Specific Questions about Collision Detection and Camera movement

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MrSOP

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Posted: 6th Apr 2006 17:59

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Hello. I copied and pasted the code section I am on in the Monster Hunt tutorial. I put in bold the parts of the code related to the 2 questions I had. Please help.

1) I think I understand the code putting the object back where it was in the event of a collision. However, i am confused on how this code could exist on the first iteration of the loop where X# and Z# are not defined yet until the next line. Please help me understand. My understanding of the tutorial's explanation is that it is done this way to prevent the "position reset" from putting the object in a condition where it would collide with another object. Is this right?

2) For the camera movement, from changing the values in the aY#-180 part adjusts the camera's perspective. I thought that if I made that a variable

CamPos# = ay#-180

and then changed the value of this variable based on the spacebar push

if Spacekey()=1 then CamPos# + 1

and then plugged in CamPos# into the original equation in place of ay#-180 it would allow me to circle the object with the camera. However it says it cannot understand the CamPos# = ay#-180. What am I missing here? I would also guess that I may need to somehow include the wrapvalue command to CamPos#?! Is this correct?

Rem Setup sync
Sync On
Sync Rate 30

Rem Make Cones and place randomly
For x = 1 to 5
   Make object cone x,50
   Position object x,Rnd(2000),0,Rnd(2000)
   Set object collision to boxes x
Next x

Rem Make sphere
Make object sphere 10,50
Position object 10,-100,0,-100
Set object collision to spheres 10

Rem Main loop
Do
   Rem Store Object angle Y in aY#
   aY# = Object angle Y(10)

Rem Control input for camera
   If Upkey()=1 then Move object 10,10
   If Leftkey()=1 then Yrotate object 10,Wrapvalue(aY#-5)
   If Rightkey()=1 then Yrotate object 10,Wrapvalue(aY#+5)

Rem Detect collision
   [b]If Object collision(10,0)>0 then position object 10,X#,0,Z#[/b]

Rem get player object position and store in X# and Z#
   X# = Object position x(10)
   Z# = Object position z(10)

Rem get new camera position and store in cZ# and cX#
   cZ# = Newzvalue(Z#,[b]aY#-180[/b],100)
   cX# = Newxvalue(X#,[b]aY#-180[/b],100)

Rem position camera
   Position Camera cX#,75,cZ#

Rem point the camera at the player object
   Point camera X#,25,Z#

Rem Refresh Screen
   Sync
Loop

+ Code Snippet

Rem Setup sync
Sync On
Sync Rate 30

Rem Make Cones and place randomly
For x = 1 to 5
   Make object cone x,50
   Position object x,Rnd(2000),0,Rnd(2000)
   Set object collision to boxes x
Next x

Rem Make sphere
Make object sphere 10,50
Position object 10,-100,0,-100
Set object collision to spheres 10

Rem Main loop
Do
   Rem Store Object angle Y in aY#
   aY# = Object angle Y(10)

   Rem Control input for camera
   If Upkey()=1 then Move object 10,10
   If Leftkey()=1 then Yrotate object 10,Wrapvalue(aY#-5)
   If Rightkey()=1 then Yrotate object 10,Wrapvalue(aY#+5)

   Rem Detect collision
   [b]If Object collision(10,0)>0 then position object 10,X#,0,Z#[/b]

   Rem get player object position and store in X# and Z#
   X# = Object position x(10)
   Z# = Object position z(10)

   Rem get new camera position and store in cZ# and cX#
   cZ# = Newzvalue(Z#,[b]aY#-180[/b],100)
   cX# = Newxvalue(X#,[b]aY#-180[/b],100)

   Rem position camera
   Position Camera cX#,75,cZ#

   Rem point the camera at the player object
   Point camera X#,25,Z#

   Rem Refresh Screen
   Sync
Loop

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Me!

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Posted: 6th Apr 2006 20:15 Edited at: 6th Apr 2006 20:16

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if Spacekey()=1 then CamPos# = CamPos# + 1

or

if spacekey() then inc CamPos#

or

if spacekey() then CamPos#=wrapvalue(inc(CamPos#))

inc stands for increment, using spacekey on its own is permissable since spacekey returns 1 (true) or 0 (false), and if/then is looking for an true/false condition, so spacekey() on its own will be either true or false and is all you need, pressed is true (=1), not pressed is false (=0)

unused variables in basic start with the value zero or null ("") in the case of strings, so the unused variables are actualy at zero on the first pass, in practice it`s best to explicitly set all your variables, but this is B.A.S.I.C, so you get quirks like that.

Dr Frankenstiens mum told him to make some new friends, not knowing where this was going to lead.

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MrSOP

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Posted: 6th Apr 2006 21:06

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thank you very much!

