Cubemap upside down.

Graphics and GPU Programming Programming

Started by JackOfAllTrades June 02, 2011 02:19 AM

6 comments, last by Yours3!f 12 years, 11 months ago

109

Author

June 02, 2011 02:19 AM

[attachment=2607:Untitled.jpg]

Not sure if you can tell form the image but the horizontal faces of my cube map are upside down. However, the up and down faces are correct. How can I fix this without flipping the image files upside down?

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bluntman

255

June 03, 2011 12:54 PM

Not sure that you can. Image files are generally stored with the origin at the top left of the image, where as OpenGL treats the origin as the bottom left of the image.

Planet rendering.

V-man

813

June 03, 2011 03:06 PM

There is 2 ways. Fix the image or fix your texcoords.
The cubemaps in GL follow the Direct3D convention of left-handed. This means that the +z and -z faces are switched. I'm not sure if that is your problem.

Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);

JackOfAllTrades

109

Author

June 03, 2011 03:22 PM

There is 2 ways. Fix the image or fix your texcoords.
The cubemaps in GL follow the Direct3D convention of left-handed. This means that the +z and -z faces are switched. I'm not sure if that is your problem.

GL cube mapping is not the same as DirectX and I should know since I am converting my rendering pipeline from directx to opengl.

Want an easy to use open source 3D video game SDK that handles Physics, Graphics, Audio, and AI right out of the box?

21st Century Moose

13,459

June 03, 2011 03:31 PM

TGAs? Check byte 17 of the header, if bit 0x20 is set you need to flip it when loading.

Direct3D has need of instancing, but we do not. We have plenty of glVertexAttrib calls.

JackOfAllTrades

109

Author

June 03, 2011 03:43 PM

TGAs? Check byte 17 of the header, if bit 0x20 is set you need to flip it when loading.

No, PNG but if I flip all images the top and bottom won't line up with the sides.

Want an easy to use open source 3D video game SDK that handles Physics, Graphics, Audio, and AI right out of the box?

dpadam450

2,403

June 03, 2011 06:54 PM

[color="#1C2837"]GL cube mapping is not the same as DirectX and I should know since I am converting my rendering pipeline from directx to opengl. [/quote]
[color="#1C2837"]Huh? The coordinates for cube mapping are DX style as V-Man said so I don't know what you mean in your above statement by not being the same. Did you try loading them into opposite coordinates? Pretty sure this is your issue.

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Yours3!f

1,534

June 04, 2011 07:30 AM

first I'd suggest playing around with the image files flipping them etc., if you get them right then you can write down which was flipped and set the texcoords accordingly. For me I think I had to flip all of them upside down, but I didn't bother dealing with the texcoords...

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