Performance Art 3: Polygons don't matter.

re: Performance Art 3: Polygons don't matter.

Mick — Wed, 29 Aug 2007 07:48:33 GMT

Interesting stuff, Torgo.

But using spec maps has one problem: You can't get a small enough highlight to get a glossy looking surface. Here's a test I did:

In 3DS Max, I cranked up the Specular Color chip to full white, and Specular Level to 999 (the maximum). Then I turned up the Specular Map Power scale to the max - 256. I then gave the matl a specular map that had full white in the RGB channel, and full white in the alpha as well. With these settings, I presume I should be getting the smallest, brightest possible specular hilight - suitable for a glossy object. But the hilight is too big, and doesn't look convincing. If I then get rid of the specular map, the hilights become much smaller - and much more convincing (though they would look better if they were smaller and brighter still).

So, two questions:

1.) Am I right in thinking that you can't get as small a highlight when using a spec map as you can without one, or am I missing a trick here?

2.) Why doesn't the exporter allow realistic highlights for glossy objects - that is, very small and very bright? Even in the tests I did without a spec map, the highlights aren't as small and bright as they would be in the real world. Is this just an oversight in the way the exporter is designed, or is it not technically possible to go smaller and brighter?

re: Performance Art 3: Polygons don't matter.

torgo3000 — Mon, 17 Sep 2007 23:07:18 GMT

You are correct, the max specular power from a map is 256 (white) and the max specular power from the level spinner is 999. We discovered this too late in the development cycle to change it and create havoc with all the content we had already made.

Additionally, because the normal is calculated into the specular hotspot, you can only get it so small. What starts happening beyond a certain power term (I used a hard-coded 1000.0 in the shader), is that the specular hotspot is so small it breaks into sub-pixel sparkling.

Things to consider:

1. The larger and flatter the surface normal, the bigger the hotspot. Try breaking up the normal with normal maps or smaller, more rounded polygon subdivisions.

2. The fresnel ramp is multiplicative, so it can only darken specular highlights. We way overused this. I wouldn't recommend using fresnel on specular unless you want to do a funky two-toned paint scheme or really tint the specular highlight.

Modelling and texturing for performance

Arno Gerretsen — Sat, 22 Dec 2007 02:34:14 GMT

Of course every designer has read the excellent blog posts by Adrian Woods on how to optimize your performance

re: Performance Art 3: Polygons don't matter.

jtanabodee — Mon, 22 Dec 2008 11:39:49 GMT

Great stuff here, I'm getting into this performance issue.

It would be nice if you have some pictures that being explained along with texts. Some parts are quite hard to imagine.