Graphics

WPF 3D - programmatically adding an image brush

Tim Huffam — Sat, 24 Jul 2010 11:39:37 GMT

If you are programmatically assigning an image as a DiffuseMaterial to your 3D model, then you need to make sure that you have created TextureCoordinates.

I was using some sample code that created a 3D object - and tried to change the brush from a color to an image. The color worked fine, but the image never showed (it was invisible). The reason was that the sample code only did mesh.Positions.Add() and mesh.TriangleIndicies.Add(). When I added the appropriate mesh.TextureCoordinates.Add() lines the image then showed. eg:

MeshGeometry3D mesh = new MeshGeometry3D();

mesh.Positions.Add(new Point3D(1, 1, 1));

mesh.Positions.Add(new Point3D(1, 1, -1));

mesh.Positions.Add(new Point3D(-7, 1, -1));

mesh.Positions.Add(new Point3D(-7, 1, 1));

mesh.TriangleIndices.Add(0);

mesh.TriangleIndices.Add(1);

mesh.TriangleIndices.Add(2);

mesh.TriangleIndices.Add(0);

mesh.TriangleIndices.Add(2);

mesh.TriangleIndices.Add(3);

// These are the lines you need to allow an image to be painted onto the 3d model

mesh.TextureCoordinates.Add(new Point(0, 0));

mesh.TextureCoordinates.Add(new Point(0, 1));

mesh.TextureCoordinates.Add(new Point(1, 1));

mesh.TextureCoordinates.Add(new Point(1, 0));

ImageBrush imgBrush = new ImageBrush(new BitmapImage(new Uri("pack://siteoforigin:,,,/myimage.png")));

//GeometryModel3D geometry = new GeometryModel3D(mesh, new DiffuseMaterial(Brushes.Green)); // this line works without the TextureCoordinates

GeometryModel3D geometry = new GeometryModel3D(mesh, newDiffuseMaterial(imgBrush));

geometry.Transform = new Transform3DGroup();

Model3DGroup group = new Model3DGroup();

group.Children.Add(geometry);

HTH

Tim

How to fade image layers using Gimp gradient/blend tool

Tim Huffam — Tue, 10 Mar 2009 14:49:34 GMT

This post will explain how to do fading (fade out a layer) in Gimp.

Assuming you have an image open...

Add a new layer
Draw the part you want faded
Right click on the layer in the Layers panel/window and select 'Add Layer Mask', then click on Add on the Add Layer Mask dialog (making sure the default value of 'White (full opacity)' is selected).
Select the Blend/Gradient tool and set the Gradient to 'FG to GB(RGB)' .
On the layer click and drag a line where you want the gradient (fade) to start and finish. The first click is where it will be faded out and the second click is where it will start to fade.
Right click on the layer in the Layers panel/window and select 'Apply Layer Mask'.

That's it.

How to make a transparent background/selection on an image using GIMP

Tim Huffam — Mon, 20 Mar 2006 14:49:00 GMT

Open your image.
Select the area you want to make transparent.
1. Select the appropriate selection tool from the Tool window or the Tools - Selection Tools menu on the Layer window. I usually use the magic wand/fuzzy select (Select contiguous region) tool or the Select regions by color tool.
2. Click in the region you want selected. Use shift-click to add more regions/colors.
  Tip: It's easier if you zoom in (View - Zoom menu) to see finer details of exactly what you're selecting.
In the Layer window (the one showing your image), select Layer - Transparency - Add Alpha Channel. If this is blanked out then it's already done. This makes sure your image can store transparency data.
Select Edit - Clear. This makes the selection transparent.
Save the file.
Note: If you save it as a PNG file, be sure to select the 'Save colour values from transparent pixels' option in the Save as PNG dialog box.

And that's it.

NOTE: IE does not support showing PNG transparencies (alpha channels) natively. There are a few work arounds for this (theres loads to be found on google) - here's MS's solution. However, personally, I find the simplest approach is to save the image as a GIF (which all major browers support transparencies for).

When saving your image as a GIF from within Gimp, it will prompt you to export it - you can select either Indexed or Greyscale - however, on the next screen (Save as GIF) be sure to check the 'Interlace' option.

HTH

Tim