glsl infinity constant

Question

Does GLSL have any pre-defined constants for +/-infinity or NaN? I'm doing this as a workaround but I wonder if there is a cleaner way:

// GLSL FRAGMENT SHADER
#version 410

<snip>

const float infinity = 1. / 0.;

void main ()
{
    <snip>
}

I am aware of the isinf function but I need to assign infinity to a variable so that does not help me.

Convoke

Using infinity saves a lot of logic in my code: <snip> float t0 = (d >= 0.) ? t : infinity; <snip> float t1 = (d >= 0.) ? t : infinity; t = min (t0, t1); <snip> – Convoke

I believe choosing a large enough value (based on your application) should easily do the trick. Say for example 1e20 – Hydrops

Using infinity seems to work fine, I was just wondering if there was a pre-defined constant for it. While I'm at it, are there constants for other things like FLT_MAX FLT_EPSILON etc the way there are in C? – Convoke

Answer 1

Like Nicol mentioned, there are no pre-defined constants.

However, from OpenGL 4.1 on, your solution is at least guaranteed to work and correctly generate an infinite value.

See for example in glsl 4.4:

4.7.1 Range and Precision

...

However, dividing a non-zero by 0 results in the appropriately signed IEEE Inf: If both positive and negative zeros are implemented, the correctly signed Inf will be generated, otherwise positive Inf is generated.

Be careful when you use an older version of OpenGL though:

For example in glsl 4.0 it says:

4.1.4 Floats

...

Similarly, treatment of conditions such as divide by 0 may lead to an unspecified result, but in no case should such a condition lead to the interruption or termination of processing.

Shifflett

Answer 2

There are no pre-defined constants for it, but there is the isinf function to test if something is infinity.

While I'm at it, are there constants for other things like FLT_MAX FLT_EPSILON etc the way there are in C?

No, there are not.

Upstairs

Answer 3

This might work?

const float pos_infinity = uintBitsToFloat(0x7F800000);
const float neg_infinity = uintBitsToFloat(0xFF800000);

"If the encoding of a floating point infinity is passed in parameter x, the resulting floating-point value is the corresponding (positive or negative) floating point infinity"

Gratuitous