Is trilinear filtering free on gamecube?

[Luminescent]

I guess my main question would be, are most cube games using 32-bit textures with trilinear filtering?

 

[Cyborg]

I cant see how you would need to ask such a question with the replies you've got already, pretty much all gamecube games dont handle 32bit, they're in 24bit. Heck, i bet that not a single one has 32bit. The difference between 32bit and 24bit is minimal when you're hooked up to a TV, its not like a monitor.

 

[Ozymandis]

The difference between 32bit and 24bit is minimal when you're hooked up to a TV, its not like a monitor.

HDTVs have pretty good color clarity. I'd imagine that you might be able to see a difference.

 

[CeiserSöze]

When running progressive scan dithering-artefacts and color banding become quite noticeable in a few gcn-titles - especially in Eternal Darkness. I don't know what the developers did but the game looks like it's using 16bit colour depth to me. Eternal Darkness is the only gcn-game where I notice the artefacts even when I'm not particularly looking for them though...

 

[Ozymandis]

When running progressive scan dithering-artefacts and color banding become quite noticeable in a few gcn-titles - especially in Eternal Darkness. I don't know what the developers did but the game looks like it's using 16bit colour depth to me. Eternal Darkness is the only gcn-game where I notice the artefacts even when I'm not particularly looking for them though...

I noticed similiar artifacts in Luigi's Mansion as well, from what I remember (I try to block my experience with that game out of my mind).

 

[Luminescent]

The reason I asked such a question pertains to the fact that I assumed 32-bit color was not the same as 32-bit textures.

Fafalada wrote:
Trilinear speed is affected by texture format - using 32bit textures, the texture cache bandwith is only half of what is needed so the fillrate gets cut in half. It's free with all other texture formats.

Thus, I assumed that the gamecube supported 32-bit textures, which I guess was meant to be stated as 24-bit color. I just cannot understand why ArtX would design the flipper to take a performance hit when implementing trilinear filtering on 24-bit texels. The gamecube is high on IQ and efficiency, at least in design philosophy, why introduce those design trade-offs.

 

[Fafalada]

Just wanted to clarify something.

The difference between 32bit and 24bit is minimal when you're hooked up to a TV, its not like a monitor.

As far as display color resolution goes, 32bit and 24bit are essentially identical, in standard configuration - 8bits per color component. The extra 8bit for destination alpha in 32bit has no impact on color banding etc. In other words, they will look the same on any display.

The use of that extra channel comes in use of various drawing routines, and lacking a destination alpha may prevent you from using some of them alltogether - but it will NOT affect the color range displayed.

There are exceptions to the 'standard' however. As mentioned before, Flipper also offers a 6bit per component mode, which gives you 6bits of destination alpha. The color range is reduced (and would look scarcely different then standard 16bit rendering) but it allows you to do the math that requires use of destination alpha.

Thus, I assumed that the gamecube supported 32-bit textures

It does.

I just cannot understand why ArtX would design the flipper to take a performance hit when implementing trilinear filtering on 24-bit texels.

Using uncompressed textures is something you will try to avoid on consoles - working with limited memory. Outside a few special cases, I can't think of many uses that really need 32bit textures, and out of those special cases, not all would even need trilinear filtering to begin with.

 

[Cyborg]

. I just cannot understand why ArtX would design the flipper to take a performance hit when implementing trilinear filtering on 24-bit texels

I guess you meant 32bit and not 24bit, cause trilinear is free for 24bit.

 

[Luminescent]

So trilinear filtering is free for 24-bit texels? Just for clarification.

 

[Zeross]

So trilinear filtering is free for 24-bit texels? Just for clarification.

Yep !
If I undestood well it's just a question of texture bandwith not a limitation of the hardware. S3TC works for textures up to 24bits not for 32bits textures it's where the problem lies in : without texture compression Flipper doesn't have enough bandwith to its texture cache.

 

[Luminescent]

So the flipper would be able to handle 32-bit color or more internally, however it is penalized when using anything more than 24-bits because of the available framebuffer bandwith and the s3tc. I am guessing that the ramdacs (or whatever hardware outputs the rgba signals to the monitor) also display only 6 or 8 bits per-component, which additionally limits the ability for 32-bits. Is this right?