2D sprite not rotating at the center origin?

Shiny Pixel · 2014-05-12T23:44:08

Whenever I rotate my sprite object, it seems to be rotating at the top-left corner. I don't know where to begin, so I'll just spill it out. This is my coordinate system, with (0,0) at the bottom-left screen. glOrtho(0.0, SCREEN_WIDTH, 0.0, SCREEN_HEIGHT, 0.0, 1.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); In my RenderScene() function, I have the following: static GLfloat rotate = 0.0f; rotate += 0.2f; // draw these in foreground sprPC.setRotationAngle(rotate); sprPC.draw(); Then the rotation code in Sprite::Draw() glPushMatrix(); glBindTexture(GL_TEXTURE_RECTANGLE_ARB, m_intSpriteID); // .... // rotating code glTranslatef( m_currentCell.width/2.0f, m_currentCell.height/2.0f, 0.0f ); //back to previous position glRotatef( m_rotateAngle, 0.0f, 0.0f, -1.0f ); //rotate glTranslatef( m_currentCell.width/2.0f, m_currentCell.height/2.0f, 0.0f ); //to the origin // draw Sprite glBegin(GL_QUADS); // bottom left glFogCoordf(f); glTexCoord2i(m_currentCell.x, m_currentCell.height); glVertex2f(m_x, m_y); // bottom right glFogCoordf(f); glTexCoord2i(m_currentCell.width, m_currentCell.height); glVertex2f(m_x + (m_currentCell.width - m_currentCell.x) * m_scale, m_y); // top right glFogCoordf(f); glTexCoord2i(m_currentCell.width, m_currentCell.y); //glVertex2f(m_x + (m_currentCell.width - m_currentCell.x) * m_scale, (m_y + m_currentCell.y) * m_scale); glVertex2f(m_x + (m_currentCell.width - m_currentCell.x) * m_scale, (m_y + m_currentCell.y) * m_scale); // top left glFogCoordf(f); glTexCoord2i(m_currentCell.x, m_currentCell.y); glVertex2f(m_x, (m_y + m_currentCell.y) * m_scale); glEnd(); // ..... glPopMatrix(); Basically, the sprite is rotating clockwise. I attached a screenshot to show what I mean. [attachment=21459:pic.png]