OpenGL rendering multiple textures on sprites - c++

Question

I'm learning OpenGL from the MakingGamesWithBen series and I'm writing a simple asteroid shooter based on his engine. I have created a system that randomly positions the asteroid sprites with random sizing, and selects a random texture path from an std::vector, and passes the path to the asteroid constructor. The sprites are drawn, however only the first texture is drawn. I've read that I need to bind those textures and switch to the relevant glActiveTexture; from my code below, how would I go about this?
void MainGame::prepareTextures() {
//compile shaders and get Texlocations
initShaders("Shaders/background.vert", "Shaders/background.frag");
GLint TexLoc = _colorProgram.getUniformLocation("bgTexture");
glActiveTexture(GL_TEXTURE0);
}
m_asteroid[i].draw():
glm::vec4 uv(0.0f, 0.0f, 1.0f, 1.0f);
//convert m_imgNum to string and remove trailing zeros
std::string strImgNum = std::to_string(m_imgNum);
strImgNum.erase(strImgNum.find_last_not_of('0') + 1, std::string::npos);
//construct filpath
std::string filePath = m_dir + strImgNum + ".png";
static Engine::GLTexture texture = Engine::ResourceManager::GetTexture(filePath, 0, 0, 32, 4);
Engine::Color color;
color.r = 255;
color.g = 255;
color.b = 255;
color.a = 255;
glm::vec4 posAndSize = glm::vec4(m_posX, m_posY, m_width, m_height);
spriteBatch.Draw(posAndSize, uv, texture.id, 0.0f, color);
Engine::ResourceManager::GetTexture():
GLTexture texture = {};
unsigned char *imageData = stbi_load(filePath.c_str(), &width, &height, &bitsPerPixel, forceBpp);
if (imageData == NULL) {
const char *loadError = stbi_failure_reason();
stbi_image_free(imageData);
fatalError(loadError);
}
//Create the texture in opengl
glGenTextures(1, &(texture.id));
glBindTexture(GL_TEXTURE_2D, texture.id);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);
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_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glGenerateMipmap(GL_TEXTURE_2D);
stbi_image_free(imageData);
glBindTexture(GL_TEXTURE_2D, 0);
texture.width = width;
texture.height = height;
return texture;
renderbatch():
void SpriteBatch::renderbatch() {
glBindVertexArray(m_vao);
for (unsigned int i = 0; i < m_renderBatches.size(); i++) {
glBindTexture(GL_TEXTURE_2D, m_renderBatches[i].texture);
glDrawArrays(GL_TRIANGLES, m_renderBatches[i].offset, m_renderBatches[i].numVertices);
}
glBindVertexArray(0);
}
I can provide any other code/clarification that may be needed!

Answer 1

Usually when not all textures are showing up, it's probably has something to do with uploading the texture by OpenGL. You could try to debug this by checking if your textures are all uploaded properly;
std::uint32_t textureId = Engine::ResourceManager::GetTexture(filePath, 0, 0, 32, 4).id;
std::cout << "texture id, should not be 0 :" << textureId << std::endl;
This could happen if you called this function not from a thread with OpenGL context.
EDIT:
Is there any reason to use a static object here?
static Engine::GLTexture texture = Engine::ResourceManager::GetTexture(filePath, 0, 0, 32, 4);
try changing that to just
Engine::GLTexture texture = Engine::ResourceManager::GetTexture(filePath, 0, 0, 32, 4);
UPDATE:
I just replaced your spitebatch.cpp/.h with the ones from Ben's github and put a simple test in your MainGame.cpp;
m_spriteBatch.begin();
asteroids.draw(m_spriteBatch);
ship.draw(m_spriteBatch);
m_spriteBatch.end();
m_spriteBatch.renderBatch();
_colorProgram.unuse();
_window.SwapBuffers();
and I can render the two uploaded textures properly;
HTH.