Backdrop Designs

 

This page shows the designs available in Backdrop, along with an explanation of the parameters. Animated images are shown in a video on the about page.

When setting parameters, please consider the following general guidelines.

1. X and Y

X increases from left to right. Y increases from top to bottom. (X=0, Y=0) refers to the top left of the screen. Occasionally, values of YMin and YMax may be set. YMin will be nearer the top of the screen, and YMin will be nearer the bottom.

2. Max and Min

When Max and Min values are shown, actual values are set randomly between these two limits.

3. Probabilities

All probabilities are between 0.0 (never happens) and 1.0 (happens every frame).

4. Colours

Colours can be selected by name, e.g. HotPink, or specified by their rgb values in the format 23,130,255. The red, green and blue numbers are within the limits 0-255. All colour change speeds are the change in r,g and b values per frame, so a colour speed change of 1 will take the red value from 0 to 255 in 255 frames. At 25 frames per second, this will take just over 10 seconds.

5. Values

In some cases, values can be set which may appear to be beyond any reasonable use. This is not an error yet to be fixed. I do not know what people want to create as artists, so have left the values as wide as possible.

 

Blended background
A blended background is a slowly changing blend of colours. The colour range is limited by setting upper and lower limits for red, green and blue colour values.

The number of blended colours is set by the grid size, which by default is set to 3. In the image on the left, the three colours across the top are cyan, lime, cyan.

The speed of change can also be set.

Circles

Circles shows popping circles on a blended background. In this case, the two background colours are set to blue, so no blend is seen.

The following parameters can be set

Colour
BackgroundColour1The background colour at the top
BackgroundColour2The background colour at the bottom
ForegroundColourThe colour of the circles
Dimensions
BorderThe border width and height within which no circles are placed
DiameterThe maximum diameter of a circle before it pops
NumberOfCirclesThe number of circles
Dynamics
SpeedThe speed of growth of the circles
Drifting points
Points of light drift around the screen like snow or flying insects, moving randomly from one direction to the next.
 
Colour
BackgroundColour1The background colour at the top
BackgroundColour2The background colour at the bottom
ForegroundColour1The colour of 1/4 of the points
ForegroundColour2The colour of 1/4 of the points
ForegroundColour3The colour of 1/4 of the points
ForegroundColour4The colour of 1/4 of the points
IntensityMaxThe maximum intensity of any point
IntensityMinThe minimum intensity of any point. When the points are generated, all intensities are set randomly between the min and max limits
Dimensions
BorderThe border width and height within which no circles are placed
NumberOfFloatersThe number of drifting points
SizeMaxThe maximum diameter of a point
SizeMinThe minimum diameter of a point
Dynamics
DriftXThe speed, in pixels per frame, of drift in the x direction
DriftYThe speed of drift in the Y direction. Both DriftX and DriftY can be positive or negative.
SpeedMaxThe maximum speed of movement in any direction of a point
SpeedMinThe minimum speed
TurnMaxThe maximum turn angle in degrees
TurnProbabilityThe probability, in each frame, of a turn taking place. If this is set to 0.04 (or 1/25), and the frame rate is 25 frames per second (fps), then on average 1 turn will occur every second. The angle of the turn will be somewhere between 0 and TurnMax degrees.
Fire
Configuring fire is straightforward enough. Four seed colours provide the blended colours of the flames, and the average flame width and flame trigger probabilities can be altered.
Fractal clouds
Colour
Colour1The cloud colour
Colour2The other cloud colour. Colours are rotated between these two extremes.
Dimensions
RoughnessThe roughness used to generate the clouds - defaults to 70
Dynamics
SpeedThe colour change speed. See the colour note at the top of this page
Visualization
LimitLowerA value between 0 and 1 creates a lower cut-off layer in the cloud
LimitUpperUpper cut-off. It should be higher than the lower limit
SmoothingPixel smoothing radius. If 1 is specified, the pixel colour will be averaged to the average of the pixel and its 8 neighbours.
Glowing panel
The glowing panel provides a framed background and a panel whose glow moves around, occasionally accompanied by a flash around the border as shown here.
 
