Incorrect vs perspective-correct attribute interpolation Interestingly, the correct formula (divide screen-space barycentric coords by respective vertex.w then normalize to sum to 1) is extremely simple yet somewhat unintuitive - ThreadSky

About ThreadSky

lisyarus.bsky.social • 122 days ago

Incorrect vs perspective-correct attribute interpolation
Interestingly, the correct formula (divide screen-space barycentric coords by respective vertex.w then normalize to sum to 1) is extremely simple yet somewhat unintuitive

1 / 2

Comments

nicebyte.bsky.social•121 days ago

best visual intuition I've seen for why this problem exists: what's "in the middle" on the screen is not necessarily "in the middle" on the surface!

eugensson.bsky.social•122 days ago

Instant PS1 feel

tomforsyth.bsky.social•121 days ago

I'd never thought of it as "normalize to 1", but I guess so? Really it's just calculate (i/w), (j/w) and (1/w) at each vertex, then screenspace interpolate, and then re-divide to get i,j then do your usual interpolation with those.

tomforsyth.bsky.social•120 days ago

Oh, just remembered I wrote a Shadertoy to show this:
https://www.shadertoy.com/view/wdjfz1

lisyarus.bsky.social•120 days ago

Nice!

jmi2k.me•122 days ago

While implementing a rasterizer in HW, this little detail was the straw that broke the camel's back (I didn't have a proper divider module).

I even really considered fully committing to the PS1 aesthetic just to avoid the issue altogether.

sassnow.ski•122 days ago

The first one is messing with my brain

Posting Rules

Be respectful to others
No spam or self-promotion
Stay on topic
Follow Bluesky's terms of service

Comments

Posting Rules

Reply