"plug-in-firepattern"

Fire Pattern Filter:

    Start from Menu:

      "<Image>/Video/Layer/Render/Fire Pattern..."

   This Plugin generates an animated fire effect.
   It can render the animation in one call, where the input drawable is copied n-times to a newly created image.
   Optional this Plugin can be called to render just one frame/phase of the animated effect.
   This type of animated call on multiple already existent layers (or frames) with varying shiftPhase parameter
   is supported by the GIMP-GAP filter all layers or by applying as filter via GIMP-GAP modify frames feature.
   Note that the render one frame per call style offers more flexibility where you can 
   apply the flame with varying shape, color and opacity for each rendered frame atomatically.

   Note that this Plugin will create an additional image when the options
   for creating fire pattern or fire shape are selected. 
   If you intend to record the Plugin using GIMP-GAP filtermacro feature
   or want to be able to reproduce the exactly same same results in another GIMP session
   You have to save this image to disc (using the XCF file format)

  Animation options:
  
    Create Image: (checkbutton)
      
      ON:  create a new image with n copies of the input drawable
           and render complete animation effect on those copies.
      OFF: render only one frame/phase of the animation effect on
           the input drawable.
           (This type of call must be selected in case you call this plug-in
           via the GIMP-GAP filter all layers feature)


     N-Frames: (spinbutton)
           Number of frames to be rendered as layer in the newly created image.
           In this mode the vertical shift per frame is calculated automatically
           for each frame varying from 0.0 to Phase Shift value.
           Select 1.0 (or multiples of 1.0) to create an animation 
           that can be played in seamless loop.
           (disabled in case Create Image: OFF is selected)
           
     Phase shift: (spinbutton)
           Vertical phase shift (movement of the fire pattern)
           where 1.0 refers to image height.
           
           In animated calls via (filter all layers) it is recommended to
           set Phase shift to value 0.0 for the first and to value 1.0
           for the last processed frame to create a seamless animation effect
           when playback of the rendered frame is done in a loop.
           
           
     
  Pattern options:
     Widgets to control the fire pattern cloud layer that is used as base
     for rendering the animated fire effect.
     
     Create Pattern:  (checkbutton)
       ON:  create firepattern cloud layer with tileable solid noise
            according to options. 
            (Creating a new pattern should be osed only in case
            rendering the first frame of an animation sequence.
            for each further frame it is recommended to turn this option OFF)
       OFF: Use external pattern layer.
            Typically you may select a fire pattern layer that was created
            for rendering the first frame of the animation.

     Stretch Height (spinbutton)
            vertical stretch factor for the fire pattern.

     Scale Pattern X/Y:  (2 spinbuttons)
            Horizontal/Vertical scaling of the random pattern that is
            created for rendering the fire pattern (cloud layer)

     Seed Pattern:  (spinbutton)
            Seed for creating random pattern (cloud1 layer) 
            use 0 for random value.
     
     Detail:  (spinbutton)
            Detail level for creating random solid noise pattern (cloud layer)
     

     Layer Pattern: (combobox)
            Select an already existing pattern layer 
            (typically from previous run, when rendering in one frame per call mode)
     

  Fireshape options:
     Widgets to control the fire shape layer that is used to control the affected
     area where to render the flames.

     Create Fireshape: (checkbutton)
            ON: create fire shape layer according to options.
            OFF: Use external fire shape layer. 

     Trapezoid: (checkbutton)
            ON: Render trapezoid shaped fire.
            OFF: render fire at full image width.