Colour
BackgroundColour1The background colour at the top
BackgroundColour2The background colour at the bottom
EdgeGlowColourThe colour of the edge glow
GlowColourThe colour of the glow on the panel
PanelColourThe colour of the panel
Edge glow
DelayThe number of frames before the edge glow starts or restarts
EdgeGlowAllSidesIf false, the edge glow moves along the top and down the right hand side. If true, this is mirrored down the left and along the bottom.
EdgeGlowLengthThe length of the glow in pixels
ReboundWhen the glow reaches the bottom right it can rebound (true) or disappear (false)
SpeedThe number of pixels the edge glow advances each frame
ThicknessThe thickness of the edge glow (2 pixels on the left)
Panel dimensions
HeightThe height of the panel
LeftThe left coordinate of the panel
TopThe top, or Y coordinate of the panel
WidthThe width of the panel
Panel glow
GlowHeightThe height of the glowing area
GlowSpeedthe speed at which the glow moves around. Once the glow reaches the edge of the panel, it rebounds the same as in Pong, or electronic tennis.
GlowWidthThe width of the glowing area
Gritty plasma
Gritty plasma provides an oscillating wave-like pattern.
Colour
Colour1One colour
Colour2The other colour
LimitToSelectedColoursIf true, the pattern oscillates between the two colours. If false, it can wrap around the full spectrum and create some more interesting patterns
Dimensions
NumberOfWavesThe plasma pattern is generated by either a single wave, or two or three intersecting waves. The more waves, the more the pattern varies, and the slower the calculation time.
Dynamics
SpeedThe colour change speed. See the colour note at the top of this page
Visualization
SmoothingA nearest neighbour smoothing function to blend out the grittiness
Horizontals
Colour
Colour 1 to 11One of 11 colours
Dimensions
NumberOfLinesThe number of lines or horizonatal bars
Dynamics
HeightMinThe minimum height a bar reaches before it starts trying to grow
SpeedMaxThe maximum speed at which the border between two bars can move up or down
SpeedMinThe minimum speed. Actual speeds are randomized between the max and min
Life
Life is reputedly the most copied algorithm in computing. Some knowledge of Conway's algorithm may help to better understand this pattern. There is a wikipedia article here.
Colour
BackgroundColour1The background colour at the top
BackgroundColour2The background colour at the bottom
ForegroundColour 1 to 4When a colour is selected, a blended mix of the four colours is created. This blend represents the ages 0 to 255.
Dynamics
AgeMaxThe maximum age a cell (in this case a pixel) reaches before it dies
CanDieOfOldAgeIf false, then AgeMax is not used in calculations
OvercrowdingLimitIf the number of alive neighbours (adjacent and immediately diagonal pixels - total 8) reaches this value, then the cell dies
SeedProbabilityThe probability of a pixel coming back to life after is has died
SuddenDeathProbabilityThe probability of a pixel suddenly dying
UndercrowdingLimitIf the number of alive neighbours (adjacent and immediately diagonal pixels - total 8) does not equal this value, then the cell dies. This is only useful for creating patterns which shrink away from the corners
Visualization
DrawBackgroundA cell which is dead or of zero age will be drawn in ForegroundColour1. To draw all zero aged cells as a blended background, set this to true.
SmoothingSmoothing in this case does not apply to colour smoothing, but to age smoothing. A number greater than 0 will produce a less grainy and more uniform pattern.
WrapIf true, then calculations are wrapped around from right to left and top to bottom. This will avoid edge effects
Moving shapes
Moving shapes provides shapes moving from left to right, with depth, so nearer shapes move faster than far shapes, producing a star field type appearance. The parameters are similar to floating shapes, with the exceptions of:
 
Visualization
ShapeCircle, disk or squares are available
Show depththe depth function is optional

 

Panels
A grid of panels of varying intensity fade in and out against a blended background. To avoid varying intensities, set IntensityMax and IntensityMin to the same value. Most of the parameters require no explanation. Here are the exceptions:
Dimensions
PanelsNotDrawnA list of panels not drawn beginning with 1 top left, 2 the next right and so on. If there are 2 panels across, then the panel below 1 will be three. To avoid drawing these three panels, enter 1,2,3 in this field
Visualization
FadeInSpeedMaxA value of 1 means the panel will fade in immediately, or appear fully on in 1 frame. A value of 0.04 at a frame rate of 25fps will mean fade in takes 1 second to full intensity
FadeInSpeedMinWith FadeInSpeedMax, provides a measure of variance so all panels do not fade in at the same speed
FadeOutSpeedMaxAs above
FadeOutSpeedMinAs above
ProbabilityOfFadeInWhen a panel has faded out, this is the likelihood of it fading back in. A value of 0.04 at a frame rate of 25fps will mean that on average, 1 second elapses before a panel fades in.
ProbabilityOfFadeOutAs above

