Sprite Rotator (Tool)

• Tool
• Editor
• Utility
• Physics
• Keyboard

SP4CEBAR 2022-09-02 22:25 (Edited)

This tool makes real-time sprite rotation possible!

It saves many uniquely rotated copies of a sprite character to a file which can be read from ROM by other programs. To view the file in your program, clone the most recent viewer.

Click here to read what is new in the latest version

How to use:

• copy the code of the most recent viewer to your project
  • set the ROM entry and source variables
  • make sure to have a character ready (from GFX designer) (can be any size)
• open this program as a tool and follow the prompts:
  • select the input file
    • you can just hit enter to use file 2 (NX character file)
  • select a character
    • you can hit enter to use character 0
  • set their size
    • the size you'd use in a sprite (0-3) exept it's (0-15) where 15 uses all characters
    • hit enter for a size of 0
  • set the start angle (in degrees)
    • hit enter to insert the value 0
  • set the rotation angle (in degrees)
    • hit enter to insert the value 360 (a full rotation)
  • set the memory cap (in decimals)
    • hit enter to use the maximum amount of memory available in the tool's RAM and the disk's ROM
  • set the output file
    • hit enter to use file 5

The viewer loads your rotated sprites via the HYPER_SPRITE(N,X,Y,C,ANGLE) subprogram, it reads metadata from the file

This tool is made exclusively for characters, It doesn't support vector images

The file:

The outdated file V1 starts with 6 bytes of metadata, the current file V3 starts with 8 bytes of metadata, then come all the character files (in 16-byte chunks), that make up larger images, these images take up (16 bytes) * (sprite size+1)^2 Here's more info about the metadata:

• I/O rom entries (2*4-bit) (is obsolete apparently)
• character of your sprite (is also obsolete, apparently)
• size (sprite) (0-15)
• amount of rotations stored
• first angle low-byte (only in V3)
• first angle high-byte (only in V3)
• last angle low-byte
• last angle high-byte

File V2 couldn't store negative angles, so there's no viewer for it posted here

SP4CEBAR 2022-09-02 22:28

I just realized that the files are always at their maximum size, that needs to be fixed

SP4CEBAR 2022-09-02 22:34 (Edited)

This program can read it
it always loads the rotated character file from ROM(5)

Load Rotated Character 3.nx | Open in app

2022-09-02 22:34

SP4CEBAR 2022-09-02 22:35

This program was essential to test it

Decode Character Test.nx | Open in app

2022-09-02 22:35

SP4CEBAR 2022-09-02 22:42

I fixed the unlimited file size

SP4CEBAR 2022-09-03 08:45 (Edited)

Update for the viewer: now it shows the full range of angles, not just until 90 degrees

Load Rotated Character 3.nx | Open in app

2022-09-03 08:45

was8bit 2022-09-03 17:16

Very cool :)

SP4CEBAR 2022-09-03 19:32

Thanks! I got inspired when I revisited one of those online games I used to play when I was a kid: potty racers 3, and I realized that those games are really quite simple to make, you only need motion physics and... rotating sprites

SP4CEBAR 2022-09-03 19:33

I found another problem: it loads characters from local ROM, it's so easy to confuse local ROM with the disk

SP4CEBAR 2022-09-03 19:40

It's fixed!

was8bit 2022-09-04 02:52

:)

SP4CEBAR 2022-09-04 13:32

Big update: file V2 is here, and it's incompatible with file V1, progress bars and displays are added

SP4CEBAR 2022-09-04 14:31

Mandatory bugfix, I switched to pokew so that I can store negative angles, this is file V3

SP4CEBAR 2022-09-04 14:44 (Edited)

Here's the new reader, it reads file V3, and it should be copied into the program that wants to use the rotated characters
Flaws:
- character memory usage of the empty space around a character
- 370 degrees is equal to 10 degrees (but instead the file writer has already set the limits and it gets really complicated)

Load Rotated Character 3L S.nx | Open in app

2022-09-04 14:44

SP4CEBAR 2022-09-05 12:01 (Edited)

I made a new file viewer:

• the bigsprite function that allows bigger sprites to be drawn, will now make the sub-sprites overlap so that it'll only show the area you want it to show: with a size of 5 it needs 4 full-sized sprites, but you don't want it to show 8x8 cells

Rotated Character Viewer.nx | Open in app

2022-09-05 12:23

SP4CEBAR 2022-09-13 08:01

Update
- artifacts are fixed! however, the edges may look a little rough

nathanielbabiak 2022-11-15 03:04 (Edited)

Hey did you know you can eliminate that grid of black dots in the rotated raster? I mentioned how here and, for an example implemented it here. In that upload there's a subprogram, BMP_ROT, and it's got this line in it:

BMP2(PX,PY)=BMP1(NEWX,NEWY)

What your upload here does is essentially this (using the notation from my upload):

BMP2(NEWX,NEWY)=BMP1(PX,PY)

Note that the changes to those indices will also change the direction of rotation.

Anyway, if you switch things around a bit, you can get rid of that black grid. :-)

SP4CEBAR 2022-11-15 14:01 (Edited)

Cool, so if I understand it correctly: my method loops through the input image's pixels, and your method loops through the output image's pixels

A while ago I closely analyzed the gaps and the rounding in of these pixel rotations in Processing and I found that indeed all points miss the rotated square, I tried to find something to predict where the gaps are going to form, the method I eventually used to get rid of the gaps was to add each pixel twice (with offset x+1), which is a terrible solution because it makes all edges rough

nathanielbabiak 2022-11-16 01:29 (Edited)

Exactly.

I'm impressed by the way - you and I saw the same issue and came to pretty similar conclusions. My initial response in that thread I linked was to over-process the pixels. (Although that method is a bit overkill!) Yours is also to over-process the pixels - with a much faster method.

It was only a day or so later when I realized the loop-through output (rather than loop-through input) would solve the same problem, and be faster too.

SP4CEBAR 2022-11-16 21:09 (Edited)

Matrixes work better on vector images, especially If you're scaling the image up
in that case, you can turn a pixel image into a vector image, and flood-fill the surface, or in this case a flood fill may not be needed, the rotated cube surface could be predicted

SP4CEBAR 2024-07-08 11:17 (Edited)

Update: the tool has been made easier to use:

• Different, more intuitive parameters are asked:
  • like the rotation angle instead of the second angle; where a rotation angle of 360 is a full rotation;
  • and the memory cap instead of the number of frames so that it can generate as many frames as possible.
• For a full rotation, it now prevents a duplicate character from being generated for 360 degrees and 0 degrees.
• For most fields, you can just hit enter to enter the value 0 or the default value, these defaults are:
  • 2 for the input file location (file 2 is the NX character map),
  • 0 for the character,
  • 0 for the sprite size,
  • 0 for the first angle,
  • 360 for the rotation angle,
  • total ROM and tool RAM available for the memory cap,
  • and 5 for the output file location.

SP4CEBAR 2024-07-08 13:48

Here's a new viewer

• the removed duplicate frame at degrees 0 and 360 required a change in the viewer.
• the big_sprite2 subprogram now uses a better integer division with a remainder and can now handle the seem between positive and negative sprite coordinates.
• the big_sprite2 subprogram won't get any seems due to slight floating points errors anymore

Rotated Character Viewer.nx | Open in app

2024-07-08 13:48