Texturing with Alpha channels in Softimage XSI v6 using the TLE

Posted on August 3, 2011 by rwmadmin

Introduction:

An oldie as well, but still viable in the Softimage workflow.

With the addition of the Texture Layer Editor or “TLE” in Softimage, things were made easier regarding texturing for all users. I finally had some time on my hands to update this little set of tutorials to version 6, although version 5 will be no different.

Steps discussed:

1. The beginning, one texture with alpha
2. Adding another texture with alpha
3. Using a B/W image for blending two textures
4. Using a bumpmap in the shader node

1. The beginning, adding a texture with an embedded alpha channel:

Let’s start with the first, most basic way to get an alpha channel to work. Assuming you -did- apply an alpha channel to your image (e.g. *.PSD, TGA), we can start up XSI.

Create an simple grid “Get>Primitive>Polygon Mesh>Grid” or a sphere “Get>Primitive>Surface>Sphere”, it doesn’t really matter in this case. Assign a material with “Get>Material>Phong” (set it to some wacky color to see the result a little better) and assign a appropriate texture projection with “Get>Property>Texture Projection>XZ” or “Get>Property>Texture Projection>Spherical”.

Note: Because there’s only one Projection available, XSI will automatically assign this to the texture. If there would be more than one Projection, XSI would pick the first one on the list.

Switch the cameraview to a “Shaded” viewport, we now have a nice gray colored object. Time to slap on a texture.

Note: You can see the alpha channel on your texture if you switch the cameraview from “Textured mode” to “Textured Decal mode”. In both cases you only see the last/latest texture you applied to the object.

We have a couple of choices here with the TLE in mind:

-We can assign a texture with “Get>Texture” and adjust it in the rendertree later by adding a layer on the Phong shader and connecting the layer to the ambient and diffuse slots.
-We can open up the “TLE” right away and start from there, that’s what we do today.

So open the TLE with “View>Rendering/Texturing>Texture Layer Editor”, or by pressing “Shift+7″ or by changing one of the viewports to the TLE.

In the “TLE” only the base layer is visible with the ambient and diffuse colors shown. Add a new layer with “Edit>Add layer” or by using the “icon button” The layer now shows one color slot and one matte slot, a blending slider, and the two base color slots. Rightclick the color slot and select your texture as a clip or add one with the “Add new from file” command.

The blending will come in at a default of 0.5. Just change this to 1.0 and your texture will be fully opaque, except for the alpha channel in the image, that is now showing the color of the Phong shader.

Open the rendertree and look what your rendertree looks like. If you don’t see anything, be sure the object is still selected and click the update button. Your rendertree and render should look something like this:

The other convenient thing of the TLE is that with the dropdown menu of the color slot,you can easily ignore or invert the alpha or multiply the result without going into the Rendertree and add all kinds of nodes.

2. Adding another texture with an embedded alpha channel:

Add another layer and rightclick the color slot to select a new texture. Change the blending again to 1.0 and your texture will be fully opaque, except for the alpha channel in the image, which will show the underlying texture and color.

3. Using a B/W image for blending two textures:

If your texture doesn’t come with an alphachannel, e.g. a jpeg file, you can use a B/W image to mask out your texture. Replace the texture in the second layer with a texture without an alpha channel. Right click the Mask slot and choose a B/W image to work with. Also select the “Use Mask Connection” option to be able to use the texture as a mask. As you can see there’s a lot of other options to play with as well. Change the blending again to something you like or want to achieve.

4. Using a bumpmap in the shader node:

As all layering of textures you can also add a bump map to your shader node. With only two ports visible we have to add the bump slot into the TLE. Just rightclick in the gray “ambient(c)” or “diffuse(c)” fields (the column will flash pink) and select the bump slot to add to the TLE. As you can see the ambient and diffuse slots are already selected.

A new column will show up next to the diffuse(c) column, with a squared “?” in the Base colors row. Right click this square, and select “More…” to browse to the Bump folder and select the Bumpmap generator node. This will add a Generator node into the Rendertree and connect it into the “Illumination/bump” slot.
(Also the “?” icon will be removed from the Base colors row now.).
Open the bumpmap generator node and select a texture to use for your bump, I used the mask texture for bump too in this example.

So that’s it for the basics. With the power of the Rendertree still there, some task became a lot simpler with the TLE. I hope it will help the people out there just starting off with XSI, as the Rendertree can be a bit overwhelming at first or confusing if you come from another 3D app.

Simple bumpmap mixing in Softimage

Posted on August 2, 2011 by rwmadmin

Introduction:

Simple bumpmapping is pretty straight forward in XSI, just by turning on bumpmapping in the texture PPG and fiddle with the settings. Or you can get a Bump map generator, get an image and work from there the same way. But what if you want to mix your bumps? You could slapping on a second texture and turning on the bump here too, adding it to the mix. But this method doesn’t produces very predictable results, so we have to look for another method.

Rendertree Setups

Most people use the “vector2color” and “color2vector” nodes in combination with the “mixer2color” node and create elaborate Render trees from this. But what if you want to just simply mix 2 simple bumps and go on to the next thing. Well, you can do this by ‘daisychaining’ the “Bumpmap generator nodes” and setting its ‘flow’.

