Posts Tagged ‘3d graphics’

AC3D Plugin: Material by Crease Angle and Planar Map by Material

Monday, June 15th, 2009

Two new plugins today!

The first plugin, Set Material by Crease Angle, sets the materials of a model based on the crease angle of the mesh. For each selected area, the plugin creates a new color in the palette and “flood-fills” the area until the angle between the surfaces exceeds the crease angle of the mesh. The result is that contiguous areas are all set with the same palette material, and a new material is applied wherever a discontinuity occurs. This allows you to easily break a model into sections along its creases for easier texture mapping, or many other purposes.

The second plugin, Planar Map by Material, actually includes three new commands.

The first command is Fit UV Coordinates to Map. This command is essentially the same as the “max” button in the TCE, forcing all UV coordinates into the 0-1 range, but unlike “max” this scales the map proportionally instead of independently on each axis.

The second command is Adjust UVs for Bilinear Filter. This is useful for game developers. This command scales your texture coordinates by a ratio of 240/256. The purpose is to create a small seam along the edge of the texture map so that if your game is using mipmapping with a bilinear or trilinear filter, the texture won’t bleed into its neighbors in your texture cache nor will it bleed into itself if you haven’t clamped the edges.

The last command, Planar Map by Surface Material, is probably the most useful of the three. Planar Map by Surface Material applies a “best fit” planar projection to all surfaces grouped by material in the current selection. If you section your model by material, this will treat each material color as a contiguous group and apply whichever planar projection fits it best in the TCE. You’ll still need to do some manual adjustment after you map it this way–especially texture packing, as this leaves plenty of room between areas so the surfaces aren’t too difficult to select–but it can save a lot of time in laying down a base mapping before you manually refine each area.

More information about each plugin is available in the readme.

Download the Material by Crease Angle plugin. (Requires Windows XP, AC3D 6.2 or above.)

Download the Planar Map by Material plugin. (Requires Windows XP, AC3D 6.2 or above.)

How to Make Two Shapes from One Prim

Wednesday, August 13th, 2008

Many times people ask me if it’s possible to create two disconnected shapes from one sculpted prim–without resorting to alpha maps. The answer is yes, you can! It can be a little tricky depending on the shape, but it absolutely can be done. Today I’ll show you how using the AC3D exporter.

Two disconnected shapes made with one sculpted prim.


Wearable Mo-Cap

Wednesday, November 28th, 2007

This new wearable motion capture system is so compact, it can even be used to capture movement in otherwise impossible environments like behind the wheel of a car!

[youtube: 350 292]

The most interesting part? The authors claim to have built their prototype from off-the-shelf components for only around $3K. Read the paper here.

What is Ambient Occlusion?

Tuesday, November 27th, 2007

Ambient occlusion is a lighting technique that is commonly used to create soft shadows on objects. Ambient occlusion isn’t used to create the type of shadows that are cast from objects with a light shining directly on them. Instead, ambient occlusion generates the type of deep shadows that appear in the corners or creases of things, where it is hard for the light to reach.

Technically speaking, ambient occlusion is a global illumination technique. However, in common usage of the term it is often referred to as a cheap alternative to global illumination. To clear up any confusion, what most renderers refer to as “global illumination” is actually an amalgamation of several techniques such as radiosity, metropolis light transport, image-based lighting or photon mapping. The actual techniques used differ slightly from renderer to renderer. Some renderers include an ambient occlusion term as part of their global illumination calculation; others do not.

Like most global illumination techniques, ambient occlusion is dependent on the other geometry in the scene. Ambient occlusion on its own generates less realistic lighting than “full” global illumination. However, ambient occlusion is much faster and less complex to calculate than other methods which is why it is still popular among game developers and in production animation.

(Left) Without Ambient Occlusion. (Right) With Ambient Occlusion
Click for larger image.