RE: [Algorithms] Real-time lightmapping

[Akbar A. <sye...@ea...>]

>I'm stuck at the part where I have to find what pixels on the lightmap the
>poly covers.
id's and uv coords..

check www.flipcode.com they got a lot of stuff there..


>be some way to sort of render the poly onto the lightmap to get what pixels
>I should be lighting using the UVs.

?
texture mapping is like gluing a texture onto a poly.
you have a lightmap, usually precomputed,  and part of a bigger texture with
id's and size positions, your usualy.
then you match up the id's, do your image changes and match,  to the
polygonol facets.
there is a panda tutorial somewhere on the net about variuos blending
modes..
check www.google.com
for lightmapping panda ?
theres a refrence to it in realtime rendering
;)


laterz,
akbar A.
;vertexabuse.cjb.net


-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of Jason
Zisk
Sent: Tuesday, November 14, 2000 1:03 PM
To: Algorithms List
Subject: [Algorithms] Real-time lightmapping


Hi everyone, if you remember I was asking about how dynamic lighting is done
on static lightmapped environments before.  I think I want to try the
"raytrace" approach for now, just because its a bit less hacky.  I'll decide
if its fast enough later.  :)

I have a lightmapped environment, the lightmap textures are already
generated (packed onto larger textures), and the polygons have lightmap UVs
set.  I have a light source, point light for now, that has a radius,
intensity, color, etc.

I'd think the algo would go like this:

find all the polys in the env that intersect the light's radius
for each of those polys
    for each pixel in the lightmap this poly covers
        convert pixel to world space
        light pixel depending on distance from light source

I'm stuck at the part where I have to find what pixels on the lightmap the
poly covers.

I'd think I could take the UV of vertex zero on the polygon, and find what
pixel in the lightmap that is on, light it.  Then I need to find some way to
find which pixel to move to next.  I'm not sure how to do that.  I could
just go left->right - up->down in a square on the lightmap, calculating the
world position of each pixel and if its not inside the polygon don't do any
lighting on it, but I'd imagine that would be incredibly slow.  There must
be some way to sort of render the poly onto the lightmap to get what pixels
I should be lighting using the UVs.

I figure once I have the pixel on the lightmap I want to light, I can just
convert it to world space and light it.  That's the easy part.  :)

Thanks for any help,

- Jason Zisk
- nFusion Interactive LLC



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