4 . 1. Graphics II

1. 4.1.Graphics II Animated image sequences, fonts and image transforms

2. Animations Animated image sequences; playback speed and image source

3. Image Sequences An image sequence is simply a series of images, displayed one after the other. If the playback is fast a series of progressive images will appear as continuous, unbroken animation. Typically, how many frame/s are needed to give the appearance of unbroken animation? A – 50 frame/s B – 30 frame/s C – 20 frame/s D – 10 frame/s E – 5 frame/s

4. Image Sequences ● TV provides either 25 or 30 frame/s (PAL = 30) ● Consider the set of 6 images: ○ At 2 frame/s it is not smooth ○ At 10 frame/s it is reasonably smooth ● A typical animated cartoon run at 12 frame/s

5. Sequence Source Images to be played back as a sequence may reside within a number of different file structures, including: ● A series of files (1 image per file) ● A continuous image strip (1 file) ● An image sheet (1 file) Aside: For best performance, all images should be stored in an image sheet, with all animations using that sheet rendered together.

6. Image Sequence Playback Animating a sequence of images

7. Image sequence playback Playback of an image sequence can be integrated into the update/draw loop as follows: During the update phase determine when the next image in the sequence should be selected to provide the target number of frames/second During the draw phase, render the current selected image Aside: The following example is based on the ImageAssetSequence within the Java code repository

8. Image sequence playback (example implementation) private BufferedImage[] images; Assuming the images are stored as an array (or an array of rectangles into a single image sheet) the following parameters can be used to offer different playback options: playCount- number of times to play the animation (-1 = loop forever, 0 = pause) homeFrame – frame to display when not animating currentFrame – current frame to display animationPeriodms – number of ms which a single playback should take animationStartTime – start time of the animation (if playback has commenced) private intplayCount; private inthomeFrame; private intcurrentFrame; private long animationPeriodms; private long animationStartTime;

9. The update() method determines the current frame that should be displayed in the animation. In turn the draw() method simply draws the current frame. public void update() { determineCurrentFrame(); } public void draw(Graphics2Dgraphics2D, intdrawX, intdrawY) { graphics2D.drawImage( images[currentFrame], drawX, drawY, null); }

10. A check is made to see if the animation has completed, in which case the playCount is reset to zero. Based on the current time, target animation period and playCount value the current frame is calculated and returned. private intdetermineCurrentFrame() { long currentTime = GetCurrentTime(); if (animinationStartTime == -1) animinationStartTime = currentTime; if (playCount > 0) { if (currentTime - animinationStartTime > (long) playCount * animationPeriodms) { playCount = 0; } } if (playCount == 0) { currentFrame = homeFrame; } else { long timeIntoAniminationPeriod = (currentTime – animinationStartTime) % animationPeriodms; currentFrame = (int) ( (timeIntoAniminationPeriod * (long)images.length ) / animationPeriodms ); } return currentFrame; } The start time will be reset to -1 anytime the play count is changed. Aside: This is a slightly different version of the ImageAssetSequence implementation – the later ensures that the end frame of the animation is always drawn at least once.

11. In-Game Fonts Displaying textual information within games

12. The expense of drawing a font… Early fonts were bitmap based. Most modern fonts (e.g. TrueType) are outline based, providing a set of line and curve equations describing the shape of each ‘glyph’ (character). When drawing a font, the outline is rendered and then filled by an ink colour. Generating text by doing this 50-60 times per second is needlessly expensive. How can we improve performance? Render text once into a bitmap and use bitmap until text changes Revert to using a bitmap font

13. In-game fonts (using Java) Load an image asset sequence holding the bitmap font characters. Create a base TextElement, holding the image sequence and a corresponding text-to-image mapping. Use the base TextElement to create text strings that can be drawn. TextElementguiText = new TextElement(this, (ImageAssetSequence) assetManager.retrieveAsset( "GUIFont" ), 0, "ABCDEFGHIJKLMNOPQRSTUVWXYZ“ + "abcdefghijklmnopqrstuvwxyz" + "1234567890`!\"$%^&*()-+={}[];:'@#~,.<>/\\? ", ""); TextElementsomeText = guiText.getMatchingElement(“Hello!"); someText.draw(graphics2D, x, y);

14. In-game fonts (using XNA) <Asset Type="Graphics:FontDescription"> <FontName>Courier New</FontName> <Size>10</Size> <Spacing>0</Spacing> <UseKerning>true</UseKerning> <Style>Regular</Style> Specify and add a SpriteFont content asset (the SpriteFont converts any installed TrueType font into an XNB sprite sheet) Load in the SpriteFont within the game. Use the SpriteBatch. DrawString() method to render text. SpriteFontspriteFont; SpriteBatchspriteBatch; spriteFont = content.Load<SpriteFont>("SpriteFont"); spriteBatch.Begin(); spriteBatch.DrawString( spriteFont, “Hello! ", position, Color.White); spriteBatch.End(); Aside: For more information on importing fonts, see: http://blogs.msdn.com/shawnhar/archive/2007/04/26/bitmap-fonts-in-xna.aspx

