One embodiment of the invention sets forth a mechanism for displaying lighting values associated with a 3-D graphics model by superimposing an overlay grid with lighting values on the 3-D graphics model. A software rendering engine computes lighting values for each frame that includes the 3-D graphics model, where each frame may have different lighting settings. An overlay grid with lighting values may be superimposed on an area defined by a light meter on the 3-D graphics model. The lighting values on the overlay grid are associated with the light meter and may vary frame-over-frame. In another embodiment, a JPEG image with a superimposed overlay grid with per-pixel lighting values covering a 3-D graphics model is generated for each frame that includes the 3-D graphics model. These JPEG images may be displayed on the screen and stored to an external memory.