Map Collision Eject
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Map Collision Eject
Hi tokumaru
As the topic states eject from tile position can you go into detail i'm aware when logical (lda _ObjectY,x..and %00000111) my object the low bits are how any pixels i'm into the block.How do I add these back is my question.Sorry if this is a newbie question but i'm also new to game coding.
As the topic states eject from tile position can you go into detail i'm aware when logical (lda _ObjectY,x..and %00000111) my object the low bits are how any pixels i'm into the block.How do I add these back is my question.Sorry if this is a newbie question but i'm also new to game coding.
Re: Map Collision Eject
I'm assuming a no on my question then,Tepples wanna help?i'm assuming add the low bits+1 back to the object postion.I apologise for my english, i'm Canadian and english is my third language .
Also sorry for the edits i had to look up French,German to English a few times
Also sorry for the edits i had to look up French,German to English a few times
Last edited by Prime on Sun Nov 29, 2015 10:01 pm, edited 5 times in total.
Re: Map Collision Eject
Could I see a bit of context, such as how you are computing this value whose low 3 bits are the penetration distance?
(Also run-ons.)
(Also run-ons.)
Re: Map Collision Eject
Yes of course this is checking the right side of my aabb
Code: Select all
blobfeetchkloop:
lda _objectlinkedlist,x ;<-- my Yposition
clc
adc #21
tay
ldx _XObjectTmp
jsr do_tilemapcollision
bcs blobfeetcollision
lda _XObjectTmp
clc
adc #7
sta _XObjectTmp
dec _tmploop
bne blobfeetchkloop
blobfeetexit:
rts
My collisionRam Map is 16x16
do_tilemapcollision:
lda _XObjectTmp ;<-- Xposition
lsr
lsr
lsr
lsr
and #%00001111 ;Karnov
sta _XTmp
tay ;<-- Yposition
lsr
lsr
lsr
lsr
asl
asl
asl
asl
ora _Xtmp
tay
lda _MapCollisiondata,y
cp #1
beq Collision
NoCollision:
clc
rts
Collision:
sec
rts
Re: Map Collision Eject
Didn't have time to check this out yet. I'm not home now, will try to take a look later.
Re: Map Collision Eject
No worries tokumaru i've Tepples helping me.tokumaru wrote:Didn't have time to check this out yet. I'm not home now, will try to take a look later.
Re: Map Collision Eject
Also Tepples can you go into deep detail or link me as i understand most of you're explanations and find it difficult to understand other members.(I can understand tokumaru&Tepples can the rest of you guys not add into the conversation until they both reply?)
Last edited by Prime on Mon Nov 30, 2015 7:51 am, edited 1 time in total.
Re: Map Collision Eject
I'm not yet in a position to sit down and understand the entire code snippet. But I did find a few things that if you clarified them I could understand better.
What are the 21 and the 7?Prime wrote:Code: Select all
blobfeetchkloop: lda _objectlinkedlist,x ;<-- my Yposition clc adc #21 tay ldx _XObjectTmp jsr do_tilemapcollision bcs blobfeetcollision lda _XObjectTmp clc adc #7
Why not just AND #$F0?Code: Select all
tay ;<-- Yposition lsr lsr lsr lsr asl asl asl asl ora _Xtmp
Re: Map Collision Eject
Very unusual way to start a topic, since not all members read everything... luckily I read almost everything that isn't SNES, music, repros or mods!Prime wrote:Hi tokumaru

When in doubt... DRAW! Here's a character (blue rectangle) running right into a wall, inside a tiny 3x3 metatile area:
Since the object moved left (something we know because the horizontal displacement was positive), we have to check all the blocks from the top right corner ($24, $04) to the bottom right corner ($24, $1F), to know whether they're solid or not. Dividing by 16, we have to look at all blocks between (2, 0) and (2, 1). If any of those blocks are solid, you'll know the object has hit a wall, which is the case here.
Now we have to figure out how many pixels to push the object back. Regardless of where the object's hospot is, and how you calculated the rightmost horizontal coordinate, you can easily tell just from looking that this coordinate is 5 pixels into the wall. Math confirms this: $24 AND $0f = $04, the fifth pixel of the metatile. You can now simply subtract 4 + 1 (since we count pixels from 0) from the object's coordinate and you can be sure that its right side will not be inside the wall anymore.
The math is a bit different for the left side, since objects enter the wall from the opposite side (column $0f):
Now we're looking at the corners ($0B, $04) and ($0B, $1F). $0B AND $0F = $0B, which is the 12th column of the metatile, but since the object is entering from the right, that doesn't mean it's 12 pixels in. The actual value you're looking for is 16 - 12 = 4, which is the same we'd get if the object was moving right, like in the previous example. In assembly, you can use a shortcut to find this number: just EOR it with $0F. $0B EOR $0F = $04, which is the number you're looking for. Now you can add that (plus 1) to eject the object from the wall.
Does this help?
Re: Map Collision Eject
I noticed now that you mentioned the mask %00000111, which makes me believe you're using 8x8-pixel blocks, not metatiles as in my example, right? If so, that's not a problem, the logic is always the same, you just have to keep the block size in mind when dividing and masking/negating bits.
Re: Map Collision Eject
[quote="tepples"]I'm not yet in a position to sit down and understand the entire code snippet. But I did find a few things that if you clarified them I could understand better.
[/code]
What are the 21 and the 7?
21 is my yposition AABB
Sorry Tepples i want help but i wasen't clear
Why not just AND #$F0
I didn't think of this
I'm new to 6502
[/code]
What are the 21 and the 7?
21 is my yposition AABB
Sorry Tepples i want help but i wasen't clear
Code: Select all
tay ;<-- Yposition
lsr
lsr
lsr
lsr
asl
asl
asl
asl
ora _Xtmp
I didn't think of this
I'm new to 6502
Re: Map Collision Eject
Thanks tokumaru & Tepples i need to read what tokumaru posted.
Now i get it thanks guys...I was having a problem with my object gravity he was to many pixels into the block.
Now i get it thanks guys...I was having a problem with my object gravity he was to many pixels into the block.
Re: Map Collision Eject
I'm coding in z80 brother but the same rules applytokumaru wrote:I noticed now that you mentioned the mask %00000111, which makes me believe you're using 8x8-pixel blocks, not metatiles as in my example, right? If so, that's not a problem, the logic is always the same, you just have to keep the block size in mind when dividing and masking/negating bits.
Re: Map Collision Eject
Tepples I'm used to this
ld b,(ix+constantYInt)
ld c,(ix+ContantYFraction)
ld l,(ix+objectYFraction)
ld h(ix+ObjectYInt)
add hl,bc
ld (ix+objectYFraction),l
ld h(ix+ObjectYInt),h
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Is this the equivalent to as 6502 has direct memory access
charlievelocitycont:
lda _blobgravityf
sec
sbc _blobconstgravityf
sta _blobgravityf
lda _blobvelocity
sbc #0
sta _blobvelocity
ld b,(ix+constantYInt)
ld c,(ix+ContantYFraction)
ld l,(ix+objectYFraction)
ld h(ix+ObjectYInt)
add hl,bc
ld (ix+objectYFraction),l
ld h(ix+ObjectYInt),h
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Is this the equivalent to as 6502 has direct memory access
charlievelocitycont:
lda _blobgravityf
sec
sbc _blobconstgravityf
sta _blobgravityf
lda _blobvelocity
sbc #0
sta _blobvelocity
Re: Map Collision Eject
Yes, that's how you typically subtract 16-bit values on 6502.