HLSL handling cases where texture isn't loaded

kodde · Aug 2010

Hey guys,

I'm following Ben Clowards HLSL DVDs and so far I'm at DVD2 at the Specular Lighting chapter.

Here's a question I've been thinking about for a while. In my experience so far when working with shaders (both CGFX in Mental Mill and HLSL with FX Composer) when you have a texture sampler and you don't load a texture it's value defaults to 0 (right?).

As it is now in the DVD I'm implementing Specularity with both a texture, a specular color value and a gloss value. These are all later on multiplied by each other in the end. If I do not load any texture at all this breaks the whole feature since it's value will be 0. So what if I want to give the user the possibility not to load a specular texture at all to have the same uniform amount and color all over the model?

Is there a way to check if a texture has been loaded? Couldn't I then with a simple if statement set this color to 1 if no texture is loaded?

Thanks.

SyncViewS · Aug 2010

Hi kodde, as far as I know, you cannot make the code check if a texture has been loaded. The workaround I adopted, and I guess is pretty standard, is to use a checkbutton widget in the UI. If it is checked the texture is taken into account, otherwise do the standard calculations without considering it.

bool specularMapEnabled
<
    //string UIType = "CheckButton";
    string UIName = "Specular Map Enabled";
> = false;

// Then in the PixelShader

    if (specularMapEnabled)
    {
        // Something like this
        float4 SpecularMapColor = tex2D(specularMapSampler, input.texCoord);
        // ...
    }
    else
    {
        // ...
    }

kodde · Aug 2010

Thanks SyncViewS.

Yeah I used that very same workaround when I was working with Mental Mill. Just thought maybe it could be handled more nicely

Xoliul · Aug 2010

You'd need to have your application (the c++ code) handle this. It's quite doable if you have access to the shader loading code, I remember I did something similar back when I still programmed c++. Unfortunately that's not really a possibility with most applications.

KikiAlex · Aug 2010

You can use a one instruction line :

 diffuseColor = tex2D(g_TopSampler,IN.UV0.xy);

diffuseColor = (diffuseColor != 0) ? diffuseColor : float4(1,1,1,1);

the ?: translates to 1 asm instruction

Xoliul · Aug 2010

What if you really have pure black in your diffuse then ? That's gonna look really weird...

HLSL handling cases where texture isn't loaded

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