Extrude Mesh Profile Along Curve With Dynamic Adjustment In Blender Geometry Nodes

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Hey guys! Ever wanted to create intricate 3D models like scrolls, but found the process a bit daunting? Well, buckle up because we're diving deep into the world of Geometry Nodes in Blender to tackle this head-on. Today, we'll be exploring how to extrude a mesh profile along a curve, dynamically changing the profile based on curvature and curve direction. This technique is perfect for creating complex shapes like decorative scrolls, ornate moldings, and much more. So, let’s get started and unleash your creative potential!

Understanding the Challenge

The main challenge here is to extrude a mesh profile – think of it as a 2D shape – along a 3D curve. This is pretty standard in most 3D software, but we're going to take it a step further. We want the profile to adapt and change as it follows the curve. Imagine a scroll that gets thicker or thinner, or twists and turns in interesting ways. That’s what we’re aiming for. The key is to control these changes based on the curve's curvature (how sharply it bends) and its direction (where it's heading). This level of control allows for incredibly detailed and organic-looking shapes.

Breaking Down the Requirements

To achieve this dynamic extrusion, we need to break down the requirements into manageable steps:

  1. Define the Profile: We need a 2D mesh that will serve as our profile. This could be a simple circle, a complex polygon, or even a custom shape you’ve designed. The profile is the fundamental building block of our extruded shape.
  2. Create the Curve: The curve will act as the path for our extrusion. Bezier curves are ideal for this because they offer smooth, controllable shapes. You can manually create these curves in Blender or import them from other sources.
  3. Extrude Along the Curve: This is where the magic happens. We’ll use Geometry Nodes to make the profile follow the curve, creating a 3D shape.
  4. Dynamic Profile Adjustment: This is the heart of our challenge. We need to figure out how to change the profile's shape, size, and orientation as it moves along the curve. This will be driven by the curvature and direction of the curve.
  5. Control and Refinement: Finally, we need to have control over the parameters that govern the profile changes. This will allow us to fine-tune the shape and achieve the desired aesthetic.

Setting Up the Scene in Blender

First things first, let's fire up Blender and get our scene ready. We’ll start by creating a new Blender file. Delete the default cube (sorry, cube!), and let’s add a Bezier curve. You can do this by pressing Shift + A, selecting Curve, and then Bezier. Now you’ve got a curve to play with!

Creating the Profile

Next, we need our profile. For simplicity, let's start with a circle. Again, press Shift + A, but this time select Mesh and then Circle. You might want to scale down the circle a bit so it’s a manageable size for extrusion. Remember, this circle is just an example; you can use any 2D shape you like.

Diving into Geometry Nodes

Now comes the exciting part – Geometry Nodes! Select the Bezier curve, and head over to the Geometry Nodes tab. Click the New button to create a new node tree. This is where we'll build the logic for our dynamic extrusion.

Building the Geometry Node Tree

The node tree is where we'll define the extrusion process. We'll start with the basics and then add the dynamic adjustments.

1. Curve to Mesh

The first node we need is the Curve to Mesh node. This node takes a curve as input and generates a mesh by extruding a profile along it. Add this node to your tree by pressing Shift + A, searching for "Curve to Mesh," and placing it between the Group Input and Group Output nodes.

2. Profile Curve

The Curve to Mesh node needs a profile curve as input. This is where our circle comes in. Drag the circle from the Outliner into the node editor. This creates an Object Info node for the circle. Connect the Geometry output of the Object Info node to the Profile Curve input of the Curve to Mesh node. Now, you should see the circle being extruded along the Bezier curve!

3. Adjusting the Curve

The default extrusion might not look exactly how you want it. You can adjust the shape of the curve in Edit Mode (Tab key). Experiment with moving the control points to create different curves and see how the extrusion changes.

Dynamic Profile Adjustment: The Fun Part!

Now for the main event: making the profile change dynamically based on the curve. This is where things get a bit more complex, but don't worry, we'll break it down step by step.

