Wrong mipmap level calculation

[bylee20]

In osg::Texture::computeRequiredTextureDimensions(), the number of mipmap levels is miscalculated with NPOT texture.

OpenSceneGraph/src/osg/Texture.cpp

Lines 2077 to 2078 in f7d9053

	numMipmapLevels = 1;
	for(int s=1; s<width || s<height; s <<= 1, ++numMipmapLevels) {}

Suppose width = height = 100 here.
The for loop will be executed 7 times for s = 1 -> 2 -> 4 -> 8 -> 16 -> 32 -> 64.
Therefore, the computed numMipmapLevels is 8.

This value will be handed over to glTexStorage3D() here:

OpenSceneGraph/src/osg/Texture2DArray.cpp

Line 358 in b8416a7

extensions->glTexStorage3D(GL_TEXTURE_2D_ARRAY, osg::maximum(_numMipmapLevels,1), texStorageSizedInternalFormat, _textureWidth, _textureHeight, textureDepth);

Now, the OpenGL specification says:

GL_INVALID_OPERATION is generated if target is GL_TEXTURE_2D_ARRAY, GL_PROXY_TEXTURE_2D_ARRAY, GL_TEXURE_CUBE_MAP_ARRAY, or GL_PROXY_TEXTURE_CUBE_MAP_ARRAY and levels is greater than ⌊log2(max(width, height))⌋+1.

Since width = height = 100, log2(max(width, height))=6.xxx and ⌊log2(max(width, height))⌋+1=7 which is smaller than computed numMipmapLevels.
This results into GL_INVALID_OPERATION error.

I am not familiar with mimap concept, so I cannot say nothing about the calculation math.
However, at least, I can tell the computed value does not satisfy the OpenGL requirement here.