floating point division by zero at line warning in Unity 5.1

Unity Engine
1

I’m getting ‘floating point division by zero’ error in all of my old Legacy Surface shaders with rim lighting at this line:
half rim = 1.0 - saturate(dot(normalize(IN.viewDir), o.Normal));

They were fine in Unity 5.0.1. Did something changed?

1 Like
2

It wasn’t fine before; warnings are displayed properly now (bugfix). You should update the shaders not to generate the warning, since they won’t necessarily work properly on all GPUs.

–Eric

3

yeah, but this code is from official page: Unity - Manual: Surface Shader examples see rim lighting example

4

Apparently that code hasn’t been updated/fixed yet.

–Eric

5

Well, seems like getting rid of normalize here fixes warning (without producing any visual difference):

half rim = 1.0 - saturate(dot(IN.viewDir, o.Normal));

6

That would imply that IN.viewDir was a zero vector, which it should never be, perhaps figure out why that’s happening before removing a normalise.

7

That is a temporary solution (to get rid of warnings), but I think viewDirection should never happen to be unnormalized in the first place

8

i’m getting the same error with the rim shader example from the docs, and i cannot seem to find a working solution.
how would i go about fixing this?

9

Since this is a compile time error I assume its not due to viewDirection being a zero vector, or any other vector being zero, but that the compiler cannot in some cases guarantee the input would never cause a divide by zero error and thus gives the warning.

If you check through Unity’s built-in shaders you’ll find all instances of cases where this would get a warning ( at least in standard shader code) now replace ‘normalize()’ with the following.

inline half3 Unity_SafeNormalize(half3 inVec)
{
    half dp3 = max(0.001f, dot(inVec, inVec));
    return inVec * rsqrt(dp3);
}

This function can be found in ‘UnityStandardBRDF.cginc’ and thus you can as of Unity 5.1 ( maybe earlier versions?) simply replace ‘Normalize()’ with ‘Unity_SafeNormalize()’.

6 Likes
10

nice, this works great!

11

I did that. It removed the warning. Great !

I then put back Normalize(), and the warning didn’t come back. I’m sure it’s the expected behavior… :stuck_out_tongue:

12

Similarly, the following line is now also generating a warning.

half2 screenUV = IN.screenPos.xy / IN.screenPos.w;

This line is a somewhat common practice in surface shader screen effects, like…

        struct Input
        {
            float2 uv_MainTex;
            float4 screenPos;
        };
        void surf (Input IN, inout SurfaceOutput o)
        {
            // Get the screen space position of the current pixel
            half2 screenUV = IN.screenPos.xy / IN.screenPos.w;

           ...
        }

Is there an alternative way of writing it? I’ve also tried ComputeScreenPos() and ComputeGrabScreenPos() from UnityCG.gcinc but the result is way off…

Or should I just do a max() like Unity_SafeNormalize() does in order to easy the compiler?

13

@Manny_Calavera : I know it’s been a while, but did you ever find a solution? If so, could you share?

14

Sorry, I haven’t found a solution. The warning is still there haunting me from time to time… :frowning:

15

A word of caution… I switched all of our shaders to Unity_SafeNormalize when this first cropped up but found it cross compiled to assorted platforms oddly. normalize on its own should be fine, every gpu probably has a normalize built in to it.

16

I have the same problem as @Manny_Calavera .

17

I see it is an old thread, but did you find any solution for this issue? I am receiving this exact warning on a shader. It is the exact line:

half2 screenUV = IN.screenPos.xy / IN.screenPos.w;