XSI Tutorial
How to use XSI Displacement map to create 3D extruded text
by Dave Lajoie
davelaj@videotron.ca
davelaj@softimage.com



The goal of this tutorial is to demonstrate the power behind XSI displacement map and its adaptive tesselation controls.

Here are the scene file and the textures




The first step: Create the image maps


Extrusion Map ( used as displacement map )

extruded.jpg (11739 bytes)

Create White text over black background with antialiasing enabled, so we don't get jaggy edges.
If your paint software doesn't support antialiased text, you can create an image map twice the resolution, and resize it once the map is completed.
Most paint software will do a decent job at resizing image and will filter the image using filtering, like bilinear interpolation.
Once the text layer is created, you simply need to duplicate the text layer, move it under the original text layer and blur it.


Transparency Map

extruded_matte.jpg (11230 bytes)

For this one, you simply need to copy the blurry text layer from the first image map and create a new image with it.
From there, you need to edit the levels to get a sharp edge out of the blurry image.
e.g.: in Photoshop, using the Adjust->levels appropriate, the input levels should be set around theses values to: 0 0.25 34



Second Step: Create the surface which will be used for displacement.

The surface has to match the image map size ratio, in order to achieve proper results ( square letters ).
A) Create a grid: Model->Get->primitives->Surface->Grid
B) Set the grid size to match the image map size. Example, if the image maps are 1024x200, you need to set the UV size to 10.24x2.0
C) Create a texture projection: while the surface is selected, click on Render->Property->Texture Projection->UV

t_grid_setup.jpg (34723 bytes)
Click image for a larger version



Third Step: Importing the image maps in XSI and add some blurring to smooth displacement.

A) Import the image maps in XSI: Go in the Render toolbar
Click on Clip->Create Clip from file, and select your image map and click OK.

B) After the clip creation is completed, XSI will open the newly created clip ppg.
In the clip ppg, go to "FX" tab, and add some blurring to the image map used for
the displacement. This is needed to avoid sharp edge during tesselation. By adding some blurring
XSI will make the top of the extrusion a rounded.

t_blur_image.jpg (28433 bytes)
Click image for a larger version




Fourth Step: Creating the rendertree

A) Select the grid and add a new material (Render->Get->Material->Phong)
B) Open a rendertree by press "7" key
C) Get two images: Click twice in Rendertree Node menu > Texture > Image
D) Get the image clips in the rendertree: click in rendertree clip menu and select the two clips you just created.
E) Get one color correction node: Click Rendertree Node Menu > Image Processing > Color Correction
F) Now you need to connect it as shown below.
G) The color correction node will be needed to adjust the displacement slope and steepness result

t_rendertree.jpg (36614 bytes)
Click image for a larger version




Fifth Step: Adjusting the Geometry Approximation to get good rounded tesselation

A) You need to apply a local GeoApprox property to the grid
Select the grid, Render->Property->Geometry Approximation
B) Go to Surface tab, and change the surface method to Parametric.
U and V step need to be set so we get even distribution of triangles over the surface.
If we have an image map 1024x200, setting the UV to 10by4 would required.
C) In the Displacement Tab, we need to change the mode to LDA ( Length/Distance/Angle ).
In order to get rounded extrusion, I used angle, since the tesselation will focus on surface angle variation.
That is where we need tesselation to occurs. The Angle value is actually a threashold value, so any polygon with a angle difference of 10 deg.
will be broken up and retesselated, until it match the criteria.
D) the Subdivisions limits allows to control the recursion process and limit how deep the tesselation will go.
In this case changing the max subdiv to higher value has more chance to add much more triangles than changing the actual angle criteria.

t_extrusion.jpg (47973 bytes)
Click image for a larger version