Author Topic: Transparent Shading on The Saturn  (Read 91 times)

20EnderDude20

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Transparent Shading on The Saturn
« on: August 13, 2018, 02:48:59 am »
I've made a demonstration of circular transparent shading by not using perspective distortion, and instead, use affine transformation and it looks fine: Now, would the shadow be corrupted by having overdraw if I skewed it, in other words, kept the coordinates parallel with each other?
« Last Edit: August 14, 2018, 12:26:59 am by 20EnderDude20 »

20EnderDude20

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Re: Circular Transparent Shading on The Saturn
« Reply #1 on: August 13, 2018, 08:47:01 pm »
Okay, so there is a solution to the perspective distortion with rectangular shadows. What you do is that you make a 16-frame animation of a square moving two points together. You would then use the palette swap trick to compress it to one texture, and you would use affine transformations for the rest. Observe: .

corvusd

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Re: Circular Transparent Shading on The Saturn
« Reply #2 on: August 13, 2018, 10:57:01 pm »
Very good ideas! Are you think about How make the change of shape when the camera rotate above the shadow?
David Gámiz Jiménez

20EnderDude20

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Re: Transparent Shading on The Saturn
« Reply #3 on: August 13, 2018, 11:02:49 pm »
Yes. The frame number of the texture depends on the view that you're looking at it from. Since it's 16 frames long, it should change about every 5 degrees within 90 degrees. When it's 0, it should be at the frame with the triangle, if it's 90, it's square. If you go above 90 degrees, you flip the texture, and the same applies there. I'm not a coder, but I can animate in Flash, so I might ask XL2 to implement a system like this, if he has time  ;). Here is a much more impressive-looking gif:
« Last Edit: August 14, 2018, 12:31:50 am by 20EnderDude20 »

20EnderDude20

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Re: Transparent Shading on The Saturn
« Reply #4 on: August 15, 2018, 11:06:16 pm »
Wait, if the ps1 used affine texture mapping for everything 3d, and if the shadow looks the same even with the warping, why didn't any developers program shadow polygons to turn off perspective correction (calculating q value, tessellation, etc.) on the Saturn?
« Last Edit: Today at 12:44:40 am by 20EnderDude20 »

ponut64

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Re: Transparent Shading on The Saturn
« Reply #5 on: Today at 01:26:48 am »
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.

 

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