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mrfusion

OpenGL texture mapping problem (based on Opengl Game Programming book)

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mrfusion    122
I''m working with the first texture mapping program from the book OpenGL Game Programming (Chapter 8). It''s the one where you map a checker pattern onto a cube. The example works as long as I use the checker.bmp file that came on the CD. If I do anything - and I mean ANYTHING to the bitmap file, the program crashes when it tries to load the texture. If I open the checker.bmp file in photoshop and save it out again without touching it (as a windows bmp file), it doesn''t work. I''ve also tried loading the original file into xnview and saving it out again, the program still crashes. I get an error that says the memory could not be "read". I''m using dev-c++ to compile. Like I said the program right out of the book works and runs fine, I just can''t get it to read any other bmp files. Is this some kind of variation on the bmp format that I don''t know about? Let me know if you''d like me to upload any files if you need more information. Thanks for any help. Tom

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mrfusion    122
I''m pretty darn sure I saved it out exactly the same way.
I''ve checked their properties and as far as I can tell, they are the same. Same size, same bit depth, same compression(none).

Maybe I could upload the two images somewhere if someone wants to look at them. (Or I could zip the whole project up with the images for a more complete examination).

Tom


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Nemesis2k2    1045
Hmmm. This is not really relevant, but which version of the programming guide do you have? I have 1.2 third edition, and in this version of the source the checkered image was generated at runtime.

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Saandman    160
I some times have this problem, too.. Not specific to OGLGP though! I also experienced this problem while reading TOTWGPG a really long time ago.

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mrfusion    122
I understand about makeing texture the power of 2, but my problem is that if I just open the original texture and save it out again (as the same kind of file) the program crashes.

Mongo very confused.......

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Myopic Rhino    2317
The problem is that our bitmap loading code wasn''t really robust. The problem is with this line:

bitmapImage = (unsigned char*)malloc(bitmapInfoHeader->biSizeImage);
For an uncompressed RGB image, it is valid for biSizeImage to be zero. In this case, you should use a combination of the biWidth, biHeight, and biBitcount members to determine how many bytes you really need for the bitmap. e.g.

  
// allocate enough memory for the bitmap image data

int imageSize = bitmapInfoHeader->biSizeImage;
if (imageSize == 0)
imageSize = bitmapInfoHeader->biWidth * bitmapInfoHeader->biHeight * bitmapInfoHeader->biBitCount/8;
bitmapImage = (unsigned char*)malloc(imageSize );

...
// read in the bitmap image data

fread(bitmapImage, 1, imageSize, filePtr);

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