Textures and Materials

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We are going to see how to add a texture with transparency to your surfaces. This is effectively a tutorial about editing materials. We will explain how to create an image as the following one:

Soap bubbles in front of a metal wall.


gif of bubble render.gif
This is the result captured in a video with a little less light.

You might have had to deal with minimal surfaces before, and for that purpose we will try to create soap bubbles. We will want to project the following soap film texture on to the surface:

Just a jpg file. Nothing special.

Textures are usually mapped to triangles by specifying the uv coordinates at each point. You can imagine uv coodinates to be a 2 dimensional vector attribute of a point that locates the vertex color by pointing at the coordinates inside a square texture image matrix. The triangle in between the vertices will then receive the image enclosed by the uv coordinates. See the image below to understand this.

Texture (left) to triangle (right) mapping. (u,v)=(0,0),(1,0),(1,1). Courtesy to http://www.opengl-tutorial.org/beginners-tutorials/tutorial-5-a-textured-cube/
Bubble Set Up

Lets take some spherical geometries to apply the texture to. Here we took one sphere and create many transformations from it together with the $parameter to animate the transformations. We have also added a point light at the upper most layer of the network for later shadows. You can move the light using a transform node or directly in the scene view.

4 spheres in time without any material yet.
Adding a light source makes looking at bubbles more fun.

Don’t forget to add a remesh node to the sphere in order to break the primitive down to an actually vertex representation fo the sphere to use textures on. Luckily, we don’t have to manually input each uv coordinate. Just throw a uvtexture node at the geometry and add a material node right after it.

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Preparing the prototype bubble.

In order to get many copies of the sphere you can use many transform nodes.

copy bubble.PNG
Copy, transform and merge the same bubble.
bubble animation.PNG
And make each bubble unique using the transformations.
Material Edit

Now that everything is set up we can make soap bubbles real by downloading the soap film texture (or use any image you want). Then go to the material pallet and add the glass material by loading it into the scene as seen in the gif below.

Adding glass into the scene.

Then specify the material of the sphere to be glass.

Selecting glass as our material for the sphere.

We can now edit the material properties of the glass and add texture to it. Note that this is the gateway for millions of adjustments that all change the appearance of the surfaces. We chose to start with the glass material as it needs the fewest modifications for a soap bubble effect. We will want to edit three things:

  • Adjust surface transparency to 0.8.
  • Select soap film texture .jpg as base surface texture.
  • Enable opacity fake caustics (for bubble shadows).
Adjusting transparency and opacity.
Selecting the texture.

That is it. Each soap bubble should now look nice when rendered.

Optional: Background with Normal Textures

Lets bring in something nice to better see the light effects the bubble has. We are going to construct a room for the bubbles.

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The room (left). The bubbles we did before (right).

To do this we will start of with a small 2×2 grid element and  and add uv coordinates to it. After the uv coordinates we copy and transform the grid using a copy and transform node. This way the uv coordinates are copied as well.

copy transform 1.PNG
Copy transform copies and translates the first grid again and again.
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Copy and transform details. 4 copies, 1 translation.

And you repeat this with another copy transform node to translate in another direction.

copy transform 2.PNG
A mesh of grids, each containing the uv coordinates to repeat the texture.

The good thing is that now we have the uv coordinates in such a way that our texture will be copied into each square. Lets make a new material to hold our texture. Go to the material pallet and load the Principled Shader into the scene.

material new.PNG
Add the principled shader. It is the default material. It is pure.

Then download a suitable periodic texture and use it for the surface. We will however present you a sweet effect using normal textures. Normal textures encode the surface normal as RGB values in the texture. This way the renderer can accurately show high detailed light reflections even though the surface is flat. You can grab a bunch of free textures with normal mappings here. We will use the following ones.

The periodic texture.
The normal texture. It is just another RGB jpg file.

When editing the new material, you will add the image texture as before and the normal texture under the Bumps & Normals tab.

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Select the normal texture in the texture path.

Next you can copy and rotate the grids to create a room. We will also display the render without normal textures just for comparison:

No normal textures.

With normal texture we get a much nicer result:

With normal textures.
Spherical textures

Another great example is the texturing of the sphere. As you know, there is no bijective mapping from the sphere to the plane, but nevertheless if a world map is created knowingly that it will be mapped to the sphere it can be made to apear seamless.

Map of earth with polar coordinates. Courtesy to this link.

The earth material we create is just a principle shader (default material) with an earth texture. We then compute the UV textures with the uv texture node using the “Polar Coordinates” option and also check the box to make them apear seamless.

Earth Render.png
A textured sphere. Not how the north pole and the wrapping has no distortions.
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Polar coordinates uv coordinates and remember to check the box at the bottom.

Like normal textures, we can also add a bump texture to highlight the mountains.

This is a bump map. White means that the render process should make them apear as sticking out. Courtesy to this link.
Earth Render Bump.png
Earth with the bump map. Now you can see the mountains.

To see how spherical textures are mapped we display another example using a grid.

This is the texture grid. Notice the high level of distortions at the poles.
grid sphere.png
This is the resulting sphere of the above texture. Notice how there seems to be no distortion at all.


Extra: Fake Water

Another trick with normal maps is to place them on blue flat surfaces to make them appear as water (very cheap effect, but at times, that is enough and it is very little effort for the computer and you).

Water normal texture. Courtesy to http://blog.simonrodriguez.fr/articles/26-08-2015_a_few_scntechnique_examples.html

Here is an example of a pianolacquer teapot in the water we just created. Note that the skylight node really helps making the scene pretty with light.

Sky light node + water normal texture + blue color. That’s it! And this teapot reminds me of the monster of Loch Ness.


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