JPH02205178A - Snowfall effect generator - Google Patents

Abstract

PURPOSE:To freely control the snowfall or the speed of a snowfall by generating 0 and 1 random data patterns, displaying a white point on a picture with being overlapped to a video signal only when data go to be 1 and moving a dot pattern from an up side to a down side in the picture. CONSTITUTION:The size of a random number to be generated is compared with the size of a numerical value to be outputted a numerical holding means 6. When the random number is larger than the output value of the numerical holding means 6, a comparator 3 outputs 0 and in the other case, the comparator 3 outputs 1. When the white point is displayed with being overlapped to the video signal only in case these data go to be 1, the pattern, for which the white points are juxtaposed at random, appears on the picture. When the period of a reset signal from a reset signal generator 2 is made longer than 1 field scanning period or 1 frame scanning period, it seems that the random pattern slowly falls down.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a video special effect generating device used in a VTR or the like, and more particularly to a snowfall effect generating device.

BACKGROUND OF THE INVENTION Conventionally, when an image of falling snow was to be superimposed on a background image to be synthesized, it was necessary to create an animation for the image of falling snow.

Problems to be Solved by the Invention However, the conventional system described above has a problem in that it is not easy to freely control the amount and speed of falling snow.

The present invention solves the above-mentioned conventional problems, and aims to provide a snowfall effect generating device that can freely control the amount and speed of falling snow.

Means for Solving the Problem In order to achieve this object, the invention of claim 1 of the present application provides a random number generator, a reset signal generator for resetting the random number generator, a numerical value holding means, and a reset signal generator for resetting the random number generator. It is comprised of a comparator that compares the output of the numerical value holding means in terms of magnitude and outputs a discrimination signal.

Further, the invention of claim 3 of the present application provides a first random number generator, a reset signal generator for resetting the first random number generator, a first numerical value holding means, and an output of the first random number generator. a first comparator that compares the output with the output of the numerical value holding means and outputs a first discrimination signal; a second random number generator; a second numerical holding means; a second comparator that compares the output of the numerical value holding means in magnitude and outputs a second discrimination signal, and has a configuration that outputs a logical product of the first discrimination signal and the second discrimination signal. are doing.

According to the structure of claim 1, the present invention generates a random data pattern of O's and 1's, and draws a dot pattern by displaying a white dot on the screen superimposed on the video signal only when the data becomes 1. The period T of the reset signal of the random number generator is T=nF i+(m+0.5)H or T=nFr+m
H H: Horizontal scanning period Fi: Field scanning period (2B2.5H) Fr: Frame scanning period (525H) nl m...Moves the dot pattern from the top to the bottom of the screen as an integer.

Further, according to the configuration of claim 3, two systems of data patterns are generated, and by taking the logical product of the data patterns, the dot pattern is moved from the top to the bottom of the screen while blinking.

EXAMPLE Hereinafter, a snowfall effect generating device according to an example of the present invention will be described with reference to the drawings. In the following description, it is assumed that the snowfall effect generating device of the present invention is used under a superimposition system.

FIG. 1 shows a block diagram of a snowfall effect generating device according to a first embodiment of the present invention. As the random number generator 1, a configuration as shown in FIG. 3, for example, can be considered. FIG. 3 shows a well-known M-series generation circuit, and the input terminal 32
When a clock is input from , an 8-pit random number sequence appears at the 8 output terminals 31 . Further, the output of each flip-flop is initialized by a reset signal from the input terminal 33. Now, assuming that the clock input to the random number generator 1 has a frequency twice (k: an integer) the frequency of the horizontal synchronizing signal, the random number generator 1 generates random numbers for IH.

The generated random number is compared in magnitude with the numerical value output from the numerical value holding means 6 in the comparator 3. Any numerical value can be set in advance in the numerical value holding means 8, and the set numerical value is always output. As a specific example of the numerical value holding means 6, a configuration such as a register that holds data transferred from an external microcomputer or the like can be considered. If the random number is larger than the output value of the numerical value holding means 6, the comparator 3 returns 01.
Otherwise, outputs 1. As a result, when the content of the numerical value holding means 6 is large, the output of the comparator 3 becomes 1 with high frequency, and when the content is small, the output becomes 1 with low frequency. If you display a white dot over the video signal only when this data becomes 1, a pattern of randomly arranged white dots will appear on the screen,
By changing the numerical value held in the numerical value holding means 6, the frequency of occurrence of 1, that is, white dots, can be controlled.

