PAINTING COLOR AND INSTANCE SCALE | UNITY

Learn how to use the Edit geometry operator node (SOP) in Houdini to add attribute painting capabilities in Unity. This allows painting of arbitrary attributes, like color, point scale, and normals, right inside Unity's Scene view.

In Houdini

1. Install and instantiate the Painting_ColorAndScale.hda example in Houdini.
2. Double click on the Painting_ColorAndScale1 to go inside its geometry (SOP) network.
3. Note the left side of the node tree starts with an imported tree mesh, fle1, which comes with the Cd attribute already added, then has the Edit_Tree Edit SOP node applied, and finally gets transformed ready for copying.
4. The right side of the node tree starts with a grid1, gets the pscale attribute added, and then has the Edit_Plane Edit SOP node applied.
5. The Edit SOP nodes allow incremental changes to any attribute and are used by Houdini Engine to allow painting.
6. We finally copy the trees onto the grid points via the copy1 SOP node.
7. Go back out of Painting_ColorAndScale1 node, right-click on it and select Type Properties.
8. In the Edit Operator Type Properties window, go to the Nodes tab.
9. It is important to note that Edit SOP nodes meant for painting, in this case Edit_Tree and Edit_Plane, have to be mentioned in the Editable Nodes field of the asset.
   

In Unity

1. Load the Painting_ColorAndScale.hda asset.
2. At the bottom of the Scene window, click the Paint button.
3. Hold Shift and Click+Drag Mouse to change the size of the brush.
4. At the top of the Scene window, set the Value to 1.0.
5. Click on the plane to paint the scale.
6. At the top of the Scene window, change the Node to Edit_Tree to paint color on the trees.
7. At the bottom of the Scene window, click the View button to get out of paint mode.
8. In the Inspector, you can change asset parameters like Rows and have the painted values be preserved.