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MrSOP

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Posted: 6th Apr 2006 21:28

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One more question actually. I was having some trouble with the matrices section of Monster Hunter3D in DBPro. Basically, in a few places, the stated code would not work how I believed it would. For example, my 3rd person object (the sphere) would move over what appeared to be a flat matrix, but move up and down on "invisible hills" as it moved across the matrix.

Here is the code for the section in question:

Sync On
Sync Rate 30
Backdrop on

Set camera range 1,5000
Fog on
Fog distance 4000
Fog color RGB(128,128,128)
Color Backdrop RGB(128,128,128)

Rem make matrix
Make matrix 1,10000,10000,20,20

Rem texture matrix
Load image "C:\grass09.bmp",1
Prepare matrix texture 1,1,1,1
Fill matrix 1,0,1

Rem Make player pawn
Load image "C:\parchment.bmp",2
Make object sphere 10,25
Texture object 10,2
position object 10,100,0,100

Rem Randomize the matrix
randomize matrix 1,125
Rem Main loop
Do
   Rem Store Object angle
   AngleY# = object angle Y(10)

Rem Control input for camera
   If Upkey()=1
      XTest# = Newxvalue(X#,AngleY#,20)
      ZTest# = Newzvalue(Z#,AngleY#,20)
      If XTest#>0 and XTest#<10000 and ZTest#>0 and ZTest#<10000
         Move object 10,10
      Endif
   Endif

If Leftkey()=1 then Yrotate object 10,Wrapvalue(AngleY#-5)
   If Rightkey()=1 then Yrotate object 10,Wrapvalue(AngleY#+5)
   X# = Object position x(10)
   Z# = Object position z(10)
   Y# = Get Ground Height(1,X#,Z#)
   Position object 10,X#,Y#+12.5,Z#
   CameraZ# = Newzvalue(Z#,AngleY#-180,100)
   CameraX# = Newxvalue(X#,AngleY#-180,100)
   Position camera CameraX#,Y#+50,CameraZ#
   Point camera X#,Y#+25,Z#

Rem Refresh Screen
   Sync
Loop

+ Code Snippet

Sync On
Sync Rate 30
Backdrop on

Set camera range 1,5000
Fog on
Fog distance 4000
Fog color RGB(128,128,128)
Color Backdrop RGB(128,128,128)

Rem make matrix
Make matrix 1,10000,10000,20,20

Rem texture matrix
Load image "C:\grass09.bmp",1
Prepare matrix texture 1,1,1,1
Fill matrix 1,0,1

Rem Make player pawn
Load image "C:\parchment.bmp",2
Make object sphere 10,25
Texture object 10,2
position object 10,100,0,100

Rem Randomize the matrix
randomize matrix 1,125
Rem Main loop
Do
   Rem Store Object angle
   AngleY# = object angle Y(10)

   Rem Control input for camera
   If Upkey()=1
      XTest# = Newxvalue(X#,AngleY#,20)
      ZTest# = Newzvalue(Z#,AngleY#,20)
      If XTest#>0 and XTest#<10000 and ZTest#>0 and ZTest#<10000
         Move object 10,10
      Endif
   Endif

   If Leftkey()=1 then Yrotate object 10,Wrapvalue(AngleY#-5)
   If Rightkey()=1 then Yrotate object 10,Wrapvalue(AngleY#+5)
   X# = Object position x(10)
   Z# = Object position z(10)
   Y# = Get Ground Height(1,X#,Z#)
   Position object 10,X#,Y#+12.5,Z#
   CameraZ# = Newzvalue(Z#,AngleY#-180,100)
   CameraX# = Newxvalue(X#,AngleY#-180,100)
   Position camera CameraX#,Y#+50,CameraZ#
   Point camera X#,Y#+25,Z#

   Rem Refresh Screen
   Sync
Loop

After searching the forums for monster hunter, it appears that it does not work correctly in DBPro. Some poster actually said he made modifications for it to work in DBPro, and posted the updated tutorial on a page...that unfortunately no longer exists.

1) Would this problem be attributed to the difference in DBC and DBP, and what about the code would need to be changed in this section to achieve the same thing (a ball moving over a terrain with visible hills)?

2) I like the monster hunter tute, but if I am going to keep running into these type problems, is there a similar tutorial that you would recommend?

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MrSOP

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Posted: 6th Apr 2006 21:37

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(sorry for the multiple posts...i didnt see an edit button or anything)

Never mind...I made a classic newbie mistake and didn't read everything thoroughly before posting. I will try out some of the terrain generators and some of the recommended tutes mentioned in the top post

sorry.

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Newcomers DBPro Corner / Specific Questions about Collision Detection and Camera movement