Fix bug 368: Specify the Levels parameter of CreateCubeTexture and CreateTexture correctly.

Fix bug 368: Specify the Levels parameter of CreateCubeTexture and CreateTexture correctly.

This fixes ATS test cases 38840,38841 (while making sure that 44095, 44096, 44097, 44100, 44101, 44102 still work)

The Direct3D spec for the 'Levels' parameter of IDirect3DDevice9::CreateCubeTexture (and IDirect3DDevice9::CreateTexture) says: "If this is zero, Direct3D will generate all cube texture sublevels down to 1x1 pixels for each face for hardware that supports mipmapped cube textures."

The 'levels' parameter can be 0 (which means "generate all texture sublevels") or a non-zero value for the actual number of levels to create (often 1 if mapmapping is disabled).
But 1x1 and 2x2 mipmapped textures are not supported, so textures with these dimensions will actually create a 4x4 texture, and set mLodOffset to 2 or 1 respectively so that the level index can be offset as appropriate.
There is only one special case (for textures with dimensions smaller than 4): when levels=1 and the texture is 2x2, it is unnecessary to create all miplevels, since the 1x1 texture will never be used.  For all other cases, all miplevels must be generated even though the upper ones will be unused in order to generate the lower ones.  If 'levels' is zero all miplevels must always be generated.
It's important to preserve the special case, to ensure that attempting to access the non-existant level produces the correct error.
So if 'levels' is zero, the 'Levels' parameter should always be zero, otherwise it's the sum of 'levels + mLodOffset'

Also, the calls to 'creationLevels' from the TextureCubeMap methods were not quite right.  Passing a zero for the second parameter causes this API to always fail, since '0' is not a power of two.  There is already a version of 'creationLevels' that takes just one parameter and works correctly, so just deleting the extra parameter fixes this problem.

BUG=https://code.google.com/p/angleproject/issues/detail?id=368

TEST=Run test cases 38840, 38841, 44095, 44096, 44097, 44100, 44101, 44102 in http://ats.macromedia.com/Players/ATS/ATS10AS3/Staging/ATS.html?dynamicXML=false&wmode=direct&section=Manual&xmlSetURL=http://fpqa.macromedia.com/crospepperbuild/XMLSets/ATS10AS3ManualPepper.xml

Review URL: https://codereview.appspot.com/6492098

[sminns, 2012-09-10 18:50:00]

For your edification, here are all the cases:

1) If levels=1, and the texture is 1x1, we'll really create a 4x4 texture with 3
miplevels (the top two will be unused, but we have to create them all to get the
bottom one (that is used)).  So level=0 will get offset by mLodOffset=2 and
therefore access level 2 (the 1x1 mipmap).  The 2x2 mipmap is level 1 and the
4x4 mipmap is level 0 (both are unused).
	Levels = levels + mLodOffset;

2) If levels=2, and the texture is 2x2, we'll really create a 4x4 texture with 3
miplevels (the top one will be unused, but we have to create them all to get the
bottom two (that are used)).  So level=0 will get offset by mLodOffset=1 and
therefore access level 1 (the 2x2 mipmap).  level=1 will get offset by
mLodOffset=1 and therefore access level 2 (the 1x1 mipmap).  The 4x4 mipmap is
level 0 and is unused.
	Levels = levels + mLodOffset;

3) If levels=1, and the texture is 2x2, we'll really create a 4x4 texture with 2
miplevels (the top one will be unused, but we need to create 2 miplevels to get
the middle one.  The bottom one will be unused and so does not need to be
created).  So level=0 will get offset by mLodOffset=1 and therefore access level
1 (the 2x2 mipmap).  The 4x4 mipmap is level 1 and is unused).  level=1 is
illegal.
	Levels = levels + mLodOffset;

4) If levels=0, and the texture is 2x2, we'll really create a 4x4 texture with 3
miplevels (the top one will be unused, but we have to create them all to get the
bottom two (that are used)).  So level=0 will get offset by mLodOffset=1 and
therefore access level 1 (the 2x2 mipmap).  level=1 will get offset by
mLodOffset=1 and therefore access level 2 (the 1x1 mipmap).  The 4x4 mipmap is
level 0 and is unused.
	Levels = 0;

5) If levels=0, and the texture is 1x1, we'll really create a 4x4 texture with 3
miplevels (the top two will be unused, but we have to create them all to get the
bottom one (that is used)).  So level=0 will get offset by mLodOffset=2 and
therefore access level 2 (the 1x1 mipmap).  The 2x2 mipmap is level 1 and the
4x4 mipmap is level 0 (both are unused).
	Levels = 0;

6) If levels=0, and the texture is 4x4, we'll really create a 4x4 texture with 3
miplevels (all of which are used).  So level=0 will get offset by mLodOffset=0
and therefore access level 0 (the 4x4 mipmap).  The 2x2 mipmap is level 1 and
the 1x1 mipmap is level 2.
	Levels = 0;
	
7) If levels=2, and the texture is 4x4, we'll really create a 4x4 texture with 2
miplevels (both of which are used).  So level=0 will get offset by mLodOffset=0
and therefore access level 0 (the 4x4 mipmap).  The 2x2 mipmap is level 1. 
level=2 is illegal.
	Levels = levels + mLodOffset;

8) If levels=1, and the texture is 4x4, we'll really create a 4x4 texture with 1
miplevel.  So level=0 will get offset by mLodOffset=0 and therefore access level
0 (the 4x4 mipmap).  All other levels are illegal.
	Levels = levels + mLodOffset;

Correct algorithm: Levels = levels ? levels + mLodOffset : 0;

[dgkoch, 2012-09-11 20:25:33]

On 2012/09/11 13:57:20, dgkoch wrote:

LGTM.  Don't forget to bump version.h as well.