Snippet Shader using multiple textures

Wingnut

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This shader will read the red channel from one texture and use that as the index to pick from a palette, which is the second texture. Red being read as 0-255 and used as the x coordinate on the top pixel row of the texture called palette. So this is a an alternate way to convert lots more without any conditionals.
It's also a great beginning for starting to write your own shaders.

GLSL is just a simple language like good ole BASIC. You need to re-think how to code in parallal though and the way to do that is to think about one pixel at a time. You write your program for ONE pixel. You can read and write textures and there's plenty of limitations of course, but even more freedom, just use your imagination.


I create a definition for pixel position at the top, sometimes you want pixels and sometimes you want normalized, so take your pick.

Hope this will get you started!

shader.glsl
Code:
uniform sampler2D ColorTexture; // source
uniform sampler2D ColorTexture2; // palette
uniform sampler2D ColorTexture3; // target

void shader(){
  
    // Get coordinate
    vec2 uv=(b3d_ClipPosition.st/b3d_ClipPosition.w)*0.5+0.5 ;    // Location as normal (0.0 - 1.0)
    vec2 p = vec2(floor(uv.x*256.0),floor(uv.y*256.0)) ;        // Location as pixel

    // Palette
    vec2 location;
    float paletteIndex = texture2D(ColorTexture, uv).r; // Read red 0-255 of sprite
    location.x = paletteIndex;    // x coord. And index that to the x position 0-255 of a texture with a width of 256 pixels
    location.y = 0.0;            // y coord. We use only top line of the palette texture
     vec4 fragColor = texture2D(ColorTexture2, location);

    // Make sure there is only one fragColor assignment in the shader
     // fragColor = texture2D(ColorTexture, uv);        // Simple texture 1 (sprite)
    // fragColor = texture2D(ColorTexture2, uv);    // Simple texture 2 (palette)

    b3d_FragColor = fragColor ;
// -------------------------------------------------------------------------------------------------
}

shader.cxs
Cerberus:
Import mojo2
Function Main()
    New MyApp
End

Class MyApp Extends App

    Field sourceImage : Image
    Field palette:Image
    Field targetImage : Image
    Field canvas : Canvas
    Field effect : ShaderEffect
    Field value : Float
    Field r:Floar, g:Float, b:Float,a:float
    
    Method OnCreate()
        sourceImage = Image.Load("sprite.png",0,0,0) ' Sprite of any size that will use red 0-255 as index to palette
        palette = Image.Load("palette.png",0,0,0) ' 256 x ? texture containing the presets
        targetImage = New Image(sourceImage.Width,sourceImage.Height)
        effect = New ShaderEffect
        canvas = New Canvas
          SetUpdateRate 0
    End
  
    Method OnRender()
        canvas.Clear 0, 0.5, 1, 1 
        effect.SetValue value
        value = value + 0.01       
        effect.Render sourceImage, palette,targetImage
        canvas.DrawRect 0,0, 256*1,256*1,targetImage,0,0,512,512
        canvas.Flush
    End

End

Class myShader Extends Shader

    Method New()
        Build(LoadString("shader.glsl"))
    End 
  
    Method OnInitMaterial:Void(material:Material)
        material.SetTexture "ColorTexture",Texture.White()
        material.SetTexture "ColorTexture2",Texture.White()
        'material.SetScalar "color_r",1
        'material.SetScalar "color_g",1
        'material.SetScalar "color_b",1
        'material.SetScalar "color_a",1
    End
  
    Function Instance:myShader()
        If Not _instance _instance=New myShader
        Return _instance
    End
  
    Private
    Global _instance:myShader
End

Class ShaderEffect

    Private
    Global _canvas:Canvas
    Field _material:Material
      
    Method New()
        If Not _canvas _canvas=New Canvas
        _material=New Material( myShader.Instance() )
    End
  
    Method SetValue:Void( value:Float )
    End
  
    Method Render:Void(source:Image,source2:Image,target:Image)
        _material.SetTexture "ColorTexture",source.Material.ColorTexture
        _material.SetTexture "ColorTexture2",source2.Material.ColorTexture ' ?
        _material.SetTexture "ColorTexture3",target.Material.ColorTexture ' ?
        _canvas.Clear 0, 0, 0, 0
        _canvas.SetRenderTarget target
        _canvas.SetViewport 0,0,target.Width,target.Height
        _canvas.SetProjection2d 0,target.Width,0,target.Height
        _canvas.DrawRect 0,0,target.Width,target.Height,_material
        _canvas.Flush
    End
  
End
 

Attachments

  • ShaderBase.zip
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