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Colas

August 04, 1999, 10:53 AM

the latest feature from 3dfx is the Tbuffer

what is T buffer (tile buffer), how to use it ?, what value it contain ?

i want to add edge antialiasing in my software engine
i have a span buffer, so i should compute a antialiased pixel at the extremity
of each spans . but how should i compute the right colour ? what rule should i apply ?

ideas: i store for each extremities of the span if it`s in foreground
if yes i compute the antialiased colour for this span`extremity but is this right ?
i need a good formulae to compute the colour


thanx all

Colas

 
Steph

August 05, 1999, 03:22 AM


For your software renderer, a simple way ( I think ) to do antialias :

if S1 is a span, S2 is the next span after S1 ( let say at the right of S1 ).

Z1 is the Z value at the right extremity of S1
P1 is the pixel at the right extremity of S1
Z2 is the Z value at the left extremity of S2
P2 is the pixel at the left extremity of S2

if |Z1-Z2|>deltaZ then P1 need antialias

( deltaZ should be zero, but for precision error I think you should
try some other values )

for each R,G,B value of P1, you can do :

P1.R=(P1.R+P2.R)*0.5;
P1.G=(P1.G+P2.G)*0.5;
P1.B=(P1.B+P2.B)*0.5;

If you want to antialias P1 and P2, you can do something like that:

Ptemp=P1;

P1.R=(P1.R*3.0+P2.R)*0.25;
P1.G=(P1.G*3.0+P2.G)*0.25;
P1.B=(P1.B*3.0+P2.B)*0.25;

P2.R=(Ptemp.R+P2.R*3.0)*0.25;
P2.G=(Ptemp.G+P2.G*3.0)*0.25;
P2.B=(Ptemp.B+P2.B*3.0)*0.25;




Steph

Colas wrote:
>>the latest feature from 3dfx is the Tbuffer
>>
>>what is T buffer (tile buffer), how to use it ?, what value it contain ?
>>
>>i want to add edge antialiasing in my software engine
>>i have a span buffer, so i should compute a antialiased pixel at the extremity
>>of each spans . but how should i compute the right colour ? what rule should i apply ?
>>
>>ideas: i store for each extremities of the span if it`s in foreground
>>if yes i compute the antialiased colour for this span`extremity but is this right ?
>>i need a good formulae to compute the colour
>>
>>
>>thanx all
>>
>>Colas

 
colas

August 09, 1999, 11:52 AM

Merci steph, c`est exactement ce que je cherchait !

Colas


 
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