Code archives/3D Graphics - Maths/Vehicle pitch and roll without child/pivot entities
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| Found Darkbasic maddening when it came to simply getting a vehicle to follow a terrain. I'm finding BB3d much easier in this respect, but figured there must be a simpler way to pitch and roll a vehicle on a terrain without resorting to child entities to get terrain height. This uses sin(yaw+offset),cos(yaw+offset) to get the midfront/back, midleft/right x,y co-ords and then uses Atan2 to calculate angles. Please feel free to let me know your ideas/improvements. Note: you'll have to specify your own terrain texture and heightmap, but the 747.x is from Hi-Toro's DeathIsland example project). EDIT by BlitzSupport (24 Jan 2007). Was just looking at this, so bundled code and media here for quick access (249 KB). |
; my car test - Phil Jones ; a look at calculating vehicle pitch and roll (on a terrain) without ; child/pivot entities ;set up screen,light & camera Graphics3D 800,600,16 SetBuffer BackBuffer() light = CreateLight(1) ;create terrain terrain = LoadTerrain("heightmap_256.bmp") TerrainDetail terrain, 3000, True ScaleEntity terrain, 50,1000,50 PositionEntity terrain,-200,0,-200 terraintex = LoadTexture("coolfloor2.bmp") ScaleTexture terraintex,.4,.4 TerrainShading terrain,1 EntityTexture terrain,terraintex ;create car/plane/tank whatever and centre it local co-ords car = LoadMesh("747.x") ScaleMesh car,100,100,100 carlength# = MeshDepth#(car)/2 ; get length from centre to front of car carwidth# = MeshWidth#(car)/2 ; get length from centre to left or right of car carheight# = MeshHeight#(car)/2: ; get height from centre To top Or bottom of car meshh = MeshHeight#(car)/2 FitMesh car, 0-carwidth,0,0-carlength,carwidth*2,carheight*2,carlength*2; just some general recentring to have car sit on plane pitch# = 0 x# = 200 y# = 600 z# = 480 speed# = 0 frontheight#=0 ; height of terrain at midpoint front of vehicle backheight#=0 ; height of terrain at midpoint back of vehicle leftheight#=0 ; height of terrain at midpoint left side of vehicle rightheight#=0 ; height of terrain at midpoint right side of vehicle th# = 0 ; height of terrain at centre of vehicle (this will averaged from front/back/left/right) PositionEntity car,x,y,z ; set up initial pos of car and camera ;RotateEntity car,0,180,0,1 ;these are just for visual ref - not needed in calculation of rotations pop = CreateCube() ScaleEntity pop,5,400,5 pfront = CreateCube() ScaleEntity pfront,5,5,5 pback = CreateCube() ScaleEntity pback,5,5,5 pleft = CreateCube() ScaleEntity pleft,5,5,5 pright = CreateCube() ScaleEntity pright,5,5,5 ;setup camera camera = CreateCamera() PositionEntity camera ,300,350,100 PointEntity camera ,car CameraRange camera,1,900000 ;MAIN LOOP +++++++++++++++++++++++++++++++++ While Not KeyHit(1) ; get current location and overall height of car x# = EntityX (car) z# = EntityZ (car) y# = EntityY (car) ; check for keypress to alter car speed (A,Z) speed = speed -.5*(KeyDown(208) And speed > -10 ) + .5*(KeyDown(200) And speed < 10 ) ; check for keypress to turn car left/right turn = (KeyDown(203)) - (KeyDown(205)) TurnEntity car,0,turn,0 yaw# = EntityYaw(car) ; CALCULATE PITCH/ROLL ++++++++++++++++++++++++++++++++ ;work out terrainheights at front/back/left/right of car anglenew# = yaw -90 ; what must be added to yaw to calculate front of vehicle's global x,z co-ords xnew# = x+Cos(anglenew)*carlength znew# = z+Sin(anglenew)*carlength frontheight# = TerrainY(terrain,xnew,y,znew); get the height at new x,y,z PositionEntity pfront,xnew,frontheight,znew ; a visual marker only - not neccessary for calculations anglenew# = yaw +90 ; what must be added to yaw to calculate back of vehicle's global x,z co-ords xnew# = x+Cos(anglenew)*carlength znew# = z+Sin(anglenew)*carlength backheight = TerrainY(terrain,xnew,y,znew) PositionEntity pback,xnew,backheight,znew anglenew# = yaw ; what must be added to yaw to calculate midleft of vehicle's global x,z co-ords xnew# = x+Cos(anglenew)*carwidth znew# = z+Sin(anglenew)*carwidth Leftheight = TerrainY(terrain,xnew,y,znew) PositionEntity pleft,xnew,leftheight,znew anglenew# = yaw + 180 ; what must be added to yaw to calculate midright of vehicle's global x,z co-ords xnew# = x+Cos(anglenew)*carwidth znew# = z+Sin(anglenew)*carwidth rightheight = TerrainY(terrain,xnew,y,znew) PositionEntity pright,xnew,rightheight,znew pitchx# = carlength*2 ; need complete length of car for x pitchy# = (backheight - frontheight); the height dif between the front and rear of car pitch = ATan2(pitchx,pitchy); atan2 will return the angle from 0,0 to x,y rollx# = carwidth*2 rolly# = (rightheight - leftheight) ; the height dif between the left and right of car roll# = ATan2(rollx,rolly); atan2 will return the angle from 0,0 to x,y RotateEntity car, pitch-90,yaw,roll-90 ; rotate car with offsets to adjust Atan2's calculation th=(frontheight+backheight+leftheight+rightheight)/4; get average of terrain heights for cars overall height PositionEntity car,x,th,z ; adjust car height MoveEntity car,0,0,speed PositionEntity pop,x,th,z ; this is just a central axis 'pole' to help see rotation angles RotateEntity pop,pitch-90,yaw,roll-90 PositionEntity camera , x+400,y+300,z+200 PointEntity camera,car UpdateWorld RenderWorld Flip Wend Stop |