pitfalls_of_OpenGL

[vinjn]

Some of them might be by design, but when it comes to real coding, it causes problems.

• glViewport and glScissor all use window coordinates, which means (0, 0) is at the left-bottom of the window, while (0, 0) is at the left-top of Direct3D window.
• OpenGL context is stored in thread-local storage (TLS), you can change the current context of a specific thread, but you can't access the same context from different threads.
• /GL/gl.h under Windows platform only has 1.0 version, you need glee / glew to get modern versions of OpenGL dynamically.
• OpenGL has no idea of window and message looping, you need platform-specific APIs
  • egl is for opengl-es, Android/iOS, it also supports windows platform.
  • wgl is for windows
  • cgl is for Mac
  • glx is for linux
  • glut is a cross-platform window system toolkit (wrappers of wgl/cgl/glx)

[vinjn]

http://stackoverflow.com/questions/2621013/how-to-create-a-fbo-with-stencil-buffer-in-opengl-es-2-0

In OpenGL ES 2.0 on iOS, you have to create a combined depth and stencil renderbuffer using GL_DEPTH24_STENCIL8_OES, and then attach it to the bound framebuffer as both GL_DEPTH_ATTACHMENT and GL_STENCIL_ATTACHMENT.

glGenRenderbuffers(1, &depthStencilRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, depthStencilRenderbuffer);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthStencilRenderbuffer);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, depthStencilRenderbuffer);

[vinjn]

http://luugiathuy.com/2011/09/create-frame-buffer-object-opengl/

On PC

fbo+rbo

glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, inScreenWidth, inScreenHeight); ... glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, depthRBO);

fbo+texture

glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH24_STENCIL8, inScreenWidth, inScreenHeight, 0, GL_DEPTH_STENCIL, GL_UNSIGNED_INT_24_8, NULL); ... glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_TEXTURE_2D, depthStencilTexture, 0);