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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<!--

.style1 {

color: #FF0000;

font-weight: bold;

}

-->

</style>

<!--

.style2 {

font-size: x-large;

font-weight: bold;

}

.style2 {font-size: xx-large}

-->

</style>

<!--

function MM_jumpMenu(targ,selObj,restore){ //v3.0

eval(targ+".location='"+selObj.options[selObj.selectedIndex].value+"'");

if (restore) selObj.selectedIndex=0;

}

//-->

</script>

</head>

<body>

<tr>

If you're new to Python

and VPython: <a href="VisualIntro.html">Introduction</a>

A VPython <a href="VPython_Intro.pdf" target="_blank">tutorial</a>

<a href="primitives.html">Pictures</a> of 3D objects

Choose an object:

<option>Choose an object</option>

<option value="cylinder.html">Overview</option>

<option value="arrow.html">arrow</option>

<option value="convex.html">convex</option>

<option value="curve.html">curve</option>

<option value="cylinder.html">cylinder</option>

<option value="ellipsoid.html">ellipsoid</option>

<option value="extrusion.html">extrusion</option>

<option value="faces.html">faces</option>

<option value="frame.html">frame</option>

<option value="helix.html">helix</option>

<option value="label.html">label</option>

<option value="lights.html">lights</option>

<option value="points.html">points</option>

<option value="pyramid.html">pyramid</option>

<option value="sphere.html">sphere</option>

</select>

Work with objects:

<option>Choose an option</option>

<option value="color.html">Color/Opacity</option>

<option value="materials.html">Materials/Textures</option>

<option value="shapes.html">Shapes Library</option>

<option value="paths.html">Paths Library</option>

<option value="defaults.html">Defaults</option>

<option value="rate.html">Animation Speed</option>

<option value="rotation.html">Rotations</option>

<option value="options.html">Additional Options</option>

<option value="delete.html">Delete an Object</option>

<option value="controls.html">Buttons/Sliders</option>

<option value="graph.html">Graphs</option>

<option value="lights.html">Lighting</option>

<option value="files.html">Read/Write Files</option>

<option value="trail.html">Leaving a Trail</option>

<option value="vector.html">Vector Operations </option>

<option value="factorial.html">factorial/combin</option>

</select>

Windows &amp Events:

<option>Choose a topic</option>

<option value="display.html">Windows</option>

<option value="mouse.html">Mouse Events</option>

<option value="mouse_click.html">   Mouse Click</option>

<option value="mouse_drag.html">   Mouse Drag</option>

<option value="keyboard.html">Keyboard Events</option>

</select>

What's new in <a href="new_features.html">Visual 5</a>

<a href="http://vpython.org" target="_blank">VPython web site</a>

<a href="license.txt" target="_blank">Visual license</a>

<a href="http://www.python.org" target="_blank">Python web site</a>

<a href="http://www.python.org/doc/2.5.2/lib/module-math.html" target="_blank">Math module</a> (sqrt etc.)

<a href="http://www.scipy.org/Documentation" target="_blank">Numpy module</a> (arrays) </td>

<tr>

</tr>

</table>

With the text object you can display 3D text. The

green 3D text shown above was created with the following statement:

text(text='My text is\ngreen',

align='center', depth=-0.3, color=color.green)

Labels were added to the display above to illustrate

some of the main attributes of the text object; the full program

text3d.py can be seen in the VPython examples. Whether you extrude into or out of the screen, the text is created so that it is readable left to right from the normal viewing position, in the +z direction. If you wish to position the text differently, change the axis from its default value of (1,0,0).

Here

is a list of text attributes:

pos; x,y,z The

location of the baseline of the text, to the left, to the right,

or at the center of the text, as per align.

align Specify 'left'

(default), 'right', or 'center'.

text The text to

be displayed, such as My Text in the example above.

