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The sprite needs to face to the left when it is moving from right to left. This is the default state of the sprite sheet shown in Figure 1 so no flip is required.
The sprite needs to face to the right when it is moving from left to right. This requires a horizontal flip on the sprite images shown in Figure 1 .
The last statement in Listing 12 calls the SpriteBatch.End method to terminate the drawing process for the current iteration of the gameloop.
By default, the Update and Draw methods are each called approximately 60 times per second or approximately once every 16.67milliseconds. This can be changed by program code but it was not changed in this program.
When the program is drawing the sprite images in the top row of Figure 1 , a new sprite image is selected for drawing only once every 175 milliseconds (seethe variable named fast ). Therefore, the same sprite image is drawn during ten or eleven successive iterations of the game loop.
When the program is drawing the sprite images in the bottom row of Figure 1 , a new sprite image is selected for drawing only once every 525 milliseconds (seethe variable named slow ). Therefore, each of the sprites in the bottom row is drawn during about 33 successive iterations of the game loop.
By drawing the sprite images 60 times per second, the image can be maintained on the computer screen with no visible flicker. By drawing the same imagemultiple times in succession, the overall visual frame rate can be slowed down to produce a pleasing animation effect.
Listing 13 shows the required call to the superclass of the Draw method, the end of the Draw method, the end of the class, and the end of the namespace.
Listing 13 . The end of the program.
//Required standard code.
base.Draw(gameTime);}//end Draw method
}//End class}//End namespace I encourage you to copy the code from Listing 14 . Use that code to create an XNA project. Compile and run the project. Experiment with the code, makingchanges, and observing the results of your changes. Make certain that you can explain why your changes behave as they do. Be sure to take the scale factorinto account as mentioned earlier .
Click here to download a zip file containing my version of the program. Extract the folder named XNA0122Proj from the zip file and save it somewhere on your disk. Start Visual C# 2010 Express and select Open Project... from the File menu. Navigate to the project folder and select the file with the extension of .sln . This should cause the project to open and be ready to run or debug as described in the earlier module titled Getting Started .
Among other things, you learned:
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