How to render a radial field in OpenGL?

OpenGL: When you mention forward rendering, does it only apply on how the light is render on a particular object regardless those objects are on screen or off screen?

• Answer:

  As I understand it, the term forward rendering is used to distinguish it from deferred rendering. (aka deferred shading) The computations which determine which parts of a surface are visible, are now usually faster and cheaper to perform than the texturing and lighting of those surfaces. Given that cost difference, it makes sense to only apply shading and lighting to those surfaces which appear in the final image, this avoids the wasted effort of lighting surfaces which are obscured. In deferred rendering solutions, an initial rendering pass is performed which resolves what is visible, and collates the positions, normals etc for each pixel in the frame.  Having done that, a second pass applies the texturing and lighting to those visible pixels.  Forward rendering is the old-school method, where all graphical primitives are rendered out, and shading calculations may be invested in surfaces which might ultimately be obscured at a later point. The right solution depends on the scene. The PowerVR GPUs which are used in mobile devices, implement deferred shading in hardware.  The screen is rendered as a set of tiles. And in processing a tile, the processor first resolves visibility, before running fragment shaders on the visible sub-pixels. Don't confuse this with forward ray-tracing, where light rays are traced from the source and may eventually reach the virtual camera.