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fix potential overflow in fog density calculation

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StapleButter
2017-07-14 00:12:35 +02:00
parent a1401e724c
commit 04172f47de
1 changed files with 7 additions and 3 deletions
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10
src/GPU3D_Soft.cpp
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@ -1545,15 +1545,19 @@ void ScanlineFinalPass(s32 y)
} }
else else
{ {
z = (z - fogoffset) << fogshift; // technically: Z difference is shifted left by fog shift
densityid = z >> 19; // then bit 0-18 are the fractional part and bit 19-23 are the density index
// things are a little different here to avoid overflow in 32-bit range
z -= fogoffset;
densityid = z >> (19-fogshift);
if (densityid >= 32) if (densityid >= 32)
{ {
densityid = 32; densityid = 32;
densityfrac = 0; densityfrac = 0;
} }
else else
densityfrac = z & 0x7FFFF; densityfrac = (z << fogshift) & 0x7FFFF;
} }
// checkme // checkme