IRF Posted April 3, 2017 Report Share Posted April 3, 2017 (edited) Another thing that I meant to point out last night, but forgot: the only moving elements that aren Edited April 3, 2017 by IRF jetsetdanny 1 Quote Link to comment Share on other sites More sharing options...
IRF Posted April 3, 2017 Report Share Posted April 3, 2017 (edited) Having thought a bit about the above, perhaps another check could be inserted just prior to the JR NZ, LOOP command: Copy L into A, apply an AND #0F, and if that sets the Zero Flag, then it's time to update the attributes for the cell-row under consideration. (N.B. the code to achieve that should be bookended by PUSH HL and then POP HL, to preserve the pointer to the lookup table at #8200). I'm not sure whether it would fit into those spare 16 bytes which Norman identified? (Which could be 18 bytes if you didn't need the JR 35366 / #8A26 at the end of the code which makes Willy run double-quick during the toilet dash.) EDIT: Actually, there would be another 11 bytes to play with (so 29 in all), since the function of the code at #8A26-#8A30 would have been performed instead by the new intervention. So it should be doable within the available space in the Main Loop - I might have a go at it when I get a moment. It would kill two birds with one stone - eliminate the 'Jagged Finger Effect' AND the 'Delayed Attribute Update Effect' (I'm still open to suggestions on the name for that one!) I think the above can be done in 26 29 bytes. That should nicely leave exactly three spare bytes, which would be best left in situ prior to the start of Norman's code (to allow a CALL to elsewhere to reinstate the Screen Flash routine - otherwise the Screen Flash effect wouldn't be able to influence the screen's PAPER colour - or alternatively to add a CALL to the Main Loop Patch Vector sub-routine). I haven't tried this out yet, but here's my first stab on the basis of studying the code (I prefer to work in hexadecimal): org #89F5 89F5 Three spare bytes Then First comes most of Norman's code, highlighted in bold: 89F5 LD HL, #8200 89F8 LD E, (HL) Start of LOOP, each iteration of which copies 32 graphic bytes across a single pixel-row (raster line) of the screen 89F9 INC L 89FA PUSH HL 89FB LD D, (HL) 89FC LD L, E 89FD LD H, D 89FE RES 5, D 8A00 LD BC, #0020 8A03 LDIR 8A05 POP HL 8A06 INC L 8A07 LD A, L 8A08 AND #0F Check if L is now exactly divisible by #10 8A0A JR NZ, LOOP If not, then we haven't yet drawn all eight pixel-rows of the current character-row to the screen, so jump back to LOOP to draw the next pixel-row 8A0C PUSH HL 8A0D LD A, L 8A0E SUB A, #10 8A10 LD L, A 8A11 LD H, #5C 8A12 OR A Reset the Carry Flag in preparation for the next command (N.B. This may not be necessary?) 8A13 SLA L This sets the Carry Flag if (and only if) we are now considering a character-row in the bottom half of the playing area 8A15 LD E, L 8A16 JR NC, #01 This jump only occurs if we are in the bottom half of the playing area 8A18 INC H Point H at the bottom half of the playing area; HL now points at the left-hand end of the appropriate character-row in the attribute buffer 8A19 LD D, H 8A1A RES 2, D DE now points at the left-hand end of the appropriate character-row in the screen's attribute file 8A1C LD BC, #0020 There are 32 bytes to copy 8A1F LDIR Copy the attributes along the current character-row 8A21 POP HL 8A22 LD A, L 8A23 OR A Check if we have finished copying the whole of the playing area (i.e. the graphic bytes and attributes for all sixteen character-rows) 8A24 JR NZ, LOOP If not, then jump back to LOOP to consider the next character-row This command marks the end of Norman's code That would then be followed by the original code which makes Willy run at double-speed during the Toilet Dash (which fortuitously fits exactly into the space where the original attribute-copying code was located): 8A26 LD A, (#85DF) 8A29 AND #02 8A2B RRCA 8A2C LD HL, #85D2 8A2F OR (HL) 8A30 LD A, (HL) Finally, the original Main Loop routine resumes at #8A31 (starting with the code which prints the current time, then the number of items collected, etc). Let's just hope it works!! :P Edited April 4, 2017 by IRF jetsetdanny 1 Quote Link to comment Share on other sites More sharing options...
jetsetdanny Posted April 3, 2017 Report Share Posted April 3, 2017 I'm unable to follow the details of this, but your effort looks impressive, Ian! It's interesting how Norman Sword will react to it :) . IRF 1 Quote Link to comment Share on other sites More sharing options...
IRF Posted April 3, 2017 Report Share Posted April 3, 2017 (edited) I just tried it out and it crashed the emulator, with random coloured squares everywhere!! Either my idea is completely off, or I've made a tiny mistake that may take ages to track down - or possibly some scenario in between!!EDIT: At first glance, I think it's something to do with the way in which I've incorrectly used the PUSH and POP commands, causing a stack overload.UPDATE: Yes, that was the problem, a PUSH in the wrong place. I've swapped the code around slightly and it works fine now. I'll edit the previous post accordingly (DONE).Please see the latest test file attached to this post. The 'Delayed Attribute Update' effect is still present, but it is much less prominent than it was before.EDIT: I've also reattached the earlier test file here (renamed slightly for clarity), which displayed the bugs prominently and has the same starting position (the Swimming Pool, with Red Air INK, Cyan Air PAPER and eight arrows at various heights), so that the 'Before' and 'After' can be compared and contrasted. FURTHER UPDATE: I've removed the files temporarily, as I want to work a bit more on the code to increase its effectiveness and efficiency. Edited April 4, 2017 by IRF Quote Link to comment Share on other sites More sharing options...
