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Using Texture Maps in 3d Modeling

Representing the world with 3d vector geometry is a challenge. It would be much more rewarding if the things we made looked more realistic! In this tutorial we look at some tricks for simulating the look of surfaces through texture mapping techniques.

Here are the ideas and techniques we will explore in this lab:
  1. Mapping a georeferenced airphoto to a Proposed Terrain Scenario
  2. Creating a partially transparent overlay (decal) to represent the ground cover of our new scenario.
  3. Using tree symbols with vertical texture mapped images
  4. Representing materials with tiled texture maps

Download the Tutorial Dataset

This tutorial uses a model of Fields Point in Providence Rhode Island. The tutorial dataset includes a model of the existing condition, a model of a proposed new terrain surface, an orthophotograph downloaded from the Rhode Island GIS web site, several tree symbols and masonry textures downloaded from the FormZ web site. The tutorial dataset also includes a readme.txt file with essential metadata about some of our image files.

Right Click to download this dataset and extract it to a directory in your C:\temp folder.

Map a Georefrerenced Airphoto to your Site Model

We have been using an aerial photo as a source of two-dimensional planimetric control for your site model. Now that we have a three dimensional model for the site, lets use it to help understand our site model.

  1. Open the model, starvegoat_solution_0.fmz Use a renderzone display to view a model of the existing site condition, Model_1_Surface
  2. Use your Surface Styles palette to create a new color map that uses the orthophoto.tif as a single tile.
  3. Go back to wireframe view and Select the object, Model_1_Surface, and bring up its texture control with M-Tool:14a,4.
  4. Look at the metadata for the image for essential information, and set up the origin, and other mapping parameters in this dialog. See Picture.
  5. Map your surface in renderzone view to see the orthophoto draped on the surface.

Create an Image Map to Represent your Proposed Land Cover

Othophotos are great, but they seldom represent the landscape with our proposed interventions. Where do we get an aerial image that represents what is in our imagination? What we will do is create an image Adobe Illustrator or Photoshop that represents the materials we want mapped onto our surface, and map this like we mapped the areial. FormZ has a handy feature that will let you make parts of your image (those parts that are pure black) to be transparent. This will allow us to see the aerial in parts of the image that are not covered by our proposal. You are wondering: "fine, but how am I supposed to make an image in Illustrator that aligns with a new terrain model that exists only in FormZ? We will begin by exporting an image from FormZ to use as a Guide.

  • View the proposed surface, Model2_Surface
  • Map the orthohoto to your proposed surface, Model)2_Surface
  • Alter the properties of the model2_contours and the water layers to show up as wireframe in a renderzone view. See Layer Properties dialog and
  • Zoom in to just beyond the extents of the site, and create a renderzone rendering. See Image of Surface with wireframe contours and
  • Note the coordinates of the corners of your site extent.
  • Export a tif image that can be used as a backdrop for a photoshop or illustrator document.

Then we go into illustrator and use our image with contours as a template for making a new ground-cover map. Illustrator will let us bring in our exported image as a backdrop, and to create other layers on top of it to show the various materials of our scenario. We will also make a black polygon that covers exactly the area of our site extent. When done, we will turn off the original image layer and export an image that is exactly the size of our site boundary. Allowing this black polygon to show in areas not covered by our new ground cover is what will be used to turn our new image-map transparent in those areas.

  1. Create a new illustrator document (or if you want to, you may open the prepared document, from the tutorial dataset.
  2. Make some layers representing the various land covers of the site. See Image
  3. Then make a black polygon that covers exactly the extent of the of the site pad. It is important to make sure that this polygon is pure black (cyan = 0, yello = 0, magenta = 0, K = 100). Also make sure that this polygon matches the extent of your site_pad, exactly.
  4. Now put your black polygon underneath everyother layer. See Image
  5. Now turn off your original image layer and any other layer that sticks out beyond the site extent, and export an image. The tutrorial dataset has an example -- groundcover.tif.
  6. To avoid having halos around your shapes, be sure to uncheck anti-aliasing in your Export tif options.

Making an Image Overlay (decal) in FormZ

Now to add our ground cover image as an overlay to our draped aerial photo on our site model. This uses a feature of FormZ that permits the stacking of partially transparent image maps. FormZ calls this feature Decal. This is very similar to mapping images. We will have to define a new surface style that uses our groundcover image as the colormap, and also uses the image as the transparancy map -- in areas that are black. Since we clipped our new image exactly to the extent of out model, we can get the coordinates of the lower-left corner by simply snapping to it and looking at the coordinate window. We can also get our image size by getting the coordinates of the Northeast corner and subtracting them.

  1. Create a new surface style using our new image, and set up its transparancy options to use a Transparency Map and then set the transparency map options to Make Only Black Areas Transparent See Image
  2. Select your Model_2_Surface object
  3. Use the Decal tool, M-Tool:14a,5 to bring up the Decal properties for the surface. The dimensions of the site-extent are in the project readme file. or See Image
  4. Now when you render your model in Renderzone mode you should see your proposed ground cover over your Areial photo! See Image

Place Some Trees with a Ready-Made Tree Symbol

So now that you know how images are mapped to objects, you can probably figure out how tree-images with black backgrounds can be mapped to horizontal panels to make vertical tree symbols. The tutorial dataset contains a library of several trees downloaded from the formZ site. You should play with placing these objects around your site. It is tricky to get the tree to be at the correct elevation. Try this trick contributed by Kenneth Francis:
  • Load the trees library
  • Make a new layer named Trees
  • Place a tree symbol
  • Turn your display to Interactive shading
  • Set your view to isometric with ctrl-1
  • Zoom in to where you want to place a tree.
  • Place a tree symbol
  • Now turn on the vertical lock tool W-Tool:2
  • After placing the tree, you should be able to interactively move it up until the bottom of the trunk just emerges from the surface.
  • Hint: You may want to turn on 'Snap to Face' W-Tool:6,13 to snap the tree anchors to your triangulated surface.
  • Another Hint: you can toggle between interactive shaded view and wire-frame with Ctrl-= and Ctrl-w.
  • Hint 2: you will have an easier time selecting your trees if you put them on their own layer and lock other layers. Even so, it may be easier to pick individual trees in wireframe mode.
  • Hint 3: your grove will look more natural if you have a diversity of sizes. To so this, select a bunch of trees and then pick the Symbol-Edit tool M-tool:10b,3. Look at the tool options, and select 'Edit Simultaneously.' This will let you rescale groups of trees at once.
  • Hint4: don't forget to take a look at tree pro -- a great tool for making tree textures and their vettor panels. If you export as Targa (tga) format, you can make tree symbols very much like the ones in the FormZ tree library. More about trees and transparency can be found in the RenderZone manual.
  • Hint 5: for casting accurate shadows, you need to adjust the 'Center of Interest' properties of your light source (in the lights pallette.) See Image, and turn on Shadows in your RenderZone options (available through "Display->Display Options->RenderZone." and set the properties of the Light direction from the Sun... right place and time: See Image.

Use a tiled Texture Map to Represent a Material

Another powerful application of texture maps is in the creation of material patterns that can be repeated. YOu can find ready-made texture maps for all sorts of materials on the web, for example, see: FormZ Downloads page.

  • Create a new surface style for stone blocks
  • Apply this as a tiled map to one of the walls in our site proposal.
  • Pay attention to the rotation of the maps to that the blocks are in line withthe wall!