Beginner's Raycasting Question - GameCreators Forum

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MadTinkerer

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Posted: 3rd Aug 2018 22:27

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It's been a while since Trig class, so I have some questions.

I'm trying to use ObjectRayCast to hit an object that the camera is looking at. The first three coordinates are, of course, GetCameraX, GetCameraY, and GetCameraZ. The last three coordinates should be GetCameraX plus something, GetCameraY plus something, and GetCameraZ plus something. Probably something to do with GetCameraAngleX, GetCameraAngleY, and GetCameraAngleZ. I probably have to multiply by something. I hypothesize that hypotenuses may be involved. Possibly the sin() function. But I don't know exactly what to do.

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Golelorn

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Posted: 4th Aug 2018 12:30

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I think this should give you the X,Z coords at the center of the screen. Just fill in a value for Y.

cx# = GetCameraX(1)
		cy# = GetCameraY(1)
		cz# = GetCameraZ(1)
		pxRaw# = Get3DVectorXFromScreen( 50, 50 ) // center of screen - my example is percentage based //may want to use GetScreenBoundsRight ()/2 and GetScreenBoundsBottom ()/2 instead?
		pyRaw# = Get3DVectorYFromScreen( 50, 50 ) // center of screen - my example is percentage based
		pzRaw# = Get3DVectorZFromScreen( 50, 50 ) // center of screen - my example is percentage based
		//// get pointer vector y added to camera's y position
		pyRelative# = pyRaw# + cy#
	 
		//// find distance between camera's y position and pyRelative#
		dist# = cy# - pyRelative#
	 
		//// calculate scaling value by finding how many times dist# goes into the camera's y position
		s# = cy# / dist#
	 
		//// find the intersection point by multiplying pointer vector by s# and adding it to the camera position. 
		//// Y shouldn't matter since the camera would see any height below the camera -  just use a value with low enough height
		new_x = cx# + pxRaw# * s#
		new_z = cz# + pzRaw# * s#

+ Code Snippet

		cx# = GetCameraX(1)
		cy# = GetCameraY(1)
		cz# = GetCameraZ(1)
		pxRaw# = Get3DVectorXFromScreen( 50, 50 ) // center of screen - my example is percentage based //may want to use GetScreenBoundsRight ()/2 and GetScreenBoundsBottom ()/2 instead?
		pyRaw# = Get3DVectorYFromScreen( 50, 50 ) // center of screen - my example is percentage based
		pzRaw# = Get3DVectorZFromScreen( 50, 50 ) // center of screen - my example is percentage based
		//// get pointer vector y added to camera's y position
		pyRelative# = pyRaw# + cy#
	 
		//// find distance between camera's y position and pyRelative#
		dist# = cy# - pyRelative#
	 
		//// calculate scaling value by finding how many times dist# goes into the camera's y position
		s# = cy# / dist#
	 
		//// find the intersection point by multiplying pointer vector by s# and adding it to the camera position. 
		//// Y shouldn't matter since the camera would see any height below the camera -  just use a value with low enough height
		new_x = cx# + pxRaw# * s#
		new_z = cz# + pzRaw# * s#

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smallg

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Posted: 4th Aug 2018 15:17 Edited at: 4th Aug 2018 15:20

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just store the position, move the camera (or a dummy object) forward (MoveCameraLocalZ()), do the raycast from the stored location to the new location, then move the camera back

+ Code Snippet

cx = GetCameraX(1)
cy = GetCameraY(1)
cz = GetCameraZ(1)
MoveCameraLocalZ(1,1000)
hitobj = ObjectRayCast(0,cx,cy,cz,GetCameraX(1),GetCameraY(1),GetCameraZ(1))
MoveCameraLocalZ(1,-1000)

life's one big game
spec= 4ghz, 16gb ram, AMD R9 2700 gpu

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MadTinkerer

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Posted: 4th Aug 2018 15:38

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Thanks, guys!

I actually found another answer in Tutorial guide 2, but both of those look like they work as well! Here's an excerpt from my version of the code:

+ Code Snippet

		camX as float
		camY as float
		camZ as float
		pointX as float
		pointY as float
		pointZ as float
		dist as integer

		camX = GetCameraX(1)
		camY = GetCameraY(1)
		camZ = GetCameraZ(1)
		pointX = Get3DVectorXFromScreen(GetPointerX(), GetPointerY())
		pointY = Get3DVectorYFromScreen(GetPointerX(), GetPointerY())
		pointZ = Get3DVectorZFromScreen(GetPointerX(), GetPointerY())
		dist = 1024

		didWeHitAnObject = ObjectRayCast(0, camX, camY, camZ, camX+(pointX*dist), camY+(pointY*dist), camZ+(pointZ*dist))

And I didn't even have to do the trig myself. Using the center coordinates of the screen instead of GetPointer also works, if you're not using the pointer to select things and/or not resetting the position of the pointer for the purposes of mouselook.

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