Python Unicode strings are supported. Currently it is not possible to display

more than a single line of text with one text object.

font Name of

the desired font; for example, 'sans', or 'serif' (default), or

'monospace' (fixed-width). You can also give specific names such

as "Times" or "Verdana". An attempt is made

to find a font name that best matches the name you specify. If

there is no match, font defaults to 'sans'.

height Height

of an uppercase letter (see above); default is 1. Specifying the

height and depth sets the scale for the entire text display. Changing

the height also changes descent and vertical_spacing, but not depth.

depth Depth

of the text, which can be a single number or a vector. For a single

number, positive means extrude toward you, out of the screen; negative

means extruded away from you, into the screen. For a vector, the

text is extruded in the direction of the vector. Default depth

is 0.2.

width Width

of the displayed text. This is "read-only" and is determined

by the text. Also, widths is a list

of the widths of all lines of text, so widths[0] is

the width of the top line, etc.

axis The axis

points along the baseline; changing the axis changes the orientation

of text. The axis is normalized to have a length of 1. The default is (1,0,0), with text going toward the right.

descent Height

of the descender on lower-case letters such as y (whether or not

there is such a letter in the text). This is typically about 0.3

times the height. This is read-only.

vertical_spacing Vertical

distance from one baseline to the next in a multiline text. The

default is set by the font you use, but you can override this by

changing the value.

color, red, green, blue Color

of the text.

material Material

such as materials.wood.

upper_left, upper_right,

lower_right, lower_left The bounding box of the displayed

text; all of these are read-only. For example, if you create

title = text(text="My Text"),

you can place a sphere at the upper left corner with the statement

sphere(pos=title.upper_left).

While height and descent indicate

the general properties of the selected font, upper_left etc.

tell you the bounding box of the actual text. For example, if the

text is "ABC", lower_left will

be at the same height as start

because there are no descenders, and if the text is "mno", upper_left will

be less than height above the baseline

because

there are no upper-case letters.

start The left-most

location on the baseline. This is read-only. Also, starts is

a list of the starts of all lines of text, so starts[0] is

the start of the top line, etc.

up Controls

the up attribute of the frame; changing up makes the text tip away

from the vertical.

spacing Makes

space between letters, specified as a fraction of height (default

is 0.03).

twosided A text object is a complex object that can take longer to render onto the screen than other objects, due to the many calculations required to generate the triangles and normals required for the display. Like all other objects (except for faces), a text object by default is two-sided (so that you see interior "walls" if you zoom inside the object). One way to get a significant speed-up is to make the object not be two-sided, by setting twosided = False.

The following code will list the True Type fonts

on your system that can be used with a text object:

fonts = shapes.findSystemFonts()

for f in fonts:

print(f)

Extracting extrusion data

The following statement provides the pos, normal, and color information needed for creating a single-sided faces object:

(pos, normal, color) = T.get_faces()

You can convert a text object directly to a faces object, though this has the disadvantage that you lose the ability to change the text attributes dynamically:

T = text(.....)

F = E.create_faces() # produces an equivalent faces object

The conversion routine makes the text object invisible and by default destroys its contents. If you wish to keep the text object for later modification, say E.create(keep=True).

The faces object uses much more memory than the equivalent text object, and it may actually take as long or longer to render. The effect on the speed depends on the details of the text object and the platform you're using. If scene.show_rendertime = True you can see the "cycle" time in milliseconds between renderings, both before and after conversion. Approximately half of the cycle time is devoted to rendering the scene, and about half to your own computations. Longer cycle times reflect longer render times; the minimum cycle time is about 30 milliseconds (about 30 renderings per second). If the scene is not very complicated, very little time is needed to render the scene, and almost all the time is given to your computations.

The create_faces() function uses the get_faces() function but also copies into the faces object the frame, material, and up attributes of the text object, makes the extrusion object invisible, and destroys its contents (unless you specify that keep=True).

See description of <a href="options.html">Additional

Attributes</a> available for all 3D display objects.

</td>

</tr>

<tr>

</tr>

</table>

</body>

</html>

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