     Flame Height: (spinbutton)
            Height of the flame (1.0 refers to full image height)

     Flame Border: (spinbutton)
            border of the flame (used for horizontally soft fade of the shape at the borders)

     FlameWidth: (2 spinbuttons)
            width of the flame at base line and
            width of the flame at flame height 
            (1.0 for full image width)

     Flame Center: (spinbutton)
            horizontal offset of the flame center 
            (0 for center, -0.5 left border +0.5 at right border of the image)

     Fire Shape:
            Select an already existing fire shape layer 
            (typically from previous run, when rendering in one frame per call mode)
            
  Render options:
  
     Create FireLayer: (checkbutton)
            ON:  Render fire pattern effect as separate layer. 
            OFF: merge rendered effect onto processed layer.
                 (it is recommended to set the Transparent BG
                 to ON too)

            (In case this filter is called via the filter all layers
            feature it is recommended to turn this option OFF)
            
     Blend Mode: (radio buttons)
            Selects the blend mode to be used to combine the fire pattern (cloud)
            layer with the fire shape layer. Following modes are available:
            "Burn"
            "Subtract"
            "Multiply"

     Transparent BG: (checkbutton)
            ON: Render fire layer with transparent background.
            OFF: render with black background.
  
     Opacity: (spinbutton)
            The opacity of the rendered flames.
     
     Reverse Gradient: (checkbutton)
             ON: use reverse gradient colors.
             OFF: use gradient colors.
     
     Gradient: (gradient button)
             Select the gradient that should be used to colorize the rendered flames.
     
     
  Action Buttons:

  Reset
    Reset all parameters to default values.

  Cancel
    Close the window without any further action.

  OK
    Close the window and render the fire effect according to the
    selected options.



  Usage Examples:

  Rendering fire with varying colors:
    For this example we use a multilayer image where each layer
    represents one frame of an animation.
    (in case this multilayer image was loaded from an animated GIF
    the mode has to be changed from Indexed to RGB before we continue)
    
    From this multilayer image start the menu Filter/filter all Layers.
    This opens a browser dialog window where the plug-in-firepattern 
    can be selected in the list of available filters.
    Set acceleration characteristics to value 1 for linear varying values
    with constant speed and press the APPLY button in the browser dialog.
    
    This starts the Fire-Pattern dialog window of the selected plug-in-firepattern
    where you can specify the options to be applied for processing the first
    layer of the multilayer image.
    
    1. st dialog step
    
    Press the reset button to init all options with default values.
    Make sure to set Phase Shift to value 0 and
    Also both the Create Pattern and the Create Fireshape checkbuttons
    shall be turned on.

    Press OK in the Fire Pattern dialog. This renders the fire on the
    first (e.g. the background) layer of your multilayer image.
    
    After rendering a dialog window with title "Animated Filter Apply"
    pops up.
    Click the "Continue" button in this dialog.
    
    2. nd dialog step
    
    The Fire-Pattern dialog window appears again where you can enter
    the options for the last layer to be processed (the top layer
    of your multilayer image)
    
    Uncheck the "Create Fireshape" checkbutton to use the same
    Fire Shape in all further frames.
    
    Enter the value 1.0 in the Phase shift spinbutton entry widget.
    Click on the gradient and select another gradient name in
    the dialog that opens on this click
    
    Press OK in the Fire Pattern dialog. This renders the fire on the
    last (e.g. the top) layer of your multilayer image.
   
    After rendering a dialog window with title "Animated Filter Apply"
    pops up.
    Click the "Continue" button in this dialog.
    
    This triggers rendering the fire effect for all further layers
    (between bg and top) of your multilayer image.    
    

  Rendering fire with varying external shape:
    In case you want render the fire with another shape (than the built in trapezoid)
    you can provide the fire shape layer in another image.
    
    For varying external shape this other image should be a multilayer image
    where each layer represents another step of the animated fire outline shape.
    (typically white at base fading to black until the desired flame height)
    It is recommended to use the same number and size for the "external"
    fireshape multilayer image and for the multilayer image where the
    fire effect shall be rendered onto.
    
    
    

  
  How it works:

  This filter generates a fire pattern (cloud) layer with tileable solid noise, and a fire shape layer.
  The fire effect is made by placing the fire pattern above the fire shape layer using "Burn" (or "subtract")
  combination mode. The animation is done by vertically shifting the fire pattern upwards slightly
  on each frame.
  The flames are built by merging the fire pattern at its shifted state with the fire shape.
  The resulting (gray flame) layer is colorized with the colors of the selected gradient.
  The mapping of the colors (and optional opacity) is done by luminance.


