Pragma unroll_loop does not work with nested code blocks

When unrolling a loop that has a block statement in it the shader breaks because it considers the first } encountered to be closing the for loop. For example this works:

#pragma unroll_loop
for ( int i = 0; i < 6; i ++ ) {

    if ( i < NUM_DIR_LIGHT_SHADOWS ) directLight.color *= getShadow( /* ... */ );

}

But this breaks:

#pragma unroll_loop
for ( int i = 0; i < 6; i ++ ) {

    if ( i < NUM_DIR_LIGHT_SHADOWS ) {

        directLight.color *= getShadow( /* ... */ );

    }

}

The problematic regex is here:

https://github.com/mrdoob/three.js/blob/dev/src/renderers/webgl/WebGLProgram.js#L224

[Mugen87]

Also, as far as I remember, it was mainly for early iPads but I wonder if iOS handles this better these days…

According to #13090, certain Macbooks with radeon cards required the loop unrool, too.

I see so is the consensus that it’s not generally needed, then?

From my point of view, it is required until the opposite can be demonstrated with a few tests. I would not blindly remove it and risk shadow breakage on user devices.

[mrdoob]

which should be just as fast as the current approach:

#unroll_loop
for ( int i = 0; i < 5; i ++ ) {

 // nested blocks for days

}
#end_unroll_loop

That seems interesting!

I prefer this syntax:

#unroll_loop_start
for ( int i = 0; i < 5; i ++ ) {

  // nested blocks for days

}
#unroll_loop_end