grain.yaml

import: 
    - ../block.yaml
    - ../generative/fbm.yaml

styles:
    filter-grain:
        mix: [block, generative-fbm]
        doc:
            author: 
                name: Patricio Gonzalez Vivo
                twitter: patriciogv
            version: 0.0.1
            tangram-version: 0.0.7
            licence: MIT
            description: |
                Apply a lens grain effect to the scene.
            examples:
                grain:
                    url: https://tangrams.github.io/tangram-sandbox/styles/grain.yaml
                    img: https://tangrams.github.io/tangram-sandbox/styles/grain.png
                    lines: 29
        ui:
            shaders:
                defines:
                    GRAIN_AMOUNT: 
                        type: number
                        label: Amount
                        range: 
                            min: 0.
                            max: 1.
                            step: 0.01
                    GRAIN_BLEND: 
                        type: dropdownArray
                        label: 'Blend mode'
                        values: ['ADD', 'SUBTRACT', 'MULTIPLY']

        test:
            grain: { uniforms: { u_tex0: "https://tangrams.github.io/blocks/test.jpg" }, blocks: { color: "    color = texture2D(u_tex0,v_texcoord.xy);" } }

        shaders:
            defines:
                GRAIN_AMOUNT: .3
                GRAIN_BLEND: 'SUBTRACT'
            blocks:
                global: |
                    #ifdef TANGRAM_FRAGMENT_SHADER
                    float grain () {
                        vec2 pos = gl_FragCoord.xy;
                        vec2 st = pos/u_resolution.xy-vec2(.5);
                        return dot(st,st)+(fbm(pos*0.6)*0.1);
                    }
                    #endif
                filter: |
                    // Apply the grain in the amount defined on GRAIN_AMOUNT
                    color.rgb = color.rgb GRAIN_BLEND (grain()*GRAIN_AMOUNT);