1. Capturing Curve Information

We need to access information about the curve, such as its curvature and direction. Geometry Nodes provides nodes for this. The Curve Parameter node gives us access to the curve's normalized length (a value from 0 to 1 representing the position along the curve) and its tangent (the direction the curve is heading).

Add a Curve Parameter node to your tree. We'll use its Factor output later to control the profile's size.

2. Calculating Curvature

Calculating curvature directly in Geometry Nodes can be tricky, but we can approximate it by looking at the change in direction along the curve. We'll use the Tangent output of the Curve Parameter node and some vector math to achieve this.

  1. Add a Vector Math node and set its operation to Normalize. Connect the Tangent output of the Curve Parameter node to the Vector input of the Vector Math node. This gives us a normalized direction vector.
  2. Add another Vector Math node and set its operation to Cross Product. We'll use this to find the vector that's perpendicular to the curve's tangent.
  3. Connect the output of the first Vector Math node to one of the vector inputs of the second Vector Math node. For the other vector input, we'll use the Normal output of the Curve to Mesh node. This will give us a vector that represents the curvature.
  4. Add a third Vector Math node and set its operation to Length. Connect the output of the second Vector Math node to its Vector input. This gives us the magnitude of the curvature vector, which we can use as a measure of curvature.

3. Controlling Profile Size with Curvature

Now we have a value representing the curvature at each point along the curve. We can use this to control the size of the profile. We'll use a Set Position node to scale the profile vertices.

  1. Add a Set Position node and place it after the Curve to Mesh node.
  2. Add a Scale node and connect its Scale input to the output of the Length node (our curvature value).
  3. Connect the Geometry output of the Curve to Mesh node to the Geometry input of the Set Position node.
  4. Connect the Position output of the Geometry input of the Set Position node to the Position input of the Scale node
  5. Connect the output of the Scale node to the Offset input of the Set Position node.

Now, you should see the profile getting larger in areas of high curvature and smaller in areas of low curvature. How cool is that?

4. Adding Twist with Curve Direction

To add twist, we'll use the Tangent output of the Curve Parameter node to rotate the profile. We'll use a Rotate Instances node for this.

  1. Add a Rotate Instances node and place it after the Set Position node.
  2. Connect the Geometry output of the Set Position node to the Geometry input of the Rotate Instances node.
  3. Add an Align Euler to Vector node and connect the Tangent output of the Curve Parameter node to its Vector input. Set the Axis to Z. This will align the Z-axis of the rotation to the curve's tangent.
  4. Connect the Rotation output of the Align Euler to Vector node to the Rotation input of the Rotate Instances node.

Now, the profile should twist along the curve, following its direction. You can adjust the twist by adding a Math node (set to Multiply) between the Rotation output and the Rotation input to scale the rotation.

Fine-Tuning and Control

We've got a dynamic extrusion, but we need to be able to control it. Let's add some parameters that we can adjust in the Modifier tab.

Exposing Parameters

  1. Profile Radius: Drag the radius input of the Circle node to the Group Input node. This creates an input in the Modifier tab where you can adjust the profile radius.
  2. Curvature Scale: Add a Math node (set to Multiply) between the Length node (curvature) and the Scale node. Drag the second input of the Math node to the Group Input node. This allows you to scale the effect of the curvature on the profile size.
  3. Twist Scale: Similarly, add a Math node (set to Multiply) between the Align Euler to Vector node and the Rotate Instances node. Drag the second input to the Group Input node to control the twist amount.

Now, you have three parameters in the Modifier tab that you can tweak to get the perfect scroll shape!

Conclusion

Congratulations, guys! You've successfully created a dynamic extrusion that changes based on curvature and curve direction. This is a powerful technique that opens up a world of possibilities for creating complex and organic shapes in Blender. Experiment with different profiles, curves, and parameter settings to unleash your creativity. This knowledge will surely set you apart in your 3D modeling endeavors. Keep practicing and exploring – the world of Geometry Nodes is vast and exciting! So go on, create some amazing scrolls and share your creations with the world. Happy blending!