On Tue, Nov 18, 2014 at 8:54 AM, Roland Scheidegger <srol...@vmware.com> wrote: > Am 18.11.2014 um 05:03 schrieb Ilia Mirkin: >> For values above integer accuracy in floats, val - floor(val) might >> actually produce a value greater than 1. For such large floats, it's >> reasonable to be imprecise, but it's unreasonable for FRC to return a >> value that is not between 0 and 1. >> >> Signed-off-by: Ilia Mirkin <imir...@alum.mit.edu> >> --- >> src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp >> b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp >> index 41b91e8..e5b767f 100644 >> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp >> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp >> @@ -2512,7 +2512,8 @@ Converter::handleInstruction(const struct >> tgsi_full_instruction *insn) >> src0 = fetchSrc(0, c); >> val0 = getScratch(); >> mkOp1(OP_FLOOR, TYPE_F32, val0, src0); >> - mkOp2(OP_SUB, TYPE_F32, dst0[c], src0, val0); >> + mkOp2(OP_SUB, TYPE_F32, val0, src0, val0); >> + mkOp1(OP_SAT, TYPE_F32, dst0[c], val0); >> } >> break; >> case TGSI_OPCODE_ROUND: >> > > I don't understand the math behind this. For any such large number, as > far as I can tell floor(val) == val and hence the end result ought to be > zero. Or doesn't your floor work like that?
I could be thinking about this backwards, but let's say that floats lose integer precision at 10.0. And I do floor(12.5)... normally this would be 12.0, but since that's not exactly representable, it might actually be 11.0. (Or would it be 11.9987? I didn't consider that possibility...) And then 12.5 - 11 = 1.5. Or am I thinking about this backwards? I guess ideally I'd do something along the lines of y = x - floor(x); return y - floor(y). That seems like it might be more accurate... not sure. _______________________________________________ Nouveau mailing list Nouveau@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/nouveau