 

Rectangles
 
Colour
BackgroundColour1The background colour at the top
BackgroundColour2The background colour at the bottom
ForegroundColour1The colour of 1/4 of the rectangles
ForegroundColour2The colour of 1/4 of the rectangles
ForegroundColour3The colour of 1/4 of the rectangles
ForegroundColour4The colour of 1/4 of the rectangles
IntensityMaxThe maximum intensity of any rectangle
IntensityMinThe minimum intensity of any rectangle. When the rectangles are generated, all intensities are set randomly between the min and max limits
Dimensions
HeightMinThe minimum height of any rectangle
NumberOfRectanglesThe number of rectangles
RotatedHeightMaxIf RotateHorizontals is set to true, this value will limit the maximum height to a value less than WidthMax if required. Otherwise, too many rectangles stretch off the top and bottom of a rectangular window.
RotateHorizontalsSet to true, will rotate the rectangles that move from left to right or right to left.
WidthMaxThe maximum width of any rectangle
Dynamics
SpeedMaxThe maximum speed of movement in any direction of a point
SpeedMinThe minimum speed
Reflections
It may help to think of this as a reflective stage with a curtain in the background. This is how I explain it below.
 
Colour
TopCentreColourReflections takes a single colour, which is the colour in the middle at the top of the screen. Cunning transforms are then applied to this single colour to generate the background
Beams
AngleMaxBeams to the left of centre lean to the left, and to the right of centre lean to the right at this angle.
BeamColourThe colour of the beams
Beam profileThe beams are drawn fading in towards the centre. The profile of the fade can be set to Bell (a bell curve), Linear (straight up and down), Square 1, a square law, and Square 2, an alternative square law.
IntensityMaxThe maximum beam intensity
IntensityMinThe minimum beam intensity
NumberOfBeamsThe number of beams
WidthMaxThe maximum width of a beam
WidthMinThe minimum width of a beam
Dynamics
SpeedMaxThe maximum speed of movement to left or right of a beam
SpeedMinThe minimum speed
Perspective
PerspectiveIntensityThe fading intensity from back to front of stage caused by the perspective
PerspectiveSpreadThe spread of the reflections on the stage from back to front. Negative numbers will show as convergence rather than spreading
Ribbons
Ribbons is a complex algorithm. It may be best to twiddle rather than to try and understand it.

The change limits are defined as DSomething or DSomething2, this refers to first and second order differentials as in dy/dx or d2y/d2x.

The switch probabilities refer to an increasing colour or other value switching from increasing to decreasing or vice versa.

The ribbons are generated from left to right, so many of the min/max pairs are used only to define starting conditions at the left.

Limits try to contain the ribbons, but are guidelines rather than absolute values.
 

Change limits
DColourMaxThe maximum change in colour. As colour is held in a 256 part blended array, a value of 1 will mean a transition from the beginning to the end of the array in 256 pixels along the x axis. As this is a max value, this is weighted by a random number, so the actual transition will take somewhere between 256 and infinity.
DColourMinThe minimum change in colour. Specifying DColourMin as 1 and DColourMax as 2 will mean an average transition of 384 pixels.
DIntensityMaxThe maximum change intensity. As the intensity range is 0.0 to 1.0, this should be a small number.
DIntensityMinThe minimum change in intensity (between 0.0 and 1.0). When the minimum value is reached as a ribbon progresses from left to right, the intensity starts increasing. Similarly, when the maximum is reached, the intensity starts decreasing.
DThicknessMaxThe maximum change in thickness
DThicknessMinThe minimum change in thickness. These numbers are used only to define the starting conditions of each ribbon at the left
Dy2MaxThe maximum 2nd order differential of y with respect to x
Dy2MinThe maximum 2nd order differential of y with respect to x. These numbers are used only to define starting conditions
DyMaxThe maximum change in y from one pixel to the next along the x axis.
Change probabilities
ColourSwitchProbabilityThe likelihood of an increasing colour value switching to a decreasing colour value, or a decreasing one switching to an increasing one
IntensitySwitchProbabilityThe likelihood of an increasing intensity value switching to a decreasing intensity value, and vice versa
ThicknessSwitchProbabilityThe likelihood of an increasing thickness value switching to a decreasing thickness value, and vice versa
ySwitchProbabilityThe likelihood of an increasing y value switching to a decreasing y value, and vice versa
Colour
BackgroundColour1The background colour at the top
BackgroundColour2The background colour at the bottom
ForegroundColour1The colour of 1/4 of the rectangles
ForegroundColour2The colour of 1/4 of the rectangles
ForegroundColour3The colour of 1/4 of the rectangles
ForegroundColour4The colour of 1/4 of the rectangles
Dimensions
NumberOfRibbonsThe number of ribbons
Dynamics
MovementSmoothingA next neighbour averaging width applied to the movement of the ribbons. A low value will look more jerky than a high one
StepsWhen moving , the first ribbon moves to the location of the second ribbon then the third and so on in sequence until is returns to its original starting position. Steps is the number of steps taken to move from the first position to the position of the next ribbon. The less steps, the faster the ribbons will appear to move
Limits
IntensityMaxThe maximum intensity reached before increasing intensity is switched to decreasing intensity
IntensityMinThe minimum intensity reached before decreasing intensity is switched to increasing intensity
ThicknessMaxThe maximum thickness reached before increasing thickness is switched to decreasing thickness
ThicknessMinThe maximum thickness reached before increasing thickness is switched to decreasing thickness.
ThicknessStartMaxAllows ribbons to begin wider or narrower than they are further right
yLeftMin, yLeftMax, yRightMin, yRightMaxAn attempt to box the ribbon generator into specified bounds. In reality, with movement smoothing and random position generation, it may or may not occur.
Visualization
ThicknessSmoothingA next neighbour averaging of ribbon thickness. A higher number creates a more curved appearance to the ribbon, a low value a more angular appearance
Spangles
Spangles are randomly generated flashes of light or darkness against a blended background. There are no challenges in the setting of parameters.
Sunset
An animated sunset or sunrise is generated
 
