Mewa Film User's Guide/Nodes Reference/UnderwaterEffect node

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About UnderwaterEffect node[edit]

Distorting the geometry of an image with a specific periodic pattern can give the illusion of being underwater. That's what this effect does.

Underwater effect

Parameters[edit]

The distortion applied to the image has the form of a wave. The parameters are the amplitude of the wave and the phase of the wave. The phase of the wave shifts the distortion wave and if animated gives a nice effect of being underwater.

Tested Hardware[edit]

The following table shows the result of tested graphics hardware on this effect.

Graphics Hardware Result
ATI RADEON X1200 Series OK
ATI RADEON XPRESS 200M Series FAILED

You can check what your graphics hardware is by selecting the menu Help >> System Info.

Source[edit]

This MFX file comes with the installation of Mewa Film. You can find it in Mewa Film installation directory inside the folder effects.

<MewaFilmNode Name="UnderwaterEffect" Release="1" Output="Image" 
HelpAddress="http://en.wikibooks.org/wiki/Mewa_Film_User's_Guide/Nodes_Reference/UnderwaterEffect_node">

<Input ToolTip="input image"></Input>

<Tab Title="Distortion">
  <UniformVariable Type="float" Name="phase">
    <UISpinner Step="0.01" Name="Phase" Default="2.0"></UISpinner>
  </UniformVariable>
  <UniformVariable Type="float" Name="amp">
    <UISpinner Step="1" Name="Amplitude" Default="2.0"></UISpinner>
  </UniformVariable>
</Tab>


<VertexShader>
void main(void)
{
gl_TexCoord[0] = gl_MultiTexCoord0;
gl_Position = ftransform();
}
</VertexShader>

<FragmentShader>
#define PI 3.1415926535897932384626433832795

uniform sampler2DRect image;
uniform int mfx_ImageWidth0;
uniform int mfx_ImageHeight0;
uniform float phase;
uniform float amp;
                                                 
void main(void)
{

  float xShift = amp / 2.0 * (1.0 + sin((4 * gl_TexCoord[0].t / mfx_ImageHeight0 + phase )* 2.0 * PI));
  float yShift = amp / 2.0 * (1.0 + sin((4 * gl_TexCoord[0].s / mfx_ImageWidth0 + phase ) * 2.0 * PI));

  gl_FragColor = texture2DRect(image, gl_TexCoord[0].xy + vec2(xShift, yShift));
  

}
</FragmentShader>

</MewaFilmNode>