Comments on: 20. OpenGL MipMap Generation http://www.swiftless.com/tutorials/opengl/mipmap_generation.html Game Programming and Computer Graphics Tutorials Wed, 01 Feb 2012 09:19:36 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Geometrian http://www.swiftless.com/tutorials/opengl/mipmap_generation.html/comment-page-1#comment-1519 Geometrian Wed, 09 Feb 2011 01:11:10 +0000 http://swiftless.com/wordpress/?p=185#comment-1519 Right, so this line: glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_LINEAR ); . . . will give undefined behavior. Right, so this line:
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_LINEAR );
. . . will give undefined behavior.

]]> By: Swiftless http://www.swiftless.com/tutorials/opengl/mipmap_generation.html/comment-page-1#comment-1518 Swiftless Wed, 09 Feb 2011 00:47:21 +0000 http://swiftless.com/wordpress/?p=185#comment-1518 Hi Geometrian, I think we got our wires crossed, when you first mentioned magnification I was thinking as I described in my response (as an effect), I now understand where you are coming from (magnification as in the magnification level of the texture, not magnification as in the effect), and agree totally. Cheers, Swiftless Hi Geometrian,

I think we got our wires crossed, when you first mentioned magnification I was thinking as I described in my response (as an effect), I now understand where you are coming from (magnification as in the magnification level of the texture, not magnification as in the effect), and agree totally.

Cheers,
Swiftless

]]> By: Geometrian http://www.swiftless.com/tutorials/opengl/mipmap_generation.html/comment-page-1#comment-1516 Geometrian Tue, 08 Feb 2011 15:33:45 +0000 http://swiftless.com/wordpress/?p=185#comment-1516 Magnification doesn't work that way. Mipmapping is designed to work only in minification. This is why, according to the spec, no mipmapping is defined for mag filters. See (http://www.opengl.org/sdk/docs/man/xhtml/glTexParameter.xml). While mipmap levels can be blown up for the purposes you describe, it can't be done simply by setting the mag filter to a mipmap. You'd need to select the actual level when you draw it in the fullscreen pass. Magnification doesn’t work that way. Mipmapping is designed to work only in minification. This is why, according to the spec, no mipmapping is defined for mag filters. See (http://www.opengl.org/sdk/docs/man/xhtml/glTexParameter.xml).

While mipmap levels can be blown up for the purposes you describe, it can’t be done simply by setting the mag filter to a mipmap. You’d need to select the actual level when you draw it in the fullscreen pass.

]]> By: Swiftless http://www.swiftless.com/tutorials/opengl/mipmap_generation.html/comment-page-1#comment-1515 Swiftless Tue, 08 Feb 2011 09:13:51 +0000 http://swiftless.com/wordpress/?p=185#comment-1515 Hi Geometrian, You're right, you can leave the mag filter as linear as this doesn't make sense to set. However it half makes sense in the case of magnification for effects such as bloom, where you take the smaller mipmap and apply it to a shape too large on purpose to get a blurry effect. I see this as magnification, albeit a skewed interpretation :P Cheers, Swiftless Hi Geometrian,

You’re right, you can leave the mag filter as linear as this doesn’t make sense to set.

However it half makes sense in the case of magnification for effects such as bloom, where you take the smaller mipmap and apply it to a shape too large on purpose to get a blurry effect. I see this as magnification, albeit a skewed interpretation :P

Cheers,
Swiftless

]]> By: Geometrian http://www.swiftless.com/tutorials/opengl/mipmap_generation.html/comment-page-1#comment-1514 Geometrian Mon, 07 Feb 2011 17:28:47 +0000 http://swiftless.com/wordpress/?p=185#comment-1514 Setting the mipmap flag in the mag filter will have undefined results. Using mipmapping for magnification doesn't make sense. Setting the mipmap flag in the mag filter will have undefined results. Using mipmapping for magnification doesn’t make sense.

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