Colour
HighColourThe colour of the sky at the top of the frame when the sun is high
HighColourLThe colour of the sky at the top of the frame when the sun is low
LowColourThe colour of the sky at the horizon when the sun is high
LowColourLThe colour of the sky at the horizon when the sun is high
SeaColourFarThe colour of the sea or ground at the horizon when the sun is high
SeaColourFarLThe colour of the sea or ground at the horizon when the sun is low
SeaColourNearThe colour of the sea or ground at the bottom of the frame when the sun is high
SeaColourNearLThe colour of the sea or ground at the bottom of the frame when the sun is high
StarColourThe colour of the stars
SunColourThe colour of the sun
SunIntensityThe intensity of the sun (0.0 to 1.0)
Dimensions
BorderThe width and height of the border around the edge in which no stars are positioned
NumberOfSparklesAs the sun rises or descends, and the sea, in its restless turmoil endeavours ever onward, its surface catches sparkles. The number of the sparkles visible in each frame can be set here.
NumberOfStarsThe number of stars in the sky. As the sun sets, they fade into view, as it rises, they fade out of view.
SkyToSeaRatioA number between 0.0 and 1.0. A value of 0.5 will produce equal sky and sea/ground areas.
StarSizeMaxThe maximum size of any star
SunDiameterThe diameter of the sun
Dynamics
DelayThe number of frames before the rising or setting begins
FadeStarsWhen set to true, the stars fade in for sunsets, and fade out for sunrises. Use this set to false, and click the randomize button to get a pleasing distribution of stars, then set it to true before playing or recording
SparkleSpeedMaxThe maximum speed at which sparkles fade in and fade out
SpeedThe speed of the movement of the sun
Visualization
DirectionSunrise or sunset
Waves
Colour
Colour1The colour of the crest of a wave
Colour2The colour at the trough
Dimensions
NumberOfWavesMore complex wave patterns are generated with more waves. Limited to a maximum of 3
Dynamics
SpeedThe speed of change, which is the phase change per frame in radians
Visualization
AmplitudeMaxSet a ceiling on the wave height

 

Acknowledgements

 

Most of the grunge work of drawing antialiased shapes comes from Computer Graphics Principles and Practice by Foley, van Dam, Feiner and Hughes

The fire routine is ported from code posted on CodeProject by David Swigger

Horizontals was inspired by a greetings card published by WH Smiths

Ribbons was inspired by a Samsung advert for Vista, but came out little like the initial intention.

The original Life algorithm was created by John Conway. http://en.wikipedia.org/wiki/Conway's_Game_of_Life

The Reflections default colour scheme is similar to the one on the startup window in Vista

The fractal cloud generation is ported from code on GarageGames by Josef Jahn

Thanks to Corinna John for her work on reading and writing AVI files

 

© Nigel Leeming 2007