A horizontal synchronization signal is input to the reset signal generator 2. The period T of the reset signal of the reset signal generator 2 output to the random number generator 1 is T = n F i + (m
+ 0, 5) H...(1) or T=n
Fr+mH H: Horizontal scanning period.

Fl: Field scanning period (282, 58).

Fr: Frame scanning period (525H) is set as an integer.The random number generator 1 initialized by the reset signal generates the same random number sequence again due to its configuration, so the period of the reset signal is If 2B2H, 263H are repeated (in formula (1), m = l, m = -LO is repeated), the same pattern will be drawn on the screen every field, and the random pattern will appear to be stationary.Period of the reset signal 263H (m=L m=o in equation (1)) and 528H (n=L in equation (2))
1, m=1), if the period is 1 to 2H longer than one field scanning period or one frame scanning period, the random pattern appears to descend slowly. At this time, the speed of descent is 1 or 2,
If n is fixed and m is increased, the speed can be <, and if m is decreased, the speed can be decreased.

By doing the above, you can obtain the effect of making it look like snow is falling, but in order to make it look even more like real snow, consider a configuration like the one shown in Figure 2.

FIG. 2 is a block diagram of a snowfall effect generating device according to a second embodiment of the present invention having a configuration in which one random number generator, one numerical value holding means, and one comparator are added.

Output of first random number generator 11 and first numerical value holding means 18
The first comparator 12 compares the magnitude with the numerical value output from the first comparator 12, and outputs a discrimination signal. Similarly, the second comparator 14 compares the output of the second random number generator 13 with the numerical value output from the second numerical value holding means 19, and outputs a discrimination signal.

The reset signal generator 15 outputs a reset signal only to the first random number generator 11. AND circuit 1 performs a logical product operation of the first comparator output and the second comparator output.
6, make this a random pattern output, and set the period of the output signal of the reset signal generator 15 to 263H or 526H as in the case of the first embodiment, the white dot will fall while blinking. Therefore, it looks more like natural snow than in the first embodiment.

As described above, according to this embodiment, when compositing an image of falling snow on top of a certain background image, etc.
The amount of snow and the speed at which snow falls can be easily controlled by changing the output value of the numerical value holding means that is compared in magnitude with the random number and the period of the reset signal of the random number generator.

In addition, in the above embodiment, the period of the reset signal of the random number generator was set to 263H, 526H, etc., but 2B28 ((1
), n=llm=-1) or 524H (n=llm=-1 in equation (2)), it is possible to realize an effect in which the random pattern rises upward.

Effects of the Invention As described above, the present invention generates a random data pattern of 0 and 1, and displays a white dot on the screen over the video signal only when the data becomes 1, thereby drawing a dot pattern and generating random numbers. By setting the period of the reset signal of the generator as shown in equation (1) or equation (2), the snowfall effect can be achieved by moving the dot pattern from the top to the bottom of the screen.
Furthermore, since it is easy to control the amount of snow and the speed at which it falls, its practical effects are great.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a snowfall effect generating device which is a first embodiment of the present invention, Fig. 2 is a block diagram of a snowfall effect generating device which is a second embodiment of the present invention, and Fig. 3 is a block diagram of a snowfall effect generating device which is a second embodiment of the present invention. It is a block diagram of a container. 4... Clock input terminal, 5... Horizontal synchronization signal input terminal, 7... Discrimination signal output terminal, 16.
...AND circuit, 17.20...clock input terminal, 21...horizontal synchronization signal input terminal, 22...
Random pattern output terminal, 31...Random number output terminal, 32...Clock input terminal, 33...Reset signal input terminal.

Claims (3)

[Claims] (1) a random number generator, a reset signal generator for resetting the random number generator, a numerical value holding means, and a comparator for comparing the output of the random number generator with the output of the numerical holding means and outputting a discrimination signal; A snowfall effect generating device characterized by comprising: (2) The output period T of the reset signal of the reset signal generator is T=mFi+(m+0.5)H or T=nFr+mH H: Horizontal scanning period Fi: Field scanning period (262.5) Fr: Frame scanning period ( 525H) The snowfall effect generating device according to claim 1, wherein n, m, . . . are integers. (3) a first random number generator, a reset signal generator for resetting the first random number generator, a first numerical value holding means, and a first numerical value holding means for the output of the first random number generator; a first comparator that outputs a first discrimination signal by comparing the output of the second random number generator with the output of the second random number generator; It is characterized by comprising a second comparator that outputs a second discrimination signal by comparing the magnitude with the output of the numerical value holding means, and outputs a logical product of the first discrimination signal and the second discrimination signal. Snowfall effect generating device.