Texture Workshop – create your own textures for visualization

Texture Workshop

You have many alternating techniques to visualize a building model in ArchiCAD. This tutorial shows you how to make suitable texture images for ArchiCAD, Artlantis or some other program that uses textures to give a ‘real-life’ feel to the modelled surfaces. Textures in ArchiCAD are shown in a 3D window when you use the OpenGL engine or with renderers in a rendering window.

The first step to successful visualization is careful and exact modelling, after which the surface texture gives a virtually real appearance to the model. A texture (sometimes called a ‘texture map’) attached to the CAD material is a picture from the real material. This picture may be produced by drawing, it can be a photograph or it can be done procedurally by programming. The following instructions tell you how to make texture images from photographs. The same steps can also be used for drawn or painted textures.

wall texture

Lens distortion which is common to point-and-shoot cameras can be avoided by using a telephoto lens.

How to take photographs for textures

Image processing will be easier if you consider these points when taking photographs.

  • Use a telephoto lens – there is less visible lens distortion than with wide angle lenses.
  • Choose soft lighting conditions when possible. During cloudy weather, sunlight scatters from the clouds and gives soft and even illumination – the contrast is lower and colours are more vivid. In sunny weather, the contrast will be higher and the highlights and shadows follow each another. While this may be a desirable effect on occasion, textures are normally better if taken in scattered light.
  • Use a tripod – texture photos can be taken even if there is less light and it makes shooting easier and more precise, especially if you are using a telephoto lens.
  • Material can also be scanned. If the material sample fits the scanner you can scan it. Light’s quality is even in a scanner.

How to process the photographs to textures

  1. Choose a picture which is evenly lit.

    skewed image

    An evenly lit but skewed picture of a brick wall.

  2. If the photograph is skewed or distorted, there are several ways to correct it. When the surface is not in a straight angle with the camera, choose Edit–Transform– Skew in Photoshop. If there is lens distortion in the photograph, use Filter–Distort–Lens Correction.

    Lens Correction

    Lens Correction in Photoshop

  3. Crop the texture’s area from the picture; for example, a square is a good shape for a texture. If the surface structure is not repeated as a square – like in a brick wall – then a rectangle can be used; there are no restrictions on the ratio of the sides. When you crop the area, note its actual size in metres as these dimensions will be needed when you attach the texture to the material in ArchiCAD or another program and want it appear naturally. A good size 1024 x 1024 pixels or some even number; here the power of two was used.

    Here the corrected photograph is going to be cropped.

    Here the corrected photograph is going to be cropped.

  4. Check and clean the seams. Choose Filter–Other–Offset to see how the edges of the picture fit together. Input the pixel amount, which is half of the picture’s edges, to the horizontal and vertical fields. Click Wrap Around. Now you can see the picture’s edges forming a cross in the middle. You can easily see if the alignment is not straight, the areas which need to be cleaned up and the differences in luminosity at the edges.

    Adjust the image size suitable for your purposes. During editing, a larger size is still beneficial; however, the size can be smaller for the textures in use.

    Adjust the image size suitable for your purposes. During editing, a larger size is still beneficial; however, the size can be smaller for the textures in use.

  5. Use paintbrush or Stamp-tool for cleaning up. Do not use blurring brushes to keep the texture clear. To correct any lighting differences, try Filter–Other–Highpass (Edit>Fade High Pass>Mode: Luminosity). After the clean up, take the offset again to return the picture to its original position. Any new seams that have appeared due to editing should also be cleaned up.

    A lens distortion corrected by Filter–Distort–Lens Cor- rection. Here the corrected photograph is going to be cropped. Adjust the image size suitable for your purposes. During editing, a larger size is still beneficial; however, the size can be smaller for the textures in use. When the offset is done the seam area will be in the centre.

    A lens distortion corrected by Filter–Distort–Lens Correction. Here the corrected photograph is going to be cropped. Adjust the image size suitable for your purposes. During editing, a larger size is still beneficial; however, the size can be smaller for the textures in use. When the offset is done the seam area will be in the centre.

  6. Save the textures in the size you are going to use them. Rendering will be faster if the texture size is optimal. If the scene has multiple texture maps, then the right size is more important. You may estimate how large the texture is when it appears in a render- ing. There is no use in having a higher resolution than what is visible. Video cards function faster if the texture size is adjusted to powers of two. Good sizes for textures are: 32 x 32 (for a simple material); 64 x 64; 128 x 128; and 256 x 256.

    Completed texture

    When the texture image is completed, you can save several copies of it in different resolutions according to your need. Here are examples in two different resolutions: 128x128 pixels and 720x720 pixels.

A texture made according to these instructions may be seamless; how- ever, if the picture contains clearly visible anomalies, the texture may look bad in rendering when they are repeated continuously. This can be avoided by erasing or softening them to make them less visible or by making the texture so large that their repetition is less obvious.

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This article was originally published in ArchiMAG 1/2010 and was written by Vesa Putkonen

Written by Vesa Putkonen

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