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Fix: Alpha test without blend

by Tom Spilman · in Torque Game Engine Advanced · 03/28/2007 (1:05 pm) · 5 replies

Here is a little change to MatInstance::setupPass() which allows alpha test materials without alpha blending:

if( mMaterial->translucent )
   {
      GFX->setAlphaBlendEnable( mMaterial->translucentBlendOp != Material::None ); // CHANGE!
      if ( mMaterial->translucentBlendOp != Material::None ) // CHANGE!
         mMaterial->setBlendState( mMaterial->translucentBlendOp );   
      GFX->setZWriteEnable( mMaterial->translucentZWrite );
      GFX->setAlphaTestEnable( mMaterial->alphaTest );
      GFX->setAlphaRef( mMaterial->alphaRef );
      GFX->setAlphaFunc( GFXCmpGreaterEqual );
      
      // set up register combiners
      GFX->setTextureStageAlphaOp( 0, GFXTOPModulate );
      GFX->setTextureStageAlphaOp( 1, GFXTOPDisable );
      GFX->setTextureStageAlphaArg1( 0, GFXTATexture );
      GFX->setTextureStageAlphaArg2( 0, GFXTADiffuse );
   }

I think this change shouldn't break anybody and still allow the previous behavior.

EDIT: Added a little state change optimization by avoiding the call to set the blend op if the blend op is disabled.
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Tom is a programmer and co-owner of Sickhead Games, LLC.

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    Torque Owner Brian Ramage
    Black Jacket Games
    #1
    03/29/2007 (11:44 am)
    OK, it's in, but missed the cutoff for 1.01. You might want to look into the HLSL "clip" command - it may give better performance than an alpha test, not sure.

    Associate Tom Spilman
    Sickhead Games
    #2
    03/29/2007 (11:51 am)
    No prob... i figured that would happen.

    In this case its a material on a standard DTS... so i don't have access to the HLSL like that.

    Torque Owner Andy Hodges
    #3
    03/31/2007 (3:59 am)
    Thanks Tom. This works great!

    Associate Tom Spilman
    Sickhead Games
    #4
    06/01/2007 (9:19 pm)
    Found another little bug with this feature in Material::onAdd()... 

    if( translucentBlendOp >= NumBlendTypes || translucentBlendOp < 0  ) // Changed == 0 to < 0
   {
      Con::errorf( "Invalid blend op in material: %s", getName() );
      translucentBlendOp = LerpAlpha;
   }

    ... this little test was making materials with translucentBlendOp set to "None" load as LerpAlpha.

    Torque 3D Owner Mark Dynna
    #5
    06/04/2007 (3:17 pm)
    Now that makes sense! I was wondering why "None" was provided as an "option" yet gave an error when it was used. Thanks Tom.