#version 300 es
precision highp float;
precision highp sampler3D;
precision lowp usampler2D;
precision lowp usampler3D;

uniform sampler2D light;
uniform sampler2D velocity;
uniform usampler2D index2Dto3D;
uniform usampler3D index3Dto2D;
uniform sampler3D voxel;

in vec2 v_texCoord;
layout (location = 0) out vec4 outLight;
layout (location = 1) out vec4 outVelocity;

uvec3 to3D(uvec2 v) {
    return texelFetch(index2Dto3D, ivec2(v), 0).zyx;
}

uvec2 to2D(uvec3 v) {
    return texelFetch(index3Dto2D, ivec3(v), 0).xy;
}

vec4 getLight(uvec3 v) {
    return texelFetch(light, ivec2(to2D(v)), 0);
}

vec4 getVoxel(uvec3 v) {
    return texelFetch(voxel, ivec3(v), 0);
}

vec4 getVelocity(uvec3 v) {
    return texelFetch(velocity, ivec2(to2D(v)), 0);
}

void main() {

    vec4 lightLast = texelFetch(light, ivec2(gl_FragCoord.xy), 0);

    uvec3 iCE = to3D(uvec2(gl_FragCoord.xy));
    vec4 lCE = getLight(iCE);
    vec4 vCE = getVoxel(iCE);
    vec4 veCE = getVelocity(iCE);
    vec3 v = vec3(0.0);

    // colision test
    if (vCE.r > 0.0 || vCE.g > 0.0 || vCE.b > 0.0) {
        if (vCE.a == 0.0) {
            outLight = vec4(0);
        } else {
            outLight = vCE;
        }
    } else {

        uvec3 iFR = uvec3(iCE);
        uvec3 iBA = uvec3(iCE);
        uvec3 iLE = uvec3(iCE);
        uvec3 iRI = uvec3(iCE);
        uvec3 iTO = uvec3(iCE);
        uvec3 iBO = uvec3(iCE);

        iRI.x += 1u;
        iLE.x -= 1u;
        iFR.y += 1u;
        iBA.y -= 1u;
        iTO.z += 1u;
        iBO.z -= 1u;

        vec4 lRI = getLight(iRI);
        vec4 lLE = getLight(iLE);
        vec4 lFR = getLight(iFR);
        vec4 lBA = getLight(iBA);
        vec4 lTO = getLight(iTO);
        vec4 lBO = getLight(iBO);

        vec4 vRI = getVoxel(iRI);
        vec4 vLE = getVoxel(iLE);
        vec4 vFR = getVoxel(iFR);
        vec4 vBA = getVoxel(iBA);
        vec4 vTO = getVoxel(iTO);
        vec4 vBO = getVoxel(iBO);

        vec4 veRI = getVelocity(iRI);
        vec4 veLE = getVelocity(iLE);
        vec4 veFR = getVelocity(iFR);
        vec4 veBA = getVelocity(iBA);
        vec4 veTO = getVelocity(iTO);
        vec4 veBO = getVelocity(iBO);


        // difference
        float dRI = lCE.a - lRI.a;
        float dLE = lCE.a - lLE.a;
        float dFR = lCE.a - lFR.a;
        float dBA = lCE.a - lBA.a;
        float dTO = lCE.a - lTO.a;
        float dBO = lCE.a - lBO.a;

        // vectoring
        v += veRI.xyz + veLE.xyz + veFR.xyz + veBA.xyz + veTO.xyz + veBO.xyz;

        v.x -= dRI;
        v.x += dLE;
        v.y -= dFR;
        v.y += dBA;
        v.z -= dTO;
        v.z += dBO;

        float intencity = 0.0;

        intencity += dot(lRI.xyz, + vec3(1.0, 0.0, 0.0));
        intencity += dot(lLE.xyz, - vec3(1.0, 0.0, 0.0));
        intencity += dot(lFR.xyz, + vec3(0.0, 1.0, 0.0));
        intencity += dot(lBA.xyz, - vec3(0.0, 1.0, 0.0));
        intencity += dot(lTO.xyz, + vec3(0.0, 0.0, 1.0));
        intencity += dot(lBO.xyz, - vec3(0.0, 0.0, 1.0));

        outLight.a += clamp(intencity / 6.0, 0.0, vCE.a);
        outVelocity.xyz = v / 6.0;

        // outLight = vec4(float(i2.x) / 512.0, 0.01,0.0,1.0);
        outLight.rgb = vec3(outLight.a);

    }


}