Texturing a Quad in OpenGL - c++

Question

So far I've learned how to create a cube with textures in OpenGL.
Now I want to change this code for texturing a Quad. I've changed the vertices + indices from a cube to a quad.
And the Quad looks like this:
The texture is completely distorted and the upper triangle is missing...
This is the code I'm using:
1.
GLfloat vertices[] = {
1.0f, 1.0f, 0.0f, 1.0f, 1.0f,
1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
-1.0f, -1.0f, 0.0f, 0.0f, 0.0f,
-1.0f, 1.0f, 0.0f, 0.0f, 1.0f
};
unsigned int indices[]{
0,1,2,
1,2,3,
};
2.
for (size_t o = 0; o < 6; o++) {
glPixelStorei(GL_UNPACK_ROW_LENGTH, breite_komplett);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, ausschnitt_x_counter);
glPixelStorei(GL_UNPACK_SKIP_ROWS, ausschnitt_y_counter);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexImage2D(
GL_TEXTURE_CUBE_MAP_POSITIVE_X + o, 0, GL_RGBA, ausschnitt_breite, ausschnitt_höhe, 0, GL_RGBA, GL_UNSIGNED_BYTE, sprite_image.getPixelsPtr());
}
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glGenerateMipmap(GL_TEXTURE_CUBE_MAP);
glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
glEnable(GL_TEXTURE_2D);
Do you have an ideas what I need to change?
Edit:
unsigned int indices[]{
0,1,2,
0,2,3
};
This is my object builder:
glGenVertexArrays(1, &obj_vao);
glBindVertexArray(obj_vao);
glGenBuffers(1, &obj_ibo);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, obj_ibo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indicies[0])* indicies_count, indicies, GL_STATIC_DRAW);
glGenBuffers(1, &obj_vbo);
glBindBuffer(GL_ARRAY_BUFFER, obj_vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices[0]) * count_vertices, vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(vertices[0]) * 5, 0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(vertices[0]) * 5, (void*)(sizeof(vertices[0]) * 3));
glEnableVertexAttribArray(1);
glBindVertexArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
Edit:
If the vertices would be like this:
GLfloat vertices[] = {
1.0f, 1.0f, -1.0f, 1.0f, 1.0f,
1.0f, -1.0f, -1.0f, 1.0f, 0.0f,
-1.0f, -1.0f, -1.0f, 0.0f, 0.0f,
-1.0f, 1.0f, -1.0f, 0.0f, 1.0f
};
Everything would be fine and the Quad looks like this:
But I need the Quad in the origin like this:
GLfloat vertices[] = {
1.0f, 1.0f, 0.0f, 1.0f, 1.0f,
1.0f, -1.0f, 0.0f, 1.0f, 0.0f,
-1.0f, -1.0f, 0.0f, 0.0f, 0.0f,
-1.0f, 1.0f, 0.0f, 0.0f, 1.0f
};
With this vertices the texture is distorted...

Answer 1

The indices of the 2 triangle primitives do not form a quad. The indices have to be:
unsigned int indices[]{ 0, 1, 2, 1, 2, 3 };
unsigned int indices[]{ 0, 1, 2, 0, 2, 3 };
3 0
+-----+ +
| / / |
| / / |
+ +-----+
2 1
When you crate the texture, the you mix GL_TEXTURE_CUBE_MAP and GL_TEXTURE_2D. That makes no sense. Either create a cubemap texture and set the parameters for the GL_TEXTURE_CUBE_MAP or create a 2 dimensional texture.
Anyway if you want to create a cubemap texture, then you have to use GL_TEXTURE_CUBE_MAP, when you set the parameters, too.
The texture coordinate for a texture cube is a 3 dimensional vector. Change the vertex coordinates for the side of the cube. e.g:
(You don't need the texture coordinates at all)
GLfloat vertices[] = {
// x y z
1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 1.0f, 1.0f, 0.0f,
-1.0f, -1.0f, 1.0f, 0.0f, 0.0f,
-1.0f, 1.0f, 1.0f, 0.0f, 1.0f
};
The center of the cube is (0, 0, 0), so you can use the vertex coordinates for the texture, too:
Vertex shader
in vec3 position;
out vec3 cubeCoord;
void main()
{
cubeCoord = position;
// [...]
}
Fragment shader:
in vec3 cubeCoord;
uniform samplerCube cubeTex;
void main()
{
vec4 color = texture(cubeTex, cubeCoord);
// [...]
}
Alternatively you can use separate 3 dimensional texture coordinates for the cubemap texture:
GLfloat vertices[] = {
// x y z u v w
1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 1.0f,
1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 1.0f,
-1.0f, -1.0f, 0.0f, -1.0f, -1.0f, 1.0f,
-1.0f, 1.0f, 0.0f, -1.0f, 1.0f, 1.0f,
};