName ',PropertyValue. ) creates an hgtransform object with the property value settings specified in the argument list.

Hgtransform objects can contain other objects and thereby enable you to treat the hgtransform and its children as a single entity with respect to visibility, size, orientation, etc. You can group objects together by parenting them to a single hgtransform object (i.e., setting the object's Parent property to the hgtransform object's handle). For example,

h = hgtransform; surface('Parent',h. )

The primary advantage of parenting objects to an hgtransform object is that it provides the ability to perform transformations (e.g., translation, scaling, rotation, etc.) on the child objects in unison.

An hgtransform object can be the parent of any number of axes children including other hgtransform objects.

The parent of an hgtransform object is either an axes object or another hgtransform.

Although you cannot see an hgtransform object, setting its Visible property to off makes all its children invisible as well.

• The references in the See Also section for information on types of transforms
• The Examples section provides examples that illustrate the use of transforms.

Transforming a Group of Objects

This example shows how to create a 3-D star with a group of surface objects parented to a single hgtransform object. The hgtransform object is then rotated about the z-axis while its size is scaled.

Create an axes and adjust the view. Set the axes limits to prevent auto limit selection during scaling.

ax = axes('XLim',[-1.5 1.5],'YLim',[-1.5 1.5]. 'ZLim',[-1.5 1.5]); view(3); grid on; axis equal

[x y z] = cylinder([.2 0]); h(1) = surface(x,y,z,'FaceColor','red'); h(2) = surface(x,y,-z,'FaceColor','green'); h(3) = surface(z,x,y,'FaceColor','blue'); h(4) = surface(-z,x,y,'FaceColor','cyan'); h(5) = surface(y,z,x,'FaceColor','magenta'); h(6) = surface(y,-z,x,'FaceColor','yellow');

t = hgtransform('Parent',ax); set(h,'Parent',t)

set(gcf,'Renderer','opengl') drawnow

Rz = eye(4); Sxy = Rz;

for r = 1:.1:2*pi  % Z-axis rotation matrix Rz = makehgtform('zrotate',r);  % Scaling matrix  Sxy = makehgtform('scale',r/4);  % Concatenate the transforms and   % set the hgtransform Matrix property  set(t,'Matrix',Rz*Sxy) drawnow end pause(1)

set(t,'Matrix',eye(4))

Transforming Objects Independently

This example creates two hgtransform objects to illustrate how each can be transformed independently within the same axes. One of the hgtransform objects has been moved (by translation) away from the origin.

Create and set up the axes object that will be the parent of both hgtransform objects. Set the limits to accommodate the translated object.

ax = axes('XLim',[-2 1],'YLim',[-2 1],'ZLim',[-1 1]); view(3); grid on; axis equal

[x y z] = cylinder([.3 0]); h(1) = surface(x,y,z,'FaceColor','red'); h(2) = surface(x,y,-z,'FaceColor','green'); h(3) = surface(z,x,y,'FaceColor','blue'); h(4) = surface(-z,x,y,'FaceColor','cyan'); h(5) = surface(y,z,x,'FaceColor','magenta'); h(6) = surface(y,-z,x,'FaceColor','yellow');

t1 = hgtransform('Parent',ax); t2 = hgtransform('Parent',ax);

set(gcf,'Renderer','opengl')

set(h,'Parent',t1) h2 = copyobj(h,t2);

Txy = makehgtform('translate',[-1.5 -1.5 0]); set(t2,'Matrix',Txy) drawnow

% rotate 5 times (2pi radians = 1 rotation) for r = 1:.1:20*pi  % Form z-axis rotation matrix Rz = makehgtform('zrotate',r);  % Set transforms for both hgtransform objects set(t1,'Matrix',Rz) set(t2,'Matrix',Txy*inv(Rz)*I) drawnow end

Setting Default Properties

You can set default hgtransform properties on the axes, figure, and root levels:

set(0,'DefaultHgtransformPropertyName',propertyvalue. ) set(gcf,'DefaultHgtransformPropertyName',propertyvalue. ) set(gca,'DefaultHgtransformPropertyName',propertyvalue. )

where PropertyName is the name of the hgtransform property and propertyvalue is the value you are specifying. Use set and get to access hgtransform properties.

For more information about transforms, see Tomas Moller and Eric Haines, Real-Time Rendering, A K Peters, Ltd., 1999.

Group Objects for more information and examples.

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