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Sample Effect: Visual Shaders

In this guide, we'll show you how to create an effect that tracks a 3D object - the glasses - to the face. You'll also add two different gradient effects, and interactivity.

This effect is one of our featured samples. You can find it by opening Spark AR Studio and selecting Get Started on on the Visual Shaders sample, or by downloading the sample content. You can adapt any of the assets in this effect in your own projects.

You'll learn about:

  1. Using 3D objects to create glasses that respond to the movement of someone's face.
  2. Creating occluders to make the effect more realistic.
  3. Using the Patch Editor to switch the frames of the glasses and their color.
  4. Adding the camera texture to an effect.
  5. Manipulating the camera texture to create the purple and black and white gradient effects.
  6. Changing the gradients when the screen is tapped.

If you want to build this effect yourself, open the unfinished effect in the sample content folder. We've already imported the assets and objects you need to help you get started quickly.

Adding the glasses

The glasses are a 3D object. To put them onto a face:

  1. Insert a face tracker by clicking Add Object and selecting Face Tracker.
  2. Drag the object glasses_25D from the Assets Panel onto faceTracker0 in the Scene Panel.

You'll see the shape of the glasses tracking the face:



To finish the glasses we need to add a material and texture.

Start by creating the material:

  1. Select the glasses_25D mesh in the Scene Panel - it will be nested under the glasses_25D object.
  2. In the Inspector, click the dropdown under Materials and select Create New Material.
  3. In the Assets Panel, rename the material glasses_mat.

You're going to apply a sequences of textures to the material - rather than just one. Later, we'll use the Patch Editor to give the user the ability to switch between each texture in the sequence by tapping the screen of the device, showing a different style of glasses each time.

We've already added the 3 textures you'll need for this sequence to the project - they're listed in the Assets Panel as design.01, design.02 and design.03.

To make the textures into a sequence:

  1. Select them all at the same time, by holding down control or command on your keyboard and clicking each texture.
  2. In the Inspector, change the Type from Single Texture to Texture Sequence.


Then create an asset called an Animation Sequence to add the texture sequence to:

  1. Click Add Asset.
  2. Select Animation Sequence.
  3. Select the animation sequence - it'll be listed in the Assets Panel as animationSequence0.
  4. In the Inspector, click the dropdown next to texture and select the sequence - design.0[1.2].

Finally, to add the sequence to the material:

  1. Select the glasses_mat in the Assets Panel.
  2. Under Diffuse in the Inspector, click the dropdown next to Texture.
  3. Select animationSequence0 from the list.

You'll now see the texture sequence on the glasses in the scene, moving very quickly.

We'll use the Patch Editor to add simple logic and interactivity so the frame only changes when the someone taps the glasses on the screen.

Adding an Occluder

Occluders hide 3D objects when they wouldn't be visible in real life.

In this effect you'll use an occluder, which in this case is face mesh with a material applied to it to hide arms of the glasses when someone turns their head.

To create an occluder:

  1. Create a face mesh as a child of the face tracker. Move it to the top of the list, so it's directly underneath the face tracker in the Scene Panel.
  2. For the face mesh, uncheck the boxes next to Eyes and Mouth, so the occluder covers the full face.
  3. In the Inspector, create a material for the face mesh, and rename it occluder_mat.

You'll need to make a few changes to the material. In the Inspector:

  1. Set the Shader Type to Flat - as we don't need this material to omit or respond to light.
  2. Set Opacity to 1% - so the material isn't actually visible in the scene.
  3. Check the box for Double Sided - because sometimes the back of the face mesh is exposed when someone turns their head.

Switching glasses frames

We'll connect a patch representing the Current Frame property of the animation sequence to a series of other patches, telling the frame to change when the glasses are tapped.

Creating the patches

To create the patches:

  1. Select animationSequence0 in the Assets panel.
  2. In the Inspector, click the arrow next to Current Frame - this will open the Patch Editor and create a patch representing this property.


Now drag the glasses_25D object from the Scene tab into the Patch Editor, to create a purple patch representing this object.



Next, right-click in the Patch Editor and select:

  1. An Object Tap patch.
  2. A Counter patch.


In the graph we're going to build, the Object Tap patch will capture a tap on the glasses in the scene.

Connecting the patches

Connect:

  1. The Object output port in glasses_25D to the Object port in Object Tap.

  2. The Tap port in Object Tap to the Increase input in the Counter patch, to send a signal telling the counter to increase each time the object is tapped.

  3. The Count port in the Counter patch to Current Frame in the design.-animation patch, to tell the current frame to change.

Set the Maximum Count to 4. This will show the 3 textures in the sequence, and no texture for the final count - so the user won't seem to be wearing any glasses at all.

The patches should be connected like this:



You can test this out in the Simulator, by clicking the gear icon in the corner of the simulator and selecting Simulate Touch.

Switching glasses color

The glasses change color when the screen is tapped. We'll use the Diffuse and Environment properties of the material applied to the glasses object to do this. When someone taps the screen, the color we set under the Enironment property will override the color set under Diffuse.

Setting the colors

Select glasses_mat. In the Inspector:

  1. Choose a Color under Diffuse - we picked black.
  2. Check the box next to Environment.
  3. Under Environment, click the arrow next to Texture to create a patch representing this property.

Your project should look like this:

Creating the logic

To set up the logic to switch colors, you'll need to create some more patches using the menu in the Patch Editor. Right-click in the Patch Editor, and select a:

  1. Screen Tap patch - to detect when a user taps the screen.
  2. Counter - to count between the 2 colors.
  3. Option Picker - to set the color options we'll count between. Change the Type to Color.

