source/backend/opengl/glsl/image_copy.glsl

layout(FORMAT, binding=0) writeonly uniform PRECISION image3D uOutput;
layout(location=1) uniform mediump sampler3D uInput;
layout(location=2) uniform ivec4 imgSize;

layout (local_size_x = XLOCAL, local_size_y = YLOCAL, local_size_z = ZLOCAL) in;

void main()
{
    ivec3 pos = ivec3(gl_GlobalInvocationID);
    ivec3 imgSize = imgSize.xyz;
    if(pos.x < imgSize.x && pos.y < imgSize.y)
    {
        vec4 dataIn =  texelFetch(uInput, pos, 0);
        imageStore(uOutput, pos, dataIn);
    }
}