Few questions.

[DEElekgolo]

So I am tired of sniffing around for information so here are a few direct questions.

How would I manage making a file system INSIDE of my .nds file rather than reading from the flash cart? Retail games seem to be able to do this and I require a more manageable way of handling my assets rather than having it stored alongside my machine code.

When looking into the display list commands I have a hard time understanding some of the data types:

400048Ch - Cmd 23h - VTX_16 - Set Vertex XYZ Coordinates (W)

Parameter 1, Bit 0-15 X-Coordinate (signed, with 12bit fractional part)
Parameter 1, Bit 16-31 Y-Coordinate (signed, with 12bit fractional part)
Parameter 2, Bit 0-15 Z-Coordinate (signed, with 12bit fractional part)
Parameter 2, Bit 16-31 Not used

I am unsure about how it manages float variables. I would imagine something along the lines of storing two integers and then dividing the two to create a float variable but I would imagine how this would act at run-time in a game.

How would one manage vertex skinning on the ds? Would I have to process each vertex on the CPU and update each frame?

[Discostew]

Check out the Nitro File System under the nds example folder for having the files contained with the program.

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For that vertex explanation, the input is not float-based, but integer-based in the form of a FIXED-POINT value. If you don't know how FIXED-POINT math works, then you should concentrate on that, as it is used extensively on the DS. For input in this case, the first 16 bits of the 32-bit input forms the X coordinate, with 1 bit for the sign, 3 bits for the whole number, and 12 bits for the fraction. The latter 16 bits forms the Y coordinate. With both X and Y together in one value, you can simply do this...

Code: Select all

 VTX_16 = X | ( Y << 16 );

Of course, the values of X and Y must be 16-bit, or you'll have problems. To add the Z coordinate, you simple send in the Z coordinate alone. As noted, the last 16 bits from the 2nd input are ignored. There are macros that will allow you to convert from a float to a FIXED-POINT value, but because the DS doesn't have an FPU, processing floats will be slow. Once you become comfortable with FIXED-POINT values, it's suggested that you work with them instead of floats. Having the values in hexadecimal form helps me work with them.

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I hadn't done any work on skinning for a long time, but I can tell you that there isn't a simple method for skinning on the DS. There are techniques that can help reduce the amount of processing you'd have to do, but it would still be pretty intensive.