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Specializing Interfaces (Direct3D 11)

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ID3DX11EffectVariable has a number of methods for casting the interface into the particular type of interface you need. The methods are of the form AsType and include a method for each type of effect variable (such as AsBlend, AsConstantBuffer etc..)

For example, suppose you have an effect with two global variables: time and a world transform.

float    g_fTime;
float4x4 g_mWorld;

Here is an example that gets these variables:

ID3DX11EffectVariable* g_pVariable;
ID3DX11EffectMatrixVariable* g_pmWorld;
ID3DX11EffectScalarVariable* g_pfTime;

g_pVariable = g_pEffect11->GetVariableByName("g_mWorld");
g_pmWorld = g_pVariable->AsMatrix();
g_pVariable = g_pEffect11->GetVariableByName("g_fTime");
g_pfTime = g_pVariable->AsScalar();

By specializing the interfaces, you could reduce the code to a single call.

g_pmWorld = (g_pEffect11->GetVariableByName("g_mWorld"))->AsMatrix();
g_pfTime = (g_pEffect11->GetVariableByName("g_fTime"))->AsScalar();

Interfaces that inherit from ID3DX11EffectVariable also have these methods, but they have been designed to return invalid objects; only calls from ID3DX11EffectVariable return valid objects. Applications can test the returned object to see if it is valid by calling ID3DX11EffectVariable::IsValid.

Effects (Direct3D 11)