Implementing Renderman from within Houdini Give the constantwidth variable a starting value of "0.008" The curve is now ready to render. Connect these two nodes to your last transform node and export the geometry through the Attribute node into a RIB. Create the attribute "width" and in "RiName" type "constantwidth". Attach this node to the "attribute" node and go into the "Renderman" tab of the Attribute node. Set the class to "primitive" and type to float. This is where you will create the "constantwidth" variable that will let the renderman interface control the curve width.Ĭreate an attribute in "attribcreate" node called "width". Create an "Attributecreate" node and attach it to a new "attribute" node. Attach another transform node, which will "freeze the transformations" according to maya terminology. Adjust it based on the project specifications. Middle click on the transform node to see bounding box data. Use this to set the spanish moss to approximately 1 unit wide by 2 units long. There is a specific proceedure to export L-Systems curves from Houdini for use in the project.Ĭonnect a transform node to the L-System. Generate Medium and High detail meshes by setting geometry type to "Tube" and changing appropriate "Rows" and "Columns" values. Finally, i set my angle to "20" to get the desired results.įor this project, the curves are generated automatically by changing the geometry type for the L-Systems to "Skeleton". These rules reference each other based on the premise, and can create very interesting results. It will then roll three times before it create another branch and executes what is within the square brackets. Rule 1 says "A" will create a branch, pitch up, move forward once, pitch up, move forward once, then execute rule "B" within that branch. Execute rule "B", move forward once, execute rule "C", move forward once, pitch down, move forward twice, roll three times, etc. The Premise, or foundation to build upon says execute established rule "D"(controls the branches beyond -Y axis), Roll Counter-Clockwise twice, Pitch Up, and rotate 180 degrees. With this basic knowlege of the system, here is a snapshot of the rules guiding this Spanis Moss: This is the basis of L-System rules:į - Move forward one step without drawing These rules can be visualized as drawing a line in a specific XYZ position with each command given. L-Systems can be governed by Rules, Functions or even conditional statements. For those interested in persuing this project and others using this meathod, I will give you a brief rundown of my L-Systems Logic. Through these examples, one can see the possibilities of compound detail with L-Systems. I proceeded to write some expressions in Houdini L-Systems to capture a similar look. These reference images demonstrate the complexity of the spanish moss. This way, you can really push the boundaries of the exercise. Using LOD the renderer selects the appropriate model to render based on the area of screen space occupied by the model.įor this project, it was important to me that I captured the complexity of the Spanish Moss, and not just model one strand. Three models of a short length of Spanish Moss (Tillandsia Usneoides) were made in Maya. The animations on this page demonstrate the support offered by RenderMan for level-of-detail (LOD).
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