IRF Posted April 3, 2017 Report Share Posted April 3, 2017 (edited) Please see the latest test file, attached here. The 'Delayed Attribute Update' effect is still present, but less prominent than it was before, I feel. If you compare the effect in the Swimming Pool between the two snapshot files (the earlier one and the 'fixed' one), there is definitely less of a pronounced 'leading edge' to Willy as he walks/jumps/falls across cell boundaries. The effect is still quite prominent for the two arrows at the top of the screen (UPDATE: not any more!), but less so for the lower arrows. Since arrows move horizontally one cell at a time, I would expect the effect's prominence to be most acute for arrows. However, I would have expected the delay between the arrow being pixel-drawn and attribute-rendered to be greater for the first arrow from the top (which occupies the second pixel-row of the top cell-row), compared with the delay for the second arrow down (which occupies the seventh pixel-row of the top cell-row). So I am a bit surprised that the effect seems to have roughly equal prominence for those top two arrows(?) UPDATE: I had made a small error when writing my patch, which I have now fixed. Still, my latest code changes seem to have improved the situation for most UPDATE: ALL of the arrows in the test file. :) EDIT: And the 'Green Legs' effect when Willy falls into 'Entrance to Hades' is greatly reduced in the latest file (although you'll have to navigate over there yourself to see that). Edited April 4, 2017 by IRF Quote Link to comment Share on other sites More sharing options...
IRF Posted April 3, 2017 Report Share Posted April 3, 2017 (edited) I don't think I've quite got the attribute part of the loop working properly. I think each cell-row is having its attributes drawn before the graphic bytes for that cell-row, but the first cell-row isn't getting coloured in until the very end of the loop (after the rest of the screen has been drawn). That's why the top two arrows haven't been 'fixed' to the same extent as the others. A further tweak is required... EDIT: I''ve cracked it! In the end I needed to use the three spare bytes which I thought I had left over, as well as an OR A which I had previously indicated would reset the Carry Flag, but which on reflection wasn't necessary for the patch to function properly. I think the improvement is now very noticeable from the 'Before' to the 'After' scenario. B) I've swapped the file which I'd previously uploaded for the 'properly fixed' version (I don't think anyone had downloaded it before I swapped it?), and I've also updated/corrected the disassembly which I provided in post no. 22 of this thread. Thanks again to Norman for his part in this fix - I was able to 'piggy-back' onto his code, in order to implement my more comprehensive patch for both the 'Jagged Finger' AND the 'Delayed Attribute Update' bugs. Edited April 4, 2017 by IRF Quote Link to comment Share on other sites More sharing options...
IRF Posted April 4, 2017 Report Share Posted April 4, 2017 (edited) I'm unable to follow the details of this, but your effort looks impressive, Ian! It's interesting how Norman Sword will react to it :) . Hopefully you won't need to be able to follow the details to appreciate the qualitative difference between the Before and After scenarios? The improvement in terms of the 'Delayed Attributes' is easily seen in the starting room (Swimming Pool), and it you wander left and then up the long staircase as far as Conservatory Roof, you can hopefully see the improvement in terms of the 'Jagged Finger' - watch Willy's sprite as he goes up the ramp (particularly as he passes from bottom to top half of the playing area), and the horizontal guardians in Conservatory Roof. EDIT: Other places to watch/compare/contrast: - watch Willy jump and fall in Front Door (highly noticeable improvement in there because the Air INK is Black against Cyan PAPER, both of which contrast well with Willy's customary White); - drop him down into Entrance to Hades; - observe the fast-moving vertical guardians in 'I'm sure I've seen this before', and 'Rescue Esmerelda'; also the beak of the horizontal Bird in both rooms, and the Arrows in the former. Edited April 4, 2017 by IRF Quote Link to comment Share on other sites More sharing options...
jetsetdanny Posted April 4, 2017 Report Share Posted April 4, 2017 Congratulations, Ian! So I was right in believing your effort was impressive ;). I can't download the the files right now, I'll have a look at them later :). Spider and IRF 2 Quote Link to comment Share on other sites More sharing options...
IRF Posted April 4, 2017 Report Share Posted April 4, 2017 (edited) Maybe it ended up impressive once I'd resolved a couple of silly mistakes! I'm still not convinced it's as byte-efficient as it could be though? Edited April 4, 2017 by IRF Quote Link to comment Share on other sites More sharing options...
IRF Posted April 4, 2017 Report Share Posted April 4, 2017 I don't think I've quite got the attribute part of the loop working properly. I think each cell-row is having its attributes drawn before the graphic bytes for that cell-row, but the first cell-row isn't getting coloured in until the very end of the loop (after the rest of the screen has been drawn). That's why the top two arrows haven't been 'fixed' to the same extent as the others. A further tweak is required... That's exactly what was happening during my previous 'semi-successful' attempt to fix the 'Delayed Attributes' bug. In fact, some of the arrows actually had red 'trailing edges' instead of red 'leading edges', particularly where an arrow occupied a pixel-row towards the bottom of its cell-row - the white attribute was being advanced ahead of the arrow's graphical bytes. A kind of 'Premature Attribute Update' effect, so to speak. I suppose the optimum fix would be, for each cell-row, to draw the top four pixel-rows, copy the attributes for that cell-row, and then draw the bottom four pixel-rows. That would balance out/minimise the 'delays' between any particular graphic byte and its associated attribute being distributed across the whole screen. It might further complicate the code though! Quote Link to comment Share on other sites More sharing options...
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