I am new to modern OpenGL VBO/VAO and I struggle with one thing: I have coded a RectangleAsset based on this tutorial, but I am not sure how to move information about texture UVs to the RactangleAssetInstance (my rectangles can have different textures).
Do I have to create new VAO for it or can I just pass the UVs by some other means? Or add second VBO for UVs? And most imporantly: what would be best practice solving this?
struct RectangleAsset {
GLuint VBO;
GLuint VAO;
};
struct RectangleAssetInstance { //this is actually more complex class in my code
RectangleAsset rect; //but tried to extract the most imporatant code
glm::mat4 transform;
Texture * texture;
void UpdateTransform(int,int,int,int);
private:
int x,y,width,height;
};
and function loading the RectangleAsset:
void GUIRenderer::init()
{
image = new Program ("vs.glsl", "fs.glsl");
glGenVertexArrays(1, &rect.VAO);
glBindVertexArray(rect.VAO);
glGenBuffers(1, &rect.VBO);
glBindBuffer(GL_ARRAY_BUFFER, rect.VAO);
GLfloat vertexData[] = {
// X Y Z U V
0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f, 1.0f,
1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
1.0f, 1.0f, 0.0f, 1.0f, 1.0f,
0.0f, 1.0f, 0.0f, 0.0f, 1.0f,
};
glBufferData(GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW);
glEnableVertexAttribArray(image->attrib("vert"));
glVertexAttribPointer(image->attrib("vert"), 3, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), NULL);
glEnableVertexAttribArray(image->attrib("vertTexCoord"));
glVertexAttribPointer(image->attrib("vertTexCoord"), 2, GL_FLOAT, GL_TRUE, 5*sizeof(GLfloat), (const GLvoid*)(3 * sizeof(GLfloat)));
glBindVertexArray(0);
}
NOTE: I plan to use RectangleAssetInstances only at one place, in one std::vector for GUI rendering(non-static gui). Might it be good idea to merge all rectangles in one VBO and VAO (and re-create it whenever UIElement is added/removed)?
Any advices learning best practices with OpenGL are welcomed.