Re: Workaround for this bug?

[Frank C. <dev...@ch...>]

On 21-Jan-05, at 1:35 PM, Keith Wiley wrote:

> On Fri, 21 Jan 2005, Frank Condello wrote:
>
>> First ensure the alpha in your art is not pre-multiplied (likely the 
>> case already) then put the sun shape in a display group under a fog 
>> object with its visibility set to false. This will ensure no fog is 
>> drawn on the sun, which is typically a desired effect on all 
>> celestial bodies. Also place a Lambert shader before the sun geometry 
>> to turn off any potential specular highlights, since they may display 
>> a similar artifact as fog.
>
> I have a question on this approach.  Is there something inherant about 
> the display group that is supposed to make this alpha-with-fog thing 
> work properly, or is that just the way you suggested to make sure the 
> fog is submitted prior to the sun object?

The latter.

> I ask because before trying to group the fog with the sun, I quickly 
> tried submiting a fog turned off just prior to submitting the sun and 
> then submitting the fog turned on again just after the sun...but the 
> alpha-fog error is still present.  Is that what you would have 
> expected?  Is the display group required?

That won't work because transparent objects are cached when submitted 
and drawn last, so you're basically disabling fog, drawing nothing, 
enabling fog, then Quesa draws the sun after the fact.

Come to think of it, I think there's a bug where Quesa doesn't respect 
fog states on transparent geometry so my recommendation may not work 
either - may depend on the Quesa version you're using...

Frank.
------------
<http://developer.chaoticbox.com>