Scaling, YXRatio, ZXRatio

Scaling ratios

Value Summary

ScalingInheritedAutomatic, Constrained, or Unconstrained
YXRatio, ZXRatioInheritedPositive real numberReal number

Graphics Primitives

ObjectsDefault Values
plot::CoordinateSystem2d, plot::CoordinateSystem3d

Scaling: Unconstrained


YXRatio: 1

ZXRatio: 2/3


With Scaling = Constrained, the graphics output is scaled like the model coordinates, i.e., circle appear as circles, spheres as spheres.

With Scaling = Unconstrained, the graphics output is scaled independently in each coordinate direction such that the graphics fits optimally into the viewing area. Circles may appear as ellipses, spheres as ellipsoids.

For Scaling = Unconstrained, the scaling ratios of the different coordinate directions in a 3D plot can be set via the attributes YXRatio and ZXRatio.

If the graphics consists of geometrical objects such as circles, pie charts, spheres etc., the setting Scaling = Constrained is appropriate. This prevents circles from being deformed to ellipses in the graphical output.

For the visualization of non-geometrical data (usually, in function plots etc.), a scaling constrained to model coordinates is usually not appropriate. Think of the graph of y = ex for , where the y values extend over the range , which is roughly . With Scaling = Constrained, the graphical output would consist of a narrow vertical strip with the side ratio y : x = 22025 : 10. Here, Scaling = Unconstrained is appropriate.

The default value is Scaling = Unconstrained. However, many "geometrical" objects in the MuPAD® plot library override this default setting via the "hint mechanism" (see section Primitives Requesting Special Scene Attributes: "Hints" in this document). Whenever such an object is plotted in a scene, the whole scene uses Scaling = Constrained. A complete list of these "geometrical objects" such as circles, spheres, cones etc. is given further up on this help page.

With Scaling = Automatic, the graphics uses Scaling = Constrained for plots in which the coordinate ranges to be displayed have a ratio close to 1 : 1 in 2D or 1 : 1 : 1 in 3D. Otherwise, Scaling = Unconstrained is used.

The attributes YXRatio = r1 and ZXRatio = r2 only have an effect in 3D with Scaling = Unconstrained. The graphical scene is scaled to a box with side ratios z : y : x = r2: r1: 1. On the screen, the bounding box of the scene looks like a box with these side ratios.


Example 1

We plot a scene containing a function graph and some circles highlighting the extrema. Because the circle sends the "hint"Scaling = Constrained, this scaling is used for the whole scene. Consequently, the circles appear as circles:

plot(plot::Function2d(sin(x), x = 0 .. 2*PI),
     plot::Circle2d(0.2, [PI/2, 1], Color = RGB::Black),
     plot::Circle2d(0.2, [3*PI/2, -1], Color = RGB::Black),
     BorderWidth = 1.0*unit::mm,
     Header = "Scaling = Constrained")

With Scaling = UnConstrained, we get a better fit of the plot in the canvas. However, the circles are deformed to ellipses:

plot(plot::Function2d(sin(x), x = 0 .. 2*PI),
     plot::Circle2d(0.2, [PI/2, 1], Color = RGB::Black),
     plot::Circle2d(0.2, [3*PI/2, -1], Color = RGB::Black),
     Scaling = Unconstrained, BorderWidth = 1.0*unit::mm,
     Header = "Scaling = Unconstrained")

Example 2

A sphere of type plot::Sphere sends the "hint" Scaling = Constrained. With this scaling, YXRatio, ZXRatio have no effect:

s := plot::Sphere(1, [0, 0, 0]):
plot(s, BorderWidth = 0.5*unit::mm, 
     Header = "Scaling = Constrained",
     YXRatio = 3, ZXRatio = 10)

We use Scaling = Unconstrained. With the default values YXRatio = 1, ZXRatio = 2/3, the objects in a 3D scene are displayed like a box with side ratios X : Y : Z = 3 : 3 : 2:

plot(s, BorderWidth = 0.5*unit::mm, 
     Scaling = Unconstrained, Header = "X:Y:Z = 3:3:2")

We request different scaling ratios:

plot(s, BorderWidth = 0.5*unit::mm, Header = "X:Y:Z = 5:5:1",
     Scaling = Unconstrained, YXRatio = 1, ZXRatio = 1/5, 
     BorderWidth = 0.5*unit::mm)

plot(s, BorderWidth = 0.5*unit::mm, Header = "X:Y:Z = 7:3:1",
     Scaling = Unconstrained, YXRatio = 3/7, ZXRatio = 1/7, 
     BorderWidth = 0.5*unit::mm)

delete s:
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