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By Design
Fixed in 5.5.X, 5.6.X
Votes
5
Found in
5.5.0p4
Issue ID
898788
Regression
No
[Metal] Half-precision literal in HLSL is translated to float literal by Metal shader compiler
Reproduction steps:
1) Open the attached project (HLSLHalfLiteralBecomesMetalFloatLiteral.zip).
2) Open "MobileBloom.shader".
3) Observe the literal "half4(0.01h, 0.01h, 0.01h, 0.01h)" in "half4 fragBloom ( v2f_simple i ) : SV_Target".
4) Select "MobileBloom.shader".
5) Open drop-down menu of the "Compile and show code" button in the inspector window.
6) Tick "Custom:", then under "Custom:" tick "Metal".
7) Push the "Compile and show code" button to view View "Compiled-Hidden-FastBloom.shader" file.
8) Observe the literal "float4(0.00999999978, 0.00999999978, 0.00999999978, 0.00999999978)" in "fragment Mtl_FragmentOut xlatMtlMain".
This doesn't occur when compiling to OpenGL.
Actual behavior:
- float4(0.00999999978, 0.00999999978, 0.00999999978, 0.00999999978) is generated in the Metal shader.
Expected behavior:
- half4(0.01h, 0.01h, 0.01h, 0.01h) is generated in the Metal shader.
Reproduced with:
2017.1.0f3, 2017.1.0b1, 5.6.0f3, 5.5.0p4
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modrickthebrave
Dec 30, 2017 23:31
Just an FYI, I noticed that Metal can have a problem with a divide by a constant value with the h suffix added to the literal, I was able to work around this issue in converting byte values to half float values via this little util method:
// This method accepts 4 byte range input values and encodes them as a half4 vector
// that works properly on A7 class hardware. The issue with A7 devices is that
// there seems to be a compler bug or range issue with an operation like (x / 255.0h).
// What should be the same operation (x / 255.0) does not show the range problem on A7.
half4
encodeBytesAsHalf4(const ushort4 b4) {
return half4(b4.x/255.0, b4.y/255.0, b4.z/255.0, b4.a/255.0);
}
max_viorama
Aug 13, 2017 21:00
i stubmbled upon the same problem in unity 2017.1 any comments to when this will be fixed, or how to work around?
Chris-Hoo
Jul 17, 2017 13:36
Hope it could be fixed in 5.6.x !
Chris-Hoo
Jul 15, 2017 17:59
ah ha~~ liar!
this bug is not fixed in 2017.1