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View Full Version : Copying of texture unables to draw?



Criss_pl
02-02-2016, 04:10 PM
I wonder how OpenGL get to know that id variable of a OGL object doesn't exist anymore... Because I noticed it does it. I have Texture class which is just a wrapper for loading an image with SOIL and id handler. Its object is member of another class which draws it etc, doesn't really matter. But the matter is: when I push drawable object (which uses Texture) to std::vector by push_back, OpenGL doesn't draw texture (it's just black). But why? ID is copied with Texture object and glDeleteTextures wasn't called, so I think I don't understand how it works. The variable which is given to glGen... functions isn't just a ID number, is it something more (I'm a little confused, I don't understand why copying breaks it) ? If I push it to vector by emplace_back (no copying), it is drawn. Below is a code of Texture class and drawing code:



class Texture
{
private:
typedef unsigned char uchar;
typedef glm::tvec2<GLint> vec2i;

public:
Texture();
explicit Texture(std::string _filePath);

public:
static std::tuple<uchar*, glm::vec2> loadImage(std::string _filePath);

GLuint getId() { return m_texId; }
vec2i getSize() { return m_size; }

private:
GLuint m_texId;
vec2i m_size;
};

Texture::Texture(std::string _filePath)
{
glGenTextures(1, &m_texId);
glBindTexture(GL_TEXTURE_2D, m_texId);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

uchar* imageData;
std::tie(imageData, m_size) = loadImage(_filePath);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, m_size.x, m_size.y, 0, GL_RGB, GL_UNSIGNED_BYTE, imageData);
glGenerateMipmap(GL_TEXTURE_2D);
SOIL_free_image_data(imageData);
glBindTexture(GL_TEXTURE_2D, 0);
}

std::tuple<unsigned char*, glm::vec2> Texture::loadImage(std::string _filePath)
{
vec2i size;
unsigned char* image = SOIL_load_image(_filePath.c_str(), &size.x, &size.y, 0, SOIL_LOAD_RGB);
return std::make_tuple(image, size);
}

/* Drawing code - Sprite class */

void Sprite::draw()
{
m_shader.use(); //opengl shader wrapper

glActiveTexture(GL_TEXTURE0);

//Sprite has a member pointer to Texture object

glBindTexture(GL_TEXTURE_2D, m_ptexture->getId());

glUniform1i(glGetUniformLocation(m_shader.getId(), "texSampler"), 0);

//here some glUniforms...

glBindVertexArray(m_vao);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

glBindTexture(GL_TEXTURE_2D, 0);
glBindVertexArray(0);
glUseProgram(0);
}

GClements
02-03-2016, 01:59 AM
It's impossible to say what's happening from the limited amount of code you posted, but a texture object exists from the point that its name is first bound with glBindTexture() until its deleted, either explicitly with glDeleteTextures() or implicitly when the last context using that texture is destroyed.