TmMolStar/src/mol-gl/shader/chunks/apply-fog.glsl.ts

export const apply_fog = `
float viewZ = depthToViewZ(uIsOrtho, fragmentDepth, uNear, uFar);
float fogFactor = smoothstep(uFogNear, uFogFar, abs(viewZ));
float fogAlpha = (1.0 - fogFactor) * gl_FragColor.a;
float preFogAlpha = gl_FragColor.a;
if (!uTransparentBackground) {
    if (gl_FragColor.a < 1.0) {
        // transparent objects are blended with background color
        gl_FragColor.a = fogAlpha;
    } else {
        // mix opaque objects with background color
        gl_FragColor.rgb = mix(gl_FragColor.rgb, uFogColor, fogFactor);
    }
} else {
    #if defined(dRenderVariant_colorDpoit)
        if (gl_FragColor.a < 1.0) {
            // transparent objects are blended with background color
            gl_FragColor.a = fogAlpha;
        } else {
            // opaque objects need to be pre-multiplied alpha
            gl_FragColor.rgb *= fogAlpha;
            gl_FragColor.a = fogAlpha;
        }
    #else
        // pre-multiplied alpha expected for transparent background
        gl_FragColor.rgb *= fogAlpha;
        gl_FragColor.a = fogAlpha;
    #endif
}
`;