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qxsl2000
05-06-2013, 07:33 AM
I'm currently using glsl to draw a skybox, but final result of my program is not my expect, the six sides of the skybox looks like all sides flipped vertically, then flipped vertically. If I make the six image (right.bmp, left.bmp, top.bmp, and so on) vertical and vertical manually in some image editor, the skybox works fine. To locate the problem within my program quickly, I just simplify my program to draw only one side, front side.

here is the relevant code :



vertics shader:

attribute vec3 VertexPosition;
varying vec3 ReflectDir;

void main()
{
ReflectDir = VertexPosition;

gl_Position = gl_ModelViewProjectionMatrix * vec4(VertexPosition,1.0);
}

fragment shader:

varying vec3 ReflectDir;
uniform samplerCube CubeMapTex;

void main() {
vec4 cubeMapColor = texture(CubeMapTex,ReflectDir );

gl_FragColor= cubeMapColor;
}



Some code within my opengl program:

This used for binding my cube map into shader.

glActiveTexture(GL_TEXTURE5);

GLuint texID;
glGenTextures(1, &texID);
glBindTexture(GL_TEXTURE_CUBE_MAP, texID);

GLuint targets[] = {
GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEXTURE_CUBE_MAP_NEGATIVE_X,
GL_TEXTURE_CUBE_MAP_POSITIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y,
GL_TEXTURE_CUBE_MAP_POSITIVE_Z, GL_TEXTURE_CUBE_MAP_NEGATIVE_Z
};

const char* baseFileName[] = {
"Right",
"Left",
"Top",
"Bottom",
"Front",
"Back"


};

for( int i = 0; i < 6; i++ ) {
string texName = string(baseFileName[i])+".bmp";

IMAGE img;
img.Load((char*)texName.c_str());
img.ExpandPalette();

glTexImage2D(targets[i], 0, GL_RGBA, img.width, img.height, 0,
img.format, GL_UNSIGNED_BYTE, img.data);

}

glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);

m_shader->compileandlink();
m_shader->useprogram();
m_shader->setUniform("CubeMapTex", 5);
m_shader->unuseprogram();

And this 's my front side vertics, it's clock-wise winding.

float extend2 = extend*.5f;
m_cube_v = new vertex_t[24];

//front
m_cube_v[0].pos[0] = -extend2;
m_cube_v[0].pos[1] = -extend2;
m_cube_v[0].pos[2] = extend2;

m_cube_v[1].pos[0] = extend2;
m_cube_v[1].pos[1] = -extend2;
m_cube_v[1].pos[2] = extend2;

m_cube_v[2].pos[0] = extend2;
m_cube_v[2].pos[1] = extend2;
m_cube_v[2].pos[2] = extend2;

m_cube_v[3].pos[0] = -extend2;
m_cube_v[3].pos[1] = extend2;
m_cube_v[3].pos[2] = extend2;

What went wrong? thank you.

qxsl2000
05-06-2013, 07:42 AM
here is my program screenshot that was totally fliped over.

image link: i1345.photobucket.com/albums/p668/nimaccc/front_zps741fc377.jpg


here is my original material:

image link: i1345.photobucket.com/albums/p668/nimaccc/original_zps3dbccf2e.jpg

Dave Driesen
05-13-2013, 02:30 PM
Hi,

Sorry -- you probably checked this, but what is loading the image?
(BMP files are saved upside down :) )

Dave Driesen