Algorithm To Convert RGB To HSV And HSV To RGB In Range 0-255 ...

I wrote this in HLSL for our rendering engine, it has no conditions in it:

float3 HSV2RGB( float3 _HSV ) { _HSV.x = fmod( 100.0 + _HSV.x, 1.0 ); // Ensure [0,1[ float HueSlice = 6.0 * _HSV.x; // In [0,6[ float HueSliceInteger = floor( HueSlice ); float HueSliceInterpolant = HueSlice - HueSliceInteger; // In [0,1[ for each hue slice float3 TempRGB = float3( _HSV.z * (1.0 - _HSV.y), _HSV.z * (1.0 - _HSV.y * HueSliceInterpolant), _HSV.z * (1.0 - _HSV.y * (1.0 - HueSliceInterpolant)) ); // The idea here to avoid conditions is to notice that the conversion code can be rewritten: // if ( var_i == 0 ) { R = V ; G = TempRGB.z ; B = TempRGB.x } // else if ( var_i == 2 ) { R = TempRGB.x ; G = V ; B = TempRGB.z } // else if ( var_i == 4 ) { R = TempRGB.z ; G = TempRGB.x ; B = V } // // else if ( var_i == 1 ) { R = TempRGB.y ; G = V ; B = TempRGB.x } // else if ( var_i == 3 ) { R = TempRGB.x ; G = TempRGB.y ; B = V } // else if ( var_i == 5 ) { R = V ; G = TempRGB.x ; B = TempRGB.y } // // This shows several things: // . A separation between even and odd slices // . If slices (0,2,4) and (1,3,5) can be rewritten as basically being slices (0,1,2) then // the operation simply amounts to performing a "rotate right" on the RGB components // . The base value to rotate is either (V, B, R) for even slices or (G, V, R) for odd slices // float IsOddSlice = fmod( HueSliceInteger, 2.0 ); // 0 if even (slices 0, 2, 4), 1 if odd (slices 1, 3, 5) float ThreeSliceSelector = 0.5 * (HueSliceInteger - IsOddSlice); // (0, 1, 2) corresponding to slices (0, 2, 4) and (1, 3, 5) float3 ScrollingRGBForEvenSlices = float3( _HSV.z, TempRGB.zx ); // (V, Temp Blue, Temp Red) for even slices (0, 2, 4) float3 ScrollingRGBForOddSlices = float3( TempRGB.y, _HSV.z, TempRGB.x ); // (Temp Green, V, Temp Red) for odd slices (1, 3, 5) float3 ScrollingRGB = lerp( ScrollingRGBForEvenSlices, ScrollingRGBForOddSlices, IsOddSlice ); float IsNotFirstSlice = saturate( ThreeSliceSelector ); // 1 if NOT the first slice (true for slices 1 and 2) float IsNotSecondSlice = saturate( ThreeSliceSelector-1.0 ); // 1 if NOT the first or second slice (true only for slice 2) return lerp( ScrollingRGB.xyz, lerp( ScrollingRGB.zxy, ScrollingRGB.yzx, IsNotSecondSlice ), IsNotFirstSlice ); // Make the RGB rotate right depending on final slice index }