15. Exercise: Using digit arrays ImageAsset[] digitImage = new ImageAsset[10]; Assume you have a series of images representing the digits 0 to 9 stored in an array Develop an approach that will take a positive integer score and graphically illustrate it using the image sequence. Start 10 mins 9 mins 8 mins 7 mins 6 mins 5 mins 4 mins 3 mins 2 mins 1 min 30 sec Finished

16. Exercise: Using digit arrays void drawScore( inttargetScore ) { intscoreFragment = targetScore; do { int digit = scoreFragment % 10; digitImages[digit].Draw( ... ) scoreFragment = scoreFragment / 10; } while(scoreFragment > 9 ); } By using the modulus (%) operator the last digit in the score can be extracted and printed. Using integer division, the last digit can then be removed and the process iterated until no more digits remain. Aside: When drawing the images, it will be necessary to ensure the draw location of each image is determined. Additionally, the score will need to be drawn right-to-left.

17. Image Manipulation Basic forms of image transform

18. To do: Consider game applicability Basic forms of image transform A number of affine image transforms can be usefully employed within games, including: Depth of view effects Object rotation Appear / disappear effects Left / right / up / down sprite reuse Rotating Resizing Fadding Flipping

19. Image Transforms (Resizing) newWidth drawResizedImage( Graphics2D graphics2D, BufferedImage image, intdrawX, intdrawY, double scaleX, double scaleY ) { intnewWidth = (int) (image.getWidth() * scaleX ); intnewHeight = (int) (image.getHeight() * scaleY ); // Optional… if desired intnewDrawX = drawX + image.getWidth()/2 - newWidth/2; intnewDrawY = drawY + image.getHeight()/2 - newHeight/2; graphics2D.drawImage( image, newDrawX, newDrawY, newWidth, newHeight, null ); } newDrawX, newDrawY For Java use: For XNA use: The source texture will be scaled to fit the destination rectangle. drawX, drawY newHeight SpriteBatch.Draw( Texture2D texture, Rectangle destinationRectangle, Colorcolor )

20. Image Transforms (Rotation) drawX, drawY drawRotatedImage( Graphics2D graphics2D, BufferedImage image, intdrawX, intdrawY, double rotationDeg ) { AffineTransformorigAT = graphics2D.getTransform(); AffineTransform rotation = new AffineTransform(); rotation.rotate( Math.toRadians(rotationDeg), drawX + image.getWidth()/2, drawY + image.getHeight()/2 ); graphics2D.setTransform( rotation ); graphics2D.drawImage( image, drawX, drawY, null ); graphics2D.setTransform(origAT); } For Java use: The source texture will be rotated around the specified origin For XNA use: SpriteBatch.Draw( Texture2D texture, Rectangle destinationRectangle, Nullable<Rectangle> sourceRectangle, Colorcolor, float rotation, Vector2 origin, SpriteEffects effects, float layerDepth )

21. drawX, drawY • Image Transforms (Fading) drawFadedImage( Graphics2D graphics2D, BufferedImage image, intdrawX, intdrawY, float alpha ) { Composite origComposite = graphics2D.getComposite(); graphics2D.setComposite( AlphaComposite.getInstance( AlphaComposite.SRC_OVER, alpha) ); graphics2d.drawImage( image, drawX, drawY, null); graphics2D.setComposite( origComposite ); } For Java use: Specify a colour with an alpha component < 256, e.g. for 50% fading new Color( ???, ???, ???, 128 ); For XNA use: drawX, drawY SpriteBatch.Draw( Texture2D texture, Rectangle destinationRectangle, Colorcolor)

22. Image Transforms (Flipping) drawHorizFlip(Graphics2D graphics2D, BufferedImage image, intdrawX, intdrawY ) { int width = image.getWidth(); int height = image.getHeight(); graphics2d.drawImage( image, drawX, drawY+height, drawX+width, drawY, 0, 0, width, height, null); } drawImage( Image img, int dx1, int dy1, int dx2, int dy2, int sx1, int sy1, int sx2, int sy2, ImageObserverobs) For Java use: SpriteEffects includes FlipVerticallyand FlipHorizontally For XNA use: drawX, drawY drawX, drawY SpriteBatch.Draw( Texture2D texture, Rectangle destinationRectangle, Nullable<Rectangle> sourceRectangle, Colorcolor, float rotation, Vector2 origin, SpriteEffects effects, float layerDepth )

23. Summary Today we explored: • The basics behind image sequence playback • How in-game fonts can be efficiently rendered • Some useful image transforms To do: • Continue to explore image repository and select graphics • Think about the types of image animation/transform and font usage in your game. • Write code snippets to load / display and animate / transform images