Subject: RE: [stella] Playfield using "inx" vs "using SLEEP" From: "Fernando Romo" <fromobal@xxxxxxxxxxx> Date: Tue, 23 Aug 2005 14:45:24 -0400 |
Thanks a lot for your comments Lee, I appreciate a lot your answer, I know that with more time and patience I will achive more interesting things. Someone told me that Stella BigList was the place in order to receive amazing feedback (I have received), so taking advantage of that comment, I would like to share with you this code that draw a square box. I know that SLEEP is used to waste time (2 machine cycles),,,,,but applied it to this code is where I did not understand, I mean, how to assume what beam light is going to do, etc., etc., ; TOP LINE lda #%11111111 sta PF0 sta PF1 sta PF2 lda #15 sta WSYNC ; I undestand very well this part sta WSYNC sta WSYNC sta WSYNC sta WSYNC sta WSYNC sta WSYNC lda #%00000000 sta PF1 sta PF2 Picture lda #15 sta COLUPF lda #%00010000 sta PF0 SLEEP 2 ; what? lda #0 sta COLUPF SLEEP 25 ; for what? lda #15 sta COLUPF lda #%10000000 sta PF2 sta WSYNC inx cpx #176 bne Picture ; BOTTOM LINE lda #15 ; I understand very well this sta COLUPF lda #%11111111 sta PF0 sta PF1 sta PF2 sta WSYNC sta WSYNC sta WSYNC sta WSYNC sta WSYNC sta WSYNC sta WSYNC sta WSYNC sta WSYNC lda #0 sta COLUPF My best regards Fernando Romo >From: "Lee Fastenau" <stella@xxxxxxxxxxxxxxx> >Reply-To: stella@xxxxxxxxxxxxxxxxxx >To: <stella@xxxxxxxxxxxxxxxxxx> >Subject: RE: [stella] Playfield using "inx" vs "using SLEEP" >Date: Thu, 18 Aug 2005 23:51:57 -0400 > >SLEEP is a handy macro by Thomas Jentzsch that's part of the DASM >distribution. You've probably read that many graphics kernels require >extremely precise timing for positioning graphics, changing playfield >values, and changing colors or other registers. SLEEP lets programmers >easily waste a specific number of CPU cycles for those purposes. > >But SLEEP isn't the only way to burn cycles, and depending on the type of >graphics kernel being built, those cycles might be needed to perform other >operations, like incrementing a counter X ("INX", which burns 2 cycles just >like "SLEEP 2"). > >Also, there are nearly as many different graphics kernels as there are >games >for the Atari 2600 and there are typically many ways to achieve a given >effect... so that difference in code to achieve the same effect isn't too >surprising. > >Before I tackled my first game, I thought there might be "one really good >kernel" that I could write and reuse over and over, because that seemed to >be the most difficult part to code. But after doing some more research and >a lot of experimentation, I discovered that _because_ the kernel is such a >critical and challenging piece of code to write, that it was the _first_ >part that everyone wrote... typically from scratch or "inspired" by another >kernel, but almost never a reused kernel from another game. > >After all, it's really the graphics that makes programming the 2600 such a >unique and rewarding experience. > >Don't get discouraged. If you keep reading and practicing, then one-by-one >the light bulbs will turn on. > >-Lee > > > -----Original Message----- > > From: Fernando Romo [mailto:fromobal@xxxxxxxxxxx] > > Sent: Thursday, August 18, 2005 5:28 PM > > To: stella@xxxxxxxxxxxxxxxxxx > > Subject: [stella] Playfield using "inx" vs "using SLEEP" > > > > Hi! > > > > I appreciate if someone of this group could help me a little bit > > regarding > > the way we use playfield. When I was reading PlayField section from > > Andrew's > > tutorial in AtariAge Web page, I understood very well the example when >he > > showed that using the X counter, I mean "inx", we can see what and where > > scanline we are going to draw,,,,,,,,,,,,,,,,BUT,,,,when I printed the > > Andrew tutorial from another web page, in that tutorial there is the >same > > example (draw square box), but using SLEEP instruction. > > > > And also when I came across with that instruction, I have not >fisnished > > to > > understand how this works?,,,,so,,,,could someone could explain me >please? > > > > I don't wnat to advance readong more things if I do not understand >that > > (SLEEP). > > > > My best regards > > Fernando Romo > > > > _________________________________________________________________ > > T1msn Search. Todo lo que buscas ahora mas rapido > > http://search.t1msn.com.mx/ > > > > Archives (includes files) at >http://www.biglist.com/lists/stella/archives/ > > Unsub & more at http://stella.biglist.com > > > >Archives (includes files) at http://www.biglist.com/lists/stella/archives/ >Unsub & more at http://stella.biglist.com > _________________________________________________________________ T1msn. Mas Ztil Cada Dma http://www.t1msn.com.mx/ Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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