Sega Saturn Development > General discussion about the Sega Saturn
Transparent Shading on The Saturn
ponut64:
There are a few possibilities.
- They did not conceptualize the shadows as polygons, whether or not they actually were.
- Development for the system never got to the point where such a thing was conceived (remember, it was premier on the market for far less time than the PS1 and N64)
- Developers of the period hadn't a grasp of perspective correction well enough to understand that any method short of absolutely correct perspective correction has its applications compared to other methods. In other words, the Saturn doesn't have to use affine texture mapping, and the PS1 is worse for it, so the thought would be counter-intuitive.
- Developers were concerned with contextual overdraw, wherein interrupting the Saturn's perspective correction meant a part of the entire polygon pipeline, which could have drastic effects on the numbers of polygon's rendered if anything went wrong. (Most critically, because the texture warping on the Saturn is more or less because non-visible vertices are no longer calculated)
- Most likely, some developers of the time actually did do this, and we just don't know.
corvusd:
To understand the problem of transparencies and the redrawing in SS. We have to dig deeper into our technical knowledge of the SS graphic pipeline.
Tessellate a Quad will not help in reducing overdraw or redrawing of pixels in the H-T VDP1.
In addition to using the VDP1 H-T (No Gouraud + H-T) has other problems added:
- If the quad is very deformed it will take up to 6 (According to documentation) drawing cycles.
- Ideally if It do not redraw any pixel, up to 2 cycles (This is a speculation on my part, being in essence the same as Gouraud.).
- Restriction of color types to work well within VDP1.
- It will never see the VDP2.
- Simple to program.
- Infinity blend layers.
- 1 Level transparency. 50% blend.
In other hand, if we use the transparency of VDP2 with sprites of the VDP1:
- It will not have redrawing problem.
- It does it in a cycle.
- Restriction of color types to work well within VDP2.
- It will not ever see the VDP1.
- More complicated to program.
- Up to 2 blend layers. 1 real transparency, other MSB Shadow function whit a lot of restrictions. Finally 1 effective transparency layers.
- Up to 32 levels of transparency.
20EnderDude20:
But a shadow’s just one color, so it shouldn’t matter that much
corvusd:
--- Quote from: 20EnderDude20 on August 16, 2018, 04:01:28 pm ---But a shadow’s just one color, so it shouldn’t matter that much
--- End quote ---
Of course it matters. 1 color or 32,000 colors not is the important. The issue is in how those colors are painted by the VDP1. Think about that deeply a time, you will see how it is not so simple.
20EnderDude20:
I know, I’ve seen perspective corrected sprites have a kind of moire pattern, but maybe that is a desirable result for some things, like for dust.
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