Shader Properties : no bool support?

Unity Engine
1

From what i can find there there’s no support for bool input for shaders? I know i could workaround this but it will be very unintuitive to users to use a float or something similar to represent a bool. Am i missing something? Why is there not a simple bool one that maps to a checkbox?

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2

Nope, you’ll have to use a float (or a range) to toggle between 1 and 0.

3

Properties were designed as graphical wrappers for uniform variables of shaders. There is no support for boolean uniform variables, thus, there are no properties for them.

Without doubt boolean uniform variables and in particular checkbox properties would be very useful and for some later version of Unity (after 4.0) they will be supported but not now.

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4

If the bool doesn’t change during runtime, you can use a preprocessor directive:

#pragma multi_compile FEATURE_OFF FEATURE_ON

In your shader you can then do:

#if FEATURE_ON
//Some code here.
#endif

To get the bool on the Inspector as a checkbox, use a MaterialEditor script. More information here:

Edit:
Even better, use a material property drawer:

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5

try this on your shader properties:

[MaterialToggle] _isToggled(“isToggle”, Float) = 0

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Or use #pragma shader_feature instead of #pragma multi_compile, then only the keywords that are used will be generated. mutli_compile will generate every permutation if it’s used or not. However multi_compile can be used on a shader and allow keywords to be changed during runtime.

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7

Here’s a great example of setting up and using Boolean properties in shaders with Material Property Drawers:

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8

Why would you use a Float for a boolean instead of Int?

9

You can use INT on Shader Property, but it will be a float (or half) inside the shader CGPROGRAM, which is the code that will be sent to the graphics card.
So there is no benefit to use float or int on the Shader Property…
Shader Property is just a map for values from Unity Engine to send it to Shader CGPROGRAM

10

That’s not quite right.

There are two reasons why you’d use a Float instead of an Int for the property.

First is because numerical material properties are always floats. Even though the properties have the option to define it as an Int, Unity ignores that and the property is always a float. Why? No idea! But that’s how it is. Material properties are always floats, unless they’re textures.

Second, is when you’re using a [Toggle] material property drawer it doesn’t matter what the value is since it’s never used by the shader. It’s just a placeholder for the inspector to use to allow the user to toggle a keyword on or off.

But that sounds like what @i9mobile said was mostly correct, and I said it wasn’t right. Well, that’s because inside the CGPROGRAM you can totally have it be a float, or int, or uint, and it absolutely matters to the shader. Just because the material itself can’t do anything but floats doesn’t mean the shader itself can’t. Unity is smart about looking at how it’s defined in the shader code and converts the value to whatever type is needed when sending it to the GPU. It just doesn’t matter in this particular case because the numerical value isn’t directly being use.

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11

That’s good to know… thanks for the explanation!

12

Hey I have another quick question… what is the difference between Float and float?

I’ve seen some shaders with:

_AnimLen("Animation length in seconds", Float) = 0

and others with:

_AnimLen("Animation length in seconds", float) = 0

I had trouble googling it because google is case insensitive and none of my other keywords narrowed the results to an answer.

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The difference is Float is what the documentation says to use, and float would produce an error that was probably too cryptic for most people to understand what it meant, so they made it work too.

Basically, there isn’t a difference.

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14

Thanks yet again bgolus. I owe you beer.

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