Delphi Graphics and Game Programming Exposed! with DirectX For versions 5.0-7.0:Special Effects                       Search Tips   Advanced Search        Title Author Publisher ISBN    Please Select ----------- Artificial Intel Business & Mgmt Components Content Mgmt Certification Databases Enterprise Mgmt Fun/Games Groupware Hardware IBM Redbooks Intranet Dev Middleware Multimedia Networks OS Productivity Apps Programming Langs Security Soft Engineering UI Web Services Webmaster Y2K ----------- New Arrivals









Delphi Graphics and Game Programming Exposed with DirectX 7.0

by John Ayres

Wordware Publishing, Inc.

ISBN: 1556226373   Pub Date: 12/01/99














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Previous Table of Contents Next Listing 11-1: Producing sine wave patterns with a bitmap interface const . . . {controls wave magnitude} MAGNITUDE = 10; {controls wave frequency} FREQUENCY = 720; . . . var . . . {the starting angle} AngleStart: Integer; implementation . . . procedure TfrmDXAppMain.FormCreate(Sender: TObject); begin . . . {initialize our starting angle} AngleStart := 0; end; . . . { — this method initializes DirectX and creates all necessary objects — } procedure TfrmDXAppMain.FormActivate(Sender: TObject); begin . . . {create a palette based on this bitmap} FPalette := DDLoadPalette(FDirectDraw, ExtractFilePath(ParamStr(0))+ ‘texasflag.bmp’); {attach the palette to the primary surface so that it takes effect} DXCheck( FPrimarySurface.SetPalette(FPalette) ); {load in the bitmap containing the flag image} FFlag := DDLoadBitmap(FDirectDraw, ExtractFilePath(ParamStr(0))+ ‘texasflag.bmp’); . . . end; . . . procedure TfrmDXAppMain.DrawSurfaces; var DestSrfcInfo, FlagSrfcInfo: TDDSurfaceDesc2; DestPtr, FlagPtr: PByteArray; DestX, DestY, StartY, AngleBegin: Integer; begin {erase the last frame of animation} ColorFill(FBackBuffer, 0, nil); try {lock the flag surface} FlagSrfcInfo.dwSize := SizeOf(TDDSurfaceDesc2); DXCheck( FFlag.Lock(nil, FlagSrfcInfo, DDLOCK_SURFACEMEMORYPTR or DDLOCK_WAIT, 0) ); FlagPtr := PByteArray(FlagSrfcInfo.lpSurface); {lock the destination surface} DestSrfcInfo.dwSize := SizeOf(TDDSurfaceDesc2); DXCheck( FBackBuffer.Lock(nil, DestSrfcInfo, DDLOCK_SURFACEMEMORYPTR or DDLOCK_WAIT, 0) ); {this positions the initial starting point of destination drawing so that the flag will be centered horizontally and vertically} DestPtr := PByteArray(integer(DestSrfcInfo.lpSurface)+ (DestSrfcInfo.lPitch*((DXHEIGHT div 2)- (FlagSrfcInfo.dwHeight div 2)))+ ((DXWIDTH div 2)-(FlagSrfcInfo.dwWidth div 2))); {increment our starting angle. this produces the motion of the wave, and a larger value will make the wave move faster. a negative value makes the wave move from left to right; positive values reverse this direction. incidentally, we never have to ‘roll over’ this value as Sin will return a value in the range -1 to 1 for any argument} Inc(AngleStart, -5); {begin iterating through each vertical strip} for DestX := 0 to FlagSrfcInfo.dwWidth do begin {we want to add 1 to the starting angle for each column in the bitmap} AngleBegin := DestX+AngleStart; {the FREQUENCY value increases the frequency of the wave across the bitmap. with a value of 360, the waves will peak and valley only once across the entire length of the bitmap. our frequency value is 720, which causes 2 peaks and valleys, and makes a nice effect. increasing or decreasing this value accordingly may simulate wind strength. this value is divided by the width of the bitmap to produce an ‘angles-per-pixel’ ratio so that the effect will spread evenly across the horizontal length of the bitmap. this value must be in terms of radians instead of degrees, so we must multiply it by (PI/180). finally, the MAGNITUDE value scales the results and produces offsets, in our example, between -10 and 10. this makes the peaks appear higher and the valleys appear lower.} StartY:=Trunc((Sin(((FREQUENCY/FlagSrfcInfo.dwWidth)*AngleBegin)* (PI/180))*MAGNITUDE)); {begin drawing the vertical strip of pixels} for DestY := 0 to FlagSrfcInfo.dwHeight do {the vertical offset is added to the vertical destination value, which may move this column of pixels up or down} DestPtr[DestSrfcInfo.lPitch*(DestY+StartY)+DestX] := FlagPtr[FlagSrfcInfo.lPitch*DestY+DestX]; end; finally {release all locks} FFlag.Unlock(nil); FBackBuffer.Unlock(nil); end; end; end. Alternatives/Enhancements The resulting animation from our bitmap transformation, while effective, is a little cheesy. We could produce a more realistic effect by applying another sine wave along the x-axis, perhaps at a 45-degree angle from horizontal. If we scaled the horizontal sine wave offset so that pixels moved left or right very little at the left side of the image, but they moved a large distance at the right side of the image, we could produce a more realistic wind effect. The result would make the flag look like it folded back on itself, and that it was attached to a flagpole. Scaling Sometimes it may be necessary to draw a bitmap image at a size other than its original dimensions. For example, we could create the illusion of a creature getting closer to the user by drawing its image larger and larger as it draws nearer. By scaling an image in this manner, we can produce the illusion of depth, or even provide zooming functionality for things like sniper scopes. Basic Theory Scaling a bitmap involves drawing the pixels of the source bitmap into the destination according to a specific ratio. This ratio determines the final size of the bitmap as it appears in the destination. The ratio is expressed as a fraction, or a floating-point number; the larger the number, the larger the bitmap, and vice versa. For example, a ratio of 2 indicates that the final bitmap will be twice as large as its original size, whereas a ratio of 0.5 indicates that the final bitmap will be half of its original size. Specifically, the ratio indicates how each pixel is mapped into the destination. If we iterate through the pixels in the destination and divide their coordinates by the scaling factor, we can determine which pixel to select from the source. This is accomplished by the following equations: Source_X := Trunc(Destination_X / Scale); Source_Y := Trunc(Destination_Y / Scale); A scaling factor less than 1 causes pixels in the source image to be skipped, thus resulting in a smaller final image. Similarly, a scaling factor greater than 1 causes pixels in the source image to be replicated, resulting in a larger final image. The following listing demonstrates this technique. Previous Table of Contents Next Products |  Contact Us |  About Us |  Privacy  |  Ad Info  |  Home Use of this site is subject to certain Terms & Conditions, Copyright © 1996-2000 EarthWeb Inc. All rights reserved. Reproduction whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Read EarthWeb's privacy statement.