Note:
Unfortuanetly for mixing displacements you cannot use this setup, you have to build yourself a more complex tree.

For the example we create a simple polygon grid, assign a lambert material, add a XZ Projection and a simple grayscale cloudtexture build in PS. For the bumps we’re using two simple B/W images with horizontal or vertical stripes.
No need for a tutorial here, right??

How to procede:

Open the Rendertree, get your first “Bumpmap generator node” and connect it to the “Bump Map” slot of the Material node, now open the PPG. Select one of the two B/W images.
(You can do this also within the PPG’s, it’s just how you prefer to work.)
If you look at the “Normal” setting, you see that there are two options for the “Base normal”.
Change the “Relative to current surface normal” setting to “Relative to input normal”.

Get your second “Bumpmap generator node” and connect it to the “normal” slot of the first generator node. Again open the PPG and select the other B/W image. For this second node the “Normal” setting should state “Relative to current surface normal” (default value).

Rendertree setup:

Mixed like this by ‘chaining’ the bumpmap generators will give us a gridlike bump. You can even turn on the bump for the image itself to add to the mix. You can just add another generator to this set, just be sure the settings match. The last node (furthest away from the material node) must always be set to “Relative to current surface normal”, the others should be set to “Relative to input normal”.

Note:
Be aware of the following limitations, mixing negative and positive bumpvalues don’t seem to work very well, and the node that connects to the Material’s bump “slot” defines the bump output. So if you turn off bump for this node, nothing behind it in the other nodes will “flow through” to the material’s bump slot. You can however turn off bumpnodes in between, or even add the bump from the texture (cloud in this case) to the mix.

Well, that’s all there is to it.

Happy bumpin’!!

Endresult

You can get the same result by turning on the bump of the cloudtexture, instead of adding another “generator” node to the rendertree.

A vector mixer node for mixing more complex setups are to be found here and here.
You can also check out the forum at xsibase for more information about bumpmapping in XSI.

Mixing matte and glossy materials with the weight node

Posted on August 1, 2011 by rwmadmin

Although this is an old tutorial written for XSI 3.01 and up, it’s still a valid workflow.

Introduction:

With the examples from the previous tutorials, it’s quite simple to go a little step further and use the capabilities of the “Mix2Colorsnode” and a B/W image for mixing two different materialtypes on one object.

Let’s start simple:

In XSI create a simple cylindrical thingy just for the sake of it, and in Photoshop create three basic files, one colorimage and two B/W images, one for bump and one for the reflection and mixing the material types.

OK, here we go: Assign the cylinder a “Phong Material” and assign a “Cylindrical Projection” to it. Assign a texture, in this case the “steelrust.tga” file. No need to set up the shader, because most of the values are driven by the textures.

The three imagefiles that I used for this example are shown in the image:

Now we have set a basic setup for our object, it’s time to open the Rendertree, and start adding some nodes.

Create an extra “Lambert” material node, an extra “Texture image” node, a “Bumpmap Generator” node and a “Mix2Colors” node.

Now disconnect the “Phong” node from the “Material” , and connect the “Mix2Colors” node back to the “Material” ‘s “Surface, Shadow and Photon” slots.

Connect the “Phong” node back into the “base_color” slot of the “Mix2Color” node, and connect the “Lambert” into the “color1″ slot of the “Mix2Color” node. Also connect the “imagenode” of the “steelrust.tga” image into the “Diffuse” slot of the “Lambert”. Now you have assigned the first image to the two materials, you can open up the “Mix2Color” node and fiddle with the Mixvalues if you want.

If you would render this in the renderregion you can see that there’s no real visual difference between the “Phong” and “Lambert” material. Now connect the extra “Texture image” node” to the “weight1″ slot of the “Mix2Color” node, and also select the image that’s going to define the reflection, in this case the “steelrustshine.tga” file.

2. Bumpmapping

To make it even more realistic, connect the “Bumpmap_generator” node into the “Bump Map” slot of the “Material”. Select the image that’s driving the bump, in this case the “steelrustbump.tga” file. Open the “Bumpmap_generator” node and set the bump to your liking.

The Rendertree now should look like this:

Note: When disconnection nodes, be sure not to click on the refresh button untill you’re finished, or your tree is gone. And nope, the Rendertree has NO undo ! ! ! !

To spice up your rendering you could try to create a HDRI pass for a boost in the reflections. So there you have it, a simple rendertree and some textures to create a bit more complicated texturing. In this case two different material types are mixed by a texture, a bumpmap is added for some extra detail
If you refresh the renderregion, the render would look something like this:

You can see how the metal is very reflective at the end, but where the corrosion starts, it’s slowly becomes a matte, rusty material. You’re not limited by just reflections, you can also use this method to add transparancy etc. to your object.

I hope you found this useful.

RowuMedia

Pushing Pixels….

Category Archives: Tutorials

Texturing with Alpha channels in Softimage XSI v6 using the TLE

Simple bumpmap mixing in Softimage

Mixing matte and glossy materials with the weight node