death by glGenTextures(), with TGA

[sealfin]

I've been slowly going through the GLUT ports of NeHe's tutorials, recoding/extending them in Carbon to comprehend better the mechanics behind them; but I've hit a wall with tutorial 6 : a recoding of the TGA texture loader originally coded by Anthony Parker kills the app every time the glGenTextures() statement is reached (or on any statements past it if glGenTextures is commented out) - any suggestions would be appreciated! thanks!


p.s. the relevant bit is right at the bottom - sorry!



typedef struct sSkin
{
GLubyte x,
y,
depth,
*skin;
GLuint id;
} tSkin;


...



//
//
signed int ISkinFile_tga(tSkin *outSkin,
char *srcFilePath)
{
GLubyte TGAHeader[12],
TGAComparisonHeader[12] = {0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0},
TGAFileHeader[6],
bytesPerPixel;
GLuint skinMemorySize,
swap,
depthType = GL_RGBA;
FILE *file;
unsigned int loop;


if((file = fopen(srcFilePath, "rb")) == NULL)
return kErr_FileOpenFailed;
if(fread(TGAHeader, 1, sizeof(TGAHeader), file) != sizeof(TGAHeader))
return kErr_TGAHeaderSizeWrong;
if(memcmp(TGAHeader, TGAComparisonHeader, sizeof(TGAHeader)) != 0)
return kErr_TGAHeaderContentWrong;
if(fread(TGAFileHeader, 1, sizeof(TGAFileHeader), file) != sizeof(TGAFileHeader))
return kErr_TGAFileHeaderSizeWrong;
if((outSkin->x = TGAFileHeader[1]*256+TGAFileHeader[0]) <= 0)
return kErr_SkinXZeroOrNegative;
if((outSkin->y = TGAFileHeader[3]*256+TGAFileHeader[2]) <= 0)
return kErr_SkinYZeroOrNegative;
if(((outSkin->depth = TGAFileHeader[4]) != 24) && (outSkin->depth != 32))
return kErr_SkinWrongDepth;
bytesPerPixel = outSkin->depth/8;
skinMemorySize = outSkin->x*outSkin->y*bytesPerPixel;
outSkin->skin = (GLubyte *)malloc(skinMemorySize);
if(fread(outSkin->skin, 1, skinMemorySize, file) != skinMemorySize)
return kErr_SkinMemorySizeDidNotEqualReservedMemorySize;
for(loop = 0;
loop < (int)skinMemorySize;
loop += bytesPerPixel)
{
swap = outSkin->skin[loop];
outSkin->skin[loop] = outSkin->skin[loop+2];
outSkin->skin[loop+2] = swap;
}
fclose(file);


// dies here (or at any other statement onwards if I comment this out) : I've tried _lots_ of variartions on this statement, with no difference.
glGenTextures(1, &outSkin[0].id);
glBindTextures(GL_TEXTURES_2D, outSkin[0].id);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
if(outSkin[0].depth == 24)
depthType = GL_RGB;
glTexImage2D(GL_TEXTURE_2D, 0, depthType, outSkin[0].x, outSkin[0].y, 0, depthType, GL_UNSIGNED_BYTE, outSkin[0].skin);
return 0;
}

[codemattic]

I dont think its endian issues since you are dealing with all glubytes.

what I would do is printf or NSLog (or use the debugger) to look at all the variables right before you get to:

outSkin->skin = (GLubyte *)malloc(skinMemorySize);

so print out skinMemorySize, bytesPerPixel, outSkin->depth, outSkin->x, outSkin->y - etc.

Im guessing that something is screwing up skinMemorySize and you arent allocating enough memory and then when you go swapping bytes you are actually screwing with your code and not the picture data.

[OneSadCookie]

It could also be that this function is being called before a valid OpenGL context has been created. Windows is far more relaxed about such issues than the Mac.

[sealfin]

thanks for the suggestion codemattic, but all those return's output to a log file, so I know it isn't them (plus I've commented out one at a time every 'if() return' error pair.)

um, I've just moved a few lines, with the result that I now get a white screen but no crash; but I'm certain what I've changed should have made no difference whatsoever, just made the code more readable... too late to do any more right now.

[kainsin]

I've had this problem before as well. Just as OneSadCookie said, make sure you have an OpenGL context all set up before calling glGenTextures. There are also a couple other functions that will crash the application if no context is created.

[sealfin]

problem is, I've already created an AGLContext (and as I've posted above, I've got past the 'crash at glGenTextures()' problem, and I'm now at the 'textures are all white' problem instead :rolleyes: )

[OneSadCookie]

glEnable(GL_TEXTURE_2D) usually fixes that one for me ;)

If not, it's most likely to be some kind of VRAM issue -- what sort of context are you creating (color size? depth size?), what size textures are you creating, and what video card are you running on?

[sealfin]

(lots of self-derisive laughter...)

yes, I'd forgotten to glEnable(); thanks OneSadCookie! (still can't believe I overlooked that...:rolleyes: )