The Rotation of Lissajous Figures
Mere static pictures do not do justice to Lissajous Figures.
When the horizontal and vertical sine wave frequencies differ by a fixed amount, this is equivalent to constantly rotating the phase between them.
The figure produced by this rotating phase appears to be a rotating 3D figure.
In addition, as in 3D wireframe images, the figure can appear to rotate in either direction, depending on how your brain interprets it. It can also spontaneously reverse the direction of rotation. (In a real 3D wireframe image the image can also appear to rotate around a different axis.)
The rotation of Lissajous Figures is something you need to see, so I am posting a program to do this.
Because the sine function is computationally intensive, the program starts out by calculating a table of sine values for a complete cycle of 360 degrees. Changing the address at which the table lookup is begun produces a sine wave with a different phase. The table address is wrapped so that the value is always valid.
By constantly increasing or decreasing the phase we produce the equivalent of having a small frequency difference. Technically, this is phase modulation. Large differences in frequency to produce integer multiples of frequencies are produced by multiplying the step size of the angles used to look up the sine value.
It is part of a program of Monitor Test Patterns that also produces Color Bars, a Crosshatch Pattern, a Dot Pattern, and a Monitor High Voltage Test.
The Color Bars are used to evaluate how well the Monitor reproduces colors.
The Crosshatch and Dot patterns are used to evaluate and adjust monitor convergence. (Don't try to
When the horizontal and vertical sine wave frequencies differ by a fixed amount, this is equivalent to constantly rotating the phase between them.
The figure produced by this rotating phase appears to be a rotating 3D figure.
In addition, as in 3D wireframe images, the figure can appear to rotate in either direction, depending on how your brain interprets it. It can also spontaneously reverse the direction of rotation. (In a real 3D wireframe image the image can also appear to rotate around a different axis.)
The rotation of Lissajous Figures is something you need to see, so I am posting a program to do this.
Because the sine function is computationally intensive, the program starts out by calculating a table of sine values for a complete cycle of 360 degrees. Changing the address at which the table lookup is begun produces a sine wave with a different phase. The table address is wrapped so that the value is always valid.
By constantly increasing or decreasing the phase we produce the equivalent of having a small frequency difference. Technically, this is phase modulation. Large differences in frequency to produce integer multiples of frequencies are produced by multiplying the step size of the angles used to look up the sine value.
It is part of a program of Monitor Test Patterns that also produces Color Bars, a Crosshatch Pattern, a Dot Pattern, and a Monitor High Voltage Test.
The Color Bars are used to evaluate how well the Monitor reproduces colors.
The Crosshatch and Dot patterns are used to evaluate and adjust monitor convergence. (Don't try to