What is up with the interlaced-like effect on transparencies in Zelda?

[kyleb]

Over the course of playing the new Zelda I found myself increasingly distracted by the way translucent effects only seem to cover every other scanline in progressive scan mode, such that the glow around text as well as things like fog and dust clouds appears discontinuous. Here is an example pic showing the effect on the glow around text:

Clearly it is something to do with the way the game is rendered, but does anyone know specifically why the transparencies in the game come out like that?

 

[StefanS]

Clearly it is something to do with the way the game is rendered, but does anyone know specifically why the transparencies in the game come out like that?

It might be the 24bit incl alpha limitation that Flipper had (and presumably Hollywood as well). We've also been seeing dithering in Wii titles. So Zelda might have opted for 6-6-6-6 colour depth format? But I am just guessing...

 

[kyleb]

Wouldn't low bit-depth would result in banding that is contours the change in translucentcy and with the distance between bands varring in relation to the to the rate of that change? The effect in Zelda other hand is always horizontal lines, always every other scanline. Perhaps they are rendering the translucent effect every other scanline in an attempt to simulate the look greater transparency while working with a low bit-depth?

 

[assen]

BTW, Viva Pinata's translucency, e.g. when you choose where to place a building and a translucent building is attached to the cursor, is implemented the same way. It's a simple case of what was called "stipple alpha" in the days when OpenGL was young at SGI . Its advantage is that it doesn't require sorting the objects and/or polygons, it's the holy grail of "order-independent transparency". Its downside is that it requires high resolution to work well, so it's less surprising to see it in Viva Pinata than in Zelda.

 

[Shifty Geezer]

In some cases it'd be acceptible to blur the translucent areas in post and elliminate all dithering.

 

[kyleb]

BTW, Viva Pinata's translucency, e.g. when you choose where to place a building and a translucent building is attached to the cursor, is implemented the same way. It's a simple case of what was called "stipple alpha" in the days when OpenGL was young at SGI . Its advantage is that it doesn't require sorting the objects and/or polygons, it's the holy grail of "order-independent transparency". Its downside is that it requires high resolution to work well, so it's less surprising to see it in Viva Pinata than in Zelda.

I've yet to play VP and my technical knowledge of rendering is rather limited, but considering your comment on avoiding the need for sorting, am I correct in assuming that the translucent effect on while placing buildings in VP is achieved by series of opaque lines with small gaps inbetween? In Zelda the lines between the gaps show translucency of their own so unless I'm missunderstanding something there is sorting going on there but less so of a work load when only rendering translucency to every other line, eh?

 

[see colon]

kyleb,
you took that shot witha digital camera, what was the display you were running it on? you were in progressive mode with component cables, i assume? i never really noticed the effect in game, but i only played zelda on an interlaced SDTV using the composite cables that came with the system. i did notice banding all over the place.

i did, however, notice the interlaced effect pre-launch in a couple screenshots, and even made a post about it on this board.

regarding the dithering, i'm not sure those are frambuffer grabs. they look almost identical to the quality that my (cheap) TV card captures from an S-Video or composite source. theres some banding for sure, but there's also a horizontal patern that looks like a low quality deinterlacer is at work.

 

[kyleb]

Yeah, I'm useing component cables at 480p. The display is an ED plasma, and I got the closeup using it's multi-display functionality to zoom in on the image so that it was showing one tile of the image upscaled for a 4x4 grid of displays. The scaline-like effect doesn't show up at all on my display either when running 480i.

 

[assen]

I've yet to play VP and my technical knowledge of rendering is rather limited, but considering your comment on avoiding the need for sorting, am I correct in assuming that the translucent effect on while placing buildings in VP is achieved by series of opaque lines with small gaps inbetween? In Zelda the lines between the gaps show translucency of their own so unless I'm missunderstanding something there is sorting going on there but less so of a work load when only rendering translucency to every other line, eh?

Yep, you're right, if there is translucency on the gaps, that would still require sorting, and would reduce the workload very little - just halve the alpha-blended pixels, reducing frame buffer bandwidth for the small part of the screen that is covered by these opaque lines of translucent objects. Considering the overall comments on Wii games' graphics (lots of fillrate and framebuffer-bandwidth eating effects compared to Gamecube) and the fact that this is a Gamecube/Wii game, I very much doubt this economy is needed or justifiable.

Maybe the scaler on your plasma TV is playing games with you? Is there bleeding of color from the background towards the opaque lines?

 

[see colon]

Yep, you're right, if there is translucency on the gaps, that would still require sorting, and would reduce the workload very little - just halve the alpha-blended pixels, reducing frame buffer bandwidth for the small part of the screen that is covered by these opaque lines of translucent objects. Considering the overall comments on Wii games' graphics (lots of fillrate and framebuffer-bandwidth eating effects compared to Gamecube) and the fact that this is a Gamecube/Wii game, I very much doubt this economy is needed or justifiable.

Maybe the scaler on your plasma TV is playing games with you? Is there bleeding of color from the background towards the opaque lines?

it could also just be carry over from GC code. the Wii might have fillrate to burn but the 'cube doesn't. graphical upgrades definatly were not on the list of changes for this game in it's migration to Wii, either. so it's pretty plausible that it was a GC optimization that was just carried over.

 

[kyleb]

Maybe the scaler on your plasma TV is playing games with you?

Nah, it's not particular to my display, I just used that shot for an example because I feel it better illustrates the issue in question than any of the the heavily compressed screenshots I could dig up around the net. But like see colon said he saw the same thing in some pre-release shots, and if you can look past the compression and zoom on translucencnt details like the clouds in this shot, you'll see the same scanline-like effect.

Is there bleeding of color from the background towards the opaque lines?

That is just it, the lines aren't opaque but rather parts of them show blending from the textures behind them.

 

[Graham]

BTW, Viva Pinata's translucency, e.g. when you choose where to place a building and a translucent building is attached to the cursor, is implemented the same way. It's a simple case of what was called "stipple alpha" in the days when OpenGL was young at SGI . Its advantage is that it doesn't require sorting the objects and/or polygons, it's the holy grail of "order-independent transparency". Its downside is that it requires high resolution to work well, so it's less surprising to see it in Viva Pinata than in Zelda.

Do you know this from playing the game or from screen shots? Saints row also does this for car windows, etc, yet I can't see it in game. And I've seen hints here and there that xenos supports some sort of MSAA sample masking.. So maybe thats it?

ok sorry back on topic...

 

[fearsomepirate]

Wind Waker did exactly the same thing. Transparencies looked fine in interlaced mode, but had that weird stippled scanline effect in progressive scan. There's one other coloring artifact unique to Wind Waker that I saw again in Twilight Princess. In certain lighting conditions, you can see these vertical lines of alternating brightness on the screen. I saw it again in TP, only it's not as obvious because it doesn't use the big, blocky coloring of Wind Waker, so the texturing hides it a little. It looks like they might have used the same engine, or at least parts of the engine.