Collision help

BlitzMax Forums/BlitzMax Programming/Collision help

RetroRusty

(Posted 2009) [#1]

I'm having some problems trying to get my head around collisions for a platform game.

I've not used BlitzMax to any extent before and would ask if any of you could please have a look at the file in the link and help me out with it?

http://www.enigma.retroremakes.com/russ/BuildMap.zip

matibee

(Posted 2009) [#2]

Whats your problem?

I noticed he falls into the level then can't walk... Line 117 moves the player down, then you check for collision. But if a collision has occured the player will be embedded in the level. Change line 120 to

PlayerY = PlayerY - 2.8

to put him back to where he was.

RetroRusty

(Posted 2009) [#3]

It's still not right. He's able to jump into parts of the level. If you move him to the left and try and jump on the level, you will see what I mean.

matibee

(Posted 2009) [#4]

Ok, Russ

Some notes;

First; checking playerX + 16 and playerX + 32 is too far over. You'd have to check PlayerX,PlayerX+16 AND PlayerX+32. Instead check half the tile width.. PlayerX + 8 and PlayerX + 24 which does a good job of averaging the correct two tiles to check.

Second; checking for stopping a fall should be an OR not an AND check. You only stopped a fall if both tiles below are occupied, when you should stop if either one is!

Third; I added a little re-adjustment to playerY so he always stops on the ground (see the While/Wend)..

Hope that helps

Function MovePlayer()
	If KeyDown(KEY_RIGHT) And TestMap(PlayerX + 32, PlayerY + 30) = 0
		PlayerDirection = 1
		PlayerX:+1
	End If
	
	If KeyDown(KEY_LEFT) And TestMap(PlayerX - 1, PlayerY + 30) = 0
		PlayerDirection = 0
		PlayerX:-1
	End If
	
	If KeyHit(KEY_SPACE)
		PlayerJump = 1
	End If
	
	If PlayerJump = 1
		PlayerY:-PlayerJumpHeight
		PlayerJumpHeight:-PlayerGavity
		If PlayerJumpHeight <= - 1.0 Or PlayerY < 32 Or TestMap(PlayerX + 16, PlayerY - 1) > 0
			PlayerFalling = 1
		End If
	End If
	
	If TestMap(PlayerX + 8, PlayerY + 32) = 0 And TestMap(PlayerX + 24, PlayerY + 32) = 0 Then PlayerFalling = 1
	
	If PlayerFalling = 1
		PlayerY:+2.8
		If TestMap(PlayerX + 8, PlayerY + 32) <> 0 Or TestMap(PlayerX + 24, PlayerY + 32) <> 0
			
			PlayerY = PlayerY - 0.5
			While TestMap(PlayerX + 8, PlayerY + 32) <> 0 Or TestMap(PlayerX + 24, PlayerY + 32) <> 0
				PlayerY = PlayerY - 0.5
			Wend 

			
			
			PlayerJump = 0
			PlayerFalling = 0
			PlayerJumpHeight = 6.3
		
		End If
	End If
End Function