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large triangles (and therefore have areas of the object where there are no vertices nearby), this can result in some visual artifacts that can detract from the otherwise very attractive looking specular lighting. The first of these problems can be seen in the left image of Figure 7 29. The image shows a cube that is facing nearly directly toward the camera and the light source, but is slightly rotated so that the rightmost corner is the only one that is reflecting the specular light. As you can see, the light has a very angular look caused by the fact that only four vertices are being used to display the entire face of the cube. The interpolation is inaccurate due to this small number of color points. The image on the right is of the exact same object and lighting configuration, except that PreferPerPixelLighting has been switched on. This property instructs XNA to calculate the specular lighting for each individual pixel that it renders, rather than just for the vertices. As will be clearly seen, the reflection looks much better: the angular lines have all disappeared, leaving a perfect round highlight in its place.

// create a textured quadric quadric = glu.gluNewQuadric(); glu.gluQuadricTexture(quadric, true);

First, the Total Qty field SUM(coiquantity) has NULL values for the two unmatched rows in the product data set This is the behavior of an outer join; columns from unmatched rows of the second data set are filled with NULL values The SUM() SQL function treats NULL values as unknown, therefore summing unknown values always results in unknown, or NULL This is a critical point to remember when doing aggregating reports If you know that NULL values may be returned from a statement, use the IFNULL() function to zero out any NULL values if appropriate You ll see this strategy in practice in Listing 7-5 Second, given the behavior of SUM(), you would assume that the COUNT() function would also return NULL since there were no matching rows This is not necessarily the case, and is the cause of numerous reporting errors.

Figure 7 29. Two cubes, without (left) and with (right) per pixel lighting enabled The second problem with specular lighting also occurs on objects with large triangles, but primarily affects specular light that is very tightly focused. Figure 7 30 shows two images of a cube that is directly facing toward the camera and the light source. The specular power has been set to 1000 for a very focused effect. Because the effect is so small, it doesn t reach any of the vertices at all. As a result, the specular light has no impact on the face. On the right is the same scene with per pixel lighting enabled. As each pixel then has its specular light individually calculated, the specular light effect clearly appears within the face.

The COUNT() function works as follows with NULL values: COUNT(*): Simply returns the number of rows in the resultset matching the GROUP BY columns COUNT(tablecolumn): Returns the number of rows having non-NULL values found in table Notice the difference in the aggregated data values in our corrected Listing 7-5 Listing 7-5 Corrected Output Using COUNT(tablecolumn) and IFNULL() mysql> SELECT -> pname -> , COUNT(coiorder_id) as "# Orders" -> , SUM(IFNULL(coiquantity,0)) as "Total Qty" -> FROM Product p -> LEFT JOIN CustomerOrderItem coi -> ON pproduct_id = coiproduct_id -> GROUP BY p.

loadTextures(); addLight(); groundShapes = new GroundShapes(FLOOR_LEN);

Of course, as you might expect, there is a downside to per pixel lighting. Because the specular component needs to be calculated for each individual pixel as opposed to each vertex, it has a much higher processing requirement. Consider the cubes in Figure 7 30: the visible face consists of more than 30,000 pixels, as compared with only 6 vertices. Per pixel lighting should therefore be used sparingly. If you have an object that is not using specular light, has no large faces, has a low specular power, or doesn t exhibit either of the problems discussed here, you will probably find a performance benefit from leaving it disabled. Experiment and find which setting provides the best balance between appearance and performance for your game.

name; +---------------------------+----------+-----------+ | name | # Orders | Total Qty | +---------------------------+----------+-----------+ | Action Figure - Football | 1 | 1 | | Action Figure - Gladiator | 1 | 1 | | Action Figure - Tennis | 1 | 1 | | Doll | 1 | 2 | | Soccer Ball | 1 | 1 | | Tennis Balls | 3 | 57 | | Tennis Racket | 1 | 1 | | Video Game - Car Racing | 0 | 0 | | Video Game - Football | 1 | 1 | | Video Game - Soccer | 0 | 0 | +---------------------------+----------+-----------+ 10 rows in set (001 sec).