Connect the 4 patches, so your graph looks like this:



In the Counter patch, set the Maximum Count is set to 2, to reflect the 2 color options we're counting between.

Finally, add the Environment color to the Option Picker by clicking on the colored square next to the second port. We picked white.

You could add more color options to this effect, by increasing the Maximum Count, and adding more colors to the Options Picker.

Using the camera texture

When someone uses an effect, the camera takes a video of what is being captured. This is called the camera texture, and can be used like any other texture in the scene.

In this effect we've changed the color of the pixels in the camera texture to create 2 color gradient effects.

To create the camera texture:

  1. Select the Camera in the Scene Panel.
  2. In the Inspector, click + next to Texture Extraction.

The texture will be listed in the Assets Panel as cameraTexture0.

To add the texture to the scene, you'll need an object and material to apply it to:

  1. Add a rectangle to your scene- it'll automatically be inserted as the child of a canvas.
  2. Rename the rectangle - we called it foreground.

You'll see a small square in the middle of your scene:



To make the rectangle fill the whole device screen:

  1. In the Inspector, click in the first box next to Size and select Fill Width.
  2. Click in the second box, and select Fill Height.

Next create a material for the rectangle, and rename it. We called it foreground_mat.

To apply the camera texture, select foreground_mat. In the Inspector:

  1. Change the Shader Type to Flat - because we don't need this material to omit or respond to light.
  2. Apply the CameraTexture under Diffuse.

This will show the user in the scene again. However, the glasses are hidden by the rectangle and camera texture:



We'll edit the layers and materials to change this.

Adding layers

At the moment, the glasses are hidden. To change this, we need to use layers so the objects render in the right order.

In the Layers Panel, create a new layer. It will be called layer1 by default - rename it foreground_layer. To help you keep track, rename the other layer glasses_layer.

In the Scene Panel, assign the face tracker, canvas and rectangle to foreground_layer.

Next we're going to make a change to the render options in the foreground material:

  1. Select foreground_mat.
  2. Click the arrow next to Advanced Render Options.
  3. Uncheck the boxes next to Use Depth Test and Write to Depth Text.

Creating the purple gradient

We used visual shaders in the Patch Editor to create the 2 gradient effects.

Creating the patches

Right-click in the Patch Editor. Select a Gradient patch and a Gradient Step patch from the menu.

In the Inspector, create a patch to represent the Diffuse Texture property of foreground_mat.

Adjusting the patches

To achieve the same gradient effect as in the finished project, you'll need to change some values in the patches:

  1. Click in the Gradient patch, and select a Vertical gradient - there are other gradients to choose from if you want to.
  2. In the Gradient Step patch, choose 2 colors - we picked orange and purple.
  3. In the Gradient Step patch adjust the start and end range to set where each color starts and finishes - we picked -0.1 for the Start Range and 0.9 for the End Range.

Connect the output of the Gradient patch to the Gradient input in the Gradient Step patch.

If we simply connected the output of the Gradient Step to the Diffuse Texture port in foreground_mat, the gradient would cover the foreground:



We need to add the CameraTexture, so the gradient patches change the colors of the pixels in the camera texture and create the gradient filter effect.

Adding the camera texture

Create a patch for the CameraTexture by dragging it from the Assets Panel into the Patch Editor.

To connect the CameraTexture, use the menu in the Patch Editor to create 3 more patches:

  1. An Add patch - to combine the camera texture with the gradient.
  2. A Dot Product patch and a Swizzle patch.


Set the second value in the Dot Product patch to 0.25, and the second value in Swizzle to xxx1.

Connect:

  1. The RGB output port in CameraTexture to the top input port in the Dot Product patch.
  2. The output of the Dot Product patch to the input in the Swizzle patch.
  3. The Output ports in the Gradient Step patch and the Swizzle patch to the Add patch.
  4. The Add patch to the Diffuse Texture port in foreground_mat.

Your graph should look like this:



And you'll see the gradient in your effect:

Creating the black and white gradient

For the black and white effect, create another Gradient patch and another Gradient step patch. Select a Circular gradient this time. Adjust the start and end range in the Gradient Step patch to 0.6 and 2. We kept the colors as black and white, but you could choose any you like.



Again, create a Dot Product, Swizzle and Add patch. Connect:

  1. The camera texture patch to the Dot Product patch.
  2. Dot Product to Swizzle.
  3. The outputs of both Swizzle and the Gradient Step patch to the Add patch.

Set the value of Dot Product to 0.45, and Swizzle to xxx1.

Here's how this part of the graph should look:



You can't see the gradient yet, because we need to connect both parts of the graph together.



Switching colors

The final step is to add the logic to switch between the two color gradients. We'll do this with the same screen tap that switches the glasses color by adding a Mix patch:

  1. Select a Mix patch from the menu in the Patch Editor.
  2. Instead of Diffuse Texture in the foreground_mat, connect the output of both Add patches to the Mix patch.
  3. Connect the Mix patch to Diffuse Texture.


We can use the Counter patch we added earlier to cause the gradients to change, at the same time as the glasses color.

To do this, simply connect the output of the Counter patch to the Alpha port in the Mix patch.

We chose the Alpha port because alpha is a value from 0 to 1. Set to 0 it's not mixing the two inputs, set to 1 the second input will take over the first.

You've now finished the glasses and gradient effect!

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