[ quesa-Bugs-905678 ] Texture filtering needs improvements

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Bugs item #905678, was opened at 2004-02-27 03:16
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Frank Condello (pox)
Assigned to: Nobody/Anonymous (nobody)
Summary: Texture filtering needs improvements

Initial Comment:
Here are the common filtering options in OpenGL.

// Nearest (Quesa's "kQATextureFilter_Fast" setting)
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MAG_FILTER, 
GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MIN_FILTER, 
GL_NEAREST);

// Linear (Quesa's "kQATextureFilter_Best/Mid" setting)
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MAG_FILTER, 
GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MIN_FILTER, 
GL_LINEAR);

// Bilinear (Not supported in Quesa)
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MAG_FILTER, 
GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MIN_FILTER, 
GL_LINEAR_MIPMAP_NEAREST);

// Trilinear (Not supported in Quesa)
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MAG_FILTER, 
GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,  GL_TEXTURE_MIN_FILTER, 
GL_LINEAR_MIPMAP_LINEAR);

Bilinear and Trilinear are commonly the only options most scene 
graphs/games support, yet neither is supported in Quesa.

Fixing this requires a few changes:

1). The "qualityFilter" member in the "TQ3CachedTexture" struct 
can't be defined as a single GLuint. It either needs min/max 
values, or should possibly be a "TQ3TextureFilter" name instead, 
that can be used as a hint when uploading the texture (but that 
means changing how and where the TQ3TextureFilter is translated 
into something OpenGL can use).

2). Mipmaps should be generated when not present in a texture 
shader for filter modes that require them. This will more closely 
match the QD3D behaviour. but also allow mips to be easily 
excluded by using a Fast/Mid filter setting.

3). Quesa needs additional TQ3TextureFilter names, and the 
meaning of existing names should be altered. I'd recommend 
something like this to maintain compatibility:
kQATextureFilter_Fast = Nearest
kQATextureFilter_Mid = Linear
kQATextureFilter_Best = Bilinear
kQATextureFilter_Trilinear = Trilinear


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