This topic contains 3 replies, has 4 voices, and was last updated by Joe Davis 6 years, 3 months ago.

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- October 22, 2010 at 6:33 pm #30324
In the PVRshell Texture in the trainingcourse 4, the texture is defined as

*TEX_SIZE = 128;**GLuint* pTexData1 = new GLuint[TEX_SIZE*TEX_SIZE];*

for (int i=0; i<TEX_SIZE; i++)

for (int j=0; j<TEX_SIZE; j++)

{

GLuint col = (255L<<24) + ((255L-j*2)<<16) + ((255L-i)<<8) + (255L-i*2);

if ( ((i*j)/8) % 2 ) col = (GLuint) (255L<<24) + (255L<<16) + (0L<<8) + (255L);

pTexData1[j*TEX_SIZE+i] = col;

}

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, TEX_SIZE, TEX_SIZE, 0, GL_RGBA, GL_UNSIGNED_BYTE, pTexData1);

delete [] pTexData1;The corresponding texture image looks like http://i51.tinypic.com/2j41y0m.jpgHowever, when I defined the same texture with the same RGB components in matlab and I got the texture image which is simlar asCan anyone give a hint why the textures images are different?Here is the matlab code*TEX_SIZE = 128;*

for i=1:TEX_SIZE

for j=1:TEX_SIZE

R = 255;

G = 255-j*2 ;

B = 255-i;

A = 255-i*2;

if (mod((i*j)/8,2))

R = 255;

G = 255;

B = 0;

A = 255;

end

pTexData(i,j,1)= R;

pTexData(i,j,2)= G;

pTexData(i,j,3)= B;

end

end

pTexData = uint8(pTexData);

imagesc (pTexData); figure(gcf)October 23, 2010 at 6:26 pm #34442Hi,

I don’t know anything about Matlab, but i and j in the Matlab version run from 1 to 128 instead of 0 to 127 in the C++ version; thus, the expression

*mod((i*j)/8,2)*will result in different values. You should use mod(((i-1)*(j-1))/8,2) in the Matlab version to take this into account.Also, in the C++ code, (i*j)/8 will be rounded down to the next smaller integer. I assume that Matlab doesn’t do this, thus you should use something like a “floor” function (I don’t know the Matlab function to round down, “floor” is just a guess), i.e.: mod(floor(((i-1)*(j-1))/8),2)

Also note that alpha is the highest-valued byte and red the lowest-valued; thus, your variable names are a bit confusing.

July 1, 2011 at 4:05 am #34443the sdk deals with either png or pvr files. jpegs need to be converted.

July 1, 2011 at 9:42 am #34444Hi cgp,

While we appreciate that your responses to several topics have been informative, we prefer not to resurrect topics that have been inactive for long periods of time. Instead, can you please create new topics to discuss these issues, or respond to topics that are still live (this way, it’s more likely that others in the community will benefit from your advice).

Thanks,

Joe