8 replies to this topic

[PacManPlus]

Is it possible to show sprites at twice the size on the 7800? If so, how?

Go easy on me - I'm trying to do the first intermission on my Pac-Man hack for the 7800 and I need the Pac-Man sprite to be twice the size on the second part.

Thanks in advance!
Bob

[kenfused]

PacManPlus, on Sat May 14, 2005 10:40 PM, said:

Is it possible to show sprites at twice the size on the 7800?  If so, how?

Go easy on me - I'm trying to do the first intermission on my Pac-Man hack for the 7800 and I need the Pac-Man sprite to be twice the size on the second part.

Thanks in advance!
Bob

You can make larger sprites but you cant scale the graphics up so you would have to create new sprite images. (you can't do a 2x or 4x zoom like on the atari 8bits (and 2600?). I don't know how easily Ms. Pacman's sprite engine could be adapted to handle the larger sprites though.

[DEBRO]

kenfused, on Sat May 14, 2005 11:57 PM, said:

PacManPlus, on Sat May 14, 2005 10:40 PM, said:

Is it possible to show sprites at twice the size on the 7800?  If so, how?

Go easy on me - I'm trying to do the first intermission on my Pac-Man hack for the 7800 and I need the Pac-Man sprite to be twice the size on the second part.

Thanks in advance!
Bob

You can make larger sprites but you cant scale the graphics up so you would have to create new sprite images. (you can't do a 2x or 4x zoom like on the atari 8bits (and 2600?). I don't know how easily Ms. Pacman's sprite engine could be adapted to handle the larger sprites though.

I thought there was a setting in CTRL or the Display List that would specify the number of bytes to fetch for a character. My understanding of that would be like doubling (if set to 2 bytes) the horizontal size of the character. Did I read that wrong?

[Schmutzpuppe]

DEBRO, on Sun May 15, 2005 12:10 AM, said:

kenfused, on Sat May 14, 2005 11:57 PM, said:

PacManPlus, on Sat May 14, 2005 10:40 PM, said:

Is it possible to show sprites at twice the size on the 7800?  If so, how?

Go easy on me - I'm trying to do the first intermission on my Pac-Man hack for the 7800 and I need the Pac-Man sprite to be twice the size on the second part.

Thanks in advance!
Bob

You can make larger sprites but you cant scale the graphics up so you would have to create new sprite images. (you can't do a 2x or 4x zoom like on the atari 8bits (and 2600?). I don't know how easily Ms. Pacman's sprite engine could be adapted to handle the larger sprites though.

I thought there was a setting in CTRL or the Display List that would specify the number of bytes to fetch for a character. My understanding of that would be like doubling (if set to 2 bytes) the horizontal size of the character. Did I read that wrong?

You are right about the CW bit in the CTRL but you misinterpret it.
With CW=0 two bytes would be read if you set a width of 1.
For example if your data starts at $c000 than $c000 and $c001 would be used for the sprite.
So the width would be doubled but by using more graphic data not doubling the pixel size.

[DEBRO]

Schmutzpuppe, on Sun May 15, 2005 8:26 AM, said:

You are right about the CW bit in the CTRL but you misinterpret it.
With CW=0 two bytes would be read if you set a width of 1.
For example if your data starts at $c000 than $c000 and $c001 would be used for the sprite.
So the width would be doubled but by using more graphic data not doubling the pixel size.

I must have relayed my assumptions wrong. This is exactly how I thought it worked.

[Schmutzpuppe]

DEBRO, on Sun May 15, 2005 3:35 PM, said:

Schmutzpuppe, on Sun May 15, 2005 8:26 AM, said:

You are right about the CW bit in the CTRL but you misinterpret it.
With CW=0 two bytes would be read if you set a width of 1.
For example if your data starts at $c000 than $c000 and $c001 would be used for the sprite.
So the width would be doubled but by using more graphic data not doubling the pixel size.

I must have relayed my assumptions wrong. This is exactly how I thought it worked.

Or maybe I just get it wrong...

[PacManPlus]

Thanks for the replies guys

I think I'm going to leave the sprite the same size and not mess with it.
I don't want to break something else...

[EricBall]

CW is only applicable for indirect mode. For example, if the DL entry pointer points to $A000 MARIA then retrieves the byte at $A000 and uses it as the LSB of a pointer to the graphics data. (The MSB being the CHARBASE register + the current DLL line number.) So if CHARBASE=$80, your DLL is 16 lines high, $A000 contains $EE and CW=1 (double byte characters) then MARIA retrieves the graphics data at $8xEE and $8xEF (where x=F down to 0) and stores it at the position given in the DL entry. It the retrieves the next byte at $A001, retrieves the graphics data at $8xyy and $8xyy+1 and stores it at position+4*2(WM=0) or position+2*2 (WM=1), and so on until it reads width number of characters. (One note - the graphics data follows holey DMA, while the characters do not.)

As suggested, if you want multiple size sprites, you have to have separate graphics data for each size. No MIP maps for MARIA.

[supercat]

PacManPlus, on Sat May 14, 2005 9:40 PM, said:

Is it possible to show sprites at twice the size on the 7800?  If so, how?

Although the 7800 supports modes with 1 or 2 bits per small pixel, or 2 or 4 bits per large pixel, the ordering of the bits is different in the different modes. Consequently, the only way to show big sprites is to have data which is sized appropriately. If you're doing a Pac-man intermission, though, this is not a bad thing--a larger "smooth" sprite would be nicer than a blocky magnified one anyway.