Neither the SCU DSP or the SH2s have barrel shifters so I guess you'd probably want to pack them using MACs. Maybe you mean the VDP1 gouraud shading function? For that you have to store 4x16-bit values in a separate table for each primitive, where the values are packed 15bpp RGB colors for each vertex. All you get is 50% blending with the background. That's also why all those high resolution Saturn games don't have shading, since they needed to use 8-bit paletted framebuffers.īut for VDP1 blending there isn't any setup involved, it's enabled by flipping a bit in one of the the primitive command words. I think they actually do technically work but don't give the expected results, which makes sense considering that those operations involve modifying colors directly. I've looked at this thread a few times over the years and this is what first made it seem pretty apparent to me that the SCU DSP was very underutilized.Ĭlick to expand.I think what you're thinking of is that stipulation that VDP1 blending and gouraud shading don't really work in the non-RGB framebuffer modes. I think I remember hearing about a game that used it to generate maps for water or something, maybe it was earlier in this thread? It makes a lot of sense for that "something else" to be the rest of the T&L. The best place to perform this calculation is probably on the SH2-DIVU, where you can run it in parallel with something else. Not that a game couldn't use it for T&L if it wanted to, it's entirely possible, but it just seems like an inefficient way to do things because it can't really do divisions for perspective reciprocal calculation. Also, if available, the amount of DMA traffic going into its data RAM. I think to really get an idea of what it's being used for you'd have to look at a game in an emulator and see how much of the DSP's time is spent being used and what the program looks like. A lot of the games on the list aren't even 3D. No doubt there are some games that used it for something, but I don't think there's anything there that suggests definitively that it's being used for T&L. I've looked at this thread a few times over the years and this is what first made it seem pretty apparent to me that the SCU DSP was very underutilized.