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Kitt3n

bumpmapping

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Hello,

I've been studying the iPhone 3d programming "Bumpy" example, which demonstrates how to do bumpmapping.
The example-code can be found here: http://examples.oreilly.com/9780596804831/readme.html

However I've noticed that the used image ( converted into a header-file in the example) appears to be strange.
The tangentspace.png texture (blue-ish) is converted into a header-file looks like below:


A32BIT TangentSpaceNormals[] = {

/* Header */
0x00000034, /* dwHeaderSize */
0x00000400, /* dwHeight */
0x00000200, /* dwWidth */
0x00000000, /* dwMipMapCount */
0x00010415, /* dwpfFlags */
0x00180000, /* dwDataSize */
0x00000018, /* dwBitCount */
0x00ff0000, /* dwRBitMask */
0x0000ff00, /* dwGBitMask */
0x000000ff, /* dwBBitMask */
0x00000000, /* dwAlphaBitMask */
0x21525650, /* dwPVR */
0x00000001, /* dwNumSurfs */

/* Data */
0x7F7FFF7F,0xFF7F7FFF,0x7FFF7F7F,...
RRBBGGRR, GGRRBBGG, BBGGRRBB,



So if I interpret that correctly, it looks like the "Green" channel is always 0xFF - i.e. it is a green-ish colored texture...
To prove it, I changed the shader to not do any normal-mapping, but instead output the color directly:


void main(void)
{

// Extract the perturbed normal from the texture:
highp vec3 tangentSpaceNormal = texture2D(Sampler, TextureCoord).yxz * 2.0 - 1.0;
// ... ... ...



and replace replace it with a "Texture2D (Sampler, TextureCoord).yxz and gl_FragColor = vec4(texel, 1);"
but that gives I get a red-tinted texture.
If I take XYZ instead, it's the green (like to be expected from the texture-data up above..)

So it's really confusing... where is my blue-ish normal-map texture? Why are the color channels mixed up?
Any clues anyone what is going on here?

Thanks for any help!

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